Myocardial perfusion pattern in patients with cocaine-induced chest pain

Cocaine-related myocardial infarction: concomitant heroin use can cloud the picture

Cocaine-related myocardial infarction is a well-known phenomenon. Concurrent heroin use can mask signs and symptoms of myocardial infarction. We discuss an unusual presentation of myocardial infarction, associated with both cocaine and heroin ("speedball") self-injection, that initially went undiagnosed.

Cocaine and cardiovascular toxicity

Over the past 10 years a great deal has been learned about the cardiovascular effects of cocaine. In particular, the acute effects of cocaine have been studied extensively. Upon acute administration cocaine increases blood pressure and heart rate, primarily through an action on the sympathetic nervous system. Cocaine also suppresses the baroreflex response and vagal tone, further contributing to its effects on heart rate. At the same time cocaine is increasing the work-load on the heart it induces coronary artery vasoconstriction, potentially leading to cardiac ischemia. At higher doses cocaine can depress ventricular function and slow electrical conduction in the heart. Both these effects appear to be mediated by cocaine's local anesthetic action. The effects of cocaine mediated by the sympathetic nervous system are greatly reduced in anesthetized animals. Further, when cocaine is administered repeatedly over a short period of time, acute tolerance can develop to the sympathomimetic effects of cocaine. In contrast, the effects of cocaine mediated by its local anesthetic action do not appear blunted by anesthesia or susceptible to acute tolerance. With chronic administration, higher doses appear to induce tolerance while lower doses may induce sensitization to cocaine's sympathomimetic effects. Cocaine also induces a variety of pathological changes in the heart, including myocardial contraction band necrosis and ventricular hypertrophy. These effects of cocaine on the heart can all contribute to potentially lethal cardiovascular events. In addition to the effects of cocaine alone, the metabolites of cocaine may also contribute to cocaine's cardiovascular toxicity, and both licit and illicit drugs used in combination with cocaine might potentially alter its cardiovascular effects.

Cardiovascular manifestations of substance abuse part 1: cocaine

Substance abuse with cocaine is associated with multiple cardiovascular conditions, including myocardial infarction, dissection, left ventricular hypertrophy, arrhythmias, sudden death, and cardiomyopathy. Cocaine has effects to potentiate the physiologic actions of catecholamines and has direct effects on voltage-dependent sodium ion channels related to local anesthetic properties. The effects of cocaine can be augmented with concomitant alcohol consumption. Acute myocardial ischemia caused by cocaine may be related to in situ thromboisis and/or coronary vasospasm. Treatment strategies for cocaine-induced myocardial infarction would include antiplatelet therapy, thrombolysis, and vasodilators (eg, nitrates, nifedipine). Beta-adrenergic blockers should not be used unless concomitant vasodilator therapy is given.

The evaluation of cocaine-induced chest pain with acute myocardial perfusion imaging

OBJECTIVE

To use myocardial perfusion imaging to determine the etiology of cocaine-induced chest pain in patients without ECG evidence of acute cardiac ischemia.

METHODS

The authors conducted a prospective study of consecutive consenting patients aged 18-70 years with cocaine-induced chest pain who reported cocaine use within three days and presented with a chief complaint of chest pain occurring within three hours and lasting longer than 15 minutes with a normal or nondiagnostic ECG. Patients were excluded if they had a clear-cut noncardiac cause of chest pain, ECG evidence of acute cardiac ischemia, history of myocardial infarction, pregnancy, or lactation, required immediate hospitalization, or were unable to consent. Patients were injected with Tc-99m tetrofosmin and imaged. Perfusion scans were independently read by two nuclear radiologists. Clinicians blinded to scan results determined patient disposition. Patients with abnormal scans were asked to return for follow-up resting scans.

RESULTS

Fourteen patients were enrolled. Twelve of the 14 patients had chest pain at the time of Tc-99m tetrofosmin injection. Ten of the 14 [(71%) 95% CI = 48% to 95%] scans were normal or within normal limits. Four of the 14 [(29%) 95% CI = 5% to 52%] were abnormal. Of the four patients with abnormal scans, two had follow-up scans that demonstrated an irreversible perfusion abnormality, and two who did not return for follow-up reported no subsequent hospitalizations for acute cardiac ischemia.

