Existing heart failure therapies are unable to reverse heart failure and do not address its fundamental cause, the loss of cardiomyocytes2. In order to induce myocardial regeneration for the myocardium and the heart valve, facilitate self-repair, improve tissue salvage, reduce or reverse the adverse-remodeling and ultimately achieve long-term functional stabilization and improvement in the heart function, novel strategies for therapeutic regeneration are being developed which are aiming to compensate for the insufficient and low intrinsic regenerative ability of the adult heart3. Similarly, valve replacement with mechanical or biological substitutes meets numerous hurdles. New approaches using multicellular approaches and new material are extensively studied. Most of those strategies depend on biomaterials that help to achieve functional integrated vasculogenesis and myogenesis in the heart/tissue. Especially for failed heart valve function a number of therapeutic approaches are common from corrective intervention to complete replacement4. However the complexity of the heart valve tissue and its high physical exposure has led to a variety of approaches, however therapeutic regeneration needs to be established. Beside other approaches alginate has been identified as one building block to achieve therapeutic regeneration.Heart failure is a growing endemic in the aging Western population with a prevalence of over 20 million people worldwideAlginate is a versatile and adaptable biomaterial that has found numerous biomedical applications which include wound healing, drug delivery and tissue engineering. Due to its biologically favorable properties including the ease of gelation and its biocompatibility, alginate-based hydrogels have been considered a particularly attractive material for the application in cardiac regeneration and valve replacement techniques. Here, we review current applications of alginate in cardiac regeneration as well as perspectives for the alginate-dependent, cardiac regeneration strategies. Alginate can be obtained with a wide range of molecular weights 7 and is characterized by long chains that contain two different acidic components; namely, α-L-guluronic acid (G) and 1,4-linked β-D-mannuronic acid (M)  see .The overall ratio of both acids, M/G, and the way in which the G and M units are arranged in the chain, can vary from one species of seaweed to another. The origin and conditions of the extraction procedure can affect the viscosity of aqueous alginate solutions, lowering it if conditions are too arduous.Laminaria hyperborea gives strong hydrogels, while Laminaria digitata gives a soft-to-medium strength hydrogels8. Bacterial biosynthesis may provide an alginate with more defined chemical structures than that obtained from seaweed-derived alginate9. Generally, alginates with low M/G ratio will give a stronger hydrogels.The strength of the alginate hydrogels can also vary from one alginate to another. For example, with a careful extraction procedure, Alginates possess several crucial properties which make them suitable for use in cardiac regeneration. The first is their ability to be dissolved in water to yield aqueous solutions with moderate viscosity, which is particularly important for formulating injectable mixtures for cardiac therapies. The second is their ability to form hydrogels in mild conditions, for example by adding calcium salt to an aqueous solution of alginate. The calcium cations displace the sodium from the alginate, and grasp the long alginate molecules together, resulting in a hydrogels see . This pr10), and therefore, it is possible to modulate degradation rates and mechanical stiffness by choice of the appropriate crosslinking agents12. Different chemical and photo based ways can be used to do some crosslinking17.In contrast to the agar gels, where the solutions must be heated to about 60–80°C (depending on type) to dissolve the agar and the gel forms when cooled below approximately 40°C, no heat is required to form the alginate hydrogel; moreover, the hydrogels do not melt when heated. The ionically-triggered gelation of alginate is chemo-reversible, while covalent cross-linking is permanent  within the pores.Depending on the freezing regime, the hydrogels could become 3D scaffold with interconnected pores ture see 32. Impor33. The paints can release the metals which may accumulate especially in seaweeds that grow close to the sea communication routes. Moreover, despite strict regulation, some ships’ owners choose to cut the exploitation costs by disposing of the waste oils directly to sea water. This may also locally increase the amount of heavy metals in seaweeds exposed to such wastes. Heavy metals have a high affinity for sulfhydryl (-SH) groups, inactivating numerous enzymatic reactions, sulphur-containing antioxidants and amino acids with subsequent increased oxidative stress. This may result in vascular disease, hypertension, coronary heart disease and myocardial infarction34.There are several potentially harmful contaminants that may be carried by alginates and even accumulated during the alginate production processes. The most important from the point of treating heart failure are: heavy metals, formaldehyde, polyphenolic compounds and bacteria. In the case of alginates derived from seaweeds, the heavy metal content depends on the area and time of plant harvesting. Despite the strict regulation many ships are painted using paints containing heavy metals that prevent the growth of marine organisms+2, Fe+2 and Fe+3 ions. Those ions have a high affinity for alginates and can accumulate in their production. Therefore, these species should be removed from alginate, especially for its use in biomedical applications35.As with all polymers, alginates can also be degraded by reactive oxidate species. The formation of these species may be catalyzed by Cu36. The negative chronotropic effect of formaldehyde in animals is caused mainly by the inhibition of sympathetic nervous activity through the central nervous system.Similarly aldehydes could be transferred from seaweed to the heart with an alginate injection, nevertheless animal studies showed that the direct action of formaldehyde on the heart plays only a minor role37. Nevertheless, Paracelsus’ law states the action of a chemical depends on the dose of active agent. It is known that certain polyphenols may have genotoxic and carcinogenic effects. Furthermore, polyphenols may indirectly inhibit iron absorption which may lead to local iron depletion. Moreover, polyphenols may interact with certain pharmaceutical agents and enhance their biologic effects38. Nothing is known about administrating polyphenols directly to the heart, therefore removing polyphenolic compounds from biomedical alginates should eliminate possible risks.Polyphenolic compounds could be found in alginates. Surprisingly most of literature sources mention its positive effect on the heart mediated by reduction of oxidative stress35. Considering that proinflammatory cytokines are now thought to play a key role in the pathophysiology of chronic heart failure39, this contaminant must be reduced, if not eliminated, from biomedical alginates.Other potential contaminants of alginates include mould, yeast and bacteria, the latter may contribute to the presence of endotoxins, mitogens and pyrogensvia bacterial biosynthesis40. This enables controlling polymer molecular weight, its distribution, proportion and arrangement of G and M segments.Importantly, ultrapure alginates with strict control of alginate specification can be obtained 35. Due to sharply defined requirements for composition and purity of biomedical alginate, the price of it is a hundred fold higher than alginates used in food industry. Therefore, to conduct early stage/ proof of concept experiments, the cheaper product may be used but only with awareness of restrictions that will require upgrading when approaching clinical applications.The production of biomedical alginates is strictly regulated by legislation enforced by a number of agencies. For example in USA the FDA is responsible for monitoring production of biomedical alginates41. Exolytic enzymes known as oligoalginate lyases are responsible for further degradation of oligomers into unsaturated monomers. Some specialized microorganisms degrade alginates and produce ethanol. This process could be efficient enough to consider alginate as feedstocks for bioconversion into biofuels and commodity chemical42.The degradation, uptake and metabolism of alginate occurs in several types of bacteria. The class of enzymes called alginate lyases (Alys) catalyzes an endolytic β-elimination reaction that leads to depolymerization of alginate into oligomers32. One benefit resulting from that discrepancy between bacteria and mammals is that enzymes such as Alys can be safely used to remove alginate from maturing cell-laden scaffolds. This was reported by Takeuchi, who enzymatically removed the alginate envelope without harming encapsulated cells in the process of production of the “living threads”21.Importantly, the same or similar degradation pathways were not discovered in mammals, thus alginate polymers are considered not to be biodegradable in the human organism44. Unfortunately such observations are insufficient to provide any insight into the fate of alginate injected in the heart. In this work, we present available reports retrospectively and our direct contribution into understanding what could happen with alginate injected into the human heart is therefore limited to identifying the niches and needs for further research. Below we are presenting several reports that can be used as a starting point for further experimental efforts.In the literature there are frequently repeated opinions describing chains of alginate to be stable under physiological conditions35. In their dissertation, they referred to the most commonly applied way of cross-linking the alginate with calcium ions. The first step to degradation in that case would be disintegration of material due to exchange of calcium ions by sodium ions in the physiological environment. The process of hydrogel disintegration and subsequently releasing alginate in its liquid form is the only way alginate from the hydrogel can leave the heart. The kinetics of this process is very difficult to anticipate and more experimental work is needed. It was clearly proven that even under physiological blood concentration of Ca2+ and Na+ ions, the alginate in a form of hydrogel can still subsist46, so it is reasonable to believe that alginate injected into the heart will be long lasting even after the concentration of Ca2+ in the hydrogel drops to the physiological level. The plasma sodium concentration47 is simply insufficient to completely hinder the cross linking effect of Ca2+46. Whenever the alginate polymer molecule finds its way into the blood, the following cascade of events occurs.Perhaps the most comprehensive, but still not gap- free discussion on alginate degradation, was proposed by Andersen and colleagues37, estimated that alginate with Mw 200000 Da will degrade to 100000 Da at pH 7.4 and 37°C in 80 days. This renders the alginate as stable in physiological conditions.After hydrogel degradation the subsequent degradation of