Excitation-contraction coupling in isolated myocardium from dogs with compensated left ventricular hypertrophy

To examine the relationship between left ventricular (LV) function and intracellular calcium modulation in the presence of myocyte hypertrophy, we compared LV muscles from nine dogs with compensated LV hypertrophy (LVH) induced by chronic aortic banding with 11 controls. Mechanical properties were studied in LV muscles (control, n = 25; LVH, n = 23) stretched to the length at which maximal isometric tension developed at 30 degrees C and stimulated at 0.33 Hz; a subset of LVH muscles was loaded with the intracellular calcium indicator aequorin. In LV myocardium from dogs with compensated LVH, both the contraction duration and calcium transients were prolonged at baseline, and the response to phosphodiesterase inhibitors was impaired in keeping with findings in both human and experimental models of pressure-overload hypertrophy and failure. However, in contrast to findings in the failing myocardium, the positive inotropic response to increasing intracellular calcium was preserved in myocardium from dogs with compensated LVH.