Objectives: Despite the recommendations to initiate β-blockade to all patients with an ST-segment elevation myocardial infarction, data concerning the timing of the administration of β-blockers are controversially discussed. In view of these controversies, we analyzed the effect of immediate vs. delayed β-blockade on all-cause mortality of patients with ST-segment elevation myocardial infarction in the Lower Austrian Myocardial Infarction Network.
Design: Nonrandomized, prospective observational cohort study.
Setting: Myocardial infarction network including the out-of-hospital emergency services, five primary-care hospitals and a percutaneous coronary intervention-capable hospital in the western part of Lower Austria.
Patients: The data of all patients with ST-segment elevation myocardial infarction defined according to the American Heart Association criteria and treated according to the treatment protocol of the network were consecutively collected. For the purpose of survival analyses, the baseline survival time was set to 48 hours after the first electrocardiogram, and in all patients with recurrent MI within the observational period, only the first MI was regarded.
Interventions: The treatment protocol recommended either the immediate oral administration of 2.5 mg bisoprolol (within 30 min after the first electrocardiogram) or 24 hours after acute myocardial infarction (delayed β-blockade).
Measurements and Main Results: In total, out of the 664 patients with ST-segment elevation myocardial infarction, 343 (n = 52%) received immediate β-blockade and 321 (48%) received delayed β-blockade. The probability of any death (baseline survival time: 48 hours after first electrocardiogram; 640 patients) was 19.2% in the delayed treatment group and 10.7% in the immediate treatment group (p = 0.0022). Also the probability of cardiovascular mortality was significantly lower in the immediate β-blocker treatment group (immediate treatment group: 9 (5.2%); delayed treatment group: 30 (13.4%); p = 0.0002). Multivariable Cox regression analysis identified immediate β-blocker therapy to be independently protective against death of any cause (odds ratio: 0.55, p = 0.033).
Conclusion: Immediate β-blocker administration in the emergency setting is associated with a reduction of all-cause and cardiovascular mortality in patients with ST-segment elevation myocardial infarction and seems to be superior to a delayed β-blockade in our patient cohort.