Two large scientific trials have shown that common pills used for decades remain beneficial for heart attack patients even with modern treatments that can prevent permanent heart muscle damage.

It remains unclear whether all patients or only some benefit from so-called beta-blockers, which are typically prescribed after anyone suffers a heart attack.

Two sharply contrasting reports were presented yesterday at a major cardiology conference in Madrid and published in the New England Journal of Medicine.

Dr. Borja Ibañez from the Carlos III National Center for Cardiovascular Research in Madrid, who led one of the trials, said, “It is not uncommon for trials to yield different results.”

He added, “It is quite unusual, however, to see two trials with clearly divergent outcomes presented on the same day.”

Ibañez said the most important agreed-upon finding is that beta-blockers reduce the risk of another heart attack, heart failure, or death in patients without heart failure but with mild heart dysfunction.

The question remains: are these pills beneficial for patients with normally functioning hearts, who make up about 80% of patients after a first heart attack?

Among companies producing beta-blockers are Mylan, Novartis, and Pfizer.

These drugs work by inhibiting the hormones epinephrine and norepinephrine, lowering heart rate and blood pressure, reducing the heart’s workload, and decreasing its oxygen demand.

Both new trials included survivors of heart attacks whose hearts still contract normally, meaning the left ventricle pumps at least 40% of the blood with each beat. Both trials followed patients for about three and a half years.

The Betami-Danbloc study involved 5,574 volunteers from Norway and Denmark and showed clear benefits. Researchers found that patients randomly assigned to receive beta-blockers had a 15% lower risk of death or cardiac problems, especially recurrent heart attacks, compared to those who did not take the pills.

However, among 8,438 participants in the Reboot trial in Italy and Spain, beta-blockers had no effect on death from any cause, recurrent heart attacks, or hospitalization due to heart failure.

Researchers reported in the European Heart Journal that among Reboot participants, those taking beta-blockers—especially women with good heart function receiving higher doses—experienced more adverse outcomes than those not taking the drugs.

In Reboot, researchers noted a 40 to 49% reduction in rates of new heart attacks, heart failure, or death among patients with mild heart dysfunction who took beta-blockers.

Ibañez said the message to cardiologists is that “we can now confidently say that beta-blockers are beneficial” for patients with mild heart dysfunction.

He added, “There remains reasonable uncertainty about their benefit” for patients whose hearts function normally.