Cm, membrane capacitance of myocyte. For action potential parameters: Steady-state (driven at 1 Hz) values are given in mean ± S.E.M. APA, action potential amplitude. Phase-0 (mV/ms), maximum dV/dt of phase-0 depolarization. MDP, maximum diastolic potential; APD20, APD50, and APD90: action potential duration at 20%, 50% and 90%, respectively, of repolarization levels. Number in parenthesis indicates number of myocytes. *P < 0.05 by group comparisons between healthy and myopathic hamsters.