Importance: Patients with peripheral artery disease (PAD) are at high risk for myocardial infarction (MI).

Objective: To characterize the incidence and types of MI in a PAD population, identify factors associated with MI, and determine the association of MI with cardiovascular mortality and acute limb ischemia.

Design, Setting, and Participants: The Study Comparing Cardiovascular Effects of Ticagrelor and Clopidogrel in Patients With Peripheral Artery Disease (EUCLID) was a double-blind randomized clinical trial conducted at 811 sites in 28 countries that randomized 13 885 patients with symptomatic PAD to monotherapy with ticagrelor or clopidogrel. Participants had an ankle-brachial index (ABI) of 0.80 or less or previous lower extremity revascularization. Median follow-up was 30 months. For these analyses, patients were evaluated for MI occurrence during follow-up irrespective of treatment. Data were analyzed from June 2017 to September 2018.

Main Outcomes and Measures:  An adjudication clinical events committee classified MI as type 1 (spontaneous), type 2 (secondary), type 3 (sudden cardiac death), type 4a (less than 48 hours after percutaneous coronary intervention), type 4b (definite stent thrombosis), or type 5 (less than 72 hours after coronary artery bypass graft). A multivariate regression model was developed by stepwise selection to identify factors associated with MI, and a time-dependent multivariate Cox regression analysis was performed to determine the association of MI with cardiovascular death and acute limb ischemia requiring hospitalization.

Results:  Of the 13 885 patients included in this analysis, 9997 (72.0%) were male, and the median (interquartile range) age was 66 (60-73) years. Myocardial infarction occurred in 683 patients (4.9%; 2.4 events per 100 patient-years) during a median follow-up of 30 months. Patients experiencing MI were older (median [interquartile range] age, 69 [62-75] vs 66 [60-72] years), more likely to have diabetes (349 of 683 [51.1%] vs 4996 of 13 202 [37.8%]) or a previous lower extremity revascularization (466 of 683 [68.2%] vs 7409 of 13 202 [56.1%]), and had a lower ABI (if included by ABI) compared with censored patients. Of the 683 patients with MI during follow-up, the most common MI type was type 1 (405 [59.3%]), followed by type 2 (236 [34.6%]), type 4a (14 [2.0%]), type 3 (12 [1.8%]), type 4b (11 [1.6%]), and type 5 (5 [0.7%]). Postrandomization MI was independently associated with cardiovascular death (adjusted hazard ratio, 9.0; 95% CI, 7.3-11.2; P < .001) and acute limb ischemia requiring hospitalization (adjusted hazard ratio, 2.5; 95% CI, 1.3-5.0; P = .008).

Conclusions and Relevance: Approximately 5% of patients with symptomatic PAD had an MI during a median follow-up of 30 months. Type 1 MI (spontaneous) was the most common MI type; however, one-third of MIs were type 2 MI (secondary). More research is needed to identify therapies to reduce the risk of MI in patients with PAD and to improve management of type 2 MI.