Intracoronary versus intravenous effects of cocaine on coronary flow and ventricular function

Cocaine-induced vasoconstriction in the human coronary microcirculation: new evidence from myocardial contrast echocardiography

BACKGROUND

Cocaine is a major cause of acute coronary syndrome, especially in young adults; however, the mechanistic underpinning of cocaine-induced acute coronary syndrome remains limited. Previous studies in animals and in patients undergoing cardiac catheterization suggest that cocaine constricts coronary microvessels, yet direct evidence is lacking.

METHODS AND RESULTS

We used myocardial contrast echocardiography to test the hypothesis that cocaine causes vasoconstriction in the human coronary microcirculation. Measurements were performed at baseline and after a low, nonintoxicating dose of intranasal cocaine (2 mg/kg) in 10 healthy cocaine-naïve young men (median age, 32 years). Postdestruction time-intensity myocardial contrast echocardiography kinetic data were fit to the equation y=A(1-e(-βt)) to quantify functional capillary blood volume (A), microvascular flow velocity (β), and myocardial perfusion (A×β). Heart rate, mean arterial pressure, and left ventricular work (2-dimensional echocardiography) were measured before and 45 minutes after cocaine. Cocaine increased mean arterial pressure (by 14±2 mm Hg [mean±SE]), heart rate (by 8±3 bpm), and left ventricular work (by 50±18 mm Hg·mL(-1)·bpm(-1)). Despite the increases in these determinants of myocardial oxygen demand, myocardial perfusion decreased by 30% (103.7±9.8 to 75.9±10.8 arbitrary units [AU]/s; P<0.01) mainly as a result of decreased capillary blood volume (133.9±5.1 to 111.7±7.7 AU; P<0.05) with no significant change in microvascular flow velocity (0.8±0.1 to 0.7±0.1 AU).

CONCLUSIONS

In healthy cocaine-naïve young adults, a low-dose cocaine challenge evokes a sizeable decrease in myocardial perfusion. Moreover, the predominant effect is to decrease myocardial capillary blood volume rather than microvascular flow velocity, suggesting a specific action of cocaine to constrict terminal feed arteries.

Role of angiotensin II and corticotropin-releasing hormone in hemodynamic responses to cocaine and stress

Cocaine produces characteristic behavioral and autonomic responses due to its unique pharmacological properties. Many of the autonomic responses resemble those to acute behavioral stress. Both cocaine and behavioral stress have been shown to evoke an increase in sympathetic nerve activity that is primarily responsible for the peripheral cardiovascular responses. We noted varying hemodynamic and sympathetic response patterns to cocaine administration and to acute behavioral stress in rats that correlate with the predisposition to develop both a sustained increase in arterial pressure and cardiomyopathies. Several lines of evidence suggest that the autonomic response patterns are dependent on the actions of central peptides including angiotensin II (Ang II) and corticotropin-releasing hormone (CRH). This is based on observations demonstrating that intracerebroventricular (icv) administration of receptor antagonists for Ang II or CRH attenuated the decrease in cardiac output (CO) and increase in vascular resistance noted in some animals after cocaine administration or startle. In contrast, icv Ang II enhances the cardiodepression associated with cocaine administration or startle. Based on this and other evidence, we propose that the autonomic response patterns to startle and to cocaine are closely related and dependent on central Ang II and CRH. Furthermore, we suggest that these central peptides may be responsible for varying predisposition to cardiovascular disease.

Peripartum care of the cocaine-abusing parturient: are we ready?

Cocaine abuse in the United States is widespread, affecting more than 30 million people. Nearly 90% of cocaine-abusing women are of childbearing age. Cardiovascular complications of cocaine intoxication include dysrhythmias, ischemia and/or infarction, and account for most cocaine-related deaths. Pregnancy enhances the cardiovascular toxicity of cocaine. While the epidemiology, pathophysiology, clinical symptomatology and implications on pregnancy of cocaine addiction in pregnancy have received significant attention over the past 25 years, far too little attention has been given to the therapeutic considerations and peripartum care of the cocaine-abusing parturients. The timely treatment of acute cocaine-induced cardiovascular toxicity in pregnancy is by far the best predictor of good maternal and fetal outcome. However, no specific treatment guidelines are currently available for cocaine-induced cardiac dysrhythmias. This article discusses briefly several agents (and considers their mechanism of action) that have been proposed for the treatment of chest pain and other cardiovascular side-effects of cocaine toxicity in pregnancy.

