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Ventricular assist devices (VADs) have been used successfully as a bridge to transplant in heart failure patients by unloading ventricular volume and restoring the circulation. An artificial vasculature device (AVD) that may better facilitate myocardial recovery than VAD by controlling the afterload seen by the ejecting heart is being developed. The AVD concept is to enable any user-defined input impedance (IM) with resistance (R) and compliance (C) components. In this study, a pulse duplicator was used to test the efficacy of the AVD concept for two control strategies in an adult mock circulation: (1) R-C in series and (2) 2-element Windkessel (R-C in parallel) using instantaneous impedance position control (IIPC) to maintain a desired value or profile of R and C. In vitro experiments were performed and the resulting cardiovascular pressures, volumes, flows, and the afterload (R and C) seen by the LV during ejection for simulated cardiac failure were recorded and analyzed. Our results indicate that setting the AVD to lower IM reduced LV volume and pressure, restored LV stroke volume, and increased coronary flow. The IIPC control algorithms are better suited to maintain any instantaneous IM or an IM profile, but are susceptible to measurement noise.

Alternative therapies for treating heart failure patients are being explored to provide effective options for patients with progressive heart failure. Cardiac assist devices that promote myocardial recovery may be a potential solution. Ventricular assist devices (VAD) have demonstrated long-term efficacy and intraaortic balloon pumps (IABP) have shown short-term successes. In this paper, testing of a hybrid counterpulsation device (CPD) that couples the attributes of device longevity (VAD) with less invasive surgery (IABP) is presented. Hemodynamic and ventricular pressure-volume responses to a 40 ml CPD and 40 ml IABP were evaluated in vitro in an adult mock circulation and in vivo in a large animal heart failure model. The CPD is a flexing diaphragm ventricle with a controlled stroke volume up to 85 cc through a single, valveless cannula. In this study, the CPD was cannulated to the brachiocephalic artery to provide 40 ml of counterpulsation support. The CPD effectively provided diastolic augmentation increasing coronary flow and afterload reduction. These results were comparable to IABP. These preliminary studies suggest that CPD may be an effective therapy for treating patients with early stage heart failure.