Effect of altered thyroid status on in vitro cardiac performance in XXXX .

@entity35 @entity1375 @entity64 @entity1378
Effect of a chronic excess or deficit of thyroid hormone on intrinsic myocardial performance in @entity35 was assessed. Animals were thyroidectomized or treated with thyroid hormone or vehicle 6-7 wk before the study. Body weight and heart weight were decreased in the @entity1375 group, and heart weight was elevated in the @entity1378 group. Hearts were removed from thyroidectomized, euthyroid or thyroid-treated animals and studied as isolated, perfused working heart preparations. Ventricular function curves were generated by increasing left atrial filling pressure, whereas outflow resistance was not varied. Coronary flow, aortic outflow (and thus cardiac output), heart rate, and peak aortic systolic pressure were measured as a function of preload. These studies showed that performance of hearts from @entity1378 animals was similar to that of euthyroid controls. Hearts from @entity1375 @entity35 had decreased rate, pressure, and cardiac output but normal @entity64 volume. Since heart weight was 55% lower than control, normalization of volume work to dry heart weight reversed the difference in cardiac output. Comparison of hearts from @entity1375 animals to control @entity35 of similar weight showed minimal differences in pump function. Thus @entity1378 did not result in altered in vitro cardiac output or peak systolic pressure as a function of changing preload when compared with age-matched euthyroid controls, @entity1375 resulted in a decreased in vitro heart rate but greater cardiac output normalized to heart weight when compared with age-matched controls and @entity1378 animals; external pacing of @entity1375 hearts yielded myocardial work parameters that were comparable to euthyroid control @entity35 of similar body weight; and cardiac efficiency was significantly greater in @entity1375 hearts than in @entity1378 hearts.(ABSTRACT TRUNCATED AT 250 WORDS)
