Myocardial dynamics during direct mechanical ventricular actuation of the fibrillating heart

Direct mechanical ventricular actuation (DMVA) is a method of non-blood contacting ventricular support. DMVA uses a pneumatically regulated, vacuum attached, flexible membrane for transfer of systolic and diastolic forces to the ventricular myocardium. The purpose of this study was to assess myocardial dynamics when DMVA supported the heart during ventricular fibrillation (VF) arrest. Adult canine (n=10) underwent left thoracotomy and were instrumented for monitoring ventricular hemodynamics. Left and right ventriculograms were obtained using cineangiography during: a) sinus rhythm (SR), and b) VF with DMVA providing total circulatory support. Images were then digitized and computer analyzed to assess valve function, pump performance, as well as RV and LV dynamics. Decreased end-diastolic volumes (^*33%) were compensated by decreased end-systolic volumes (^*75%), thereby maintaining stroke volume and increasing ejection fraction (^*30%) during DMVA vs. SR, (^*p<0.05). Marked increases in diastolic filling rates documented DMVA's diastolic effect during VF (111 vs. 233 milliseconds, DMVA vs. SR, p=0.003). Cartesianal coordinate analysis of wall motion dynamics revealed characteristic configurational changes during DMVA. These findings demonstrate DMVA's ability to provide diastolic actuation. Diastolic actuation addresses the rate-limited, passive ventricular filling inherent to direct cardiac compression (DCC) when supporting the VF arrested heart. Studies are needed to compare diastolic assist and systolic wall-motion influences during DMVA and DCC support of the failing heart.