Association between medication adherence and cardiovascular outcomes among acute coronary syndrome patients

Abstract

Background: Medication adherence to guideline-recommended therapy is important and associated with a lower rate of death and major adverse cardiovascular events (MACE) among patients with acute coronary syndrome (ACS). Objective: This retrospective study aimed to evaluate medication adherence in four classes of guideline-recommended medicines (antiplatelets, ACEIs/ARBs, beta-blockers, and statins) among patients discharged with ACS and to assess the association between patients’ adherence to each medication and the occurrence of MACE including all causes of death, myocardial infarction, unstable angina, heart failure, stroke, atrial fibrillation or coronary revascularization. Methods: The electronic medical records of patients with ACS admitted at a tertiary teaching hospital in northern Thailand between January 1, 2010 and December 31, 2015 were reviewed. Medication adherence was evaluated from a hospital database of prescription refills using the medication gap technique with ≥90% as a cut-off for full adherence and <90% as partial adherence. Results: Of 256 patients, the mean age was 65.9 (±13.0) years. The median percentage of medication adherence in the dual antiplatelet group, ACEI/ARB group, beta-blocker group, and statin group were 94.7, 93.6, 93.1, and 93.1%, respectively. Sixty-two patients (24.2%) experienced MACE after a median follow-up of 1.5 years. Patients with ≥90% adherence of beta-blockers had a significantly lower risk of MACE than those with <90% adherence: HR = 0.47, 95% Cl, 0.26–0.87, p = 0.016, adjusted with potential confounders. No other significant associations were observed. Conclusions: Medication adherence of each medication was above 90%. ACS patients with at least 90% adherence to beta-blockers had a lower risk of MACE than those having less than 90% adherence, but no other significant associations were found for other medications.