β-Blocker Underuse in Secondary Prevention of Myocardial Infarction

Abstract

OBJECTIVE To review the clinical benefits of β-blockers as secondary prevention following a myocardial infarction (MI) and to address the reasons that clinicians are reluctant to use β-blockers in specific patient populations. DATA SOURCES MEDLINE was searched for articles published from January 1966 to October 2002. Relevant studies were identified by systematic searches of the literature for all reported studies of associations between β-blocker underuse and secondary prevention of MI. Additional studies were identified by a hand search of references of original or review articles. STUDY SELECTION AND DATA EXTRACTION English-language human studies were selected and analyzed. DATA SYNTHESIS Associations were observed in studies of β-blocker use as secondary prevention of MI. A lower rate of β-blocker treatment occurred in older patients and in patients with comorbid conditions such as diabetes, heart failure, chronic obstructive pulmonary disease, asthma, and peripheral arterial disease. In addition, underuse was attributed to the perception of high rates of adverse events associated with β-blockers. β-Blocker use as secondary prevention of an MI can lead to a 19–48% decrease in mortality and up to a 28% decrease in reinfarction rates. Nonetheless, β-blockers are significantly underused in many patient populations due to concomitant disease states. Due to their normal physiologic deterioration, the elderly are at an increased risk of low cardiac output and bradycardia when given a β-blocker; therefore, they should be started on a low dose that is then slowly titrated. In diabetic patients, β-blockers can impair glucose control leading to hypoglycemia; therefore, post-MI diabetic patients must routinely monitor their blood glucose levels. In patients with decompensated heart failure, β-blocker use can lead to further cardiac depression, but lower oral starting doses with slow titration can reduce this risk. β-Blockers can induce bronchospasm in patients with chronic obstructive pulmonary disease or asthma, but cardioselective β-blockers and appropriate use of medications such as albuterol can minimize these effects. Finally, in patients with peripheral arterial disease, with the exception of hypertensive patients with Reynaud's phenomenon, β-blockers can be used safely. The only absolute contraindications to β-blockers are severe bradycardia, preexisting sick sinus syndrome, second- and third-degree atrioventricular block, severe left ventricular dysfunction, active peripheral vascular disease with rest ischemia, or reactive airway disease so severe that airway support is required. CONCLUSIONS Overall, the cardiovascular benefits of β-blockers as secondary prevention of MI significantly outweigh the risks associated with their use.