A retrospective study on adherence to secondary prevention medications after coronary bypass surgery

OBJECTIVES: We assessed adherence to statins, beta-blockers and renin-angiotensin system (RAS) inhibitors after coronary artery bypass graft surgery and factors associated with non-adherence.

METHODS: This nationwide retrospective cohort study included all individuals undergoing coronary artery bypass surgery from 22 May 2007 to 20 December 2018, at Landspitali-the National University Hospital (n = 1536). Data on dispensed prescriptions were retrieved from the National Prescription Medicine Registry. Adherence was estimated by the proportion of days covered up to 2 years after hospital discharge, with cut-offs for strict adherence and non-adherence at over 80% and under 50%, respectively. Multivariable logistic regression was used to assess variables associated with non-adherence.

RESULTS: Criteria for strict adherence were met by 39.2%, 36.9% and 30.1% of patients for statins, beta-blockers and RAS inhibitors, respectively. Non-adherence criteria were met for 14.4%, 25.9% and 43.6% of patients for statins, beta-blockers and RAS inhibitors, respectively. High Hospital Frailty Risk Score Class (statins: odds ratio (OR) 2.29, confidence interval (CI) 1.02-4.86; RAS inhibitors: OR 2.06, CI 1.04-4.04), concomitant aortic valve replacement (statins: OR 1.64, CI 1.11-2.38; RAS inhibitors: OR 1.78, CI 1.26-2.52) and a new prescription for a medication class following surgery (statins: OR 2.87, CI 2.06-4.01; beta-blockers: OR 1.70, CI 1.32-2.18; RAS inhibitors: OR 6.95, CI 5.27-9.25) were associated with non-adherence.

CONCLUSIONS: Non-adherence to medical therapy after coronary artery bypass surgery is common. Patients with a higher burden of frailty and patients naive to the medical treatment of coronary artery disease should be a target group for efforts to increase medication adherence.