What are Beta Blockers — and what the REBOOT trial showed

What Are Beta Blockers?

Beta blockers are medicines that slow down your heart and make it work more gently. They do this by blocking the effects of a stress hormone called adrenaline (also known as epinephrine). When adrenaline is blocked, your heart beats more slowly and with less force, which lowers blood pressure and reduces strain on the heart.

Doctors commonly prescribe beta blockers for:

• High blood pressure (hypertension)

• Irregular heartbeats (arrhythmias)

• Heart failure (especially certain types)

• Chest pain (angina)

• Migraine prevention

• Anxiety symptoms like a racing heart before public speaking

Not all beta blockers are the same. Some mainly affect the heart, while others affect both the heart and other parts of the body, like the lungs. Your doctor chooses the right type depending on your health condition.

Examples include:

• Metoprolol and bisoprolol – mainly affect the heart

• Propranolol – works on the heart and other parts of the body

• Carvedilol – also relaxes blood vessels by blocking another type of receptor

In short, beta blockers help take the pressure off your heart and can also calm symptoms linked to stress and anxiety.

The REBOOT Trial — What It Was and Who Led It

The REBOOT trial was a large study carried out in Spain and Italy to answer an important question: Do all people who have had a heart attack really need to take beta blockers long-term, even if their heart is still pumping fairly well?

Traditionally, beta blockers are prescribed to almost everyone after a heart attack. But many of the older studies that supported this practice included patients whose hearts were weaker than those of many patients today. REBOOT focused on people who had a heart attack but whose heart’s pumping ability (called the ejection fraction) was still normal or only slightly reduced (40% or higher).

In the trial, thousands of patients were randomly assigned to two groups:

• One group continued to take beta blockers after leaving the hospital.

• The other group did not take beta blockers.

This way, researchers could see whether routine use of beta blockers in this specific group of patients made a difference in survival or risk of future heart problems.

The study was coordinated by the Spanish National Center for Cardiovascular Research (CNIC) along with several hospitals. The lead investigators included Dr. Borja Ibáñez and Dr. Xavier Rosselló. Dr. Valentín Fuster, who is the General Director of CNIC and a world leader in cardiology, supported the work and commented on the results.

Key findings from REBOOT and related analyses

• No clear benefit for most people with normal heart pumping (LVEF ≥40%).
  REBOOT found that in people whose heart was still pumping well after a heart attack, taking a beta blocker long-term did not reduce the combined risk of death, another heart attack, or hospital admission for heart failure. This challenges the old practice of automatically giving beta blockers to almost everyone after a heart attack.

• A concerning signal in women (subgroup finding).
  A more detailed analysis suggested that women who took beta blockers after a heart attack had worse outcomes than women who did not — a small but important difference. This was not seen in men. The finding needs careful interpretation and more study, but it has raised questions about whether women might need different doses or closer follow-up.

• Similar overall safety profile.
  The main trial did not show a big difference in side effects between people taking and not taking beta blockers.

What other studies and analyses still show

• People with weaker hearts still benefit.
  Separate studies and pooled analyses show that patients whose heart pumping is reduced (lower ejection fraction) do benefit from beta blockers. In other words, the REBOOT result applies mainly to people whose hearts are relatively healthy after the heart attack — not to those with clear heart weakness.

• Side effects and dosing matter.
  As expected, beta blockers can cause tiredness, slow heartbeat, cold hands, and similar effects. Some signals from REBOOT suggest higher doses may have been linked to worse outcomes in certain groups (for example, some women), so doctors should pay attention to dose and side effects.

Bottom line: REBOOT suggests we should stop automatically giving long-term beta blockers to every patient after a heart attack when their heart function is normal. Instead, treatment should be individualized — keeping beta blockers for people with weaker hearts or other clear reasons to use them.

What this means for clinicians and patients

• Individual decisions, not one-size-fits-all.
  Doctors should consider each patient’s age, sex, symptoms, other illnesses, and how well their heart pumps when deciding whether to continue beta blockers after a heart attack. People with reduced heart function or other good reasons should usually stay on the medicine.

• Don’t stop medicines suddenly.
  If you are taking a beta blocker, don’t stop it on your own. Stopping suddenly can be harmful. Talk with your cardiologist or GP before making any changes.

Broader implications and future research

REBOOT has prompted new studies and more analyses. Researchers now want to figure out: who exactly benefits from beta blockers, whether women need different doses, and how to tailor treatment based on individual risk. Guidelines will likely be updated as experts review the full evidence. Until then, doctors will weigh REBOOT’s findings alongside existing research and each patient’s situation.

Everyday life — what patients may notice on beta blockers

Many people on beta blockers feel fewer palpitations and tremors and do well on the medicine. Some people, however, notice unwanted effects like tiredness, dizziness, slower heartbeat, cold hands, or lower exercise capacity. For short-term anxiety relief (like before a speech), some doctors may prescribe low-dose beta blockers — but they’re not the first choice for long-term anxiety treatment. If side effects are a problem, patients should discuss dose changes or alternatives with their doctor.

Conclusion — concise takeaways

• Beta blockers remain important for patients with weakened heart pumping (reduced ejection fraction) and for other clear conditions.

• REBOOT found no overall benefit from routine long-term beta blockers after heart attack when the heart’s pumping is preserved; and it found a concerning signal in a subgroup of women. These results support tailoring treatment to the individual.

• Talk to your doctor before stopping or changing any heart medicine.

The Bottom Line

For patients recovering from a heart attack who still have reasonably good heart function, long-term beta-blocker therapy made no difference in survival, preventing another heart attack, or avoiding heart failure hospitalization.

In other words, in today’s era of modern cardiac care—where almost everyone gets stents, statins, and strong antiplatelet therapy—beta-blockers no longer appear to offer extra protection for this group of patients.

Related Articles:
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Sources:

• New England Journal of Medicine
  https://www.nejm.org/doi/10.1056/NEJMoa2504735

• Centro Nacional de Investigaciones Cardiovasculares
  https://www.cnic.es/en/noticias/nejm-lancet-cnic-led-reboot-clinical-trial-challenges-40-year-old-standard-care-heart

• European Society of Cardiology
  https://www.escardio.org/The-ESC/Press-Office/Press-releases/Beta-blockers-did-not-reduce-cardiovascular-events-in-selected-heart-attack-patients-in-the-REBOOT-trial

• European Heart Journal
  https://academic.oup.com/eurheartj/advance-

• Lancet / individual-patient data meta-analysis on β-blockers and LVEF subgroups.
  https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(25)01592-2/fulltext