Texture features were extracted from the images, compared on a group level, and correlated to the diagnostic outcome (CMR-verified versus non CMR-verified AM). Several features showed good to excellent reproducibility with very large differences between the groups, and moderate to strong correlation with the diagnostic outcome, suggesting that CMR texture analysis is a promising diagnostic tool for patients with clinically suspected AM. Furthermore, findings indicate that CINE imaging, which is currently used for the evaluation of cardiac function, might be a useful non-contrast-based technique for tissue characterization in patients with clinically suspected AM.Cardiac magnetic resonance (CMR) has emerged as a useful tool in the diagnostic work-up of patients with clinically suspected acute myocarditis (AM), yet the diagnosis remains challenging. The purpose of this proof-of-concept study was to evaluate if data-driven texture analysis has the feasibility to automatically distinguish between patients with and without CMR-verified AM using T2-weighted, late gadolinium enhancement, and CINE imaging. In particular, the present study investigated if functional CINE imaging could be used as a novel tissue characterization technique. Twenty patients with clinically suspected AM, separated into CMR-verified ( Myocarditis is an inflammatory disease of the myocardium with a heterogenous clinical presentation and large spectrum of underlying etiologies . ConsequCardiac magnetic resonance (CMR) has emerged as a useful non-invasive imaging tool in the diagnostic work-up of patients with clinically suspected acute myocarditis (AM), where late gadolinium enhancement (LGE) and T2-weighted images are conventionally used to target the myocardial inflammatory process, including the presence of edema and necrosis/fibrosis ,4,5,6. TTexture analysis is a novel post-processing technique that attempts to objectively characterize image regions based on their texture content. In this sense, the texture content refers to variations in the intensity values, or gray levels in the image. For example, tissue qualities described by terms such as patchy, focal, rough, or smooth can be mathematically transformed into texture features that characterizes the specific appearance of the tissue quantitatively . The fulIn clinical practice, CINE imaging is used to provide morphological and functional information of the heart, focusing on the detection of ventricular dysfunction and pericardial effusion . HoweverAccordingly, the aim of this proof-of-concept study was to evaluate the feasibility of texture analysis to distinguish between patients with and without CMR-verified AM using conventional T2-weighted and LGE imaging, as well as CINE imaging. In particular, the present study investigated if functional CINE imaging could be used as a novel tissue characterization technique.n = 21) [n = 9) as well as suboptimal image quality (n = 5). In the end, we identified ten appropriate patients with CMR-verified AM (n = 10) and ten patients with non CMR-verified AM (n = 10) based on T2-weigted and LGE imaging according to the original Lake Louise Criteria (LLC) [p-value = 0.65). Basic patient characteristics are summarized in Fifty-five patients who underwent a conventional CMR study between February 2013 and October 2017 due to a clinically suspected AM were retrospectively identified from our clinical imaging database. Based on the guidelines of the European Society of Cardiology Working Group on Myocardial and Pericardial Disease, patients with clinically suspected myocarditis were included if ≥1 clinical presentation and ≥1 diagnostic criteria (excluding CMR results) were fulfilled . Medicaln = 21) , or due ia (LLC) , which w2; acquisition matrix = 232 × 181; slice thickness = 8 mm; reconstructed in-plane resolution = 0.66 × 0.52 mm2) were acquired. LGE images were acquired ~10 min after administration of gadolinium agents . CINE imaging was performed using balanced steady-state-free-precession imaging sequences .CMR imaging was performed on a 1.5T scanner  using a five-channel cardiac phased array coil. After standardized patient-specific planning, a series of T2-weighted, LGE, and CINE images were acquired in long and short axis views using retrospective electrocardiographic gating during a gentle expiratory breath hold. T2-weighted images with black blood Short Inversion Time Recovery fat suppression . The CMR diagnosis of AM was based on the original LLC using T2 weighted and LGE images ,14.Image segmentation and texture analysis were performed on all short axis CMR images using a freely available software package  ,16. ThreNormalization of gray-level values was performed within the texture analysis software by rescaling the histogram data to fit within μ ± 3σ , to correct for intra- and inter-scanner intensity variations . TextureTo determine the intra-observer reproducibility, the segmentation of the region of interest was repeated once in a subset of ten randomly selected patients, evenly distributed between both study groups. Texture features that were highly reproducible were then compared between groups to study their ability to depict AM.R), where absolute values ≥ 0.4 were regarded as moderate, ≥0.6 as strong, and ≥0.8 as very strong correlation [p-value of less than 0.05 was regarded statistically significant.Statistical calculations were performed with MATLAB . All continuous data are presented as means and standard deviations, unless otherwise stated. The reproducibility was assessed by computing intraclass correlation coefficients (ICC) and their 95% confidence intervals using single measurements, absolute-agreement, and a 2-way mixed-effects model. ICC-values between 0.75 and 1.0 were considered highly reproducible, with a “good” to “excellent” level of agreement . Texturerelation . TestingFor all imaging techniques, most of the extracted texture features were found to be highly reproducible. The number of reproducible features was slightly higher for the CINE technique in comparison to the T2-weighted and LGE techniques (248 vs. 237 and 206).n = 11, 118, and 161 for T2-weighted, LGE, and CINE). Many of the robust and significant features displayed moderate to strong correlation with AM  and as shown in As illustrated in The present proof-of-concept study demonstrates the feasibility of texture analysis to automatically distinguish between patients with and without CMR-verified AM using T2-weighted, LGE, and CINE imaging. In particular, the findings suggest that non-contrast-based CINE imaging can be used to detect myocardial changes associated with AM, even when imperceptible to the human eye. Hence, CINE imaging seems to be a promising tissue characterization technique for the evaluation of AM and, as such, it might be an alternative contrast-free approach for patients with severe renal impairment.Non-contrast CINE imaging is the gold standard for the assessment of biventricular volumes and function  and is iAs recommended by the original LLC, both T2-weighted and LGE imaging are included in the CMR protocol to visualize inflammatory edema and necrosis/fibrosis in the myocardium ,22. StilTexture-based analysis has the advantage of being able to extract quantitative markers from qualitative images, and, as such, has the feasibility to be used in longitudinal follow-up studies of patients with clinically suspected AM. Further, this data-driven analysis technique enables automatic extraction of image-based features and, thereby, offers more time efficient and robust evaluations of patients with clinically suspected AM. Since such analyses will not rely on the ability of an observer, subtle changes in the myocardial tissue due to an AM may not go undetected. A large variation in the diagnostic performance of the original LLC has been reported by several studies (AUC = 57–90%), probably due to the fact that it depends on a qualitative analysis of signal intensities on T2-weighted, early gadolinium enhancement, and LGE images, and hence, may miss cases with subtle myocardial changes [A strength of the present study design was the inclusion of a relevant reference cohort to address the diagnostic clinical reality. As such, the study did not use healthy controls as reference but included only patients with clinically suspected AM (CMR-verified AM versus non CMR-verified AM). However, the retrospective nature of the study and its small number of included patients might have introduced a selection bias. Even though the present cohort displayed very large differences between groups and was sufficiently large for a feasibility study, the true diagnostic potential of CINE imaging and texture-based CMR imaging as biomarkers for the diagnosis and phenotyping of AM needs to be evaluated in larger prospective cohort studies. Accordingly, the results of this proof-of-concept study should be interpreted with caution.The present feasibility study shows that texture analysis is a promising diagnostic tool for patients with clinically suspected AM using T2-weighted, LGE, and CINE imaging. Furthermore, the findings suggest that CINE imaging, which is used in clinical routine for the evaluation of cardiac function, might be a useful novel non-contrast-based technique for tissue characterization in patients with clinically suspected AM. However, future studies are needed to substantiate our findings.


