Two new randomized trials - REBOOT and SMART-DECISION - just rewrote a 40-year standard of post-heart-attack care. For patients whose heart function stayed normal after their heart attack, beta blockers offered no benefit. In women, they may have been associated with worse outcomes. Cardiology guidelines worldwide are about to move. Here is the full data, the limits, and what to do.
Anatomical human heart model. The REBOOT trial finding applies specifically to patients whose heart function (LVEF) stayed above 40 percent after their heart attack. Photo: Wikimedia Commons, CC BY-SA 3.0.
1. The Finding in One Frame
REBOOT Trial - 2026 results
- Patients: Over 8,400 post-heart-attack survivors with preserved heart function (LVEF above 40 percent)
- Randomization: Beta blocker vs no beta blocker, within 2 weeks of hospital discharge
- Follow-up: Average 3.7 years
- Result: No significant difference in death from any cause, repeat heart attacks, or hospitalization for heart failure
- Women's sub-analysis: Higher risk of death, repeat MI, or heart failure hospitalization in the beta-blocker group
2. What Was the Standard of Care - And Why
Beta blockers (metoprolol, atenolol, bisoprolol, carvedilol and others) have been post-heart-attack textbook for 40 years. Photo: Wikimedia Commons, CC BY-SA 4.0.
Beta blockers became routine post-heart-attack care in the early 1980s after the Beta-Blocker Heart Attack Trial (BHAT), sponsored by the NHLBI. That trial showed a clear mortality benefit in the post-heart-attack population of that era.
The critical context: 1981 was a different cardiology world.
| Treatment Era | Background Care |
| BHAT (1981) | No widespread angioplasty, no stents, limited statins, limited dual antiplatelet therapy |
| REBOOT (2026) | Modern revascularization (stents, PCI), high-intensity statins, DAPT, ACE inhibitors / ARBs, SGLT2 inhibitors |
In other words: the patient walking out of a 2026 hospital after a heart attack is already on a much fuller protective regimen than the 1981 patient. The marginal benefit a beta blocker added in 1981 may simply have shrunk to zero - or in some patients, may have flipped negative - against today's baseline.
3. The Female Subgroup Finding
The female-patient sub-analysis is the part of REBOOT that is hardest to dismiss. Women taking beta blockers had a higher risk of death, repeat heart attack, or hospitalization for heart failure compared with women who did not take them. This is a directional reversal, not just an absence of benefit. It is also consistent with a longstanding concern that beta-blocker dosing and pharmacokinetics differ between men and women in ways post-1981 trials never fully addressed.
The clinical implication: even if guidelines continue to recommend beta blockers for narrowly indicated subgroups (reduced ejection fraction, heart failure), the sex-specific evidence will force a more careful conversation between cardiologists and female patients about whether the drug is right for them.
4. SMART-DECISION: It's Safe to Stop
Published alongside REBOOT this month, the SMART-DECISION trial showed that stable post-heart-attack patients without left ventricular dysfunction or heart failure could safely discontinue a beta blocker they were already taking - with non-inferior outcomes compared to those who continued.
Together, REBOOT and SMART-DECISION form a coherent two-part picture:
- REBOOT: Do not start a beta blocker in this population - it does not help.
- SMART-DECISION: If you are already on one, you can stop - it does not hurt.
5. Who STILL Benefits from Beta Blockers
This is the most important section and the part most likely to be lost in news coverage. The REBOOT finding is narrow. Beta blockers remain beneficial for:
| Indication | REBOOT applies? |
| Reduced ejection fraction (LVEF below 40 percent) | No - keep taking, benefit established |
| Diagnosed heart failure | No - keep taking, benefit established |
| Certain arrhythmias (atrial fibrillation, etc) | No - drug indication is separate |
| Hypertension management | No - different evidence base |
| Post-MI, LVEF over 40%, no other independent indication | Yes - REBOOT says no benefit |
Do not stop a prescribed medication based on a news article. Talk to your cardiologist.
6. The Guideline Question
Major cardiology bodies - the American Heart Association, the American College of Cardiology, and the European Society of Cardiology - update their post-MI treatment guidelines on a roughly 2 to 4 year cycle. With REBOOT and SMART-DECISION now both in the literature, expect guideline working groups to convene over the summer of 2026, with provisional guidance likely by late 2026 and full revised guidelines in 2027.
Several large health systems may move faster than the formal guidelines and adjust their internal post-discharge protocols within 3 to 6 months.
7. What to Ask Your Cardiologist
If you or a family member is on a beta blocker after a heart attack:
- What was my ejection fraction at discharge? If above 40 percent, REBOOT may apply.
- Is the beta blocker prescribed specifically for the heart attack, or for another indication (heart failure, arrhythmia, blood pressure)?
- Given REBOOT and SMART-DECISION, would you consider discontinuation - and on what timeline?
8. The Bigger Pattern
REBOOT is part of a larger 2020s pattern: long-standing standards of care are being re-tested against modern baseline therapy, and a non-trivial fraction of them are not surviving the re-test. Aspirin for primary prevention. Routine PSA screening past 70. Routine post-MI beta blockers. The mechanism is the same: when baseline care improves, the marginal benefit of any single drug shrinks - sometimes to zero, sometimes below.
9. What to Watch Next
- Full REBOOT publication - the New England Journal of Medicine or European Heart Journal version will give us the granular subgroup data
- AHA / ACC / ESC guideline statements - provisional guidance likely by Q4 2026
- Health system pilot programs - large integrated health systems (Kaiser, Cleveland Clinic, Mayo) often move on internal protocols before formal guidelines
- Sex-specific cardiology research - the female subgroup finding should accelerate funding for women-specific cardiac drug research, an area chronically underfunded
Sources
- ScienceDaily: Common heart drug taken by millions found useless and possibly dangerous (May 2026)
- European Society of Cardiology: REBOOT trial press release
- European Heart Journal: Beta-blockers after MI - effects according to sex in REBOOT
- Medscape: Stable patients may safely end beta blockers post-MI (SMART-DECISION)
- ABC News: Doctors may need to rethink decades of routine beta blocker use
- Mount Sinai: Beta blockers may offer no benefit after heart attack, women can have worse outcomes
- ClinicalTrials.gov: NCT00000492 - Beta-Blocker Heart Attack Trial (BHAT, 1981)