alginate will depend on the rate of cleavage of the glycosidic linkages in polymer chains. Anderson et al.48. To monitor the fate of alginate following intravenous, intraperitoneal and subcutaneous administration into mice, they developed a method based on the covalent incorporation of tyrosinamide into the alginate chains. The product could be radioiodinated to a high specific activity. Twenty-four hours after intravenous administration the larger polymer fraction remained in the circulation and did not readily accumulate in any of the tissues, while the low molecular weight fraction  of the injected polymer was excreted in the urine. At the same time point after intraperitoneal injection almost all dose of labeled alginate transferred from the peritoneal cavity to the blood compartment. Following subcutaneous administration, more than 70% of the injected dose was retained at the site of injection at 24h.The exact mechanism of alginate processing in the human body has not been yet elicited. The only light on that matter was illuminated by Duncan et al.49. The side effect is to increase chain flexibility which leads to forming weaker gels. The degradation of alginates can also be enhanced by Gamma irradiation50. In that case, the degradation seems to follow the pattern of random depolymerization with no preference for specific residues35.Even if the hydrogel decomposes, the average molecular weights of many commercially available alginates are higher than the renal clearance threshold of the kidneys. Therefore, the alginates should be carefully composed of a molecular weight, to enable controlled degradation and complete or close to complete removal from the body. To serve the proposed governing degradation rates, there are a few well-described tools. For example, at pH 7.4, alkaline β elimination is dominating the degradation path. This may be increased 5-fold by introducing to alginate chains the Periodate oxidate residues51, depends on the concentration of calcium. The calcium injected into the heart with alginate hydrogel may cause long lasting environmental changes to surrounding tissue45, which may result in impaired myocardial function and cardiac relaxation and ultimately in heart failure52. Therefore, to avoid the risk, the amount of the calcium in the hydrogel should be close to physiological levels. In one report authors used 1% (wt/vol) alginate and 0.3% (wt/vol) calcium gluconate53 so the concentration of Ca+2 is about 28 mg in 100 mL of hydrogel, while normal blood calcium concentration is up to 10.5 mg per 100 mL. This makes the question of kinetics of release of calcium from alginate hydrogel even more vital.Many signaling pathways of cardiac cells, especially regulating heart performanceCurrently the most advanced clinical trials, involving alginate based systems, for cardiac regeneration, includes Algisyl-LVR™ sponsored by LoneStar Heart, Inc  and PRESERVATION 1 sponsored by Bellerophon BCM LLC . These trials were preceded by extensive animal studies , the key part of which is summarized below.54. During an open-chest procedure, dogs received the injection mixture prepared by combining sodium-alginate aqueous solution with calcium cross-linked alginate hydrogel. Two weeks after the last microembolization, material was applied by 7 injections into the LV wall, halfway between the base and the apex, see The group of Randal J Lee evaluated the efficacy of alginate hydrogel implants in dogs with heart failure (HF) induced by repetitive coronary microembolizationThese encouraging preclinical results have led to the initiation of clinical investigation for intramyocardial delivery of alginate implants in patients with acute myocardial infarct (MI).®, were classified as a medical device , consist of Na+-alginate and Ca2+-alginate55, are dedicated for patients with enlarged left ventricle (LV) resulting from a mitral valve regurgitation, MI, arrhythmias and ischemia. The product comprises alginate that is administered directly into the left ventricle wall using up to 19 injections. Alginate remains in the heart muscle acting to increase pumping efficiency, reduce left ventricular wall stress, and prevent further dilation and negative remodeling of the left ventricle  and other cardiomechanical parameters, all summarized in Also in human studies57, transplantation or Left Ventricular Assist Devices (LVADs). Moreover, as a one-time procedure, it is less time consuming, more efficient and cost-effective in comparison to active implantable devices that require a power source. Since the group of patients in the Lee studies was small, namely two patients with non-ischemic and four patients with ischemic dilated cardiomyopathy, and follow-up of 3 months only on one patient, the results were to be confirmed in clinical trials on a wider group of 76 patients . Final data collection date for primary outcome measure was assigned on April 2014, but the estimated study completion date is April 2016. This study is ongoing and no results currently posted on ClinicalTrials.gov.The other advantages of this alginate based treatment are that it does not interfere with drug therapies and procedures such as valve or bypass surgery59. The authors found that alginate-hydrogel injections in addition to standard medical therapy for patients with advanced chronic HF was more effective than standard medical therapy alone for improving symptoms and exercise capacity. Thirty-five patients were treated with thoracotomy assisted, alginate-hydrogel injections59. Alginate-hydrogel treatment was associated with improved peak oxygen uptake on cardiopulmonary exercise59 at 6 months compared to control. Also six-minute-walk-test distance improved in alginate-hydrogel-treated patients versus patient treated by standard medical therapy. The study was conducted at 14 centres in Australia, Germany, Italy, the Romania, and Netherlands, however researchers should have indicated more precisely what “standard medical therapy” means, as it may be an important variable. Unfortunately, the 30-day surgical mortality was 8.6% (3 deaths) which is not superior but neither inferior in comparison to the outcome of other devices currently under investigation, for example HeartNet device60 , the Parachute device61 (Cardikinetix), Revivent device62 (Bioventrix).”Subsequently, the manufacturer of Algisyl-LVR , instigated a research grant with the objective of comparing alginate-hydrogel injections with standard medical therapy to determine the impact on clinical outcomes in patients with advanced heart failure53. In this study rats were used as a model. Calcium-crosslinked alginate solution was prepared from an aqueous solution by mixing it with calcium gluconate solution. Importantly, for temporal tracking of the injectable alginate biomaterial in infarcted hearts, biotin-labeled alginate was used. This was injected into the infracted area 7 days after anterior myocardial infarction. In situ formed hydrogel occupied 50% of the scar area. Alginate was replaced by connective tissue within 2 months, echocardiography studies showed that injection of alginate biomaterial reduced left ventricular diastolic and systolic dilatation, and dysfunction. The results were compared to those achieved by neonatal cardiomyocyte transplantation and were found to be superior  solution can be used to harvest solidified alginate63. Perhaps this is due to recent reports describing anti-mineralization effect of alginate on porcine and human cardiac valves64.Authors concluded that injection of bioabsorbable, 65. They prepared calcium cross-linked alginate solution that undergoes liquid to hydrogel phase transition as previously studied after injection into the infarct-related coronary artery in swine. Examination of hearts harvested 2 hours after injection showed that the alginate crossed the infarcted leaky vessels and was deposited as hydrogel in the infarcted tissue . They used the aqueous mixture of sodium alginate and calcium gluconate as a bioabsorbable cardiac matrix for preventing negative ventricular remodeling following acute myocardial infarction68. During standard catheterization procedure, the hydrogel is injected via the coronary artery into the damaged heart muscle. Here injected material perfuses and polymerises in sites in between the cells and fibers of damaged tissue. This provides physical support of the heart muscle during repair and recovery. It is claimed that alginate gradually dissipates and is excreted through the kidneys after healing69. While the author concluded on the safety and efficacy of this approach in human patients, no condition improvement was reported. Ongoing clinical trials involve approximately 300 patients who had successful percutaneous coronary intervention following acute ST-segment (ST-specific part of echocardiogram) elevation myocardial infarction .These promising results have led to the launching of clinical investigations of intracoronary delivery of alginate biomaterial in patients with acute MI by Bellerophon  or ions, gives the polymer more tailored capacities compared to neutral macromolecules. More than 200 different alginate grades and alginate salts are now offered. When considered for local injection or oral delivery , the type of hydrogel used is obviously crucial. Alginates polymers are one of the most extensively explored mucoadhesive biomaterials thanks to very good cytocompatibility and biocompatibility, biodegradation and sol-gel transition properties. But beyond the chemical composition and re-swelling approach chosen, multiple mechanisms can be considered to control the release speed of a compound using alginate. First, the size of the hydrogel can be controlled; a higher surface area will provide more “space” for the molecule to diffuse through the hydrogel. The permeability of the hydrogel is obviously critical as is the density of the polymer that controls it which can control the how easily the molecules can diffuse through the polymer network.The potential use of the different alginate hydrogels as pharmaceutical excipients has not yet been fully evaluated but alginate is likely to make an important contribution in the development of polymeric delivery systems. The precise chemical degradation mechanism and approaches in the choice of alginate for drug deliveries was previously broadly reviewed73. For example, Vascular endothelial growth factor (VEGF) entrapped in the alginate hydrogel has a steady and continuous release for more than one month74. Free VEGF is degraded within 72 h post-injection while VEGF injected within the alginate hydrogel is detectable up to 15 days after injection. Moreover, to enhance affinity to angiogenic factors, alginate can be sulfated such that it mimics the structure of heparin75  followed by platelet-derived growth factor-BB (PDGF-BB) with alginate hydrogels could induce a functional improvement and angiogenic effect which is greater than single factors after myocardial infarction in a rat model77. The results of this study highlight the potential of combining alginate with other biopolymers for application in cardiac regeneration strategies.Finally, alginate has been blended with a conductive polymer namely, polypyrrole to enhance cardiac cells–implant interaction. The alginate polymer blend was injected into