Altered myocardial mechanics in diabetic rabbits

Diabetes mellitus may lead to congestive heart failure in humans, independent of atherosclerotic coronary artery disease. Previous studies have explored the myocardial effects of chronic diabetes in dogs and rats with somewhat divergent results. Therefore the current study examined papillary muscle function in rabbits made diabetic with 140-150 mg/kg intravenous alloxan compared with that of age-matched controls. The period of diabetes was 3 days (study 1), 1 mo (study 2), 3 mo (study 3), and 6 mo (study 4). The duration of isometric and isotonic contraction and relaxation were markedly prolonged in diabetes from studies 2, 3, and 4. Shortening velocity was diminished in diabetics from studies 1, 3, and 4. A blunted inotropic response to increasing stimulus frequency was observed in diabetics. Changes in resting tension were not consistently observed, suggesting that passive muscle stiffness is not altered. These findings indicate that previous work on diabetic rats can be extended to diabetic rabbits and suggest that chronic diabetes diminishes contractility and prolongs the duration of contraction in mammalian hearts.