Faculty Bibliography

Failure of the right ventricle represents a significant clinical problem and may have different causes, with rates varying between 5% and 50% in patients supported by a left ventricular assist device (LVAD). However, treatment options and device development for right ventricular failure (RVF) have significantly lagged behind those for LVADs. Newer technologies designed or adapted for RV support are needed to provide adequate long-term circulatory support. In this review, we discuss (1) the significance of RVF and its physiologic implications, (2) device constraints affecting treatment options for RVF, and (3) implantable VADs potentially available for RV support.

BACKGROUND: We recently reported using bench testing that the Thoratec HeartMate II at 6,000 rpm contributed to hemodynamics when the heart had not recovered well, making weaning assessment questionable. In this bench study, we characterized hemodynamics and pump flow of the HeartWare HVAD at 1,800 rpm, the lowest speed commonly used to assess clinical recovery. METHODS: The HVAD was operated in a mock loop at 1,800, 2,400, and 3,000 rpm. We acquired pressure-flow curves in each steady state. In pulsatile mode with the pneumatic ventricle (heart simulator) activated, pump flow, total flow, and aortic pressure (AoP) data were obtained under conditions simulating normal heart function or heart failure. RESULTS: A large regurgitant flow during diastole was confirmed during normal heart function at 1,800 rpm support; however, the net flow was zero, and there was no difference in mean AoP between 1,800 rpm support and no HVAD support. In contrast, in the heart failure condition, HVAD flow at 1,800 rpm significantly contributed to mean AoP and total flow, because there was less regurgitant flow. CONCLUSIONS: Similar to the results for the HeartMate II at 6,000 rpm, we found that the net pump flow generated by the HeartWare HVAD at 1,800 rpm depends on the degree of residual left ventricular (LV) function. In the setting of improved LV function, at 1,800 rpm we noted a large regurgitant flow. Although this "marker" can serve as a useful indicator for recovery, assessing recovery at this speed is flawed unless measures are taken to prevent regurgitant flow.

End-stage heart failure affects thousands of children yearly and mechanical circulatory support is used at many points in their care. Extracorporeal membrane oxygenation supports both the failing heart and lungs, which has led to its use as an adjunct to cardiopulmonary resuscitation as well as in post-operative cardiogenic shock. Continuous-flow ventricular assist devices (VAD) have replaced pulsatile-flow devices in adults and early studies have shown promising results in children. The Berlin paracorporeal pulsatile VAD recently gained U.S. Food and Drug Administration approval and remains the only VAD approved in pediatrics. Failing univentricular hearts and other congenitally corrected lesions are new areas for mechanical support. Finding novel uses, improving durability, and minimizing complications are areas of growth in pediatric mechanical circulatory support.

Appropriate early anticoagulation after left ventricular assist device (LVAD) implantation has not been established with practices ranging from no anticoagulation to early heparinization. The goal of this study was to evaluate the efficacy and morbidity of three strategies before initiating oral anticoagulation therapy. This was a noninterventional, retrospective, matched historical control cohort study. The primary and secondary endpoints were thrombotic complications (TCs) and bleeding up to 30 days post-LVAD implantation. There was a significant difference in the overall rate of TCs between strategies (p = 0.017). The incidence of TCs was significantly lower in the heparin group versus no bridging (4.9 vs. 27.0%, p = 0.008) on univariate analysis. On multivariate analysis, heparin was independently associated with a lower odds of TCs (odds ratio [OR], 0.10; 95% confidence interval [CI], 0.01-0.85). No differences were observed in bleeding between groups (p = 0.127) on univariate analysis; however, heparin was independently associated with increased odds of bleeding compared with no bridging on multivariate analysis (OR, 2.93; 95% CI, 1.15-7.43). Compared with no bridging, bivalirudin did not significantly differ in TC or bleeding events. Heparin seems to be the most effective regimen to use post-LVAD implantation but may increase the patient's risk for bleeding.