Hemodynamic and Left Ventricular Pressure-Volume Responses to Counterpulsation in Mock Circulation and Acute Large Animal Models

Abstract

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.

A Novel Subcutaneous Counterpulsation Device: Acute Hemodynamic Efficacy During Pharmacologically Induced Hypertension, Hypotension, and Heart Failure

“…Using the ECG, IABP inflation should be initiated at the upstroke of the T-wave during ventricular repolarization immediately after the aortic valve closes, and deflation must begin before the end of ventricular diastole (6) to ensure that the balloon deflates and aortic resistance is low. Our computer simulations (15) as well as the present and previous studies (15)(16)(17)(18) indicate that if CPD ejection is delayed until after isovolumetric relaxation when the coronary resistance is lowest, a modest additional increase in coronary artery flow is noted as compared with the inflation timing for an IABP. Similarly, by triggering CPD filling prior to the beginning of ventricular systole and completely filling the device before the aortic valve opens, LV ejection pressure decreases and translates directly into greater reductions in ventricular workload.…”

“…Subsequent studies demonstrated that the CPD functioned by the same counterpulsatile mechanism as an IABP and that hemodynamic benefits were comparable to or better than an IABP under normal (16) and monensin-induced heart failure conditions (18).…”

The Future of Adult Cardiac Assist Devices: Novel Systems and Mechanical Circulatory Support Strategies

“…Although the Symphony operates similarly to an IABP, the delivery of support is fundamentally different 86,87 . The surgical configuration does not influence the internal impedance of the aorta, and device filling and ejection are less dependent on timing than an IABP.…”

“…With an IABP, inflation occurs immediately after aortic valve closure, and deflation must begin before the end of ventricular diastole to ensure that the balloon deflates and aortic resistance is low 88 . In contrast, theoretical work suggests that adjustment of the timing of filling and ejection of the Symphony may permit modest tradeoffs between improved coronary flow and left ventricular workload 86,87 . Consequently, subtle variations in the delivery of support may have important utility for incremental patient management on an individualized basis.…”

“…Consequently, subtle variations in the delivery of support may have important utility for incremental patient management on an individualized basis. For example, ejection of the Symphony may be delayed until after isovolumetric relaxation when the coronary resistance is lowest, which may result in a modest additional increase in coronary artery flow as compared to an IABP 86,87 . If filled prior to the beginning of ventricular systole before the aortic valve opens, a large decrease in left ventricular ejection pressure translates into a large reduction in ventricular work.…”