CONCLUSION

Perfusion imaging did not demonstrate reversible ischemia in most patients (12/14, 86%) with cocaine-induced chest pain without ECG evidence of ischemia. These results suggest that cocaine-induced chest pain in most patients without ECG evidence of ischemia is not due to acute ischemia.

Evaluation of chest pain in the emergency department

The evaluation of chest pain in the emergency setting should be systematic, risk based, and goal driven. An effective program must be able to evaluate all patients with equal thoroughness under the assumption that any patient with chest pain could potentially be having an MI. The initial evaluation is based on the history, a focused physical examination, and the ECG. This information is sufficient to categorize patients into groups at high, moderate, and low risk. Table 14 is a template for a comprehensive chest-pain evaluation program. Patients at high risk need rapid initiation of appropriate therapy: thrombolytics or primary angioplasty for the patients with MIs or aspirin/heparin for the patients with unstable angina. Patients at moderate risk need to have an acute coronary syndrome ruled in or out expediently and additional comorbidities addressed before discharge. Patients at low risk also need to be evaluated, and once the likelihood of an unstable acute coronary syndrome is eliminated, they can be discharged with further evaluation performed as outpatients. Subsequent evaluation should attempt to assign a definitive diagnosis while also addressing issues specific to risk reduction, such as cholesterol lowering and smoking cessation. It is well documented that 4% to 5% of patients with MIs are inadvertently missed during the initial evaluation. This number is surprisingly consistent among many studies using various protocols and suggests that an initial evaluation limited to the history, physical examination, and ECG will fail to identify the small number of these patients who otherwise appear at low risk. The solution is to improve the sensitivity of the evaluation process to identify these patients. It appears that more than simple observation is required, and at the present time, no simple laboratory test can meet this need. However, success has been reported with a number of strategies including emergency imaging with either radionuclides such as sestamibi or echocardiography. Early provocative testing, either stress or pharmaceutic, may also be effective. The added value of these tests is only in their use as part of a systematic protocol for the evaluation of all patients with acute chest pain. The initial evaluation of the patient with chest pain should always consider cardiac ischemia as the cause, even in those with more atypical symptoms in whom a cardiac origin is considered less likely. The explicit goals for the evaluation of acute chest pain should be to reduce the time to treat MIs and to reduce the inadvertent discharge of patients with occult acute coronary syndromes. All physicians should become familiar with appropriate risk stratification of patients with acute chest pain. Systematic strategies must be in place to assure rapid and consistent identification of all patients and the expedient initiation of treatment for those patients with acute coronary syndromes. These strategies should include additional methods of identifying acute coronary syndromes in patients initially appearing as at moderate or low risk to assure that no unstable patients are discharged. All patients should be followed up closely until the cardiovascular evaluation is completed and, when possible, a definitive diagnosis is determined. Finally, this must be done efficiently, cost-effectively, and in a manner that will result in an overall improvement in patient care.

Predictors of coronary artery disease in patients with cocaine-associated myocardial infarction. Cocaine-Associated Myocardial Infarction (CAMI) Study Group

PURPOSE

To identify clinical criteria predictive of underlying coronary artery disease in patients with cocaine-associated myocardial infarction.

PATIENTS AND METHODS

Using a retrospective cross-sectional study design at 29 acute care hospitals, we identified 70 patients with cocaine-associated myocardial infarction who had a determination of the presence or absence of coronary artery disease. Clinical characteristics of patients with coronary artery disease (> 50% stenosis on cardiac catheterization or reversible ischemia on stress test) were compared with patients without coronary artery disease (< 50% stenosis on cardiac catheterization).

RESULTS

Compared with patients without coronary artery disease (n = 21), patients with coronary artery disease (n = 49) were older (42 versus 31 years; P < 0.001), had more traditional cardiac risk factors (2.3 versus 1.5; P < 0.001), more frequent history of hypertension (odds ratio [OR], 5.3; 95% confidence interval [CI], 1.4 to 20.4); more frequent family history of myocardial infarction (OR, 4.4; 95% CI, 1.3 to 15.1), more bradydysrhythmias (OR, 8.0; 95% CI, 1.0 to 65.5), and more likely to have an inferior infarct location (P = 0.04).

CONCLUSION

Age, number of cardiac risk factors, location of myocardial infarction, and bradydysrhythmias predict underlying coronary artery disease in patients with cocaine-associated myocardial infarction. If validated, this knowledge may be used to develop a medically appropriate, cost-effective evaluation strategy for patients following cocaine-associated myocardial infarction.