132 ACTION POTENTIAL CHANGES IN CARDIOMYOPATHIC TURKEYS

Abstract

Arrhythmias are commonly observed in turkey poults(TK) inbred for congestive cardiomyopathy(CCM). We examined the possibility that alterations of transmembrane action potentials(AP) in left(LV) and right ventricular(RV) muscle fibers from CCM TK might contribute to development of arrhythmias. Resting membrane potential (RMP), AP amplitude, maximum rate of AP phase O(dV/dt max) and APD₉₀ in LV tissue (35°C) from CCM hearts as a group did not differ significantly vs control(Con) hearts; APD₅₀, however, was reduced in myopathic LV (201±6(SE) msec vs 228±9 in Con, P<0.05). In RV tissue, RMP was increased (P<0.01), and both APD₅₀ (186±5 msec vs 206±4 in Con, P<0.01) and APD₉₀ (208±4 msec vs 228±3 in Con, P<0.01) were shortened in CCM hearts. Since severity of cardiac dilation and hypertrophy may vary in CCM TK, the effects of hypertrophy on AP characteristics were examined. The only AP characteristic which distinguished LV tissue from CCM hearts with significant hypertrophy (ie 80% increase in heart/body wt ratio) from LV tissue in CCM TK without hypertrophy, was a reduced dV/dt max in the former (98±6 vs 274±26 V/sec, P<0.01). On the other hand, dV/dt max in hypertrophied and Con RV were similar while APD₅₀ and APD₉₀ in hypertrophied RV were shortened (174±7 vs 202±6 msec, P<0.01; 193±6 vs 224±5 msec, P<0.01). In summary, this study has identified AP abnormalities in ventricular muscle cells which may be associated with the occurrence of arrhythmias in this model of congestive cardiomyopathy.

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