the infarct zone of the rat heart. At 5 weeks post-treatment, the blend yielded significantly higher levels of arteriogenesis when compared with the alginate only treatment group and the saline control group. In addition, the blend enhanced infiltration of myofibroblasts into the infarct area78. Electrical, signal may be transduced with different rate, around the alginate island; this may cause re-entry circuit and in fine arrhythmia79. Problem of that nature occurred when ischemic heart failure was treated by skeletal myoblast transplantation80. The one way of solving that problem would be to implant cardio-defibrillator (ICD), which can send a high-energy electrical signal to eliminate arrhythmias. Unfortunately, this device causes a highly unpleasant sensation felt by the patient81. In a different study it was shown that arrhythmia was avoided when undifferentiated human ESCs surgically delivered onto the infarct area in a 68-year-old patient were embedded into a fibrin scaffold82. This is encouraging evidence indicating the importance of applying hydrogel to enhance performance of cell-base therapies.In fact, all efforts aiming to enhance and control the conductivity of alginate based systems are substantial84. Building on this advantage, Dvir and colleagues85 constructed a patch by seeding neonatal rat cardiac cells isolated from the LV of 2 days old rat heart in Matrigel (authors failed to describe manufacturer of Matrigel) supplemented with a mixture of angiogenic and prosurvival factors (insulin-like growth factor-1 (IGF-1), stromal-cell derived factor 1 (SDF-1), and VEGF into macroporous alginate scaffolds. To promote maturation of vasculature the patch was cultured for a week in the rat omentum and transplanted into post-infarction rats. One month after implantation the patch showed electrical and structural integration with the host myocardium  see –D. While see –D. 89; nevertheless, RGD-peptide -modified-alginate is versatile, thus it was also used to encapsulate human Mesenchymal Stem Cells (MSCs) for the transfer  derived from small intestinal submucosa. It was used to prepare a tubular tricuspid valve that showed physiological growth, remodeling and preserved function101. Its superior mechanical properties make it an extremely interesting candidate to test as a base for cardiac patches or to produce heart valve leaflets, see Another potentially useful material for a variety of heart repair strategies is bacterial nanocellulose102. For the full range of physiological flow conditions tested, the electrospun gelatin-chitosan polyurethane demonstrated good biocompatibility and cell retention properties103.Also, chitin and chitosan  were successfully used to produce scaffold for heart leaflets104. For example elastomeric poly(glycerol sebacate) (PGS) was reported to support in vivo remodeling of cell-free synthetic graft into a neoartery106. Sohier and colleagues proposed applying nano-fibrillar anisotropic poly-(ε-caprolactone) (PCL), as a substrate for heart valve engineering107.Synthetic polymers may also potentially be used in therapies related to heart failure and tissue engineering108.In their outstanding report Baaijens and coworkers claimed using poly-ε-caprolactone bisurea strips to modulate macrophage polarization within scaffolds and trigger specific immune response to enhance deposition of sulphated glycosaminoglycans and collagen on the scaffolds to support tissue remodeling32.Thanks to a variety of crosslinking approaches, alginate can form versatile and tunable hydrogels, suitable for carrying cells and developing 3-D cellular microenvironments. Alginate can be modified with a variety of biological agents to promote matrix-cell interactions, guide 3-D cell organization, modulate cell fate and promote cellular integration109, alginate as a vehicle for delivering cardiac progenitors cells and their derivatives, alginate-supported generation of the new cardiomyocytes, and alginate-assisted activation of endogenous cardiac progenitor cells.Alginate-based biomaterials for the treatment of MI is entering the clinical trials stage, therefore understanding the mechanisms by which these therapies affect LV remodeling, cardiac function and cardiac electrophysiology becomes a pivotal issue. Despite progress made in cardiac patches and injectable alginates, much of its potential remains unexplored, including alginate-mediated reprogramming of non-cardiomyocytes into cardiomyocytesTo fully utilize alginate in those applications several challenges still need to be addressed. Firstly, more cell-interactive alginate derivatives are required to offer a better precision in controlling cell organization, differentiation, growth and function. Governing at the micro- and nano-scale, the spatial distribution of signaling and topographical cues are key tools for designing cell-interactive systems. Next, more tunable alginate-based release systems need to be developed to improve their safety, obtain local effects and increase sustainability. The focal point of these efforts is the sequential release of drugs  while on-demand drug release could take place in response to signals derived from cells  and external cues .19. Valvular interstitial cells (VICs) and aortic root sinus smooth muscle cells (SMCs) were encapsulated separately into alginate/gelatin blend before printing the heart valve root. After one week of culture, the mechanical properties of the acellular scaffolds were much lower than those of the cell-laden 3D printed hydrogels. What is now needed is further advancement in 3D deposition methods, focusing on eliciting oriented growth of the cells and the ECM, which may further enhance cardiac tissues regeneration110.Recent achievements in the solid free-form fabrication of alginate-based constructs for heart valve tissue engineering illustrate the vital direction in which the cardiac regeneration techniques may develop. Duan et al. used a Fab@Home bioprinter to prepare scaffolds from gelatin/alginate -blended hydrogels11. Fibers consisting of encapsulated cells (“living” threads) are an attractive option since cells are provided directly into the dedicated location within the structure avoiding time-consuming cellular diffusion through the construct (see 11.Although 3D printing of alginate based hydrogels is a powerful and feasible technique, effort is also needed to explore other free-form fabrication technologies. For example fibers made out of alginate could be processed using weaving, knitting and braiding see 10,11. Firuct see , H10,11.It is difficult to deny that replacing vital organs and tissues with fabricated composites still does not meet all the sophisticated biological and physiological requirements and reproducing their characteristics remains elusive. Many properties of alginate are not unique taken separately, but the fact that alginate combines them all makes it a valuable material that could be used to approach the challenges ahead.


LV global longitudinal strain also improved . Change in T1 time was not significant . Highly sensitive troponin T was lower at follow up . In incident HD patients, 6-months of HD was associated with improvements in LV mass, strain and troponin. These findings may reflect improvement in known cardiac tissue abnormalities found in patients over the first year of HD.Patients commencing on haemodialysis (HD) have an increased risk of cardiovascular events in the first year after starting HD compared to those patients established on HD longer. Left ventricular (LV) hypertrophy and abnormal myocardial strain predict mortality. There may be changes in the myocardium of incident HD patients over a 6-month period of HD which may explain changes in cardiovascular risk. We used CMR to consider changes in LV mass, myocardial strain and T1 mapping. We examined changes in pre-dialysis highly sensitive troponin T. 33 patients undergoing HD for <12 months were recruited. Participants underwent CMR at baseline and after 6-months of standard care. 6-months of HD was associated with reduction in LV mass index (Baseline: 78.8 g/m Presence of LVH on HD commencement is associated with increased risk of cardiovascular and all-cause mortality3. The pathophysiology of myocardial disease in HD is complex and in addition to myocardial hypertrophy, involves pump dysfunction, ventricular dilation and myocardial fibrosis5. This pathophysiology of cardiovascular disease in HD patients is incompletely understood, especially why incident HD patients have greater risk of sudden death over the first year of HD than those established on HD for longer6.Cardiovascular disease is a major cause of morbidity and mortality amongst hemodialysis (HD) patients. Echocardiography studies demonstrate that up to three quarters of patients commencing HD have left ventricular hypertrophy (LVH)7. CMR is better able to characterize cardiac tissue. Although it is not possible to use gadolinium contrast in these patients because of concerns regarding nephrogenic systemic fibrosis8, newer non-contrast techniques to characterize cardiac tissue are emerging. Recently, native T1 mapping identified abnormalities in uremic hearts compared to healthy volunteers, and co-morbid matched patients10. These abnormalities are in keeping with those demonstrated using gadolinium contrast and have been verified in CKD patients with adequate renal function to permit gadolinium use12.Cardiac Magnetic Resonance imaging (CMR) is a leading tool for examining the hearts of HD patients. CMR is highly reproducible in these patients where changing volume status make echocardiography less reliable13. Reduction in magnitude of peak strain is associated with reduced myocardial contraction and could be associated with fibrosis14. CMR GLS has been demonstrated to be impaired in several renal populations, including in CKD, incident and prevalent HD patients, as well as correlating with cardiac histology in animal models of kidney failure15.Myocardial strain, often measured as global longitudinal strain (GLS), a measure of myocardial deformation throughout the cardiac cycle, is more directly associated with cardiomyocyte metabolism than LV ejection fraction (LVEF)We undertook an observational study to interrogate the hearts of incident HD patients over a 6-month period. We sought to identify detectable changes in cardiac structure, function and composition using CMR. We assessed associations between these and clinical data. We hypothesized that haemodialysis would affect myocardial contractility  and could reduce or reverse diffuse fibrosis, measured by native T1 mapping. We hypothesized changes in biomarkers associated with myocardial stress would occur (highly-sensitive troponin T (hs-TropT) and N-Terminal Pro-B type Natriuretic Peptide (NT-ProBNP)).Thirty-four patients consented to participate; 32 participants completed baseline imaging, one participant died after consenting but prior to study visit, another withdrew consent before imaging. Twenty-four participants (75% of consented participants) completed baseline and follow-up visits. Six participants were transplanted during the study and 2 participants withdrew consent. No participants died during follow up. Mean participant age was 61.2 ± 13.4 years, 62.5% were male. Median duration of HD at baseline was 5 months (interquartile range (IQR) 3.8–8 months). Baseline demographic data for study participants completing the study are shown in Table 2 versus follow up LVMI 69.9 ± 19.3 g/m2, p = <0.001  reduced following 6 months of HD. Baseline LVMI was 78.8 ± 18.6 g/mNative T1 times were unchanged following 6 months of HD. Baseline global T1 time: 1263.4 ± 24.8 ms, follow up global T1 time; 1259.3 ± 32.2 ms, p = 0.59. Mean septal T1 time baseline; 1277.4 ± 28.2 ms, follow up 1271.5 ± 35.4 ms, p = 0.50.