Heart disease, as well as systemic metabolic alterations, can leave a ‘fingerprint’ of structural and functional changes in the atrial myocardium, leading to the onset of atrial cardiomyopathy. As demonstrated in various animal models, some of these changes, such as fibrosis, cardiomyocyte hypertrophy and fatty infiltration, can increase vulnerability to atrial fibrillation (AF), the most relevant manifestation of atrial cardiomyopathy in clinical practice. Atrial cardiomyopathy accompanying AF is associated with thromboembolic events, such as stroke. The interaction between AF and stroke appears to be far more complicated than initially believed. AF and stroke share many risk factors whose underlying pathological processes can reinforce the development and progression of both cardiovascular conditions. In this review, we summarize the main mechanisms by which atrial cardiomyopathy, preceding AF, supports thrombogenic events within the atrial cavity and myocardial interstitial space. Moreover, we report the pleiotropic effects of activated coagulation factors on atrial remodeling, which may aggravate atrial cardiomyopathy. Finally, we address the complex association between AF and stroke, which can be explained by a multidirectional causal relation between atrial cardiomyopathy and hypercoagulability. Atrial cardiomyopathy accompanying AF is associated with thromboembolic events, such as stroke . AF and First, we briefly discuss the relation between AF and atrial cardiomyopathy, and those animal studies that have contributed to elucidating the role of specific pathogenic stimuli on the development of different types of cardiomyopathies. Subsequently, we focus more extensively on the link between atrial cardiomyopathy and thrombogenic events. We review the most relevant atrial structural and molecular changes that predispose patients to thrombogenesis within the atrial cavity and myocardial interstitial space. From this point of view, we elaborate on the pleiotropic effect of coagulation factors and their role in atrial cardiomyopathy. Finally, we address the complex association between AF and stroke.Atrial fibrillation (AF) is the most common sustained tachyarrhythmia in clinical practice. The prevalence of AF rises steeply with age . It has In this sense, the atria may act as the ‘coalminers canary’ of the circulation, due to its apparent sensitivity to hemodynamic and metabolic abnormalities, with AF as its most relevant clinical manifestation. Very few AF patients do not have any of the known risk factors. For this reason, the concept of ‘lone AF’, in the broader sense of idiopathic AF without underlying causative pathology, has been gradually abandoned .In recent years, the term ‘atrial cardiomyopathy’ has been proposed to describe ‘any complex of structural, architectural, contractile or electrophysiological changes affecting the atria with the potential to produce clinically relevant manifestations’ . In thisFrustaci et al. reported that even in patients fitting the definition of ‘lone AF’ used at that time, histological evidence of occult atrial cardiomyopathy  was apparent ,15,16. IAtrial fibrosis is one of the most extensively studied aspects of atrial cardiomyopathy in patients . Anné anAtrial biopsies for a detailed assessment of atrial cellular electrophysiology and atrial tissue structure are only available in a limited subset of patients, typically those undergoing cardiac surgery for valvular or coronary artery disease, and not in healthy control subjects. Many of these patients have multiple underlying diseases, often of unknown duration, that could lead to atrial cardiomyopathy. Therefore, the exact relation between AF risk factors and atrial cardiomyopathy is often difficult to ascertain in patients.Many of the disease entities that are associated with an increased risk of AF in patients have been investigated in animal models . For praThe progressive, self-perpetuating nature of AF has been investigated in goat and dog models of AF maintained by rapid atrial pacing. The progression of AF in these models can be explained by the fact that AF causes changes in the atria that increase the stability of the arrhythmia. These changes include a shortening of the action potential duration and effective refractory period  and alterations in tissue structure . The latter process includes altered connexin expression, myocyte hypertrophy and atrial fibrosis ,32,33. WIn contrast, a dog model of congestive heart failure (CHF) induced by rapid ventricular pacing (RVP), did show a pronounced early phase of myocyte apoptosis and necrosis in the first 1–2 days, and a pronounced increase in overall (replacement) fibrosis after 3–5 weeks, a stage at which clinical signs of decompensating heart failure had developed ,41. InteAtrial dilatation is a strong predictor of AF, occurring as a result of numerous risk factors for AF, e.g., CHF and valvular disease, as well as from AF itself . AlthougThe effects of noncardiac risk factors for AF on the atrial structure have been less extensively investigated in animal models. In a sheep model of obesity, atrial conduction heterogeneity and increased AF stability were associated with fibrosis and fatty infiltration . In a raAgeing, arguably one of the most relevant AF risk factors, leads to increased endomysial fibrosis . In a stSimilarly to structural remodeling, the pattern of atrial electrical remodeling can differ between patient populations and between animal models . As mentInformation about the sex of the animals included in animal studies is often not reported, creating a knowledge gap in the biological processes underlying the risk factors for atrial remodeling in males and females. Nonetheless, major risk factors for atrial cardiomyopathy differ by sex, with more hypertension, valvular heart disease, AF recurrence, and AF-related stroke in women, but more coronary artery disease and higher AF prevalence in men ,53,54,55Atrial cardiomyopathy accompanying AF is associated with thromboembolic events. AF patients show increased cardiovascular mortality due to sudden death, HF and stroke. The risk of developing thromboembolic stroke increases five-fold after patients have developed AF ,60.The pathogenesis of thrombus formation during AF is multifactorial and results from changes in physiological processes leading to aberrant blood flow/stasis in the fibrillating atria, endothelial dysfunction/changes in endothelial structure, and hypercoagulability . These mAtrial contractile remodeling leads to reduced and/or dyssynchronous atrial contraction and wall motion disturbances. This results in blood stasis, which critically contributes to thrombogenesis.During the first days after AF onset, loss of synchronized atrial contraction goes hand in hand with electrical remodeling processes . InteresThe loss of atrial contractility contributes to thrombogenesis via multiple other mechanisms. As recently demonstrated by Spartera and colleagues, a left atrial myopathic phenotype, including reduced left atrial function, is associated with altered left atrial flow characteristics in patients at moderate-to-high risk of stroke, regardless of a history of AF . In factThe deterioration of endothelial function in atrial cardiomyopathy can also result from inflammatory processes. As recently reviewed elsewhere, systemic and local  inflammation is a well-documented phenomenon in AF ,77. WithDuring the complex etiology of atrial cardiomyopathy, with a variety of molecular and structural changes taking place in the atrial tissue, pro-thrombotic and pro-inflammatory changes may also be observed within the interstitial space of the atrial myocardium itself . For exaNevertheless, EAT is associated with fatty infiltration from the epicardial layer, which may cause disorganized conduction within the atria . MoreoveFor example, increased macrophage infiltration has been observed in the atrial myocardium of patients with atrial fibrillation . Sun et Due to their proximity to cardiac cells, macrophages are also important mediators of electrical and structural remodeling processes, which may contribute to the pathogenesis of AF . For exaFinally, the association between AF and stroke might also be due to the common causes and shared etiologies of both conditions. For example, coronary artery disease can lead to ischemia in the atrial myocardium. AF can also lead to atrial supply demand ischemia, as described in a pig model . IschemiAnother mechanism that contributes to thrombogenesis in AF and in other atrial cardiomyopathies consists of alterations in blood constituents which confer a hypercoagulable state .Hypercoagulability in AF patients is often reflected by increased systemic platelet activation, elevated concentrations of pro-thrombotic indices  and altered fibrinolytic activity .Interestingly, the activation of the coagulation system in AF may not be homogeneous throughout the body. Some studies have shown that platelet activation and thrombin generation markers were elevated in the atria of patients within minutes after AF induction, or as a consequence of rapid atrial pacing (RAP) in animal models, compared to peripheral circulation ,95. ThesNevertheless, it is still not fully clarified whether “lone AF” (AF in the absence of apparent comorbidities) is sufficient to cause a pro-thrombotic state, or whether the presence of other underlying comorbidities and risk factors is required.In a study on young very-low-risk patients with paroxysmal AF, no hypercoagulable state was observed. However, these patients did have increased levels of Factor (F) IXa–antithrombin complexes, suggesting the presence of a pre-thrombotic state . Due tooFrom this point of view, diabetes mellitus is a well-established risk factor for stroke in patients with AF . The risElderly people show a subtle increase in plasma levels of pro-coagulant factors, sometimes accompanied by a decrease in anti-coagulation and fibrinolytic factors .In other words, coagulation enzyme activity seems to be age-dependent, which may explain the additional stroke risk during AF.Unpublished data from our group indicate that advanced age and AF synergistically increase thrombin generation potential in goats with four weeks of atrial fibrillation, suggesting that advanced age may serve as a “second pro-coagulant hit” and may potentiate the effect of AF, leading to a pro-thrombotic state.Few studies have investigated the possible effect of activated coagulation factors on cardiac remodeling, although this may be crucial to unravel the pathophysiology of atrial cardiomyopathies such as AF.Activated coagulation factors, such as thrombin and FXa, can modulate physiological and pathological processes, such as inflammation and fibrosis, which may contribute to atrial cardiomyopathy  102,103103. ThesRecently, hypercoagulability has been described to play a role in the progression of AF . The in To understand the mechanisms responsible for these effects, we investigated the direct effect of activated coagulation factors, thrombin and FXa, on primary cardiac fibroblasts (CFs) . In thisFinally, FXa can also play a role in cardiomyocyte hypertrophy. Unpublished data from our group have shown that FXa inhibition, via rivaroxaban treatment, prevented AF-related atrial myocyte hypertrophy in a goat model of persistent AF. Myocyte hypertrophy can be induced by different stimuli during AF. One example is atrial