ELECTROCARDIOGRAPHIC EVIDENCE FOR COCAINE CARDIOTOXICITY IN CAT

Recent case studies suggest that cocaine overdose may produce life-threatening cardiac arrhythmias. We therefore investigated its effects on the electrocardiogram (leads II and V1) and arterial blood pressure in cats anesthetized with pentobarbital. Cocaine was administered by intravenous infusion over a 2-min interval at 1 mg/kg in 10 cats. In 5 out of 10 cats an additional infusion of 3 mg/kg cocaine was also administered after hemodynamic and electrocardiographic parameters had returned to control values (i.e., within 10 min). During and following infusion of 1 mg/kg cocaine, no significant change in heart rate or systolic or diastolic blood pressure were found, however the QRS duration increased by 38% (from 46 ± 5 to 64 ± 12 ms) (p < 0.01). Evidence for bundle branch block and (or) premature ventricular beats was observed in 9 out of 10 cats after 1 mg/kg cocaine. Infusion of a further 3 mg/kg cocaine in five cats significantly lowered diastolic blood pressure (from 98 ± 18 to 64 ± 28 mmHg; 1 mmHg = 133.3 Pa) (p < 0.01), and further prolonged QRS to 79 ± 14 ms, a 75% increase from the mean control value (p < 0.01). In addition, 1st and 2nd degree atrioventricular block, ventricular extrasystoles, and ectopic rhythms (AV junctional or idioventricular) were observed in four out of five cats given 3 mg/kg cocaine. Mean plasma concentrations of cocaine were 1.37 ± 0.39 μg/mL (4.28 ± 1.22 μM) (n = 5) at the end of a 1 mg/kg infusion and 2.93 ± 0.43 μg/mL (9.16 ± 1.34 μM) after a 3 mg/kg infusion (n = 3). These data indicate that doses of cocaine similar to those reported to occur in patients suffering from cocaine cardiotoxicity can produce marked disturbances in cardiac conduction and arrhythmias in an anesthetized cat model.