Effect of duration of depolarisation on contraction of normal and hypertrophied feline ventricular myocytes

Objective: The aim was to test the hypothesis that the prolongation of action potential duration in hypertrophied feline myocytes causes the contractions to be of long duration. Methods: Left ventricular hypertrophy was induced by slow progressive pressure overload after banding the ascending aorta of young cats. Single myocytes were en/.ymatically dissociated for whole cell patch clamp studies. Cell shortenings were induced by stimulated action potentials (in current clamp mode) and by step depolarisations using voltage clamp to control the duration of depolarisation. Results: Action potential duration measured at 50% repolarisation (0.5 Hz) was significantly longer in hypertrophied myocytes, at 688(SEM 43) ms, n = 25, v 396(17) ms, n = 22, in control myocytes (p