The many roles of beta blockers

Since the 1960s, beta blockers have been the most effective medicines for treating and managing many heart diseases. Today, they are one of the most prescribed classes of drugs in the United States.

“Beta blockers can treat a wide range of heart-related problems, and perhaps best of all, they’re inexpensive and thus widely available for most people,” says cardiologist Dr. Patrick O’Gara with Harvard-affiliated Brigham and Women’s Hospital.

Here’s a look at how beta blockers work, who may need them, and how their use has changed (or not) over the years.

How beta blockers work

Beta blockers lower blood pressure and slow the heart rate. The process works like this.

Many cells throughout the body have what’s known as beta receptors. There are beta receptors in the heart, blood vessel walls, lungs, kidney, and even the brain. These receptors are stimulated by the stress hormones epinephrine and norepinephrine. Depending on the organ, the effects vary. In the heart and blood vessels, epinephrine and norepinephrine tend to accelerate heart rate, increase the force of heart contractions, and tighten blood vessel walls.

Beta blockers work by blocking beta receptors. This action prevents epinephrine and norepinephrine from binding to these receptors and thereby inhibits their action inside cells. This, in turn, reduces stress on the heart, slows the heart rate, and lowers blood pressure. Of the many available beta blockers used to treat heart conditions, doctors most often prescribe metoprolol (Lopressor, Toprol XL) or carvedilol (Coreg).

Old and new uses

Many of the original heart-related uses for beta blockers have remained the same over the decades. For instance, people take beta blockers to manage atrial fibrillation (afib), an irregular and rapid heart rhythm. People with coronary artery disease take them to prevent chest pain.

Doctors have long suggested taking a beta blocker if you have heart palpitations (a skipped, extra, or irregular heartbeat) caused by premature ventricular contractions. You also can be prescribed the drug as part of the standard therapy for heart failure — a condition in which the heart can’t pump enough blood to provide your body with the oxygen and nutrients it needs.

However, the use of beta blockers has evolved in some areas. For a long time, beta blockers were a mainstay for treating high blood pressure. Now, doctors have more effective therapies, such as calcium-channel blockers, ACE inhibitors, and angiotensin-receptor blockers. “Beta blockers still may be prescribed if these other therapies have not worked,” says Dr. O’Gara.

Beta blockers play a major role in treating heart attacks. Most heart attacks are caused by insufficient blood flow to a portion of the heart, depriving heart tissue of oxygen. People hospitalized for a heart attack are given a beta blocker to slow their heart rate and reduce stress on heart muscle cells, which helps limit permanent damage.

In the past, beta blockers were continued indefinitely after hospital discharge to protect against future heart attacks. However, new research suggests that might not be necessary for people whose heart was not damaged.

In a study published April 18, 2024, in The New England Journal of Medicine, researchers recruited 5,020 people (average age 65) who’d had a heart attack and had no significant heart damage based on an ejection fraction of at least 50%.

Ejection fraction reflects how well the heart’s left ventricle pushes out blood. An ejection fraction above 50% probably means there is no significant heart damage.

Participants were randomly assigned to take a daily beta blocker or a placebo. They were followed for an average of 3.5 years. Afterward, the scientists found that the beta blockers provided no overall benefit. The risk of a second heart attack or death from any cause was similar regardless of whether people took the beta blocker or the placebo. The two groups also did not differ significantly in the risk of being hospitalized for afib or heart failure.

According to Dr. O’Gara, the findings challenge the conventional belief that beta blockers are universally beneficial and necessary after a heart attack. “This should start a conversation about the future role of beta blockers for these patients,” he says. “If there is no heart damage from the attack, many people can do fine using aspirin therapy and a high-dose statin to protect against another heart attack.”

Like any medication, beta blockers have side effects. The most common are a slow heart rate and feeling cold, fatigued, or lethargic. If you suffer from any of these, talk with your doctor about modifying your dosage.

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