stretch as a consequence of AF-related increased atrial pressure. However, the protective effect of FXa inhibition in our study suggests that activated coagulation factors  may directly or indirectly contribute to myocyte hypertrophy. This observation agrees with a recent report by Guo et al., who described that exposure of rat neonatal cardiomyocytes to FXa induced hypertrophy and the increased expression of NPPA  via the activation of either PAR-1 or PAR-2 . FurtherIn recent years, the interaction between AF and stroke has been shown to be far more complicated than initially believed. The traditional hypothesis was that AF causes a reduction in the blood flow velocity, activation of coagulation factors in the blood and endothelial remodeling that in combination explain the enhanced risk for stroke in patients with AF. This hypothesis explains the association between AF and stroke largely by monodirectional causation from comorbidities to AF, to the activation of coagulation factors and ultimately to stroke , left.The substudy of the ASSERT trial by Bambatti et al. was the first to demonstrate that many strokes occur not only during the weeks and months after an AF episode but also before AF has occurred . AdditioIn addition, AF and stroke might share common pathophysiological pathways, which may explain the association between the two entities due to the existence of a common underlying cause. In recent years, evidence has emerged that many comorbidities cause complex pathophysiological changes in the atrial wall, an atrial cardiomyopathy, that exposes the patients to an increased risk of stroke, as well as to an increased risk of AF.For example, coronary artery disease causes ischemia in the atrial wall, which is known to increase the expression of TF on myocytes . The resIn summary, we believe that the association between AF and stroke is due to a multidirectional causal relation between atrial cardiomyopathy and hypercoagulability, which provoke each other but also share common underlying causes.


In this review, we describe the new class of medical devices with the most current results reported in preclinical models and clinical trials.Congestive heart failure (HF) is a devastating disease leading to prolonged hospitalization, high morbidity and mortality rates, and increased costs. Well-established treatments for decompensated or unstable patients include medications and mechanical cardiac support devices. For acute HF decompensation, new devices are being developed to help relieve symptoms and recover heart and renal function in these patients. A recent device-based classification scheme, collectively classified as DRI According to the universal definition, “heart failure (HF) is defined as a clinical syndrome with symptoms and/or signs caused by a structural and/or functional cardiac abnormality and corroborated by elevated natriuretic peptide levels and/or objective evidence of pulmonary or systemic congestion” . In addiChronic HF affects about 2% of the adult population worldwide. However, its prevalence is age-dependent, ranging from less than 2% in people < 60 years old to more than 10% in those older than 75 years . ProjectA wide variety of drugs, devices, and procedures are available to improve survival and functional class in patients with HF –7. Patie2P2S, the classification scheme categorizes the devices according to their mechanism and suggested indication. New device-based treatments are being developed to treat specific pathways in patients with decompensated HF. Although the physiopathology is complex, patients with acute decompensated heart failure (ADHF)  present Around 30% of the blood volume circulates in the arterial circulation, and the rest is confined to the venous system. Because of its large capacitance, the abdominal venous system is the main reservoir for blood volume in the body. In addition, the abdominal venous reservoir responds to sympathetic stimuli by promoting vasoconstriction and shifting fluid from the abdominal system into the circulation. In patients with HF, the shifted volume overloads and worsens peripheral congestion, increases cardiac venous return, and raises cardiopulmonary filling pressures, thus worsening pulmonary congestion.Vasodilators (nitroprusside and nitrates) dilate venous and arterial vessels. Nitrates act mainly on peripheral veins, whereas nitroprusside affects the arterial and venous systems. Vasodilators reduce the venous return, resulting in less congestion, lower afterload, and a consequent relief of symptoms. Recently, splanchnic nerve modulation has been proposed for treating congestive HF . The conTwo studies  have tesAlthough procedural complications  —is implanted subcutaneously in the abdomen and automatically and continuously moves fluid from the abdominal cavity to the bladder, where it is excreted from the body  and showed improved renal function  and decreased CVP .The Reprieve System™  is another new decongestion device for improving outcomes for patients with ADHF. The goal in using the Reprieve device is to achieve a target fluid balance. The system comprises a peripheral or central infusion port and a Foley urinary catheter that is connected to an external console. The Reprieve System constantly measures the patient’s urine output and infuses a volume of hydration fluid sufficient to maintain a set fluid-balance rate. Two clinical trials provided results on the use of this technology. Target-1 and Target-2 (NCT03897842) trials evaluated the device in 19 patients with congestive HF and preexisting impaired renal function, respectively . The finThe heart is innervated by the cardiac plexus of nerves situated at its base. Cardiac branches are derived from both the sympathetic and parasympathetic nervous systems. In a dog model , cardiacThe catheter-based cardiopulmonary nerve stimulation  is a 16-French catheter device that is inserted percutaneously through the right jugular vein and positioned in the right pulmonary artery . The CPNvia left subclavian vein access. The neurostimulator is then connected to the catheter and is used to deliver autonomic nerve stimulation therapy for up to 96 h. At the 2019 Transcatheter Cardiovascular Therapeutics (TCT) symposium  is a purpose-built electrical stimulation catheter placed percutaneously in the left brachiocephalic vein ymposium , investivia the thoracic and lymphatic ducts. As a consequence of HF, lymphatic drainage of edema in the periphery, abdominal organs, and lungs is reduced  , 34. CRSP = 0.004) from before to after the procedure. In a larger prospective, observational study  was first tested in nine patients requiring mechanical circulatory support during complex percutaneous coronary intervention (PCI) . The proal study , 18 patiThe Aortix  is an axial-flow pump that is positioned in the aorta to provide short-term hemodynamic support. The device functions to promote a higher pressure in the distal abdominal aorta , 40. Thevia the femoral artery) and enables better flow to the kidneys. No clinical data have been published, but the preclinical data are encouraging.Second Heart Assist  is another investigational device that promotes circulatory support for patients with decompensated HF and CRS who are at high-risk for PCI. This stent-based impeller pump is percutaneously inserted  or venous congestion at the abdominal cavity.The preCARDIA balloon catheter device  is placed in the superior vena cava (SVC) for intermittent occlusion. Controlled by a pump, the preCARDIA device unloads the heart, decreasing its filling pressures and helping to achieve decongestion in HF patients . In a pr2O led to renal dysfunction caused by tubular epithelial necrosis. In clinical medicine, an elevated IAP (≥ 8 mmHg) has also been correlated to renal dysfunction . Moreover, venous congestion is emerging as an important cause of renal dysfunction in patients with CRS, and the term “congestive nephropathy” has been proposed for this new concept . Animal function  and to afunction .p < 0.00001) as did right atrial pressure. The clinical trial is completed, but no results are available.Different devices can be placed below, above, or even within the kidney to reduce kidney congestion. For example, the Doraya catheter  is a manageable flow-reducing device implanted in the infrarenal IVC for up to 12 h. The temporary mechanical obstruction of flow reduces central venous pressure, renal afterload, and venous returns, thus relieving congestion on the heart, lungs, and kidneys. Two published cases  have demDecreased renal perfusion and vasoconstriction trigger tubular hypoxia and are part of the complex mechanism of kidney function impairment in patients with HF . Vasodilde novo AHF , patients with ADHF have changes in myocardial heart contraction and pulmonary function as well as renal dysfunction and intraabdominal changes. Combined, these factors make HF a complex disease to manage, and compensating for these changes with medications is challenging. A multidisciplinary HF management program is mandatory for evaluating patients; this approach ensures that the correct investigations are conducted and that an accurate diagnosis is made. Then, the appropriate evidence-based therapy may be initiated to treat the mechanism that is identified as the primary cause of the acute decompensation. A team approach for HF care has been demonstrated to reduce mortality and hospitalizations in high-risk patients , and theHF has an enormous impact on quality of life. Regardless of the status of left ventricular function , the risk-adjusted analyses for the composite of mortality and rehospitalization are similar for all groups . BecauseAnother crucial step related to safety and efficacy is the quality of the clinical trials performed for testing new devices. Conducting a relevant clinical trial obviously involves a straightforward research question, adequate inclusion/exclusion criteria, randomization, placebos/shams, a reasonable sample size, and planning for interim analyses. However, researchers must focus on appropriate and applicable outcomes for clinical problems that will benefit patients. The use of surrogate endpoints, such as laboratory markers, might lead to inconclusive results or futile benefits that are not clinically relevant. An interim analysis focused on safety and efficacy should be performed because it allows for making evaluations and decisions during the study and confirms safety endpoints . Our perNew technologies can be challenging from the beginning because the precise indication for use and the success and failure criteria are not completely defined. The devices mentioned in this review compose a new class; therefore, specific criteria must be established to avoid their empirical evaluation. For example, a comparable situation was seen in cardiology with definitions for stent thrombosis  and tranFinally, in this review, we discuss future devices that will help treat decompensated HF. Although this device-based therapy is not intended to replace current HF treatments, each one is expected to act at specific pathways of the decompensation, thus improving patient outcomes.CO and KL made substantial contributions to literature research, conception and design, interpretation of data, and drafting the manuscript. AE and EP contributed to revising the manuscript critically for important intellectual content. All authors read and approved the final version.