−1, follow up strain rate 1.184 ± 0.46 s−1, p = 0.01. There was no significant change in early diastolic strain rate from baseline to follow up. Baseline early diastolic strain rate 1.04 ± 0.33 s−1, follow up early diastolic strain rate 1.16 ± 0.43 s−1, p = 0.14.Reflecting improved myocardial compliance, magnitude of GLS and strain rate both increased following 6 months of HD. Baseline GLS: −17.9 ± 5.3%, follow up GLS-21.6 ± 6.1%, p = <0.001  pg./ml, follow up 2317 (IQR 1559–7028 pg/ml p = 0.44). There was a reduction in hs-tropT from baseline to follow up (Baseline median hs-TropT: 38.8 (IQR 24.5–49.5) pg/L, follow up: 30.8 (IQR 18.9–57.6) pg/L, p = 0.02).There was no change in URR, blood pressure (BP) or ultrafiltration volumes from baseline to 6 months follow up. Weight at end of dialysis the session before imaging was unchanged from baseline to follow up. There were no significant changes in any routinely collected blood test results during the study.There were correlations between baseline LVMI and baseline septal T1 time . At follow up, this correlation was not statistically significant . Similarly, global T1 time at baseline correlated with baseline LVMI (Pearson’s R = 0.585 p = 0.003), however follow up global T1 time was not correlated with follow up LVMI . The difference in LVMI over the study period also correlated with difference in septal T1 time , but not difference in global T1 time . There was no association demonstrated between EDV, ESV or LVEF and T1 times.At baseline, GLS was related to LVEF , LVMI , EDV  and ESV , LVMI , EDV . There was no correlation between difference in LVMI and the difference in GLS.At baseline, GLS correlated with global native T1 relaxation time  and with septal T1 . At follow up this relationship was not seen: follow up GLS and global native T1 , follow up GLS and septal T1 . There was no correlation between change in GLS and change in native T1 times. There were no relationships between strain rate or early diastolic strain rate and native T1 time.At both baseline and follow up, there were no correlations demonstrated between any measure of NT-proBNP, hs-tropT or any LV indices, native T1 or myocardial strain.Overall there was a pattern of improvement in cardiac parameters in some participants but not others. Figure Septal T1 times improved in 66.7% of patients. Patients whose septal T1 time improved had higher baseline septal T1 compared with those whose T1 time did not improve . By follow up, septal T1 time was lower in the ‘improving’ group compared to the ‘non-improving’ group .Patients with reduction in septal T1 over the study duration had evidence of reduced myocardial contractility at baseline, as their baseline GLS was reduced in magnitude compared to those whose T1 time did not fall . By follow up, there was no significant difference in GLS between the groups.2, non-improvers: −3.3 ± 5.7 g/m2, p = 0.009).Although overall LVMI was no different at baseline or follow up in septal T1 time improvers versus non-improvers, the difference in LVMI over during the study was greater in those whose T1 time fell . There was no difference in incidence of diagnosis of congestive cardiac failure, hypertension, ischemic heart disease, previous myocardial infarction or diagnosis of diabetes between those whose septal T1 fell and those whose septal T1 did not.This is the first study to investigate effects of 6-months of HD on incident HD patients utilizing multi-parametric CMR with native T1 mapping and feature tracking myocardial strain analysis. We observed trends suggesting that there is an association between HD and an improvement in myocardial biomechanics (identified by feature-tracking derived GLS), and regression of LVH. These results require validation in a larger cohort of patients.15. That regression in LVMI and improvement in GLS and strain rate occurred together is suggests that the higher the LVMI, the less efficient left ventricular contraction and relaxation are and that as LVMI regresses, the ventricle becomes more compliant. As suggested by correlation of reduction in septal T1 relaxation times with reduction in LVMI, our study findings may indicate that as LVMI regresses, fibrosis also regresses, resulting in improved myocardial biomechanics leading to enhancement in GLS and strain rate. However, without histological confirmation, this is speculative.The improvements in GLS and strain rate are encouraging. Previous studies have shown that GLS measured using speckle tracking echocardiography correlates with other markers of uremic cardiomyopathy, including fibrosis on histology16. Another study considered echocardiographic changes in patients with end stage renal disease and heart failure17. Echocardiography was performed up to 3 months prior to HD initiation and again 8.6 ± 5.2 months after starting HD. There was a significant reduction in LVMI (mean reduction 24.3 ± 35.4 g/m2). The authors concluded this was due to improvement in volume status17. Although improved volume status is possibly a factor in the reduction in LVMI seen in our study, we saw no changes in EDV or ESV. Additionally, mean ultrafiltration volumes for 30 days prior to imaging did not change from baseline to follow up. Supporting the notion that change in LVMI in our study was not purely related to volume changes, there was no change in patient weight from baseline to follow up. However, we cannot exclude that overall improvement in volume status contributed to regression in LVMI and improvements in myocardial strain. Conversely, a continued rise in LVMI after dialysis initiation has been demonstrated using echocardiography, however it may be that timing of imaging, changing volume status or other co-morbidities in previous work contributed to this difference18.Regression of LVMI in incident HD patients has been demonstrated previously. Regression in LVMI over time in patients new to HD was shown in an observational echocardiography study, where LVMI regressed in 48% of patients following one year of HD12.Additionally, our data do not support the theory that LVMI regression and improvement in GLS were due to better BP control, as there was no difference in BP from baseline to follow up. Similarly, other makers of dialysis efficacy such as URR, calcium and phosphate were unchanged. That the changes in imaging abnormalities are independent of BP is not entirely surprising. A CMR study comparing patients with CKD and hypertensive patients, showed that LVMI was highest in the CKD group and that GLS was worse in the CKD group despite the hypertensive group having the highest BP21, without tissue correlation, we cannot be certain that changes in LVMI, myocardial strain and T1 times are reflective of an improvement in myocardial tissue abnormalities.We did not observe reductions in either global or septal T1 relaxation times over the study duration, although there was an absolute difference in magnitude of T1 time of 5 ms. A larger sample size, or longer follow up duration may have led to a statistically significant change in T1 time as there were some indications in the study that T1 is interrelated to other markers of tissue abnormality. In fact, baseline septal T1 correlated with both GLS and LVMI. Change in septal T1 time also correlated with the difference in LVMI over a 6-month period. However, despite supporting evidence from histological studies3. Echocardiography derived GLS also predicts mortality in patients with CKD23.Although this was a relatively small single centre study, improvements seen in CMR derived cardiac parameters are of potentially important clinical significance. Participants whose T1 times improved had higher baseline T1 relaxation times and poorer baseline GLS. The possibility of regression to the mean should be considered. To attempt to address this, we investigated the effect of paired measures and the effect of regression to the mean by ANCOVA analysis- p 0.001 for LVMI, and p < 0.001 for GLS. Reassuringly, even after weighting for within subject change, the difference in measurements was still significant. It is too early to tell whether the patients whose cardiac parameters improved will subsequently have reduced cardiac morbidity and mortality. However, there is a reasonable body of evidence that LVH in HD is associated with an increased cardiac morbidity, cardiac mortality and all-cause mortality10. However, we used a multi-parametric CMR protocol and biochemical markers so our study population was well characterized. Future studies would include a multicentre approach with larger sample size, and potentially with histological validation of T1.Limitations of our study include it being single centre, and small sample size. Patients were recruited on average with a 5 month HD duration. Our power calculation was based on data using gadolinium, to reproduce our work it would be possible to base sample sizes on T1 data in dialysis patientsIn summary, this study demonstrated that in incident HD patients, 6 months of HD was associated with improved LVMI and myocardial strain. Although no significant difference in T1 times from baseline to follow up was seen, change in septal T1 time associated with change in LVMI. We consider that these findings reflect improvement in tissue abnormalities known to be associated with renal failure. However, without tissue correlation we cannot be certain - future studies with findings correlated with cardiac histology are of interest.24. All patients provided written, informed consent and received usual thrice weekly dialysis care for the study duration. Participants who underwent renal transplantation during follow up were withdrawn from the study.Thirty-four HD participants consented to participate in the Cardiac Uraemic fibrosis Detection in DiaLysis patiEnts study (CUDDLE study ISRCTN99591655). The West of Scotland Research Ethics Service (13/WS/0301) approved the study. The study was carried out in accordance with the declaration of Helsinki. Participants were eligible if they had been receiving HD for <12 months. Exclusion criteria included atrial fibrillation as this impairs cardiac-gating of images, or CMR contraindications25. A cine short-axis stack of the LV was performed. Basal, mid and apical T1 maps were acquired using motion-corrected, optimized, modified Look-Locker inversion recovery sequences without contrast. Typical T1 acquisition parameters were: slice thickness 6.0 mm, voxel size: 1.9 × 1.9 × 6.0 mm, field of view 340 mm × 272 mm, flip angle 35 degrees, minimum T1 180 ms, inversion-time increment 80 ms, repetition time 267.84 ms, bandwidth 1085 Hertz/pixel.All participants underwent CMR on a post-dialysis day on a 3 T scanner  at baseline and after 6-months of HD. Patients who underwent dialysis on a Monday/Wednesday/Friday schedule were imaged on a Tuesday