LOAD-INDEPENDENT ANALYSIS OF A PULSATILE RIGHT-VENTRICULAR ASSIST DEVICE

Background: Right ventricular assist devices are becoming increasingly used as both a bridge to heart transplantation and as a means of temp orary support after cardiopulmonary bypass. There has also been a resu rgence of interest in pulsatile devices fueled by anecdotal, clinical reports. However, a load-independent analysis of biventricular functio n after right ventricular assistance comparing a pulsatile versus a co ntinuous-flow right ventricular assist device has not been performed, and we hypothesize that a pulsatile device is less detrimental to card iac function than a conventional, nonpulsatile pump. Methods: Sixteen dogs (20 to 25 kg) were instrumented through a median sternotomy for p lacement of left ventricular and right ventricular epicardial dimensio n transducers in the major, minor, and septal-free wall axes. Intracav itary micromanometers were placed in both ventricles as well. Baseline pressure-dimension data were collected, and the right atrium and pulm onary artery were cannulated. Right ventricular bypass with the use of a pneumatically driven pulsatile right ventricular assist device (SV = 60 ml; n = 7) or a conventional continuous-flow centrifugal right ve ntricular assist device (n = 9) was instituted for a 4-hour duration. Animals were than weaned from right ventricular support and decannulat ed. After bypass, biventricular function data were then collected. The load-insensitive stroke work-end diastolic volume relationship known as preload recruitable stroke work was derived and expressed as a frac tion of baseline function along with conventional hemodynamic indexes, cardiac output, and pulmonary vascular resistance. Results: Results o f this analysis show no significant benefit to either right ventricula r or left ventricular function (right ventricular preload recruitable stroke work index: 0.863 +/- 0.3 [pulsatile] versus 0.849 +/- 0.2 [con tinuous], left ventricular preload recruitable stroke work index: 0.88 0 +/- 0.4 [pulsatile] versus 0.821 +/- 0.3 [continuous] after pulsatil e right ventricular support. Likewise, cardiac output (1.4 +/- 0.1 [pu lsatile] versus 1.5 +/- 0.2 [continuous] L/min) and pulmonary vascular resistance (4.8 +/- 1.0 [pulsatile] versus 3.2 +/- 1.1 [continuous] W ood Units) were not significantly different in either study group. Con clusions: We conclude from these data that pneumatically driven pulsat ile right ventricular assist devices provide no additional benefit to myocardial performance beyond that of conventional, nonpulsatile pumps . Further studies investigating a speculative benefit from pulsatile c irculatory support are necessary to further define a potential role fo r these novel devices.