Quality improvement programs have shown increased use of β-blockers post–myocardial infarction (MI), but there are no data on whether appropriate doses are administered.

In a prospective registry that enrolled consecutive patients with MI, we evaluated β-blocker dosing at discharge after MI and 3 weeks later and assessed clinical predictors for treatment with very low doses. We studied 1,971 patients (70.8% male) with a mean age of 63.9 ± 13.7 years, of whom 48.2% had an ST-elevation MI.

β-Blocker utilization rates following MI were 93.2% at discharge: 20.1% received <25% of target dose, 36.5% received 25% of target dose, 26.4% received 26% to 50% of target dose, and 17.0% received >50% of target dose. Between discharge and 3 weeks, 76.4% had no change in β-blocker dose, with 11.9% and 11.6% having their dose reduced and increased, respectively. Absence of hypertension, acute percutaneous coronary intervention, older age, and no angiotensin-converting enzyme inhibitor therapy were consistent predictors of treatment with very low β-blocker doses.

Underdosing of β-blockers is highly prevalent among patients post-MI. This represents an important opportunity in quality improvement for the care of patients who have suffered an MI.