Studies show higher rates of myocardial infarctions (MI) with HIV and aging. Abacavir (ABC) has also been associated in some studies with an increased risk of cardiovascular (CV) events. To assess the relative impact of one intervention to reduce MI risk in HIV patients versus another, we modelled the impact of interventions that address traditional risk factors and replacing ABC on predicted MI rates. While other HIV antivirals have been associated with elevated MI risk, we used ABC as an example of the impact of changing HIV treatment in addition to a focus on traditional risk factors.
Strategies for reducing MI rates in HIV patients were compared over 10 years using a decision tree model. Assumptions about the effectiveness of smoking cessation counseling, substitution of ABC with an alternative regimen, anti-hypertensive and anti-hyperlipidemia medication use were based on publications from the HIV or general population. We adjusted for sex, age, and presence of the four MI risk factors. Interventions were compared based on published data on the probability of success of changing the risk factor and the impact of changing it when successful. For smoking cessation, the impact was based on published quit rates following counseling, 36.5% after one year and 10% annual relapse rate.
In the base case of 50-year old HIV positive male smokers who only replaced ABC, there was a 46% reduction in the MI rate compared to those who continued ABC (0.31/ 100 vs. 0.58/ 100 PY). Men who are counseled and treated for smoking cessation which resulted in an 11% MI rate reduction versus those who did not attempt smoking cessation (0.52/ 100 vs. 0.58/ 100 PY). Over 10 years, compared to no MI intervention, ABC substitution prevented more MIs than counseling about smoking (2.64 vs 0.63 MIs per 100 persons). The impact of treating hypertension and hyperlipidemia was a 19% and 31% reduction in MI risk, respectively (see Table).
By incorporating the impact of CV risk factor modification based on real world data, this model suggests that replacing ABC, which can be accomplished in most patients, is potentially more impactful in reducing MI risk than interventions solely on traditional risk factors. While this model does not account for all tobacco risks, findings highlight the role that ABC substitution can have on MI risk over time compared to antismoking, hypertension and lipid lowering interventions. Interventions to address all CV risk factors are warranted.