No Risk of Myocardial Infarction Associated With Initial Antiretroviral Treatment Containing Abacavir: Short and Long-Term Results from ACTG A5001/ALLRT

Background. Observational and retrospective clinical trial cohorts have reported conflicting results for the association of abacavir use with risk of myocardial infarction (MI), possibly related to issues that may bias estimation of treatment effects, such as time-varying confounders, informative dropout, and cohort loss due to competing events. Methods. We analyzed data from 5056 individuals initiating randomized antiretroviral treatment (ART) in AIDS Clinical Trials Group studies; 1704 started abacavir therapy. An intent-to-treat analysis adjusted for pretreatment covariates and weighting for informative censoring was used to estimate the hazard ratio (HR) of MIs after initiation of a regimen with or without abacavir. Results. Through 6 years after ART initiation, 36 MI events were observed in 17,404 person-years of follow-up. No evidence of an increased hazard of MI in subjects using abacavir versus no abacavir was seen (over a 1-year period: P =.50; HR, 0.7 [95% confidence interval {CI}, 0.2-2.4]); over a 6-year period: P = .24; HR, 0.6 [95% CI, 0.3-1.4]); these results were robust over as-treated and sensitivity analyses. Although the risk of MI decreased over time, there was no evidence to suggest a time-dependent abacavir effect. Classic cardiovascular disease (CVD) risk factors were the strongest predictors of MI. Conclusion. We find no evidence to suggest that initial ART containing abacavir increases MI risk over short-term and long-term periods in this population with relatively low MI risk. Traditional CVD risk factors should be the main focus in assessing CVD risk in individuals with human immunodeficiency virus infection.