Cardiac performance in rats with renal hypertension.

To evaluate cardiac performance in renal hypertension more precisely we determined cardiac function curves for 12 normotensive rats and 11 other rats with two-kidney Goldblatt hypertension. The hypertensive group (BP = 134 +/- 8 mm Hg) showed significant cardiac hypertrophy (44 +/- 1% increased ratio of heart weight to body weight, P less than 0.01) and markedly increased left ventricular stroke work with a moderate but not significant increase in left ventricular end-diastolic pressure (LVEDP) (5.9 +/- 0.8 vs. 4.7 +/- 0.4 mm Hg). We evaluated cardiac function by recording left ventricular end-diastolic pressure, stroke volume (SV), and cardiac output (CO) (by electromagnetic flowmeter) during rapid alteration in venous return. Analysis of variations of stroke volume vs. left ventricular end-diastolic pressure showed that renal hypertension is accompanied by a significant decrease in ventricular performance [SV = 0.0190 + 0.0509 LVEDP - 0.0025 (LVEDP)2 + 0.0001 (LVEDP)3] compared to the normotensive group [SV = 0.0430 + 0.0644 LVEDP - 0.0040 (LVEDP)2 + 0.001 (LVEDP)3]. The alterations in stroke volume and cardiac output were associated with a lack of significant changes in the work performed at matched end-diastolic pressures. The data indicate that chronic renal hypertension is accompanied by a depression of cardiac reserve which is not revealed by measurements of cardiac output and left ventricular end-diastolic pressure at rest. This impairment in cardiac function might be related to either diminished cardiac contractility or reduced left ventricular compliance; the latter possibility is in accord with our finding of a 2-fold increase in the hydroxyproline content (P less than 0.001) and a significant decrease in the DNA concentration of ventricular tissue.