To evaluate if a fully-automatic deep learning method for myocardial strain analysis based on magnetic resonance imaging (MRI) cine images can detect asymptomatic dysfunction in young adults with cardiac risk factors.An automated workflow termed DeepStrain was implemented using two U-Net models for segmentation and motion tracking. DeepStrain was trained and tested using short-axis cine-MRI images from healthy subjects and patients with cardiac disease. Subsequently, subjects aged 18–45 years were prospectively recruited and classified among age- and gender-matched groups: risk factor group (RFG) 1 including overweight without hypertension or type 2 diabetes; RFG2 including hypertension without type 2 diabetes, regardless of overweight; RFG3 including type 2 diabetes, regardless of overweight or hypertension. Subjects underwent cardiac short-axis cine-MRI image acquisition. Differences in DeepStrain-based left ventricular global circumferential and radial strain and strain rate among groups were evaluated.The cohort consisted of 119 participants: 30 controls, 39 in RFG1, 30 in RFG2, and 20 in RFG3. Despite comparable (>0.05) left-ventricular mass, volumes, and ejection fraction, all groups  showed signs of asymptomatic left ventricular diastolic and systolic dysfunction, evidenced by lower circumferential early-diastolic strain rate , and lower septal circumferential end-systolic strain  compared with controls. Multivariate linear regression showed that body surface area correlated negatively with all strain measures (<0.01), and mean arterial pressure correlated negatively with early-diastolic strain rate (<0.01).DeepStrain fully-automatically provided evidence of asymptomatic left ventricular diastolic and systolic dysfunction in asymptomatic young adults with overweight, hypertension, and type 2 diabetes risk factors. Worldwide shifts toward sedentary lifestyles and suboptimal diets have led to increased prevalence of global obesity and obesity-related comorbidities such as hypertension , 2. BothEchocardiographic examinations can be non-diagnostic or have inconclusive findings, especially in obese patients . In suchThus, we sought to evaluate if a fully-automatic deep learning method for myocardial strain analysis based on cardiac cine-MRI can detect asymptomatic dysfunction in asymptomatic young adults with overweight, hypertension, and T2DM cardiac risk factors.2; hypertension was defined as either actively under pharmacological treatment or three consecutive blood pressure measurements ≥ 140/90 mmHg; T2DM was defined as either actively under pharmacological treatment or a HbA1c level ≥ 48 mmol/mol measured prior to the MRI exam. All subjects were classified into one of the following age- and gender-matched groups: controls including all subjects without risk factors; risk factor group 1 (RFG1) including all overweight subjects with neither hypertension nor T2DM; RFG2 including all hypertensive subjects without T2DM, regardless of the presence or absence of additional overweight; RFG3 including all subjects with T2DM, regardless of the presence or absence of additional overweight or hypertension  scanner  with a 60-element phased-array body coil. Experienced operators used a retrospective electrocardiogram (ECG)-gated steady-state free precession sequence to acquire short-axis cines covering the heart from atria to ventricular apex during a series of breath-holds. Each cine contained 25 cardiac phases with 6 mm slice thickness, and 4 mm interslice gaps. Short-axis acquisition parameters were: repetition time 38.92–44.52 ms, echo time 1.15–1.31 ms, flip angle 43–46°, field of view 300–453 × 225–453 mmThe DeepStrain workflow uses a pair of cine-MRI stacks at two different time frames . A cardipost-hoc test by Bonferroni was used to examine differences among groups. Multivariate linear regression analysis was used to identify the independent association of the clinical variables body surface area, mean arterial pressure, and HbA1c on global strain measures. A p-value <0.05 was considered statistically significant. Data were analyzed using Python .Demographic variables were expressed as mean ± standard deviation, and strain-related variables as mean [95% confidence interval]. Variables were tested for normality with a Shapiro-Wilk test and for homogeneity of variance using Levene's test. One-way analysis of variance (ANOVA) with p < 0.001). Furthermore, there were no significant differences between groups in LV mass, volumes, and ejection fraction  including the control group with 30 subjects; RFG1 with 39 overweight subjects; RFG2 with 30 hypertensive subjects, including 13 (43%) with additional overweight; RFG3 with 20 T2DM subjects, including 11 (55%) with additional overweight, 1 (5%) with additional hypertension and 8 (40%) with both . The ECGfraction .p < 0.05) relative to controls   .−1 ; p < 0.05), RFG2 , and RFG3  relative to controls   compared to controls   . Radial  −1.51]) . There wp < 0.001; p < 0.001), early-diastolic SR , and systolic SR . Mean arterial pressure was negatively associated with early-diastolic circumferential SR (p < 0.01), while HbA1c was not significantly associated with strain measures , RFG2 , and RFG3  compared to controls  (p < 0.01), RFG2 , and RFG3  compared to controls . Radial strain was decreased in the anterior (p < 0.01), inferior (p < 0.001), and lateral (p < 0.001) walls of RFG1 and RFG3 compared to controls  . Notablycontrols .DeepStrain analysis of standard short-axis cine-MRI images identified evidence of ALVDD and ALVSD in asymptomatic young subjects with at least one cardiovascular risk factor including overweight, hypertension, and T2DM, but without presence or history of cardiovascular disease. Despite comparable LV mass, volumes, and ejection fraction to controls, all RFGs showed impairment of LV circumferential early-diastolic SR as well as regional circumferential end-systolic strain. On multivariate linear regression analysis, body surface area correlated negatively with all strain measures, and mean arterial pressure was a negative correlate of circumferential early-diastolic SR. Our results are consistent with similar studies in older adults with similar risk factors. However, most studies have predominantly focused on one or two risk factors groups, which makes comparisons across the three groups difficult due to differences in software and operator. Our study is the first to report reference strain values across control, overweight, hypertension, and T2DM populations using a single user-independent, fully-automatic strain analysis software.2 was used. Further, we found that both circumferential and radial early-diastolic SR were inversely associated with body surface area, which is an important finding because body surface area is a prognostic indicator of adverse outcomes in heart failure. In hypertensive subjects without diabetes, reduction in circumferential early-diastolic SR values proportional to standard echocardiography grading of diastolic function has also been reported  to symptomatic stage C heart failure begins with ALVDD, followed by ALVSD, overt systolic dysfunction, and finally by symptomatic heart failure , 9. Althrtension . In factrtension , 29. Simrtension . Furtherrtension . In lineTo our best knowledge, the current study is the first to apply an end-to-end deep learning-based workflow for myocardial strain analysis detection of ALVDD and ALVSD in risk populations, an approach that offers several advantages over traditional techniques. Firstly, there are no explicit assumptions about myocardial tissue properties imbedded into the model , which is common in conventional methods , while tThe results presented in this study were based on cine-MRI images acquired using a 3.0 T MRI scanner with a custom 60-element coil. However, DeepStrain could potentially capture similar abnormalities using other clinical scanners. For instance, DeepStrain was trained using images acquired using both 1.5 T and 3.0 T MRI scanners , therefoThe DeepStrain model used in this study was based on five populations covering a wide spectrum of cardiac anatomy and function, which reduces the bias toward a single heart condition. Specifically, the training cohort included groups with dilated and hypertrophic cardiomyopathy, myocardial infarction, and abnormal right ventricle. Obesity and obesity-related comorbidities often result in structural abnormalities such as LV hypertrophy, potentially leading to obesity cardiomyopathy, hypertensive heart disease or diabetic cardiomyopathy. Thus, the inclusion of the cardiomyopathy cohorts during training was particularly important. Nevertheless, in this study, the RFGs showed normal anatomy compared to the control group based on measures of volume and mass. Therefore, further validation in patients with more advanced cardiac diseases is necessary and might require additional training. In addition, validation in larger cohorts and comparisons to commercial software are necessary to further demonstrate the clinical utility of DeepStrain.DeepStrain currently does not support long-axis images, therefore longitudinal