or Thursday, Tuesday/Thursday/Saturday patients were imaged on Wednesdays or Fridays. A double radio-frequency array coil (anterior and posterior) was used. The imaging protocol included cine magnetic resonance with steady-state free precession and T1 mapping sequences9. For T1 maps, LV contours were drawn onto colour-enhanced spatially co-registered maps. The anterior right ventricular insertion point was used as reference and T1 maps were segmented corresponding with the American Heart Association (AHA) 16-segment model26. Segmental AHA regions were delineated by user-defined border delineation on Siemens Argus software. T1 times were measured in each segment. Care was taken to ensure adequate margins from tissue interfaces such as between the blood pool and myocardium. After removal of any segments affected by artefact, global T1 time was calculated as the mean of remaining segments. Septal T1 time was calculated by averaging remaining AHA anteroseptal, inferoseptal, and septal segments . To determine GLS, strain rate and end-diastolic strain rate feature-tracking software  was used. On horizontal long-axis cine acquisition, the end-diastolic frame was identified for each image and endocardial borders were delineated. The delineated contour was then automatically propagated throughout the cardiac cycle and GLS, strain rate and early diastolic strain rate calculated27.LV indices were analysed by a single blinded observer as previously describedPre-dialysis blood samples at baseline and after 6-months follow up were frozen (−80 °C) and thawed for analysis of hs-tropT and NT-proBNP in a single batch using validated assays . All samples were analysed using manufacturers’ protocols and calibrations. Routine blood tests including haemoglobin, urea reduction ratios (URR), albumin, corrected calcium and phosphate were available from electronic patient records (EPR). EPR were used for medical and dialysis history including pre-and post-dialysis weights and ultrafiltration volumes 30 days prior to imaging.Statistical analyses were performed using SPSS version 22 . Normality was tested using visual distribution checks and the Kolmogorov-Smirnov test. Paired t tests (for parametric data) and Wilcoxon-Signed Rank tests (for nonparametric data) were used to compare continuous indices between time points within HD patients. Independent t tests (for parametric data) and Mann-Whitney U tests (for nonparametric data) were used to compare between group differences. Correlations between continuous indices were assessed using Pearson’s and Spearman’s correlation coefficients for parametric and nonparametric data, respectively.11 as at commencement of this study design there were no data to inform distribution of T1 times in HD patients.The power calculation was based on mass of fibrotic tissue detected with gadolinium as previously publishedData from patients studied with gadolinium showed that distribution of fibrosis, when present was normally distributed with standard deviation 7 g. If the true difference in mean difference in volume of fibrotic tissue detected at CMR in matched pairs is 4.5 g, we determined 27 patients were needed (paired t-test at 0 and 6 months) to detect this difference with power of 90% and type I error probability of 0.05. Allowing for a 20% dropout due to transplant, death and co-morbid disease, we aimed to recruit 35 patients.


This technology also facilitates assessments of organ viability to be undertaken prior to transplantation, thereby minimizing the risk of primary graft dysfunction. The application of a tailored approach to DCD heart transplantation that focuses on organ resuscitation at the time of procurement, ex situ preservation, and pre-transplant assessments of organ viability has facilitated the successful clinical application of DCD heart transplantation. The transplantation of hearts from DCD donors is now a clinical reality. Investigating ways to optimize the resuscitation, preservation, evaluation, and long-term outcomes is vital to ensure a broader application of DCD heart transplantation in the future.Cardiac transplantation has become limited by a critical shortage of suitable organs from brain-dead donors. Reports describing the successful clinical transplantation of hearts donated after circulatory death (DCD) have recently emerged. Hearts from DCD donors suffer significant ischemic injury prior to organ procurement; therefore, the traditional approach to the transplantation of hearts from brain-dead donors is not applicable to the DCD context. Advances in our understanding of ischemic post-conditioning have facilitated the development of DCD heart resuscitation strategies that can be used to minimize ischemia-reperfusion injury at the time of organ procurement. The availability of a clinically approved  Cardiac transplantation is the “gold-standard” treatment for eligible patients with advanced heart failure. Despite adverse changes in the donor and recipient populations, posttransplant outcomes continue to improve with a median survival of 11 years . Over thFollowing the first publication of brain death criteria in 1968 –9, cardiDonation after circulatory death describes the procurement of organs from donors that have been declared dead based on circulatory criteria Figure B 10). E. E10). EThe Maastricht classification system is used to describe four different categories of DCD donors according to the circumstances of the donor’s death Table  19, 20), 2019, 2Donation after circulatory death hearts experience a period of warm ischemia during the progression to circulatory arrest and declaration of death Figures B,C, the Multiple authors have attempted to describe the potential impact of DCD on the numbers of heart transplants that could be performed. Noterdaeme et al. examined deceased donor data from a single center in Belgium . Over a The approach to DBD heart transplantation displayed in Figure Simply applying the standard DBD approach for heart procurement and preservation to the DCD context is unlikely to allow for adequate resuscitation of the DCD heart to provide a viable organ Figure B. The DCUnderstanding the physiologic impact of donor extubation and warm ischemia on the DCD heart is fundamental to developing a successful resuscitation strategy . After evia the NHE. In the DCD context, however, intracellular acidosis develops concurrently with the depletion of ATP stores. The combined effect of increased NHE activity and inhibition of the sodium–potassium ATPase produces a pathological accumulation of intracellular sodium  stores and anaerobic metabolism, which cause intracellular acidosis, activation of the sodium–hydrogen exchanger (NHE), and sodium influx into the myocyte , 31. Them Figure A  device and preserved in a normothermic and beating state until eventual transplantation . Th. Th35). n Figure , 36. Then Figure , 35.At the time of organ procurement, the DCD heart is energy deplete and vulnerable to the influx of sodium and calcium upon reperfusion. The reactivation of ATP production in the calcium-overloaded myocyte after prolonged ischemia can propagate calcium oscillations and the development of hypercontracture Figure  37, 38), 3837, 3In 1986, Murry et al. first demonstrated that repetitive periods of brief ischemia could protect the myocardium from a subsequent period of prolonged ischemia and established the concept of ischemic pre-conditioning . In 2003The activation of prosurvival kinases at the time of reperfusion confers powerful cardioprotection against IRI through inhibition of the MPT pore, and activation of the reperfusion injury salvage kinase (RISK) and survivor activating factor enhancement (SAFE) pathways , 49, 50.via the NHE and calcium influx via reverse NCX ..via the The cardioprotective effects of NHE inhibition in IRI are well documented. Cariporide has been shown to limit myocardial IRI in clinical trials –67 and tPharmacologic inhibitors of reverse-mode NCX have also been investigated as a means of minimizing calcium influx into the myocyte during reperfusion Figure . NCX inhvia non-activating sodium currents that may exacerbate calcium overload during reperfusion  trial that describe the clinical outcomes of standard criteria DBD hearts preserved using the OCS have been recently published (The Transmedics organ care system (OCS) is the only clinically available ESHP device, and the results of the ublished . The OCSublished . The PROublished ; howeverublished .Donor heart preservation using ESHP has been utilized in numerous pre-clinical studies of DCD heart transplantation , 140–142Despite the successful clinical application of donor heart preservation using the OCS, many questions regarding the optimal conduct normothermic ESHP remain unanswered . The optThe OCS utilizes a whole blood-based perfusate to ensure adequate myocardial oxygen delivery. Preservation using a whole blood-based perfusate may improve donor heart preservation compared to a solution in which the plasma component has been removed. This observation may be related to the antioxidant and anti-inflammatory properties of albumin and other plasma proteins, and the metabolic substrates present in donor plasma . PreviouThe development of myocardial edema is common during ESHP, which may cause diastolic dysfunction and limit the safe preservation interval . The OCSAnother important variable impacting the development of myocardial edema is the perfusate solution oncotic pressure. The OCS priming solution contains mannitol as an oncotic agent; however, the oncotic pressure of this solution has not been reported. We have utilized a perfusate solution comprised of STEEN Solution™  and whole donor blood , 143. STThe coronary perfusion pressure may also impact the development of myocardial edema. Inadequate perfusion pressure may compromise myocardial oxygen delivery, while excessive pressure may damage endothelial cells . The tarPrevious studies have demonstrated that myocardial function declines in a linear fashion during ESHP, even when normal hearts undergo prolonged perfusion , 143. SuHypothermic perfusion has been investigated as an alternative means of supporting aerobic metabolism and minimizing DCD heart exposure to cold ischemia during the preservation interval. The myocardial oxygen demand of a hypothermic and arrested heart is only 0.14 mL/100 g/min , and oxyContinuous cold oxygenated perfusion of DCD hearts has consistently been shown to provide superior preservation and improved functional recovery compared to cold-static storage –159. RecHypothermic perfusion appears to improve DCD heart preservation compared to cold-static storage; however, a significant limitation of this method is that assessments of organ viability are limited to evaluating the metabolic (lactate metabolism) and biomarker profile of the organ. Since the heart is preserved in a hypothermic and arrested state, assessments of organ function are not possible. Future research is required to determine if hypothermic perfusion provides myocardial preservation equivalent to that of normothermic perfusion, and clarify the role of hypothermic perfusion in DCD heart transplantation.The traditional approach to cardiac transplantation involves evaluation of heart structure and function within the donor following declaration of brain