Follow-up Dosing of Guideline-Indicated Medications After Myocardial Infarction: Insights from the Acute Myocardial Infarction Quality Assurance (AMIQA) Canada Study.

BACKGROUND

Achieving the target doses of indicated medications after myocardial infarction (MI) is associated with improved outcomes and is a marker of the quality of care. We studied the use and follow-up dosing of core cardiac medications among patients with MI complicated by depressed left ventricular ejection fraction (LVEF). Our objective was to determine whether adherence to evidence-based medication dosing is associated with receipt of follow-up LVEF imaging or progression of LVEF within 6 months of follow-up care.

METHODS

The Acute Myocardial Infarction Quality Assurance (AMIQA) Canada study enrolled 501 patients (mean age 63 years; 22.6% female) with acute MI and LVEF ≤ 45%, from 14 Canadian centres. Patients were followed for 6 months to determine their adherence to post-MI follow-up recommendations. We assessed use and dosing of beta-blockers, angiotension-converting enzyme inhibitors, angiotensin II receptor blockers, mineralocorticoid receptor antagonists (MRAs), and statins, and compared changes in LVEF among those taking ≥50% vs < 50% of the target dose in the follow-up period.

RESULTS

At 6 months, the mean percent target dose was ≤ 50% for beta-blockers, angiotension-converting enzyme inhibitors, and angiotensin II receptor blockers, but it was 70.8% ± 46.9% for MRAs, and 86.8% received high-intensity statin. Only use of MRA was associated with follow-up LVEF reassessment (P < 0.001). Receiving ≥ 50% of the target dose was not associated with changes in LVEF.

CONCLUSIONS

Except for statins, most patients were not receiving target doses of indicated medications after MI with reduced LVEF. Follow-up dosing was not associated with LVEF reassessment or improvement in LVEF. Future quality-improvement initiatives may require distinct strategies for improving adherence to recommendations for medication dosing vs follow-up imaging.