Adherence to All Prescriptions After Heart Attack Improves Outcomes

Post-myocardial infarction patients who had each of their preventive medications on hand at least 80% of the time had significantly lower rates of major vascular events or revascularization than controls.

Patients who are highly adherent to all of their prescription medications are less likely to be readmitted to the hospital following a heart attack, according to a new study conducted by researchers from CVS Caremark and Brigham and Women’s Hospital. The results of the study indicate that patients who were adherent less than 80% of the time had no reduction in risk, suggesting that this widely used definition of adherence is a useful threshold.

Although many studies have demonstrated the benefits of medication adherence, there is little evidence regarding precisely what level of adherence is required and whether adherence to all prescriptions is necessary to improve outcomes. The new study, published in the January 2014 issue of the American Heart Journal, analyzed data from the MI FREEE trial to determine the impact of adherence on clinical outcomes for patients after myocardial infarction.

The analysis included trial patients who had filled a prescription for a beta-blocker, statin, angiotensin-converting enzyme inhibitor, or angiotensin receptor blocker after hospital discharge for myocardial infarction. Medication adherence was evaluated based on the portion of days covered for each medication prescribed, and patients were categorized based on their level of adherence. Patients who achieved a medication possession ratio of 80% or greater were categorized as adherent, those with a ratio from 60% to 79% were categorized as partially adherent, and those who were covered less than 60% of the time were categorized as non-adherent. Readmission rates for a first major vascular event, including myocardial infarction, unstable angina, stroke, and congestive heart failure, and coronary revascularization were assessed for all patients and compared across all 3 levels of adherence.

The results indicated that patients categorized as adherent to all medications included in the study were significantly less likely to experience major vascular events or undergo revascularization compared with control patients. Adherent patients had a 24% reduced hazard of experiencing a major vascular event or undergoing revascularization compared with controls, while non-adherent patients saw no reduction in risk. Surprisingly, there was no significant difference in the risk for vascular event between partially adherent patients and non-adherent patients. For example, patients who were partially adherent to beta-blockers had an average medication possession ratio of 71%, compared with just 49% among non-adherent patients, but risks of major vascular events or revascularization were equivalent among these patients.

The results indicate that adherence to all preventive medications by patients who have had a myocardial infarction is necessary in order to reduce the risk of re-admittance. The findings also provide support for defining optimal adherence as a medication possession ratio of 80% or greater, the study authors suggest, adding that interventions to improve adherence are needed.

“[I]nterventions that simplify treatment regimens, remind, and motivate patients about the importance of taking their therapies as prescribed may hold substantial promise and should be explored further,” they conclude.