Nonadherence risks highlighted for MI patients
medwireNews: Study findings indicate that very high medication adherence is necessary, but rarely achieved, in patients in the acute phase after a myocardial infarction (MI).
Only 43% of 4015 patients filled at least 80% of their prescriptions for statins and/or ACE inhibitors during the 6 months after being hospitalised with an MI, report Valentin Fuster (Icahn School of Medicine at Mount Sinai School, New York, USA) and co-researchers.
And adherence was even poorer among 12,976 patients with stable atherosclerotic disease, with just 34% filling at least 80% of their prescriptions over 12 months.
The team used the “standard” threshold of 80% to indicate full adherence, and found this threshold to be associated with improved outcomes in the MI group. Those with full adherence had an 18.9% rate of major adverse cardiovascular events (MACE) over 2 years, compared with 26.3% among nonadherent patients (<40% prescriptions filled).
By contrast, partial adherence (40–79% prescriptions filled) did not reduce risk for MI patients; they had a 24.7% rate of MACE, which was not significantly less than the rate among nonadherent patients.
Partial adherence did offer protection to patients with stable atherosclerotic disease, however, being associated with a MACE rate of 12.18% compared with 17.17% for nonadherence. Full adherence offered the greatest protection, with adherent patients having a 2-year MACE rate of 8.42%, but significance was lost after the team excluded MACE that occurred during the adherence assessment period.
In an accompanying editorial, Paul Armstrong and Finlay McAlister, both from the University of Alberta in Edmonton, Canada, stress that the apparent benefits of 80% and 40% adherence in the MI and atherosclerotic cohorts, respectively, “are not true effect thresholds” because of the arbitrarily selected cutoffs.
“The fundamental message is that the more adherent patients were, the better they fared”, they write in the Journal of the American College of Cardiology.
“To make definitive statements about how much of a therapy needs to be taken to achieve a clinical effect, more refined data on actual medication consumption and pathophysiological surrogate markers, such as blood pressure or cholesterol levels, are needed.”
Greater medication adherence was also associated with reduced hospital costs during follow-up, in both cohorts. In the MI cohort, for example, full adherence was associated with annual per patient cost savings of US$ 440 (€ 389) for MI hospitalisation and $ 844 (€ 746) for revascularisations, relative to nonadherence.
Armstrong and McAlister observe that few interventions to date have successfully improved adherence, but also note evidence that most patients rarely discuss medication adherence with their cardiologist and that cardiologists hardly ever identify nonadherent patients.
“Thus, as a bare minimum, our first step as clinicians must be to routinely ask about adherence with all of our patients at every visit and to encourage them to take their medications as instructed”, they say.
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