Cardiovascular disorders associated with cocaine use: myths and truths

Cocaine produces a pattern of cardiovascular responses that are associated with apparent myocardial ischemia, arrhythmias, and other life-threatening complications in some individuals. Despite recent efforts to better understand the causes of cocaine-induced cardiovascular dysfunction, there remain a number of unanswered questions regarding the specific mechanisms by which cocaine elicits hemodynamic responses. This review will describe the actions of cocaine on the cardiovascular system and the evidence for the mechanisms by which cocaine elicits hemodynamic and pathologic responses in humans and animals. The emphasis will be on experimental data that provide the basis for our understanding of the mechanisms of cardiovascular toxicity associated with cocaine. More importantly, this review will identify several controversies regarding the causes of cocaine-induced cardiovascular toxicity that as yet are still debated. The evidence supporting these findings will be described. Finally, this review will outline the obvious deficits in our current concepts regarding the cardiovascular actions of cocaine in hope of encouraging additional studies on this grave problem in our society.

Effects of cocaine on the coronary arteries

BACKGROUND

A number of studies have documented myocardial ischemia and infarction associated with cocaine use. Mismatch between myocardial oxygen supply and demand from cocaine-induced vasoconstriction and increased myocardial workload are often invoked as the major postulated mechanism by which cocaine induces myocardial ischemia. This article reviews the literature studying the effects produced by cocaine on the coronary arteries to provide insight into the various pathophysiologic mechanisms by which cocaine triggers acute cardiac ischemia or infarction.

METHODS

We reviewed the published literature describing the effects of cocaine on the coronary arteries. A MEDLINE search of English language articles published between 1985 and 2000 was performed. Key words included coronary arteries, coronary vasoconstriction, vasospasm, coronary vasodilation, cardiac vasculature, myocardial ischemia, platelets, thrombosis, and cocaine. Both animal and human studies were included. The bibliographies of identified articles were also explored for additional sources of information.

RESULTS

A recreational dose of cocaine increases the heart rate by approximately 30 beats/min. It also increases the blood pressure by 20/10 mm Hg. These increases are modest, are equivalent to mild exercise, and are not believed to be sufficient to result in myocardial ischemia in the majority of cases. Animal and human studies have documented cocaine-induced early coronary artery vasodilation as shown by a decrease in coronary perfusion pressure ranging from 13% to 68%. This was followed by a more sustained vasoconstriction demonstrated by a decrease in epicardial coronary artery diameter ranging from 5% to 30% with various doses of cocaine by various methods of administration. These changes alone are also an unlikely explanation for cocaine-induced myocardial ischemia. Therefore neither increases in myocardial workload nor hemodynamic changes are sufficient to explain cocaine-induced myocardial ischemia. However, evidence also exists that cocaine activates platelets and promotes thrombosis, resulting in intracoronary thrombus formation. Cocaine may also promote premature and more severe coronary atherosclerosis.

CONCLUSION

The etiology of cocaine-induced myocardial ischemia is complex and is likely to be multifactorial. It appears to be the result of coronary artery vasoconstriction, intracoronary thrombosis, and accelerated atherosclerosis.

Spontaneous coronary artery dissection associated with cocaine use: a case report and brief review

Isolated, spontaneous dissection of the coronary arteries in the absence of trauma is an unusual but well-documented occurrence. Fewer than 50 cases have been reported in males in the English language literature, and only one case, nonfatal, was associated with cocaine use. We present the second overall and the first fatal case of cocaine-associated spontaneous coronary artery dissection and a brief review of the literature on coronary dissection and the cardiovascular effects of cocaine use. The mechanism of cocaine's toxicity on the heart and vasculature is complex, multifactorial, and predominantly related to cocaine's adrenergic properties. The increased arterial blood pressure from cocaine's inotropic and chronotropic effects combined with its direct vasoconstrictive effect leads to increased shear forces on the coronary endothelium. This elevated stress may be responsible for the formation of an intimal tear and the subsequent dissection of the coronary artery. If the dissected portion of the arterial wall is displaced enough to significantly occlude the true lumen, infarction can result. In light of this possibility, coronary artery dissection must be considered in young patients presenting with symptoms of cardiac ischemia and a history of cocaine use.

