Biventricular systolic function in young lambs subject to chronic systemic right ventricular pressure overload

Abstract

In various clinical situations of congenital heart disease, the right ventricle (RV) is subject to a chronic systemic pressure overload which affects biventricular function and may progress to the development of RV failure. Young lambs (2–3 wk old) underwent adjustable pulmonary artery banding (PAB) at systemic (aortic) level for 8 wk. Biventricular function was determined by using load-independent indexes of global ventricular contractile performance by the end-systolic pressure-volume relationship (ESPVR) using the conductance catheter at baseline and during dobutamine infusion. PAB resulted in a significant fivefold increase in RV end-systolic pressure (12–64 mmHg) and a doubling of the RV-to-left ventricular (LV) wall thickness ratio ( P < 0.01). RV global contractile performance increased significantly, as indicated by an increased slope of the ESPVR. Compared with age-matched control lambs, cardiac output decreased from 2.6 to 1.6 l/min ( P < 0.05) whereas heart rates were equal. In contrast with RV volume, LV volume decreased significantly after PAB ( P < 0.01), whereas the LV-ESPVR slope was unchanged. In the PAB group, the RV, but not the LV, showed a reduced response to dobutamine. We concluded that chronic RV pressure overload for 8 wk results in diminished pump function despite compensatory increased RV global contractile performance.