death Figure A. Similaex situ assessments of organ viability during the preservation interval  ≤12 mmHg, and a left-ventricular EF ≥ 50% on transesophageal echocardiography  ≥2.5 L/min/miography . Interesansplant . These rEarly investigators sought develop techniques for the resuscitation, preservation, and transplantation of hearts from donors that had suffered an anoxic arrest, in an era when little was known about IRI, immunosuppression, or extracorporeal perfusion –171. Chr1, and nifedipine could facilitate successful transplantation following 40 min of warm ischemia  and demonstrated that controlled reperfusion with a tepid blood cardioplegia could facilitate successful transplantation in pigs . To miniThe first report of clinical DCD heart transplantation in the modern era was published by Boucek et al., describing three pediatric transplants performed between 2004 and 2007 at Denver Children’s Hospital . Each do2 was measured with a pulmonary artery capillary wedge pressure of 13 mmHg. The authors suggested that hearts from Maastricht category III donors might be suitable for use in clinical transplantation. This report again prompted ethical debate surrounding the postmortem restoration of mechanical cardiac function using cardiopulmonary bypass in a donor that had been declared dead based on cardiorespiratory criteria . Hearts preserved on the OCS underwent continuous perfusion during transplantation to further minimize exposure to ischemic injury.Finally, Messer et al. described nine adult clinical DCD heart transplants performed using the NRP approach , clinicain vivo functional assessments and transplanted . Conversely, the heart that required veno-arterial ECMO following transplant displayed an acceptable lactate profile during preservation on the OCS. These results highlight the need for further research regarding assessments of organ viability prior to transplant. Importantly, this study also demonstrates that DCD hearts with extended WITs may still be considered for transplantation, provided the FWIT remains <30 min and acceptable myocardial function is demonstrated. Finally, the authors utilized continuous myocardial perfusion during transplantation. In the PROCEED II trial, donor hearts were exposed to 83 min of additional cold ischemia during implantation (Two recipients required mechanical circulatory support posttransplant; however, all patients were weaned from support and discharged from hospital after 15–80 days Table . Interesantation . TherefoThese recent clinical reports have demonstrated encouraging short-term outcomes following DCD heart transplantation; however, the impact of the warm ischemic insult sustained following WLST on long-term outcomes is unknown. Ischemic injury occurring during DBD heart transplantation has been linked to the development of graft vasculopathy and myocardial fibrosis –197, andThe recent clinical reports of DCD heart transplantation have demonstrated encouraging short-term outcomes using Maastricht category III donors, with 100% hospital survival following a mean hospital length of stay of 32 days. The limited data currently available suggest that 29% of DCD heart transplant recipients will require temporary mechanical circulatory support; however, all patients have been successfully weaned from support and the majority exhibit normal biventricular function on follow-up echocardiogram. As the experience with DCD heart transplant grows, assessments of organ viability may improve and the need for posttransplant mechanical circulatory support may be reduced. It appears that both the DPP and NRP approaches to organ resuscitation can be used successfully to facilitate DCD heart transplantation; however, further research is required to determine if one approach is superior to the other. While these short-term results are encouraging, the impact of the warm ischemic insult sustained following WLST on long-term outcomes is unknown. Ischemic injury occurring during DBD heart transplantation has been linked to the development of graft vasculopathy and myocardial fibrosis –84, and Advances in our understanding of pharmacologic post-conditioning have facilitated the development of controlled reperfusion strategies that can successfully resuscitate the DCD heart. The clinical availability of the Transmedics OCS now allows donor heart preservation in a beating state and a means to limit exposure to additional cold ischemia prior to transplantation. As technology evolves, the ability evaluate DCD hearts during EHP will improve our ability to identify viable organs. Investigating ways to optimize the resuscitation, preservation, evaluation, and long-term outcomes of these hearts is vital to ensure a broader application of DCD heart transplantation in the future.CW, SM, SL, JC, DHK, and DJK: manuscript preparation and revisions. JN and DHF also contributed to manuscript preparation and revisions.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


To evaluate the early and mid-term results of pulmonary trunk reconstruction using a technique in which autogenous tissue is preserved in situ in pulmonary atresia patients with a ventricular septal defect (PA-VSD).The pulmonary artery was reconstructed using autogenous tissue that had been preserved in situ and a bovine jugular venous patch in 24 patients who were diagnosed with PA-VSD (the observation group). The traditional operation using a bovine jugular venous conduit was performed in 40 other cases of PA-VSD (the control group).In the observation group, all patients survived and recovered successfully without complications. Follow-up echocardiography 2–10 years after the procedure showed that the reconstructed right ventricular outflow tract (RVOT) and pulmonary artery were patent, showing no evidence of flow obstruction. Only mild regurgitation of the bovine jugular vein valve was observed. In the control group, early postoperative death occurred in two cases. Another two patients had obstruction of the anastomotic stoma and underwent conduit replacement surgery within 2 weeks of the initial procedure. During the 2–10 years of follow-up care, six patients presented with valvular stenosis of the BJVC, with a pressure gradient of more than 50 mmHg.The technique for preserving autogenous tissue to reconstruct the pulmonary posterior wall is a satisfactory method for treating PA-VSD. Pulmonary atresia with ventricular septal defect (PA-VSD) is a rare and complex cyanotic congenital heart malformation that has a high incidence of early mortality. Although surgical interventions have been employed successfully for a number of years, the long-term prognosis has remained poor with an increased incidence of sudden death . In 1955At the Second Xiangya Hospital of Central South University from January 2007 to December 2015, 24 children who had been diagnosed with PA-VSD underwent a pulmonary artery reconstruction technique in which autogenous tissue was preserved in situ. In the control group of 40 other PA-VSD patients, the Rastelli procedure was conducted, in which a BJVC was placed from the right ventricle to the pulmonary artery confluence . Following a thorough examination of the left and right branches of the distal inherent pulmonary artery, the blind end inherent pulmonary artery (BE), visceral layer of pericardium (VLP) and the long fibrous cord of pulmonary atresic tissue (PAT) Fig. , a rightX2 test, Log-rank test and Gehan-Breslow-Wilcoxon test were performed to determine differences between the two groups. The critical alpha level for these analyses was set at p < 0.05.Data are expressed as the mean ± SE and median. All statistical calculations were performed using the Statistical Product and Service Solutions 14.0 software (SPSS Institute). The mean bypass and cross clamp times were similar in the observation and control groups. The postoperative ventilator support time, the duration of stay in the intensive care unit (ICU), and postoperative residence time were also not significantly different between the groups Table . Postope2/m2, suggesting no severe hypoplasia of the pulmonary artery, which indicates that a patient would be a suitable candidate for radical repair.PA-VSD accounts for approximately 2% of all congenital heart disease cases and is one of the most common causes of cyanosis and hypoxemia in neonates. The pathological anatomic characteristics of PA-VSD include VSD, intramuscular or valvar atresia of the pulmonary artery, an overriding of the aorta, and PDA or MAPCAs. According to the classification presented by Castaneda et al., there are four types of PA-VSD . In thisCurrently, the most common method of radical repair for the treatment of PA-VSD is the classical Rastelli procedure, in which a right ventriculotomy is repaired with an artificial patch. Following the ligation of the co-existing PDA or MAPCAs, the remnant pulmonary trunk is excised, the proximal end is closed, and a vascular prosthesis is then used to connect the right ventricle and the pulmonary artery.Despite the short-term success of employing different conduit modifications of the Rastelli procedure , 12–14, a is the radius of the pipe, and R is the curvature radius of the curved pipe (Fig. Another problem with using an extra-cardiac conduit is that it is difficult to achieve a physiologic linear flow. In the 1920s, Dean  describeipe Fig. . The lowTo address the problems described, the 24 cases in this study were radically repaired using a procedure in which autogenous tissue was preserved in situ to reconstruct the pulmonary posterior wall. During the follow-up care period, only mild regurgitation of the bovine jugular vein valve was observed in all patients. In the control group, two patients had severe anastomotic stenosis and underwent a further conduit replacement procedure in the early postoperative stage, four patients underwent balloon valvuloplasty and two patients underwent conduit replacement due to stenosis of the BJVC. The most significant differences between the procedures described in the observation group and the control group are as follows: 1. The was a more efficient relief of the right ventricular outflow tract obstruction. 2. The linear bloodstream flow solved the problem of right ventricular overload compared with a traditional conduit that involves the grade climbing of non-linear bloodstream flow. 3. A valved conduit reduced regurgitation, even when there was a gap present between the posterior wall and the bovine valve leaflets. It is important to note, however, that the minimal pulmonary regurgitation did not affect the function of the right ventricle. 4. This technique avoided the severance of remnant pulmonary trunk. Because the preserved autologous vascular bed could stimulate the continual development of the residual pulmonary trunk, young patients, especially children, who receive this procedure will generally not require future conduit replacement. 5. This surgical technique is suitable for PA and does not carry a risk of the major coronary arteries crossing the RVOT.Reconstructing the pulmonary posterior wall by using in situ autologous tissue is a satisfactory method for treating PA-VSD. Increasing the sample size and continued follow-up care are necessary to fully assess the long-term benefits and advantages of the procedure.


