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ARTICLE

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

Richard P. Shannon, MD, FACC^* , Michael A. Mathier, MD^* and You-Tang Shen, MD

^* Department of Medicine, Allegheny General Hospital and the Cardiovascular & Pulmonary Research Institute, MCP Hahnemann University School of Medicine, Pittsburgh, Pennsylvania, USA
New England Regional Primate Research Center, Harvard Medical School, Southborough, Massachusetts, USA
Merck Research Laboratories, West Point, Pennsylvania, USA

Manuscript received April 7, 1999; revised manuscript received October 15, 1999, accepted December 29, 1999.

Reprint requests and correspondence: Dr. Richard P. Shannon, Department of Medicine, Allegheny General Hospital, 320 East North Avenue, Pittsburgh, Pennsylvania 15212

OBJECTIVES

Cardiovascular complications of cocaine use represent an important clinical problem, yet the mechanisms by which cocaine predisposes to myocardial ischemia are poorly understood.

BACKGROUND

The effects of cocaine on the coronary circulation have been studied extensively in experimental animal models, but have failed to recapitulate the clinical findings reported in humans who use cocaine.

METHODS

We studied 12 conscious, chronically instrumented dogs and 5 conscious, chronically instrumented baboons to determine whether there were important 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 in baboons (+0.60 ± 0.09 from 1.94 ± 0.09 mm Hg/ml/mm) compared with dogs (+0.35 ± 0.09 from 2.24 ± 0.10 mm Hg/ml/min). Although myocardial oxygen consumption responses were similar between species, there was a significant difference (p < 0.05) in oxygen delivery between baboons (+164 ± 47 from 705 ± 59 ml of oxygen per minute) and dogs (+397 ± 51 from 656 ± 33 ml 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 was not observed in baboons. Consequently, cocaine caused a significant increase in myocardial oxygen extraction and decreased coronary sinus pH in baboons, but not dogs.

CONCLUSIONS

Cocaine caused greater coronary vasoconstriction and greater requirements for oxygen extraction in baboons compared with dogs.

Abbreviations and Acronyms   Ao mean = mean aortic pressure   CBF = coronary blood flow   CVR = coronary vascular resistance   EPI = epinephrine   IV = intravenous   LV = left ventricular   LVdP/dt = derivative of LV systolic pressure with respect to time   LVEDP = left ventricular end-diastolic pressure   MVO2 = myocardial oxygen consumption   NE = norepinephrine

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