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 temporary support after cardiopulmonary bypass. There has also been a resurgence of interest in pulsatile devices fueled by anecdotal, clinical reports. However, a load-independent analysis of biventricular function after right ventricular assistance comparing a pulsatile versus a continuous-flow right ventricular assist device has not been performed, and we hypothesize that a pulsatile device is less detrimental to cardiac function than a conventional, nonpulsatile pump. METHODS: Sixteen dogs (20 to 25 kg) were instrumented through a median sternotomy for placement of left ventricular and right ventricular epicardial dimension transducers in the major, minor, and septal-free wall axes. Intracavitary micromanometers were placed in both ventricles as well. Baseline pressure-dimension data were collected, and the right atrium and pulmonary 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 ventricular assist device (n = 9) was instituted for a 4-hour duration. Animals were then weaned from right ventricular support and decannulated. 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 fraction of baseline function along with conventional hemodynamic indexes, cardiac output, and pulmonary vascular resistance. RESULTS: Results of this analysis show no significant benefit to either right ventricular or left ventricular function (right ventricular preload recruitable stroke work index: 0.863 +/- 0.3 [pulsatile] versus 0.849 +/- 0.2 [continuous], left ventricular preload recruitable stroke work index: 0.880 +/- 0.4 [pulsatile] versus 0.821 +/- 0.3 [continuous] after pulsatile right ventricular support. Likewise, cardiac output (1.4 +/- 0.1 [pulsatile] versus 1.5 +/- 0.2 [continuous] L/min) and pulmonary vascular resistance (4.8 +/- 1.0 [pulsatile] versus 3.2 +/- 1.1 [continuous] Wood Units) were not significantly different in either study group. CONCLUSIONS: We conclude from these data that pneumatically driven pulsatile 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 circulatory support are necessary to further define a potential role for these novel devices.

Duke Scholars

Author Peter Kent Smith Surgery, Cardiovascular and Thoracic Surgery