To overcome the problems of common techniques, including lack of accuracy and robustness against partial-voluming and heart-rate variability, we introduce a systolic saturation-recovery T1-mapping method. The Saturation-Pulse Prepared Heart-rate independent Inversion-Recovery (SAPPHIRE) T1-mapping method was modified to enable imaging during systole. Phantom measurements were used to evaluate the insensitivity of systolic T1-mapping towards heart-rate variability. In-vivo feasibility and accuracy were demonstrated in ten healthy volunteers with native and post-contrast T1-mappping during systole and diastole. To show benefits in the presence of RR-variability, six arrhythmic patients underwent native T1-mapping. Resulting systolic SAPPHIRE T1-values showed no dependence on arrhythmia in phantom (CoV < 1%). In-vivo, significantly lower T1  and ECV-values (0.20 ± 0.03) than during diastole  were measured, with a strong correlation of systolic and diastolic T1 (r = 0.89). In patients, mis-triggering-induced motion caused significant imaging artifacts in diastolic T1-maps, whereas systolic T1-maps displayed resilience to arrythmia. In conclusion, the proposed method enables saturation-recovery T1-mapping during systole, providing increased robustness against partial-voluming compared to diastolic imaging, for the benefit of T1-measurements in arrhythmic patients.Myocardial T In addition to late gadolinium enhancement as a robust standard for focal fibrosis, even diffuse cardiac pathologies can now be assessed with T1-mapping, the non-invasive alternative to biopsy2.Cardiac magnetic resonance imaging enables the assessment of cardiac anatomy and function and the detection of myocardial fibrosis, which is linked to numerous cardiovascular adverse cardiovascular events like heart failure, arrhythmia and sudden cardiac death1-maps are obtained by acquiring multiple sample points on a longitudinal magnetization recovery curve after magnetization preparation. Imaging at the same cardiac phase yields co-registered images, henceforth referred to as base-images, and pixel-wise curve fitting allows for spatially resolved quantification of T13. Pre- and post-contrast T1-mapping further permit estimation of the extracellular volume (ECV) fraction. Both biomarkers have shown to be predictors of mortality in cardiovascular disease and bear promise for risk stratification4.T1-mapping6. Hence, imaging during systole, exploiting increased myocardial thickness, has recently been proposed7 and demonstrated improved quality in patients with atrial fibrillation8. However, the modified Look-Locker inversion recovery (IR) technique (MOLLI)3 was used in these studies, which is known to underestimate T1-values9, and to be affected by the patient’s heart-rate10 and various imaging parameters11. Alternatively, saturation-recovery (SR) T1-mapping, as realized by the Saturation-recovery single-shot acquisition (SASHA)12 technique, provides more accurate T1-values, for the trade-off against reduced precision. A hybrid version of IR and SR, called Saturation-Pulse Prepared Heart-rate independent Inversion-Recovery (SAPPHIRE)10, has been proposed to enable accurate T1-quantification with increased precision compared to saturation-recovery only. However, systolic imaging cannot be performed with the previously proposed SASHA and SAPPHIRE sequences, as the preparation time between R-wave detection and systolic imaging is insufficient for magnetization recovery, leading to low SNR in base-images and compromising T1-fit quality.However, partial-volume effects at the interface between myocardium and blood-pool corrupt quantification accuracy and impair reproducibility in T1-mapping and ECV-calculation at 3T and to provide robust image quality in patients suffering from arrhythmia.The purpose of this study is to develop a method for systolic saturation-recovery T1-maps was simulated in a 650 × 650 pixel numerical phantom, representing a mid-ventricular short-axis of the left-ventricular (LV) myocardium, left- and right-ventricular (RV) blood, and epicardial fat 13. Systolic images were designed with reduced LV diameter (70%) and increased myocardial thickness (140%) (16). Ten base-images were generated by assigning signal values to the compartments calculated from Bloch simulations of the SAPPHIRE signal equation . Additive Gaussian noise was subsequently added (SNR = 60). Mis-triggering effects were mimicked by replacing diastolic by systolic base-images in randomized order. The share of systolic images was calculated in terms of four arrhythmia factors, with standard deviations of 0%, 30%, 60%, and 70% of the mean RR length (667 ms), based on previous literature14. Each variant was simulated 50 times and analyzed for mean T1 (accuracy) and standard-deviation across repetitions (precision).The influence of mis-triggering artifacts on conventional SAPPHIRE T1-mapping variant consists of a hybrid saturation/inversion-recovery magnetization preparation and 10 ECG-triggered readouts . The average scan time in healthy subjects was 10 sec, in patients 12 sec, trading-off the higher number of images against the faster heart rate. In systole, the limited time between the R-wave and imaging yields insufficient signal for conventional SR T1-mapping. To overcome this, the saturation-pulse is played in the preceding heartbeat after imaging  only, to obtain maximal recovery. Five images are additionally prepared with an inversion-pulse (adiabatic full passage tan/tanh pulse15) between the R-wave and image acquisition, with linearly spread inversion-times.The proposed T2, slice-thickness = 6 mm, field-of-view = 350 × 263 mm2, bandwidth = 1240 Hz/px, #k-space-lines = 57, linear profile-ordering, startup-pulses = 5 Kaiser-Bessel, GRAPPA-factor = 3. Diastolic T1-maps were acquired with longer acquisition windows using the following parameters (“diastolic parameter set): TR/TE/α = 2.6 ms/1.0 ms/35°, in-plane resolution = 1.7 × 1.7 mm2, slice-thickness = 8 mm, field-of-view = 440 × 375 mm2, bandwidth = 1085 Hz/px, #k-space-lines = 139, linear profile-ordering, startup-pulses = 5 Kaiser-Bessel, GRAPPA-factor = 2. Modified Look-Locker Inversion Recovery (MOLLI)3 T1-maps were acquired in the 5(3)3 scheme with the diastolic parameter set for both diastolic and systolic acquisition. For the latter, the acquisition window was shortened and shifted towards the systole.Images were acquired at a 3T MRI scanner  with a 30-channel receiver coil array. For systolic acquisition, a single-shot balanced Steady-State Free Precession (bSSFP) readout was used with the following parameters (“systolic parameter set”): TR/TE/α = 2.6 ms/1.0 ms/35°, in-plane resolution = 1.2 × 1.2 mm1 in systole, scans were performed in seven vials containing agarose gel, doped with various concentrations of a gadoterate meglumine contrast agent . Heart-rate variability was simulated by a pause of random duration before the R-wave, resulting in RR-interval standard-deviations of 0, 200, 400, and 500 ms, respectively.To study the influence of arrhythmia on TThis prospective study was approved by the Institutional Review Board II, Medical Faculty Mannheim, Germany, and written informed consent was obtained from all volunteers. We hereby confirm that all experiments were performed in accordance with relevant guidelines and regulations.1-mapping with six different variants: (a) diastolic MOLLI, (b) systolic MOLLI, (c) diastolic SAPPHIRE with ‘diastolic parameter set’, (d) systolic SAPPHIRE with ‘systolic parameter set’, (e) systolic SAPPHIRE with ‘diastolic parameter set’ and shortened trigger delay and (f) systolic SAPPHIRE with ‘systolic paramter set’ and an increased number of base images (15 images).As a preliminary substudy, five healthy volunteers  underwent native T1-mapping before and 15 min after injection of 0.2 mmol/kg Dotarem. T1-maps were acquired in three short-axis slices during systole with the proposed method and during diastole with conventional SAPPHIRE. Timing for systolic acquisition was visually determined from short-axis cine images. To avoid a systematic influence of contrast agent washout, sequence and slice orders were randomized. Blood samples were drawn to measure blood hematocrit for ECV calculations.Ten healthy volunteers  underwent T1-mapping in a mid-ventricular short-axis slice with systolic and diastolic SAPPHIRE. They partially displayed substantial arrhythmia during the scan, as can be seen in Table Six patients  underwent native T1-estimation, a 3-parameter least-squares fit to the T1-recovery curve was performed. T1-map quality in numerical simulation was evaluated with standard-deviation maps. In phantom, T1-times were analyzed in manually drawn ROIs. In vivo, pixel-wise fitting was performed to generate T1-maps, followed by segmentation according to the AHA-16-segment-model16, with estimation of T1 and ECV as mean per segment. Precision was defined as the intra-segment variation in terms of standard-deviation. Blood T1-times were evaluated from manually drawn ROIs in the LV-blood-pool. Diastolic T1-maps were estimated with magnitude-images after polarity restoration3. Phase-sensitive fitting was used in systole by subtracting the phase of the non-magnetization-prepared base-image from the remaining images. The resulting phase difference was thresholded 17 to yield a signal polarity map, which was finally multiplied to all systolic base-images.MATLAB R2014a  was used for image evaluation and statistics. For T1-evaluation, myocardial thickness was evaluated in healthy volunteers as the area between manually drawn LV endo- and epicardial borders in systole and diastole and in all slices. To estimate the effect of partial-voluming, the full-width-at-half-maximum (FWHM) of T1-intensity line profiles from the LV to the RV blood-pool across the center of the septum was determined. The lack of a clearly depicted RV blood-pool in apical slices prevented their inclusion in the FWHM-analysis.To