Electrophysiological effects of left ventricular hypertrophy. Effect of calcium and potassium channel blockade.

Abstract
BACKGROUNDTo define the arrhythmogenic effects of left ventricular hypertrophy (LVH) in the intact heart, we carried out a detailed electrophysiological assessment in our previously validated feline aortic-banding model and then tested the effects of agents that blocked either the slow inward calcium or voltage-dependent potassium channel.METHODS AND RESULTSWe measured intraventricular and interventricular conduction times, excitability thresholds, ventricular effective refractory periods, and monophasic action potential duration at several sites in cats with LVH as well as in concurrent control (sham-operated) cats. In addition, we assessed vulnerability to ventricular arrhythmia using direct measurement of ventricular fibrillation (VF) thresholds and by standard techniques of programmed stimulation. Despite finding no difference between LVH and sham-operated cats in mean values for several electrophysiological parameters, the former group was significantly more vulnerable to VF, with more spontaneous VF...

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