Approximately, 1.5 million cases of myocardial infarction (MI) occur each year. An estimated 5% to 10% of patients who survive an MI die within the first year after the index event, and half are rehospitalized. Studies have demonstrated that medications such as aspirin, β-blockers, ACE inhibitors, and statins taken after MI are associated with improved short- and long-term outcomes, providing protection against subsequent cardiovascular events. Despite proven benefits, a large proportion of patients who have had an MI appear to discontinue use of their prescribed medications over time. Most medications should be taken indefinitely, but long-term data on factors affecting medication adherence are lacking.
New Data on Medication Adherence
In a study published in the October 2009 American Journal of Medicine, my colleagues and I published an analysis assessing patients hospitalized with MI from 1997 to 2006 to determine adherence to statins, β-blockers, and ACE inhibitors/angiotensin receptor blockers (ARBs). The study also looked at factors that appeared to be associated with improved adherence. Data demonstrated that adherence to guideline-recommended medications decreased over time, with 3-year medication continuation rates of 44%, 48%, and 43% for statins, β-blockers, and ACE inhibitors/ARBs, respectively. Our findings illustrated that many patients discontinued use of prescribed cardioprotective medications after MI, with less than half continuing medications 3 years after their MI. Results were particularly striking because the study included patients who were well-insured with relatively low out-of-pocket expenses for prescription drugs. Considering the insurance status of the patients assessed, adherence is presumably even worse among the general population.
Assessing Adherence Factors
A potential cause of poor medication adherence after MI may be a “knowledge translation issue.” Patients may be unaware of why they should be taking medications prescribed to them. Also, they may not fully understand the potentially life-saving benefits achieved by medication adherence or the risks of discontinuing use of these agents. Drug regimens may be too complex or inconvenient for patients to follow, causing patients to forget to take or refill prescriptions. Certain lifestyles may also affect patients’ abilities to adhere to their medication regimens. More research is still needed to determine and understand the factors behind medication discontinuation.
Enrollment into cardiac rehabilitation programs appeared to be associated with improved adherence in the short and long term, and it may contribute to the observed improvement in outcomes among MI participants. Cardiac rehabilitation programs generally include counseling about the specific disease processes, developing effective exercise programs, helping patients change their modifiable risk factors, and counseling patients about the appropriate use of prescribed medications.
It’s possible that mostly health-conscious patients who are already more likely to be adherent to medication are the ones who enroll into cardiac rehabilitation programs. Nonetheless, physicians should encourage patients to enroll in the hopes that they will encourage better patient follow-up, providing them with a basic understanding of the benefits of medication adherence after MI. Larger randomized trials are underway to further analyze other potential interventions to improve adherence. Ultimately, the hope is that we will better understand the types of problems that patients experience after they have an MI so that we can help them avoid medication discontinuation and the problems that may result from it.