24-year-old with history of smoking tobacco and cannabis • dyspnea • chest tightness

THE CASE

A 24-year-old man with a history of smoking tobacco presented to the hospital with acute-onset chest tightness and dyspnea shortly after smoking cannabis. He was otherwise healthy and hemodynamically stable upon arrival to the emergency department. An electrocardiogram (EKG) was obtained.

THE DIAGNOSIS

The EKG showed ST-segment elevation in the inferolateral leads, consistent with an acute myocardial infarction (AMI) (FIGURE 1). The patient was immediately transported to the cardiac catheterization laboratory, where coronary arteriography demonstrated a normal right coronary artery (FIGURE 2A). Diffuse thrombosis without atherosclerosis was seen throughout the left coronary arteries, including the left main artery, distal left anterior descending (LAD) artery, first diagonal branch of the LAD artery, ostial and proximal left circumflex (LCx) arteries, and first obtuse marginal (OM) branch of the LCx artery (FIGURE 2B).

DISCUSSION

The most common cause of AMI is underlying coronary atherosclerosis;¹ however, AMI may occur due to in-situ thrombosis, thromboembolism, or coronary artery vasospasm, especially due to cocaine or other substance abuse. Occasionally, coronary arteries may be damaged due to viral myocarditis, autoimmune vasculitis, dissection of the ascending aorta, or dissection of a coronary artery, especially during pregnancy and postpartum.^2,3

Cannabis and tobacco increase cardiovascular events

Smoking cannabis has been shown to increase adrenergic activity, resulting in an increased heart rate and elevated arterial pressure.^4,5 These changes may increase myocardial oxygen demand and may result in a decrease in myocardial oxygen supply due to a decrease in the diastolic time.⁶ Smoking cannabis can also increase carboxyhemoglobin levels, which may compromise tissue oxygenation.

Smoking cannabis may predispose individuals to acute myocardial infarction and should be considered in the differential for AMI without coronary atherosclerosis.

The risk for AMI has been shown to increase within the first hour of smoking cannabis.⁵ A few reports have documented cases of acute coronary syndrome following cannabis use; the majority of affected patients presented with chest pain within hours of smoking cannabis and were found to have a thrombus in a coronary artery, which was then treated medically or with percutaneous coronary intervention.⁷ Rare cases of cardiovascular death following cannabis use have also been reported.^7,8

It has been suggested that coronary artery vasospasm may occur from cannabis use, which may precipitate thrombosis; however, this is not well defined.⁹ It is not clear if vasospasm was the inciting factor for thrombus formation in this case, as there was extensive and diffuse thrombus far greater than that expected solely from coronary artery vasospasm.

Continue to: AMI without atherosclerosis? Consider thrombosis