strain was not reported. From a technical perspective, a joint model that uses both short and long axis images would be needed to enforce consistency in the evaluated deformation. For instance, such model could be based on recently published cine-MRI data with both long and short axis views . The smaIn young adults with overweight, hypertension, and T2DM risk factors, early-diastolic SR suggested ALVDD, and regional alterations in end-systolic strain indicated ALVSD despite preserved ejection fraction. These results demonstrate that the application of DeepStrain in routine cardiac MRI studies would fully-automatically offer useful information about the underlying biomechanical motion using standard short-axis cine-MRI data.The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.The studies involving human participants were reviewed and approved by Medical Ethical Committee of the University Medical Center Groningen (No. 2016/476). The participants provided their written informed consent to participate in this study.MM contributed with implementation and analysis of strain methodology. GS, MB, and NP contributed with data acquisition. MM and GS analysed and interpreted that data and drafted the manuscript. All other authors revised the drafted manuscript, contributed critical intellectual content, and approved the final version of the manuscript.This work was supported by the Dutch Heart Association (2016T042) and in part by the U.S. National Cancer Institute under Grant 1R01CA218187-01A1.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.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. 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Early detection of subclinical cardiotoxicity of immune checkpoint inhibitor (ICI) therapy can be challenging.To evaluate subclinical cardiac dysfunction using two-dimensional speckle tracking imaging (2D-STI) and three-dimensional echocardiography in Chinese patients.Fifty-five consecutive patients with malignant tumors treated by immunotherapy were included. They were examined by echocardiography before immunotherapy and after immunotherapy. Left ventricular ejection fraction (LVEF) was calculated in three-dimensional imaging. Moreover, left ventricular global longitudinal peak systolic strain (LVGLS), left ventricular global circumferential peak systolic strain (LVGCS), right ventricular global longitudinal systolic strain (RVGLS), right ventricular free wall longitudinal peak systolic strain (RVFWLS), and tricuspid annular plane systolic excursion (TAPSE) were evaluated. Clinical and laboratory parameters were recorded. Cardiac toxicity events were defined as the presence of heart failure symptoms, LVEF reduction, and increase in troponin. Subclinical cardiac toxicity was defined as cardiac dysfunction associated with ICI treatment, with absent or delayed ICI-associated cardiotoxicity clinical symptoms.P = 0.000; 18.29 ± 6.23 vs. 14.57 ± 3.81, P = 0.0001; and (–18.45 ± 4.65)% vs. (–14.98 ± 3.85)%, P = 0.0001, respectively]. LVGLS , TAPSE , and RVGLS  were decreased after ICI immunotherapy. Kaplan-Meier curve analysis showed that LVGLS was more sensitive than the cardiac toxicity events to assess ICI-related subclinical cardiac dysfunction (log-rank P = 0.205). The ROC curve showed that the cutoff value of ΔLVGLS was -13%.Compared with baseline, the LVGLS, TAPSE, and RVGLS significantly deteriorated after ICI treatment , identifier [ChiCTR1800016216].[ Immune checkpoint inhibitors (ICIs) including PD1/PDL1 were the novel immunotherapy drugs for various cancers; however, early detection of subclinical cardiotoxicity ICI therapy has been challenging . AccordiEchocardiography enables the identification of left ventricular dysfunction, cardiac valves, and pericardial diseases and is one of the most important clinical tools in the diagnosis and management of myocardial damage. However, the traditional ultrasound indices are not sufficiently sensitive for the detection of early changes in cardiac function . Two-dimThe study protocol was approved by the medical Ethical Review Boards of the Tianjin Medical University Second Hospital (number: KY2018K090). The study was registered with the Chinese Clinical Trial Registry (registration number: ChiCTR18000162216). All participants provided informed consent. A total of 55 consecutive patients hospitalized in the Urology department and Oncology Department of Tianjin Medical University Second Hospital from June 2018 to October 2020 who were naive to ICI treatment were enrolled in the study.The inclusion criteria included the following: (1) 18–90 years old, (2) cancer confirmed by histopathological results, and (3) normal liver and renal function.The exclusion criteria were patients with existing (1) heart failure, (2) myocardial infarction, (3) myocarditis, (4) cardiomyopathy, (5) severe valvular diseases, (6) patients who were pregnant or were lactating, (7) patients with poor echocardiography image qualities, and (8) those with less than 6 months survival.Laboratory findings included cardiac enzymes , blood routine test (hemoglobin and platelet levels), liver function , renal function , glucose and thyroid function , and clinical history including gender, age, height, weight, blood pressure, heart rate, hypertension, diabetes mellitus, heart diseases, smoking, and alcohol intake history, which were recorded at baseline. Transthoracic echocardiograms were performed before immunotherapy, and pre-ICI and after ICI administration.The echocardiographic images were performed in the left recumbent position of the patients. Echocardiographic measurements were based on current guidelines for assessing cardiovascular structure and function. All patients underwent transthoracic echocardiography using a Philips IE33 ultrasound system equipped with an X5-1 (2.5–3.5 MHz) probe. Images of at least five cycles of sinus rhythm were digitally stored in the original Digital Imaging and Communications in Medicine format for offline analysis. The images were recorded in the following standard views: parasternal long-axis view, parasternal short-axis view, apical four-chamber view, apical three-chamber view, and apical two-chamber view.via the maximum and minimum areas of the right ventricle [(RVAmax–RVAmin)/RVAmax]. The tricuspid annular plane systolic excursion (TAPSE) was measured in the M mode of the four-chamber view. Mitral inflow velocities and mitral annulus velocities were obtained by pulsed and tissue Doppler echocardiography, respectively. Left atrial volume (LAV) was measured in three-dimensional echocardiography.Left atrial diameter (LAD), left ventricular end-diastolic diameter (LVEDD), left ventricular end-systolic diameter (LVESD), left ventricle posterior wall thickness (LVPWT), and interventricular septum thickness (IVST) were measured in the parasternal long-axis view. The right ventricular area change rate (RVFAC) was calculated The QLAB 10.8 software was used to analyze the images offline. The left ventricle was divided into 17 myocardial segments, and the GLS was calculated as the average longitudinal strain at the end of the systole. The left ventricular global circumference strain (GCS) was measured in the parasternal short-axis views  according to the software instructions. The right ventricular longitudinal strain and free-wall longitudinal strain were measured accordingly at AP4 view. Left ventricular end-systolic volume (LVESV), left ventricular end-diastolic volume (LVEDV), and 3D LVEF were calculated in three-dimensional echocardiography imaging of a four-chamber view.Cardiac toxicity was defined as LVEF less than 53% or decreasing more than 10% in LVEF or 15% in GLS when compared with the baseline value , 8. In at-test. Categorical data were presented as numbers (%) and compared through the chi-square test. The data were analyzed using two-tailed tests, and P < 0.05 indicated that the difference was statistically significant. Subgroup analysis was performed. Cox regression was employed for survival analysis. ICI-related cardiotoxicity occurred time and survival cumulative percentage was analyzed through the Kaplan–Meier curve, and the P-value was calculated by log-rank test. The receiver operator characteristic (ROC) curve was done for analyzing LVGLS.The IBM SPSS statistics 20.0 software  was used for statistical analysis. All continuous variables were expressed as means ± standard deviation and compared by paired In total, 55 patients met the criteria of this study. Among them, 40 (72.3%) were male patients with a mean age of 62, 17 patients had hypertension, nine patients had diabetes mellitus, five patients had a history of cardiovascular diseases, and 23 patients had a smoking history. Their cardiac enzymes , routine blood results (hemoglobin and platelet), and liver and renal function  were within normal ranges. The baseline clinical data of the patients are shown in P = 0.064] had no significant change after ICI treatment. mPAP , IVST , LVEDD , LVEDS , LVPWT , E/e’ ratio , LAD , and LAV  were significantly increased and LV3DEF  was significantly decreased, while they were in normal range either before or