Method for High Accuracy Differential Pressure Measurements Using Fluid-Filled Catheters
The advantage of measuring differential pressure using fluid-filled catheters is that the system is relatively inexpensive, but the readings are not accurate and affected by the common mode pressure (CMP) distortion. High accuracy differential pressure measurements are required in various biomedical applications, such as in fluid-dynamic test rigs, or in the cath-lab, from cardiac valves efficacy to functional assessment of arterial stenoses. We have designed and built a unique system in which the pressure difference was measured along the fluid flow inside a rigid circular tube using a fluid-filled double-lumen catheter. The differential pressure measurements were taken across two side-holes near the catheter distal tip, spaced apart by 3 cm. The goal was to overcome the CMP error, which significantly distorted the output differential pressure signal and to formulate a restoration factor. A restoration formula was developed based on simultaneous gauge pressure measurements, and was tested in several different cases. Several representative cases are presented and show that the common mode artifact was reduced by factors of 12–27. The restored pressure gradient signal was validated using direct pressure drop measurements, and showed very good agreement.
Image-Based Predictive Modeling of Heart Mechanics.
Personalized biophysical modeling of the heart is a useful approach for noninvasively analyzing and predicting in vivo cardiac mechanics. Three main developments support this style of analysis: state-of-the-art cardiac imaging technologies, modern computational infrastructure, and advanced mathematical modeling techniques. In vivo measurements of cardiac structure and function can be integrated using sophisticated computational methods to investigate mechanisms of myocardial function and dysfunction, and can aid in clinical diagnosis and developing personalized treatment. In this article, we review the state-of-the-art in cardiac imaging modalities, model-based interpretation of 3D images of cardiac structure and function, and recent advances in modeling that allow personalized predictions of heart mechanics. We discuss how using such image-based modeling frameworks can increase the understanding of the fundamental biophysics behind cardiac mechanics, and assist with diagnosis, surgical guidance, and treatment planning. Addressing the challenges in this field will require a coordinated effort from both the clinical-imaging and modeling communities. We also discuss future directions that can be taken to bridge the gap between basic science and clinical translation.
Response of Serum Proteome in Patients Undergoing Infrarenal Aortic Aneurysm Repair
Background:Postoperative organ dysfunction in conventional surgery for abdominal aortic aneurysm (AAA) is associated with a complex inflammatory reaction, with activation of coagulation and fibrinolysis. A prospective,observational study was performed to define the complex plasma proteomic changes after AAA repair and to identify factor(s) that may affect myocardial function in uncomplicated procedures. Methods:Ten patients undergoing infrarenal AAA repair were investigated. Eight subjects subjected to major abdominal surgery served as controls. Hemodynamic changes were continuously monitored by using the pressure recording analytical method technique. The time course of plasma proteins was investigated after induction of anesthesia and at different times after surgery (6 h, 12 h, 24 h, 36 h) by using two-dimensional difference gel electrophoresis, matrix-assisted laser desorption/ionization-time of flight mass spectrometry, and Western blot. The effects of plasma on the functional properties of isolated rat ventricular myocytes were also investigated. Results:In AAA patients alone, 18 spots were found to change more than two-fold in expression level, spot identification revealing an increased thrombin generation 6 h after surgery. At the same time cardiac cycle efficiency significantly reduced versus baseline (–0.5 ± 0.9 vs. 0.18 ± 0.3 in AAA patients, P < 0.01; 0.4 ± 0.1 vs. 0.2 ± 0.3 in control surgery, not significant; P < 0.01 group × time interaction at ANOVA). Plasma obtained 6 h after AAA surgery dose-dependently inhibited contractile function of control rat myocytes (percent shortening fell by 51% with 10% of AAA plasma and was abolished with 20% of AAA plasma, P < 0.001 for both). The inhibitory response was abolished by thrombin antagonism. Conclusions:These findings show for the first time the possible role of thrombin generation within the complex activation of inflammatory response in causing hemodynamic instability in the early postoperative period after AAA surgery.