Coronary vascular responses to short-term cocaine administration in conscious baboons compared with dogs

OBJECTIVES Cardiovascular complications of cocaine use represent an importa nt clinical problem, yet the mechanisms by which cocaine predisposes to myo cardial ischemia are poorly understood. BACKGROUND The effects of cocaine on the coronary circulation have been stu died extensively in experimental animal models, but have failed to recapitu late the clinical findings reported in humans who use cocaine. METHODS We studied 12 conscious, chronically instrumented dogs and 5 consci ous, chronically instrumented baboons to determine whether there were impor tant species differences in the response to cocaine. RESULTS Comparable doses of intravenous cocaine caused similar increases in left ventricular systolic, diastolic and mean arterial pressure in the two species. However, the peak coronary blood flow response in baboons (+/-8 /- 3 from 47 +/- 6 ml/min) was less compared with dogs (+15 +/- 4 from 41 /- 4 ml/min), while the coronary vascular resistance response was greater i n baboons (+0.60 +/- 0.09 from 1.94 +/- 0.09 mm Hg/ml/mm) compared with dog s (+0.35 +/- 0.09 from 2.24 +/- 0.10 mm Hg/ml/min). Although myocardial oxy gen consumption responses were similar between species, there was a signifi cant difference (p < 0.05) in oxygen delivery between baboons (+164 +/- 47 from 705 +/- 59 mi of oxygen per minute) and dogs )+397 +/- 51 from 656 +/- 33 mi of oxygen per minute) that was attributable to a significant (p < 0. 05) increase in hemoglobin concentration in dogs (+2.1 +/- 0.5 g/dl) that w as not observed in baboons. Consequently, cocaine caused a significant incr ease in myocardial oxygen extraction and decreased coronary sinus pH in bab oons, but not dogs. CONCLUSIONS Cocaine caused greater coronary vasoconstriction and greater re quirements for oxygen extraction in baboons compared with dogs. (J Am Coil Cardiol 2000;35:1347-54) (C) 2000 by the American College of Cardiology.