Left ventricular pump function in renal hypertensive dogs with cardiac hypertrophy.

We compared open-chest left ventricular (LV) pump performance after autonomic blockade under controlled loading conditions in normal dogs and in dogs where chronic renovascular hypertension had produced moderate concentric LV hypertrophy (LVH). Mean LV pressure (MLVP) provided a measure of ventricular load independent of vascular properties. We found an inverse relationship between MLVP and cardiac index (CI) in both groups when peripheral resistance was altered at constant left atrial pressure. However, CI declined significantly less in LVH hearts as MLVP was increased. The slope of the linear MLVP-CI plot (LV source resistance) was 1.91 times the value observed in normal dogs. LVH hearts developed more steady-flow external power than their normal counterparts, and the power optimum was reached at a much higher mean arterial pressure. Isovolumic maximum rate of LVP rise was 1.28 times higher in LVH than normal dogs (P less than 0.01) in proportion to the increase in wall thickness. Our results suggest that additional muscle with normal contractile properties and greater emptying due to the increased wall-to-lumen ratio accounted for the increased pump performance in LVH.