Combined renovascular hypertension and diabetes in rats: a new preparation of congestive cardiomyopathy.

Myocardial function, electrophysiologic characteristics, and structure were studied in rats with both renovascular hypertension and streptozotocin-induced diabetes (HD). Ventricular papillary muscles from untreated rats with HD showed a marked slowing of isometric and isotonic contractions. Peak developed tension and peak shortening were preserved, except in one animal with findings of congestive heart failure. Transmembrane action potentials increased fivefold in duration. Myocardial interstitial fibrosis was frequently observed. Physiologic parameters of rats with HD treated by left nephrectomy, captopril, and insulin were very similar to those of age-matched controls. The mortality rate of rats with HD was 43% over 5 to 6 months in the first study. In a second study, spontaneously dying rats with HD were compared with those deliberately killed. A 55% mortality was observed over 7 months. Myocardial structural damage and histologic evidence of congestive heart failure were more frequent in spontaneously dying rats with HD. Combined renovascular hypertension and diabetes in rats appears to be a new preparation of congestive cardiomyopathy.