Long-term electrophysiological abnormalities resulting from experimental myocardial infarction in cats.

Abstract

Chronic electrophysiological abnormalities in cats surviving experimental myocardial infarction (MI) were recorded 1 wk-6 mo. following single-stage ligation of multiple distal tributaries of the left coronary artery system. Sixteen of 32 long-term MI cats (50%) had a propensity to ventricular ectopic activity (VEA), as established by at least 1 of 3 criteria: spontaneous VEA on ECG prior to death (8 of 32 cats; 25%); accelerated ventricular escape rhythms during vagal stimulation (7 of 21; 33%); and rapid automatic activity of the isolated left ventricle in tissue bath (11 of 32; 34%). Cellular electrophysiological abnormalities in surviving subendocardial tissue overlying the MI scar were recorded in 29 of 32 preparations (91%). Focal areas of action potential (AP) abnormalities were interspersed between areas of normal activity. AP abnormalities were of 3 types: prolongation of AP duration; shortening of AP duration; and low amplitude action potentials. Type 1 abnormalities were recorded most commonly between 1 wk and 1 mo. after MI, and rarely were recorded later. Type 2 abnormalities began to appear 1 1/2 mo. after MI and were most common at 3-6 mo. Type 3 abnormalities were recorded at any stage. At 3 mo. after MI and beyond, surviving cells were histologically normal, despite continued AP abnormalities and propensity to VEA. A persistence of deranged cellular electrophysiology occurred for up to 6 mo. after MI.