Shear Stress, Energy Losses, and Costs: A Resolved Dilemma of Pulsatile Cardiac Assist Devices

Sayed Nour,Daniel Carbognani,Qinmei Wang,Juan Carlos Chachques,Daya Yang,Jia Liu,Guifu Wu,Gang Dai

doi:10.1155/2014/651769

Abstract

Cardiac assist devices (CAD) cause endothelial dysfunction with considerable morbidity. Employment of pulsatile CAD remains controversial due to inadequate perfusion curves and costs. Alternatively, we are proposing a new concept of pulsatile CAD based on a fundamental revision of the entire circulatory system in correspondence with the physiopathology and law of physics. It concerns a double lumen disposable tube device that could be adapted to conventional cardiopulmonary bypass (CPB) and/or CAD, for inducing a homogenous, downstream pulsatile perfusion mode with lower energy losses. In this study, the device's prototypes were tested in a simulated conventional pediatric CPB circuit for energy losses and as a left ventricular assist device (LVAD) in ischemic piglets model for endothelial shear stress (ESS) evaluations. In conclusion and according to the study results the pulsatile tube was successfully capable of transforming a conventional CPB and/or CAD steady flow into a pulsatile perfusion mode, with nearly physiologic pulse pressure and lower energy losses. This represents a cost-effective promising method with low mortality and morbidity, especially in fragile cardiac patients.

Highlights

Mechanical cardiac assist devices (CAD) disturb endothelial function and hemodynamics [1, 2]
Present CAD can be identified in two categories: devices that increase coronary blood flow during diastole in order to improve the oxygenation and the performance of the myocardium, that is, the intra-aortic balloon pump (IABP) and the enhanced external counterpulsation pump (EECP) [8, 9]; these devices must be synchronized with heartbeat and they are unsuitable in case of cardiac arrhythmia and devices that unload and bypass the heart pump either partially as achieved by left ventricular assist devices (LVAD), right ventricular assist devices (RVAD), and extracorporeal membrane oxygenation (ECMO) or completely like with biventricular assist devices, cardiopulmonary bypass (CPB) [10,11,12]
Reduction of the pulsatile perfusion curve amplitude was directly proportional to distance between aortic cannula and tube position; that is, I > II > III

Summary

Introduction

Mechanical cardiac assist devices (CAD) disturb endothelial function and hemodynamics [1, 2]. Present CAD can be identified in two categories: devices that increase coronary blood flow during diastole in order to improve the oxygenation and the performance of the myocardium, that is, the intra-aortic balloon pump (IABP) and the enhanced external counterpulsation pump (EECP) [8, 9]; these devices must be synchronized with heartbeat and they are unsuitable in case of cardiac arrhythmia and devices that unload and bypass the heart pump either partially as achieved by left ventricular assist devices (LVAD), right ventricular assist devices (RVAD), and extracorporeal membrane oxygenation (ECMO) or completely like with biventricular assist devices, cardiopulmonary bypass (CPB) [10,11,12] These devices are lumped models, designed for driving Newtonian compressible fluids inside closed pressurized hydraulic circuits implementing rigid tubes with fixed diameters [13, 14]. Installations conduits between cardiovascular tissues and CAD create dead space with important zones of energy losses [15]

Objectives

Methods

Results

Conclusion