after ICI treatment. Compared with the baseline data, the LVEF, LVGLS, LVGCS, TAPSE, RVGLS, and RVFWLS were significantly worsened after ICI treatment  (P = 0.001), TAPSE , and RVGLS  were below their normal range individually after ICI immunotherapy. Echocardiography results are shown in Compared with the pre-ICI data, RVFAC  . LVEF, LP = 0.205) (Fifty-five patients enrolled in the present study were followed up for 220 days. Six (10.9%) patients died, 15 (27.3%) patients had more than 15% LVGLS decrease, 10 (18.2%) patients had cardiac toxicity (LVEF reduced by 10% and less than 53%), and four (7.3%) patients developed interstitial pneumonia. The KM curve analysis showed that the standard of LVGLS decreased by more than 15% and was more sensitive than the cardiac toxicity events to assess ICI-related subclinical cardiac toxicity, but there was no statistical significance (log-rank = 0.205) . Kaplan–= 0.205) . Cox reg= 0.205) . The ROC= 0.205) .The present study showed that LVGLS, RVGLS, and TAPSE were significantly reduced to less than the normal range after ICI administration. Decreased LVGLS reflected left ventricular dysfunction while RVGLS and TAPSE reflected right ventricular dysfunction. By contrast, other parameters including LVEF, LVEDD, LVEDS, and RVFAC were within normal limits following ICI immunotherapy. Thus, it would appear that LVGLS, RVGLS, and TAPSE are more sensitive indices for the early detection of ICI-related subclinical myocardial toxicity.Recent reports have expanded the effect of ICI therapy on the cardiovascular system to include an increase in cardiac dysfunction without myocarditis, arrhythmias, venous thromboembolic disease, accelerated atherosclerosis, and atherosclerosis-related cardiovascular events . The risPrevious studies found that the cutoff value of RVGLS and RVFWLS was –17.3 and –19.5%, respectively , 11. In Left and right ventricular toxicity can occur simultaneously . LVGLS aOur early findings found no obvious increase in cTnI or NT-proBNP during follow-up, except in two cases. Laboratory parameters, including cTnI or NT-proBNP, were not optimum guidance for cardiotoxicity. Lena et al.  reportedThere were several limitations of our study. First, a small number of patients were enrolled, and a single-center study was included. Further investigations in a multicenter and larger pool pattern will be needed to confirm the potential role of 2D-STI and 3D echocardiography in predicting ICI-related subclinical myocardial toxicity. Second, the heterogeneity of the patients was inevitable not only due to the small group of patients but also the complexity of individuals. Third, the follow-up study time was not sufficiently long, and the prognostic value of the different echocardiography indexes in the PD1/PDL1-related cardiotoxicity has not been thoroughly elucidated to date.The cardiotoxicity of PD1/PDL1 immunotherapy can manifest as impaired left and right ventricular systolic function. LVGLS, RVGLS, and TAPSE are more sensitive indices for the early detection of subclinical cardiotoxicity.The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.The studies involving human participants were reviewed and approved by Medical Ethical Review Boards of the Tianjin Medical University Second Hospital. The patients/participants provided their written informed consent to participate in this study.HF was responsible for the manuscript concept, design, and definition of intellectual content. AX and MY were responsible for data analysis, statistical analysis, and manuscript preparation. XZ, GM, TW, and GZ were responsible for the literature search, clinical studies, and data acquisition. HH was responsible for manuscript editing and review. All authors contributed to the article and approved the submitted version.


Wilson assumed that the ventricular gradient (VG) is independent of the ventricular activation order. This paradigm has often been refuted and was never convincingly corroborated. We sought to validate Wilson’s concept by intra-individual comparison of the VG of sinus beats and ectopic beats, thus assessing the effects of both altered ventricular conduction (caused by the ectopic focus) and restitution (caused by ectopic prematurity). We studied standard diagnostic ECGs of 118 patients with accidental extrasystoles: normally conducted supraventricular ectopic beats  and aberrantly conducted supraventricular ectopic beats  or ventricular ectopic beats . In each patient, we computed the VG vectors of the predominant beat,  The ventricular gradient (VG), defined as the integral of the ECG amplitude over the QT interval, has intrigued many investigators since it was introduced by Wilson et al. in 1931 —when vecOur here-described work aims to further contribute to verifying the paradigm of an activation-independent VG. The following introduction discusses the concept of the VG and defines the electrophysiological mechanisms that play a key role in experiment design and in interpreting the observations made by both others and ourselves in order to test the concept of an activation-independent VG.In 1957, Burger mathematically derived a formula for the VG in 3D vectorcardiographic space. He showed that VG, computed as the 3D integral of the heart vector over the QT interval, is proportional to the volume integral of the 3D action potential duration gradients over the heart . This caIn the same publication, Burger pointed out that the ventricular gradient  equals the sum of the areas covered by the course of the heart vector during the QRS complex and during the T wave, briefly called the QRS integral and the T integral, respectively.Like the QT integral, the QRS and T integrals are vectors, of which the spatial directions identify the QRS and T axes, respectively. The angle between the QRS and T integrals is the QRS-T angle. The relations between the QRS and T integrals, the QRS-T angle, and the ventricular gradient can be associated with specific ECG phenomena like concordance/discordance; this is extensively discussed and illustrated in several papers, including those by Draisma et al. , Man et Our current study focuses on the 3D QT integral/spatial VG, leaving the QRS integral, the T integral, and the spatial QRS-T angle out of consideration.Burger assumed that In 1983, Geselowitz theoretically showed that the QRST integral is determined by spatial heterogeneity in the area under the action potential, rather than by heterogeneity in action potential duration alone [Notably, the term “ventricular gradient” is somewhat confusing because the VG is computed from the ECG as the spatial integral of the course of the heart vector. According to Burger’s relationship, this spatial QT integral equals the volume integral of action potential gradients in the heart, which is also not a gradient in the true sense of the word. However, because “ventricular gradient” has become a generally accepted term, it is not practical to change it, though it is essential to realize its physiological and mathematical background.The mathematical concepts formulated by Burger  and GeseThe presumed independence of the ventricular activation order potentially renders the spatial VG useful in ECG diagnostics. When, in a patient, the QRST morphology changes while the VG remains the same, these changes should have been caused by differences in the depolarization order, not by changes in the intrinsic electrophysiological properties of the cardiac myocytes. However, when both the ECG and the VG change, the electrophysiological properties of the myocardium must have changed too. This property of the VG could be helpful in, for example, detecting acute ischemia in patients with a new left bundle branch block (BBB). If the acute ischemia causes the new BBB, not only the ECG but also the VG of this patient should have changed due to ischemia-based action potential changes. If the new BBB is caused by a local defect in the conduction system but unrelated to acute ischemia, the VG is expected to remain unchanged.However, for decades the concept of VG conduction independence has met with criticism. Simonson et al.  did not According to the formulae of the ventricular gradient developed by Burger  and GeseAfter it became possible to reliably measure myocardial action potentials ,18, the Electrical restitution is an electrophysiological mechanism that plays a role in experiments or observations intended to provide evidence in favor or against the concept of an activation-independent VG. Experiments intending to study abnormal activation sequences often need premature stimulation to ensure pacemaker capture. The same holds for ectopic beats that might serve as an “experiment of nature” to alter the cardiac activation order: in most cases, ectopic foci must fire prematurely to become manifest ectopic beats. Hence, an abnormal ventricular activation sequence generally requires premature stimulation or a premature extrasystole. However, prematurity alters the action potential morphology.The electrophysiological effects of premature stimulation of the heart are commonly described by the electrical restitution curve, originally