assess the amount of myocardial tissue suited for T1-standard-deviation to mean T1. For statistical comparison of systole and diastole in vivo, T1- and ECV-values were studied with a paired student’s t-test, and T1-precision with a Mann–Whitney-U-test (significance for p < 0.05).In phantom, a coefficient of variation (CoV) was calculated as the ratio of T1-map quality in terms of blurring at myocardial borders, with increasing severity at higher degrees of arrhythmia . Partial-volume effects showed a higher impact on diastolic than on systolic T1-maps, as shown by a LV septal cross-section plot in Fig. 1-times at septal borders are clearly elevated towards the blood-pools, leaving only the inner region of the septum unaffected of partial-voluming. In systolic T1-maps, however, larger plateaus for the estimation of myocardial T1-times are available, as reflected by the significant increase in mean FWHM  compared to diastole. Corresponding native T1-maps of a healthy volunteer, where the increase in myocardial thickness from diastole to systole is clearly depicted, are shown in Fig. −4). Systolic and diastolic T1 display strong positive correlation (r = 0.89) .89) Fig. .Figure 31-mapping results in five healthy volunteers are visualized in Fig. 1-times  are significantly lower than systolic SAPPHIRE T1-times  (p < 10−6), which is in accordance with previous literature13. No significant difference between MOLLI T1-times acquired in diastole  and in systole  was found (p = 0.8) in this initial cohort. Diastolic SAPPHIRE T1-times  are significantly higher than systolic SAPPHIRE T1-times  when the optimized ‘systolic parameter set’ is used for the latter (p < 10−3). Systolic SAPPHIRE T1-times acquired with the ‘diastolic parameter set’ were higher than the previous two  in average. However, due to the limited cohort size no significance was found in the differences between systolic and diastolic parameter sets, despite this major difference in the average value. Systolic SAPPHIRE with 15 base images , yielded T1-times comparable to the systolic SAPPHIRE with 10 base images in terms of T1-time and precision  (p = 0.2).The results of a preliminary comparison of different Tin-vivo systolic (a) and diastolic (b) pre- and post-contrast SAPPHIRE T1-maps in ten healthy volunteers. Excellent T1-map quality, a high contrast and homogeneous T1-values, indicating high precision, were achieved. Bullseye-plots on the right show that systolic SAPPHIRE T1-times  are significantly lower than diastolic T1-times  . Accordingly, systolic and diastolic ECV-values (0.20 ± 0.03/0.21 ± 0.03) show significant differences (p = 0.03).Figure 1-maps from a patient suffering from arrhythmia during the scan (c). Due to mis-triggering-induced motion between the base-images, significant artifacts are visible with diastolic SAPPHIRE (b), extending throughout the LV-myocardium and being most severe in the septum. No such artifacts are observed with systolic SAPPHIRE (a), displaying resilience to arrythmia. For both systole and diastole, patient T1 was clearly elevated compared to T1 in healthy, as shown in (d). In patients, mean mid-ventricular systolic T1-values (1582 ± 48 ms) are significantly lower than distolic T1 (1633 ± 74 ms) (p = 0.0311).Figure 1-mapping sequence SAPPHIRE was modified to robustly measure myocardial T1 during systole in arrhythmic patients. Excellent T1-map quality was achieved in healthy volunteers and arrhythmic patients, despite the short and early systolic acquisition window. In healthy, a significant difference between systolic and diastolic T1- and ECV-values was found, most likely to be explained by reduced partial-volume effects in systole.In this study, the saturation-recovery T1-mapping techniques, SAPPHIRE has predefined delays after saturation and inversion, enabling robust and accurate T1-mapping across subjects with different heart-rates. However, numerical simulations revealed a degrading effect of mis-triggering on diastolic T1-mapping. Accordingly, T1-mapping in arrhythmic patients showed that major variations in diastolic duration led to artifacts. The problem stems from the single fixed trigger-time for multiple image acquisitions: If the diastolic phase shortens significantly during imaging, the trigger-time extends beyond the occurrence of the next R-wave. The systolic phase, however, is not subject to shortening in all common arrhythmias18, enabling a stationary time for imaging with a lower risk of mis-triggering. However, due to the brevity of the quiescent period and the high myocardial mobility, systolic T1-mapping is performed with shorter acquisition windows to minimize temporal blurring. Diastolic methods commonly employ acquisition windows up to ~360 ms, which extends far beyond systolic quiescence. For systole, a higher GRAPPA-factor (GRAPPA = 3 versus 2) and an increased bandwidth were chosen to reach a temporal resolution of ~160 ms. This trade-off led to decreased precision in systolic T1-maps of healthy volunteers. Future studies will focus on employing advanced acceleration techniques20, potentially exploiting the interdependence between the baseline images21, in order to mitigate this loss in precision. In systole, moreover, a smaller slice thickness of 6 mm (versus 8 mm in diastole) was chosen to avoid partial volume effects with the high signal from the adjacent blood pool, which is particularly important in systolic imaging as the cardiac long axis is substantially shortened during the contraction. A preliminary comparison in five healthy volunteers between the proposed systolic SAPPHIRE method and the systolic SAPPHIRE method with the ‘diastolic parameter set’ and only one modified parameter (imaging phase) led to a higher mean value in the latter case. However, due to the small sample size of five volunteers, no statistically significant difference could be shown.Unlike inversion-recovery T22 or contrast-variation-adapted optical flow23 have been proposed to improve parameter map quality and decrease spatial variability by alleviating breathing motion effects24, which are mostly translational. Mis-triggering and imaging during systole, however, are non-translational. Moreover, saturation-recovery yields, compared with inversion-recovery, low baseline SNR, further reducing the effectiveness of registration algorithms13. Imaging during systole, on the other hand, robustly ensures image co-registration regardless of baseline SNR and without extensive post-processing with dedicated non-rigid contrast-adapted registration methods.An alternative to mitigate motion artifacts from mis-triggering is image co-registration. However, substantial contrast variations between the base-images hamper the use of conventional methods. Dedicated registration algorithms based on image synthetization1-fitting, as previously proposed for inversion-recovery25, is performed based on phase-images.Usually, to allow fitting of magnitude-images to a parameter model with negative values, base-images are sorted by their TI and point-wise successive flipping of polarity is performed until best fit is reached. In systolic SAPPHIRE, both TI and the saturation-time TS are variable, so this scheme could lead to wrong polarity assignments for large variations in TS. Therefore, phase-sensitive T1-times are in good agreement with a study on saturation-recovery at 3T13, which estimated diastolic T1-times of 1578 ± 42 ms and ECV-values of 0.20 ± 0.02. The present study found systolic SAPPHIRE T1 to be significantly shorter than diastolic SAPPHIRE T1, which agrees with previous studies using systolic MOLLI at 3T26. As one explanation, Kawel et al. presume a lower myocardial blood-volume concentration during systole. A potentially more dominant effect might be the reduction of partial-voluming, achieved by imaging at increased myocardial thickness. This might explain why no significant differences between systolic and diastolic T1 where found in other studies, where only small ROIs were drawn, thoroughly excluding borders and therefore partial-voluming27. Yet the comparison of diastolic and systolic MOLLI in the preliminary substudy of this work showed no difference. However, too small of a sample size might have induced lack of significance.Reported diastolic T26. Again, this might be due to less partial-voluming with the blood-pool, leading to lower native T1 and higher post-contrast T1, conjointly resulting in a lower ECV for systole.Systolic ECV was found to be significantly lower than diastolic ECV, which is as well in agreement with other publications at 3T28. Furthermore, the proposed approach could be readily performed at 1.5T, which remains to be examined in future work.The present study has several limitations. A relatively small cohort of healthy volunteers, carefully selected to yield healthy myocardium with no age-related diffuse fibrosis, was recruited. Patients were not chosen from this strictly confined age-group and displayed various underlying pathologies, but other types of arrhythmia might also benefit from systolic acquisition. To facilitate integration into the clinical scan protocol, a single native mid-ventricular slice was acquired per patient, preventing segmentation according to the AHA-16-segment-model and ECV-estimation. In future work combination with slice-accelerated imaging will be explored to allow assessment of three left-ventricular slices in the scan protocol1-mapping even in patients suffering from arrhythmia. Increased temporal resolution was achieved for the trade-off against slightly reduced precision. Systolic T1-mapping enabled imaging at increased myocardial thickness, resulting in significantly lower systolic T1-times and ECV-values. Hence, the proposed technique might be an alternative to diastolic T1-mapping, for clinical cohorts which displaying substantial variation in the RR-interval.In conclusion, our results show that the systolic SAPPHIRE saturation-recovery technique facilitates T