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Background There is a lack of evidence regarding the benefits of β-blocker treatment after invasively managed acute myocardial infarction (MI) without reduced left ventricular ejection fraction (LVEF). Methods and results TREatment with Beta-blockers after myOcardial infarction withOut reduced ejection fraction (REBOOT) trial is a pragmatic, controlled, prospective, randomized, open-label blinded endpoint (PROBE design) clinical trial testing the benefits of β-blocker maintenance therapy in patients discharged after MI with or without ST-segment elevation. Patients eligible for participation are those managed invasively during index hospitalization (coronary angiography), with LVEF >40%, and no history of heart failure (HF). At discharge, patients will be randomized 1:1 to β-blocker therapy (agent and dose according to treating physician) or no β-blocker therapy. The primary endpoint is a composite of all-cause death, nonfatal reinfarction, or HF hospitalization over a median follow-up period of 2.75 years (minimum 2 years, maximum 3 years). Key secondary endpoints include the incidence of the individual components of the primary composite endpoint, the incidence of cardiac death, and incidence of malignant ventricular arrhythmias or resuscitated cardiac arrest. The primary endpoint will be analyzed according to the intention-to-treat principle. Conclusion The REBOOT trial will provide robust evidence to guide the prescription of β-blockers to patients discharged after MI without reduced LVEF.

Patients with an uneventful course during hospital stay, which represent from 30 to 50% of all myocardial infarction survivors, still have an incidence of new coronary events up to 7% during the first year of follow-up. To assess the value of radionuclide angiography in predicting new coronary events in this low risk population, 93 patients without evidence of left ventricular failure or recurrent postinfarction angina underwent rest and exercise radionuclide angiography and treadmill exercise testing before hospital discharge. During follow-up (16 +/- 5 months, range 12 to 32) 14 patients developed new coronary events: two patients died, four had a new myocardial infarction and the remaining eight had unstable angina. There were no differences regarding clinical variables, the results of the exercise test and the resting ejection fraction, between patients with or without new coronary events; however, patients without events during follow-up exercised longer during both exercise treadmill test and exercise radionuclide angiography. Resting end-diastolic and end-systolic volume indexes were higher in patients presenting coronary events (122 +/- 50 vs 92 +/- 32 ml.m-2, P < 0.05, 69 +/- 47 vs 47 +/- 26 ml.m-2, P < 0.05). These patients also had a higher incidence of wall motion abnormalities in more than one area (64 vs 28%, P < 0.02). During exercise, ejection fraction increased significantly in patients with an uneventful outcome (49 +/- 13 to 56 +/- 14%, P < 0.01), while it did not change in their counterparts (46 +/- 14 to 45 +/- 14%, NS).(ABSTRACT TRUNCATED AT 250 WORDS)

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