Mechanical Cardiac Assistance and Replacement

Effects of unloaded reperfusion on mitochondrial function in the postischemic myocardium

The effect of mechanical unloading on recovery of postischemic myocardial performance, high energy phosphate content, and mitochondrial function was tested in an isolated working rabbit heart model. After 30 min of global ischemia, prolonged unloaded reperfusion could prevent complete loss of contractility, deterioration of mitochondrial function, and depletion of the ATP pool as was found when only short-term unloading was performed. Aortic flow recovered to 21% of preischemic control, and left ventricular dP/dt max to 46% (p < 0.05 vs. short-term unloading). OPR and ADP/O stabilized at 42 and 72%, respectively (p < 0.05 vs. short-term unloading), and ATP at 33% of control (p < 0.05 vs. short-term unloading). These results show the beneficial effect of prolonged unloading in postischemic hearts.

Flow patterns and endothelial cell morphology in a simplified model of an artificial ventricle

The aim of this study was to delineate the flow patterns in a non-unidirectional flow field inside a ventricle-shaped cell culture chamber, and examine the resulting morphology and integrity of the endothelium in select regions of the monolayer. The chamber was perfused by pulsatile flow, and the coherent motion of the fluid was studied using flow visualization aided by image analysis. Four distinct flow patterns were discerned and examined: central jet, flow impingement, flow separation, and recirculating eddies. The influence of these patterns on endothelial cell morphology was assessed after 20 h of exposure to flow. There were no signs of damage to the endothelium in the jet region nor was there evidence of cell alignment with the flow. Yet, there were changes in cell morphology and cytoskeletal architecture as compared to control. By contrast, within the eddies where the flow was highly disturbed, there was apparent damage to the endothelium. Thus, exposure of cells to random velocity fluctuations in regions of quasi-static flow compromises the integrity of the monolayer. Identification of such sites and acquisition of the knowledge necessary to protect the cells from denudation will be valuable for the endothelialization efforts of cardiac prostheses.