Systolic and diastolic unloading by mechanical support of the acute vs the chronic pressure overloaded right ventricle

Abstract

Background: Right ventricular (RV) mechanical support is well described in cases of sudden increase in RV afterload. In cases of chronic RV pressure overload (e.g., pulmonary arterial hypertension), it has rarely been described.

Methods: The pulmonary artery was banded in 18 sheep. In the acute group (n = 9), we immediately implanted a Synergy Pocket Micro-Pump. Blood was withdrawn from the right atrium to the pulmonary artery. In the chronic group (n = 9), this pump was implanted 8 weeks after banding. Hemodynamics and pressure-volume loops were recorded before and 15 minutes after pump activation.

Results: Low-flow RV mechanical support significantly improved arterial blood pressure in both groups, but cardiac output only in the acute group. Intrinsic RV contractility was not affected. The RV contribution to the total right-sided cardiac output was 54% ± 8 in the acute group vs 10% ± 13 in the chronic group (p < 1.10^-5), indicating a more profound unloading in the latter. Diastolic unloading (reflected by decreases in central venous pressure, end-diastolic pressure and volume, and ventricular capacitance) was successful in both groups. Decreases in pressure-volume area and RV peak pressure reflected successful systolic unloading only in the chronic group.

Conclusions: Low-flow RV mechanical support improved arterial blood pressure in both conditions but caused a more profound unloading in the chronic group. Diastolic unloading was successful in both groups, but systolic unloading was successful only in the chronic group. The potential use of low-flow mechanical support for a chronic pressure overloaded right ventricle warrants further research to assess its long-term effects.

Keywords: low-flow support; pulmonary hypertension; right ventricular assist device; right ventricular pressure overload.