defined by Bass in 1975 . In expeVG changes due to S1S2 restitution are caused by restitution heterogeneity in the heart: regional differences in the APD change in response to the premature stimulus. The study by Srinivasan and colleagues , set up When the restitution curves measured at various sites in the heart run parallel, changes in action potential duration due to a premature stimulus will be the same, and the VG will not be affected. When the restitution curves are not parallel, the regional action potential changes are not the same, which implies restitution heterogeneity and, as a consequence, changes in the VG.From the data published by Srinivasan and colleagues, it is difficult to predict what will happen in a specific case, characterized by a certain degree of prematurity and a specific stimulus site or the site of origin of a ventricular extrasystole. Restitution curves were only measured, and pacing was only performed at a limited number of sites. However, a general conclusion can be that there may be situations with given prematurity and a stimulus site in which all APDs exhibit a similar change and the VG will not or barely change, while there may also be situations in which this is not the case. Particularly in situations involving stimuli with higher prematurity  the curves are sometimes less parallel, while left-ventricular endocardial pacing seems to induce the most heterogeneous restitution curves.Another more complex manifestation of electrical restitution is the dependence of APD on stimulation cycle length. Franz et al.  showed tLaboratory experiments in preparations from dog hearts have shown that, after adaptation to a step decrease in CL, epicardial action potentials shorten more than endocardial action potentials . This heCardiac cells are electrically connected; electrotonic currents flow through gap junctions between cells as a consequence of differences in intracellular potential . This imTo investigate the presumed independence of the VG on the ventricular activation order, Lux and colleagues made body surface potential maps in dogs with various pacing modalities, measured QRST integrals at all 192 electrode sites  and constructed QRST iso-area maps ,31. TheyIn our view, these observations, in which electrotonic effects are used to explain the possible dependence of the VG on ventricular activation order, are not essentially different from the S1S2 restitution curve measurements by Srinivasan and colleagues .In intact hearts, S1S2 restitution curves cannot be measured for isolated areas: they necessarily include the electrotonic effects of the activation-recovery pattern associated with the site of stimulation/origin of the extrasystole.As well as including ventricular extrasystoles as per Cosma et al.’s study, we included patients with supraventricular extrasystoles;Instead of comparing the ventricular gradient vector magnitude of the sinus beat and extrasystole, we compared the ventricular gradient vectors, thus considering any differences in magnitude, direction, and combinations as a change;We included the prematurity of the extrasystoles in our analysis.In conclusion, we consider the S1S2 restitution curves as measured by Srinivasan and colleagues  as a valAnonymous, retrospective, observational.The ECG shows a normal sinus rhythm;The ECG shows at least one spontaneous supraventricular or ventricular ectopic beat;The predominant supraventricular beat has a well-identifiable J point, allowing for reliable determination of the QRS duration;The predominant beat does not fulfill the criteria for a strict left bundle branch block (LBBB) configuration .ECGs were drawn from the ECG database of the Leiden University Medical Center (LUMC) in which, since 1986, the ECGs recorded in the LUMC have been stored. Within an arbitrarily chosen 10-month period, we collected all technically sound digital standard 10-s 12-lead ECGs of patients > 18 years old that satisfied the following criteria:Of note: the wording “predominant beat” refers to the most frequently occurring beat in a particular ECG recording; it may have a normal or pathological QRST waveshape, depending on the patient.The ECG facilitated a reliable baseline assessment throughout the entire recording, including the ectopic beat of interest;A context of at least four predominant supraventricular beats preceding the ectopic beat, as well as at least one predominant supraventricular beat immediately following the ectopic beat with a compensatory pause, was required;To ascertain stable cellular electrophysiology, the minimum four predominant supraventricular beats preceding the ectopic beat had to pass a check for rhythmic regularity: ECGs with intervals between predominant beats that differed more than 10% from the average interval were excluded;In ECGs that contained multiple ectopic beats that satisfied the selection criteria, only the first ectopic beat was analyzed;In patients with multiple ECG recordings that satisfied the selection criteria, only the first recording was analyzed (to prevent double inclusion of patients).For this study, we applied an ECG selection strategy to ascertain several conditions that were technically needed for reliable ECG analysis. ECGs were excluded if they did not comply with one or more of the following conditions:The ECGs were analyzed and generally characterized by the Glasgow Royal Infirmary (GRI) software , thus laThe ECGs were additionally analyzed by the Leiden ECG Analysis and Decomposition Software (LEADS) . BrieflyFor the purpose of this study, ectopic beats also had to be analyzed. Given ectopic beats usually miss an isoelectric segment preceding their onset, they do not contribute to baseline estimation. To facilitate the analysis of a separate ectopic beat, a special experimental version of the LEADS program was developed, in which the ectopic beats were baseline-corrected, with the baseline as calculated from the surrounding predominant beats in the ECG recording.The magnitude of the difference vector between the VGs of the ectopic and predominant beats: The magnitude of the difference between the VG magnitudes of the ectopic and predominant beats: The angle α between the VGs of these two beats.From the variables produced by LEADS, we calculated the prematurity of the ectopic beat . From the VG vectors of the predominant and ectopic beats, We divided the ectopic beats into three categories: supposed supraventricular origin and normal conduction , supposed supraventricular origin and aberrant conduction , and supposed ventricular origin (V).Comparisons of the initial 20 ms in the predominant and ectopic beats have been made by careful inspection of the ECGs in a multi-channel display of all ECG leads over 10 s by four of the authors  jointly, thus removing subjectivity as much as possible. The decision about the similarity of the initial 20 ms of the ectopic and predominant QRS complex was taken on the basis of similar polarity and rate of rise/fall ,39,40,41The separation into ectopic beats of supposed supraventricular origin with and without aberrant conduction, and ectopic beats of supposed ventricular origin, was made to contrast the influence of solely restitution on the VG (by comparing ectopic beats of supposed supraventricular origin and sinus beats) and the combined influences of restitution and activation order differences on the VG (by comparing sinus beats on one hand and aberrantly conducted ectopic beats of supraventricular origin and ectopic beats of ventricular origin on the other hand).To compare After querying the ECG database, 375 ECGs matched the inclusion criteria, of which 257 ECGs were excluded due to the reasons listed in 2; 72.8% of patients had a BMI > 25.0 kg/m2; 25.4% of patients were obese (BMI > 30.0 kg/m2). p < 0.001), slopes close to 1, and, for the linear regression forced through the origin, an R-squared value that explains nearly all variance in the dependent variable.p = 0.04) and in patients with ventricular ectopic beats (p < 0.001). No other statistically significant differences emerged, although the impression arises that the VG magnitudes of the predominant beats of patients with aberrantly conducted supraventricular ectopic beats and of patients with ventricular ectopic beats are smaller than those of patients with normally conducted supraventricular ectopic beats. The limited number of patients with normally conducted supraventricular ectopic beats (N = 6) and the unpaired statistical testing precluded further conclusions regarding this observation.We investigated the dependence of the VG on activation order and restitution by analyzing standard diagnostic ECGs with a spontaneous ectopic beat, measuring intra-individual differences between the VGs of predominant and ectopic beats in 118 patients  with varEctopic VG vector magnitudes were significantly larger than predominant VG magnitudes for SA and V, but not for SN ectopic beats . VG diffIf we would interpret the VG magnitude as measuring the heterogeneity of ventricular action potential (AP) morphologies, the conclusion would be that ectopic beats bring about an increase in AP