Long-term use of beta-adrenergic blockers has been shown to decrease mortality in patients who have sustained a myocardial infarction (MI). Despite evidence from several clinical trials, follow-up studies have shown that physicians prescribe these agents to only 30 to 50 percent of patients after a myocardial infarction. Physician reluctance to prescribe these agents may be associated with patient characteristics that are presumed to be contraindications, such as older age, poor left ventricular function, a history of chronic obstructive pulmonary disease (COPD) and the use of diuretic drugs. Gottlieb and colleagues examined data from the Cooperative Cardiovascular Project to identify which patients benefit from treatment with beta blockers by comparing risk factors and mortality rates in high- and low-risk patients.
The Cooperative Cardiovascular Project is a program designed to evaluate the care of Medicare patients who have had a myocardial infarction. Its primary intent is to evaluate the relationship between treatment and outcomes. The medical records of more than 200,000 patients with myocardial infarction who had been prescribed a beta blocker at the time of hospital discharge were included in the study. Most of the patients were older than 65 years. Data on ejection fraction and serum creatinine levels were available for most patients. Mortality rates of patients who received a beta blocker were compared with those who did not, based on a time-to-event analysis. Approximately 95 percent of the patients were followed for two years.
Only 34 percent of the patients in the study group received beta blockers at the time of hospital discharge; very elderly patients, black patients and patients considered to be the sickest were the least likely to receive this therapy. In addition, patients who had low ejection fractions, a history of congestive heart failure, COPD, elevated serum creatinine levels or type 1 diabetes mellitus were also less likely to receive beta blockers. Patients undergoing more aggressive treatments, such as thrombolysis or angioplasty, were more likely to receive beta blocker therapy. Overall, patients who received beta-blocker therapy had fewer risk factors for mortality, including younger age, better left ventricular ejection fraction and fewer coexisting illnesses, than those who did not receive beta-blocker therapy.
Evaluation of individual subgroups revealed that treatment with beta blockers was associated with a reduction in mortality of 40 percent in patients who had sustained a myocardial infarction but had no other complications. A reduction in mortality of 40 percent occurred in patients with COPD or non–Q-wave infarctions. A reduction of 36 percent occurred in patients with diabetes mellitus. However, treatment with beta blockers resulted in a reduction in mortality of only 28 percent in black patients; in patients older than 80 years and patients with a left ventricular ejection fraction below 20 percent, mortality rates decreased only 32 percent.
The authors conclude that mortality from myocardial infarction was reduced in every subgroup of patients who received beta blockers. However, as previous studies also reported, these drugs are widely underused. Had beta blockers been prescribed more widely, more than 19,000 deaths could have been prevented in this cohort of over 200,000 patients. In addition to otherwise healthy patients, those with heart failure, pulmonary disease, advanced age and non–Q-wave infarctions may benefit from therapy with beta blockers after a myocardial infarction.