Exaggerated cardiovascular effects of cocaine in conscious dogs with pacing-induced dilated cardiomyopathy

Background: The aim of this study was to explore the characteristics and mechanisms of the cardiovascular effects of cocaine in dilated cardiomyopathy. Methods and Results: We studied the cardiovascular responses to acute intravenous cocaine (1 mg/kg) in 8 conscious, chronically instrumented dogs before and after the development of dilated cardiomyopathy induced by rapid ventricular pacing. To help elucidate the role of altered baroreflex function in mediating the cardiovascular effects of cocaine, we also studied responses in 3 conscious, chronically instrumented dogs that had undergone surgical sinoaortic baroreceptor denervation. Cocaine produced greater increases in heart rate (+57 ± 8% from 112 ± 5 beats/min versus +28 ± 3% from 100 ± 4 beats/min; P