heterogeneity. We must realize, however, that the VG is—like many other ECG phenomena—subject to cancellation. Hence, when including cancellation in the VG interpretation, it may be more correct to interpret the VG as the net resulting AP heterogeneity. Depending on the net resulting AP heterogeneity of an individual patient’s predominant beat  with the VG of a QRST complex with a different ventricular activation order, we should take into account that several physiological mechanisms can alter the APD distribution in the heart, and thus affect the QRST integral in Burger’s formula. Only when the APDs remain the same, or lengthen or shorten homogeneously, is the VG unaffected because the spatial differential (nabla) in the Burger formula remains unaffected. Examples can be seen in Our current study suggests that restitution effects cause heterogeneous APD changes throughout the heart, thus affecting the cell-to-cell APD gradients (the nabla in Burger’s formula). This would mean that intra-individual VG comparisons should be made either at equal heart rates . Alternatively, comparisons should be made between the VGs derived from the predominant QRST complex and derived from a non-premature extrasystole or from an incidental QRST complex with an intraventricular block.Because the effects of autonomic nervous system (ANS) activity are non-homogenously distributed over the heart, e.g., with different APD responses in the epicardium and endocardium, ANS activity should preferably be the same during the time of occurrence of the reference QRST pattern and that of a deviating QRST pattern. Constant ANS activity is likely the case when a single extrasystole interrupts a regular supraventricular rhythm. The extrasystole will usually have a lower stroke volume, hence the systolic pressure of the pulse wave in the aorta and carotid arteries will be lower (or even absent) for the extrasystolic beat. This has, via the arterial baroreflex, consequences for the parasympathetic and sympathetic ANS outflow . This causes an increase in heart rate and in cardiac contractility. However, such reflex responses occur only after a delay of one or more seconds, not during the extrasystole itself. Hence, the VG of a single non-premature extrasystole or the VG of an interrupting sinus beat with an intermittent bundle branch block can be compared with the VG of the predominant beat.Beats with a different electrical ventricular activation order than the reference beat, e.g., a heartbeat with an incidental intraventricular block, a ventricular extrasystole, or a paced beat, necessarily cause different electrotonic currents. As already discussed in the introduction, due to electrotonic currents, action potentials of a certain myocardial region are influenced by action potentials of neighboring regions within the space constant (1–2 mm). The net result is that action potentials of a specific myocardial region will be influenced by action potentials from different neighboring regions if the trajectories of the depolarization or repolarization wavefronts change. To our knowledge, the influence of electrotonic effects in VG validation studies cannot be controlled. It is also difficult to assess. If differences are measured between the VGs computed from the predominant supraventricular QRST complex and computed from a non-premature extrasystole, it is likely to attribute this to electrotonic effects rather than to restitution effects.A final mechanism that may methodologically complicate a VG validation study is mechanoelectrical coupling. When measuring the VG in a QRST complex that differs from the predominant QRST complex because of a deviating ventricular activation pattern, the mechanical forces that develop as a function of time in the ventricles are different from the forces in the predominant QRST complex. Due to mechanoelectrical coupling , action potential morphology changes occur, and the VG will change. Again, this is difficult to measure in an epiphenomenon such as the ECG. Electrocardiographic imaging could possibly be helpful in assessing APD changes due to electrotonic effects or mechanoelectrical coupling.Our observations were made in humans, whereas several elementary studies on the VG were performed in dogs ,31,32,33In contrast to previous studies, which all had a limited amount of cases, we studied a larger number of subjects, allowing for statistical analysis.The relatively large amount of subjects allowed for the observation of a rich variation of prematurity, which permitted the study of prematurity as a possible relevant factor in VG variability.Our computations were the first in which the differences between ventricular gradients were expressed as VG difference vector magnitude rather than the VG magnitude difference. In our computations, any change in the VG, be it an increase, a decrease, or a rotation, contributes to the difference between two VG vectors.Compared to previously published research, our study is of additional interest due to a number of methodological aspects in the study design:Because our study is an “experiment of nature”, the site of the ectopic pacemaker and its prematurity could not be controlled. This left us with an analysis of the pooled data of a patient group in which the individually different ectopic pacemaker sites and prematurities between patients have to replace experimentally controlled variations in ectopic pacemaker site and prematurity within subjects.Another limitation is the uncertainty in the baseline estimation of the ectopic beats. Because the VG is an ECG-amplitude integral, it is sensitive to baseline errors. Due to the prematurity of ectopic beats, it is not possible to accept the voltage immediately preceding that beat as an isoelectric reference (as we routinely do in sinus beats). Instead, we had to construct an interpolated baseline that was assessed with the aid of the isoelectric reference amplitudes associated with the sinus beats immediately preceding and following the ectopic beat.The VG of the predominant beat could be computed in an averaged beat, whereas the VG of the ectopic beat was necessarily computed in a single beat, which is more susceptible to noise. However, because of careful visual checking of the baseline assessment and excluding patients with a failed baseline, the remaining errors cannot explain the sometimes-large differences between the VGs of the predominant and ectopic beats within certain patients.Another limitation is the uncertainty regarding the classification of premature beats with strict LBBB configuration. We have classified these as beats of supraventricular origin with aberrant conduction (this was the case in 10 patients). However, there is a possibility that strict LBBB beats can also be generated by right ventricular ectopy. Although such extrasystoles often impress with an LBBB-like pattern, it is not known if these beats comply with the strict LBBB criteria. However, in our view, this uncertainty is not relevant to the conclusion of our study.A final limitation is that the VCGs were not directly recorded, e.g., by a Frank VCG-recording system, but instead were mathematically synthesized by the Kors transformation . The impHowever, there are some limitations:During the period in which the VG concept was formulated, it was considered important because of its presumed independence of ventricular activation order. In this way, the VG could help to diagnose ECG changes in a given subject as a change in either ventricular conduction or in the electrophysiological properties of the ventricular myocardium. Later, additional use of the VG in risk assessment was proposed . Both aWe compared, within patients, the ventricular gradient of their sinus beat and of a supraventricular normally conducted extrasystole, a supraventricular aberrantly conducted extrasystole, or a ventricular extrasystole. Ventricular gradient differences were expressed as ventricular gradient difference vector magnitudes. The prematurity of the extrasystoles was included in our analysis and interpretation. We sometimes observed large differences between the ventricular gradients of the sinus beats and those of the extrasystoles, especially when the extrasystoles had prematurity of <0.80. We concluded that the tenet of the conduction-independent ventricular gradient does not hold in this study group but also reasoned that a methodologically correct comparison of ventricular gradients would require equal heart rates or a spontaneous or stimulated ectopic beat that is not premature.As a final remark, it should be stated that a possible invalidation of Wilson’s premise of a conduction-independent VG would not imply that the VG has no diagnostic potential in electrocardiography. Changes in the VG occurring in a clinical setting, in which the ventricular activation order is presumably not altered, may indicate pathology-associated action potential changes. An example is the VG change observed in pulmonary hypertension, caused by changes in the right-ventricular action potentials due to mechano-electrical feedback as a consequence of elevated right-ventricular pressure .