ABNORMAL ACTION-POTENTIAL CONDUCTION IN ISOLATED HUMAN HYPERTROPHIED LEFT-VENTRICULAR MYOCARDIUM

Introduction: Cardiac hypertrophy is associated with an increased inci dence of arrhythmias that result from altered action potential configu ration or propagation velocity, These variables were measured in isola ted preparations of human left ventricular myocardium and correlated w ith the degree of hypertrophy. Methods and Results: Cardiac mass was e stimated by echocardiography and cell diameter was measured from fixed isolated specimens; the two variables correlated significantly, Actio n potential duration was measured under field stimulation but was inde pendent of the degree of hypertrophy; however, the duration was longer in septal preparations (405 +/- 12 msec, 37 degrees C, 1-Hz stimulati on) than in papillary muscles (342 +/- 11 msec), Conduction velocity d ecreased progressively as cell diameter increased both in septal and p apillary muscle preparations, Cable analysis showed that the variation of conduction velocity could be accounted for adequately by an increa se of the intracellular, resistivity of the preparations. Conclusion: The data suggest that conduction defects occur in a progressive manner in human hypertrophy,which would provide an important substrate for d ysrhythmias in human left ventricular hypertrophy and could result fro m a decrease of electrical coupling between adjacent myocardial cells.