Nitric oxide inhibition intensifies the depressant effect of cocaine on the left ventricular function in anaesthetized pigs

Myocardial ischaemia and left ventricular dysfunction have been described in cocaine users. Whether nitric oxide (NO) inhibition may potentiate the effects of cocaine on coronary circulation and ventricular function is still unknown. In order to test this hypothesis, 38 pentobarbital-anaesthetized pigs were instrumented for systolic blood pressure, coronary blood flow, left ventricular dp/dt, cardiac output, left ventricular end-diastolic and end-systolic lengths and shortening fraction. The pigs were randomized into three groups: control group: i.v. saline (n = 5); group 1: i.v. cocaine, 10 mg kg-1 over 20 min (n = 17); group 2: the same doses of cocaine 30 min after i.c. L-NAME 20 microg/kg min-1 infusion (n = 16). In order to know whether the observed effects were specific of NO inhibition, in five pigs i.c. L-arginine was simultaneously infused with L-NAME, in five pigs i.c. NTG, an endothelial-independent vasodilator, was simultaneously infused with L-NAME before cocaine was administered, and in nine additional pigs the proximal left anterior descending (LAD) flow was reduced to around 20% of the basal value by means of a mechanical occluder before cocaine was administered. Cocaine i.v did not change the coronary blood flow, while it induced a significant reduction in cardiac output, left ventricular dp/dt and shortening fraction (15 +/- 4-8 +/- 4%, P < 0.05). When cocaine was administered after L-NAME infused i.c. during 30 min, a significantly more severe reduction of the shortening fraction (12 +/- 3-4 +/- 2%, P < 0.0001) was induced; this effect was abolished by simultaneous perfusion of L-arginine i.c. NTG. The results when cocaine was administered after the 20% LAD flow reduction by mechanical occluder did not differ from those of cocaine alone. NO inhibition intensifies the cocaine-induced left ventricular dysfunction.

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

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.

Molecular characteristics of cocaine-induced cardiomyopathy in rats

Cocaine abuse induces severe cardiomyopathy. To investigate the molecular effects of acute and prolonged administration of cocaine, mRNAs encoding markers of either mechanical overload, as atrial natriuretic factor (ANF) and alpha- and beta-myosin heavy chains, or fibrosis as type I and III procollagens, were quantitated in the left ventricle of rats 4 h after one injection of cocaine (40 mg/kg, n = 7), or 14 (n = 15) and 28 days (n = 10) after chronic infusion of cocaine (40 mg/kg per day). Plasma cocaine and benzylecgonine concentrations were both significantly augmented during the infusion while plasma levels of triiodothyronine and thyroxine were lowered. Acute injection of cocaine induced ANF gene expression. Cocaine treatment during 28 days resulted in left ventricular hypertrophy (+ 20% after 24 days, P < 0.05) with normal blood pressure, associated with an accumulation of mRNAs encoding ANF and type I and III collagens (+66% and +55%, P < 0.05). Such a chronic treatment also induced a shift from the alpha- to the beta-myosin heavy chain gene expression (-40% and +50%, P < 0.05). In conclusion, cocaine activates markers of both hemodynamic overload and fibrosis. Such an activation may result from direct and/or indirect effects of the drug such as myocardial ischemia, mechanical overload and/or hypothyroidism.

Immediate effects of intravenous cocaine on the thoracic aorta and coronary arteries. A transesophageal echocardiographic study

STUDY OBJECTIVES AND DESIGN: Arterial vasoconstriction is thought to play a role in the etiology of cocaine-induced cardiovascular complications, but little is known about the immediate effects of cocaine on the thoracic aorta and coronary arteries. To examine these effects, we used transesophageal echocardiography to examine the thoracic aorta and coronary arteries before and immediately after intravenous (i.v.) cocaine (1.2 mg/kg) in 15 subjects.

MEASUREMENTS AND RESULTS

Immediately after cocaine infusion, average heart rate, systolic BP, and double product were increased compared with baseline (22%, 15%, 35%, respectively). There was no significant change in the diameters of the ascending aorta (27.5 vs 27.1 mm; p = 0.85), the descending aorta (19.8 vs 20.4 mm; p = 0.62), or the left main coronary artery (4.3 vs 4.7 mm; p = 0.15). However, there was a trend for an increase in coronary blood flow immediately after cocaine (226 vs 309 mL/min; p = 0.10).

CONCLUSIONS

We conclude that in the 15 subjects studied, there was no evidence of thoracic aorta of coronary artery vasoconstriction immediately after i.v. cocaine. Instead, we found that the diameters of the thoracic aorta and the left main coronary artery were unchanged, and that there was a trend for augmentation of coronary artery blood flow.