Creatine kinase (CK), CK-MB fraction, and myoglobin have low specificity for the diagnosis of ischemia, as cocaine can induce skeletal muscle injury and rhabdomyolysis.9,12 Cardiac troponins demonstrate a superior specificity compared to CK and CK-MB and are thus the preferred cardiac biomarkers in diagnosing cocaine-associated MI.12
Initial management and disposition. Patients at high risk for cardiovascular events are generally admitted to a monitored bed.13 Immediate reperfusion therapy with primary percutaneous coronary intervention is recommended in patients with ST-elevation MI (STEMI). Treatment with thrombolytic agents is associated with an increased risk of intracerebral hemorrhage and lacks documented efficacy in patients with CACP. Thrombolysis should therefore only be utilized if the diagnosis of STEMI is unequivocal and an experienced cardiac catheterization laboratory is unavailable.14,15
Patients with unstable angina (UA) or non-ST-elevation MI (NSTEMI) are at higher risk for further cardiac events in a similar manner to those with ACS unrelated to cocaine. These cases might benefit from early cardiac catheterization and revascularization.16 Because of the increased risk of stent thrombosis in cocaine-users, thought to be due to recidivism, a detailed risk-benefit analysis should be undertaken prior to the implantation of cardiac stents.
Other diagnostic tests, such as stress testing and myocardial imaging, have not shown significant accuracy in diagnosing MI in this setting; moreover, these patients are at low overall risk for cardiac events and mortality. Consequently, an extensive diagnostic evaluation might not be cost-effective.7,10,13,17 Patients who have CACP without MI have a very low frequency of delayed complications.3,17 As such, cost-effective evaluation strategies, such as nine- or 12-hour observation periods in a chest pain unit, are appropriate for many of these low- to moderate-risk patients.13 For all CACP patients, the most critical post-discharge interventions are cardiac risk modification and cocaine cessation.13
Normalizing the toxic effects of cocaine with medications.
Aspirin: While no specific study has been performed in patients with CACP and aspirin, CACP guidelines, based on data supporting ACS guidelines for all patients, recommend administration of full-dose aspirin given its associated reduction in morbidity and mortality.18,19 Furthermore, given the platelet-stimulating effects of cocaine, using aspirin in this setting seems very reasonable.
Benzodiazepines: CACP guidelines support the use of benzodiazepines early in management to indirectly combat the agitation, hypertension, and tachycardia resulting from the stimulatory effects of cocaine.18,20 These recommendations are based on several animal and human studies that demonstrate significant reduction in heart rate and systemic arterial pressure with the use of these agents.21,22
Nitroglycerin: Cardiac catheterization studies have shown reversal of vasoconstriction with administration of nitroglycerin. One study demonstrated a benefit of the drug in 49% of participants.23 Additional investigation into the benefit of benzodiazepine and nitroglycerin combination therapy revealed mixed results. In one study, lorazepam plus nitroglycerin was found to be more efficacious than nitroglycerin alone.24 In another, however, use of diazepam in combination with nitroglycerin did not show benefit when evaluating pain relief, cardiac dynamics, and left ventricular function.25
Phentolamine: Phentolamine administration has been studied much less in the literature. This nonselective alpha-adrenergic antagonist exerts a dose-dependent reversal of cocaine’s vasoconstrictive properties in monkeys and humans.26,27 International guidelines for Emergency Cardiovascular Care recommend its use in treatment of cocaine-associated ACS;27 however, the AHA recommends it less strongly.18
Calcium channel blockers: Calcium channel blockers (CCBs) have not shown promise as first-line agents. While catheterization studies demonstrate the vasodilatory properties of verapamil, larger studies looking at all-cause mortality conclude that CCBs might worsen mortality rates,28 and animal studies indicate an increased risk of seizures.29 At this time, CCBs are recommended only if cardiac symptoms continue after both benzodiazepines and nitroglycerin are administered.18