Cannabis tied to more perioperative heart attacks but fewer venous clots
A review of five studies covering 44,312 surgical patients found cannabis users had a 46% higher risk of heart attack during or soon after surgery. The same analysis linked cannabis use to a 22% lower risk of venous thromboembolism, though researchers said this does not prove protection. Authors urged patients to tell their anesthesiologist about marijuana use for safety.
The findings come from a review of five studies involving 44,312 people who had surgery, presented at ANESTHESIOLOGY 2026. Besides the higher myocardial infarction signal, researchers saw no meaningful associations with stroke, respiratory failure, acute kidney injury, or death. A separate observed link suggested lower venous thromboembolism risk, but the authors said this does not demonstrate protection.
THC can raise heart rate, blood pressure, and cardiac oxygen demand, and may provoke coronary artery spasms. These effects may matter under anesthesia and surgical stress. Patients are advised to report how often, in what form, and when they last used cannabis, since this can shape monitoring, anesthesia choices, blood-thinning decisions, or whether to postpone elective surgery.
As cannabis use grows and remains legal in many states, more surgical patients may need to discuss use with anesthesia teams. This could improve safety through tailored monitoring and planning, while also prompting broader patient education about potency and cardiovascular risks. The mixed findings—higher heart attack risk but lower clot risk—may complicate counseling and encourage further research, but they do not by themselves change clinical guidance.