The Impact of Gender on Beta Blocker Efficacy

Beta blocker drugs have long been considered a first-line treatment after a heart attack and have been proven effective for other cardiovascular conditions, such as high blood pressure, arrhythmias and congestive heart failure.

A large, international study concluded that the effectiveness of beta blockers may vary depending on the specific patient and their underlying heart condition. This finding will likely reshape clinical guidelines both in the U.S. and elsewhere.

A recently published landmark study found that patients who had a normal-functioning heart soon after a myocardial infarction did not benefit from beta blockers. The use of them may in some women — though not in men — may contribute to a higher risk of death and hospitalization. 

“It will make every cardiologist rethink treatment,” says Claudia Martinez, M.D., an interventional cardiologist with the University of Miami Health System. “And it will lead to more precision medicine, treatment tailored to the patient.”

This does not mean, however, that patients should stop taking their prescribed beta blockers on their own.

Speak to your cardiologist about any change in medication or treatment.

Pinpointing the effectiveness of beta blockers, particularly as it relates to women, is good news, she adds, because recuperating patients who can skip beta blockers after a heart attack will suffer from fewer side effects.

Known as the REBOOT trial (an acronym for Treatment with Beta-Blockers after Myocardial Infarction without Reduced Ejection Fraction), researchers followed 8,505 patients across 109 hospitals in Spain and Italy. Some were randomly assigned to receive beta blockers after hospital discharge, while others were not prescribed this medicine. All received standard follow-up care.

Researchers discovered that there was no difference between the two groups when considering recurrent heart attack, hospitalization for heart failure or rates of death.

However, a subgroup of women taking beta blockers actually experienced problems — a 2.7% higher risk of mortality during the almost four years they were studied. The higher risk applied to women who had normal cardiac function after a heart attack. Normal cardiac function was defined as having a left ventricular ejection fraction of 50% or higher.

What does ejection fraction mean?

Ejection fraction measures how efficiently your heart is able to pump out blood to the rest of your body. The higher number, usually between 50 and 70, means your heart is healthy. The lower fraction shows your heart’s difficulty in supplying blood.

Patients with reduced ejection fraction (<40%) or those with arrhythmias still benefit from beta blockers, says Dr. Martinez.

These drugs remain essential for managing heart rhythm and preventing further cardiac events in these populations. Beta blockers are actually a commonly prescribed medication used for the treatment of various conditions, including glaucoma, overactive thyroid, essential tremor and portal hypertension. These drugs work by blocking the effects of adrenaline in your body, slowing heart rate, reducing stress on the heart, and relaxing blood vessels. About 10% of the U.S. population takes them, according to the National Center for Health Statistics.

“We have been using them for years and years. They will continue to be standard treatment for the population that needs them,” she says.

The results of the REBOOT study didn’t surprise Dr. Martinez, as it dovetails with the evolution of therapies for heart attack patients.

Since the introduction of beta blockers in the 1960s, treatments for heart attacks have advanced considerably. Now, patients who arrive at the hospital are immediately treated with blood thinners and stents. Preventive therapies also have improved, including better imaging and interventions that target underlying causes. Most heart attack survivors today have normal ejections fractions of at least 50%.

In a statement from the American College of Cardiology agreed that “for patients with no signs of heart failure and a normal ejection fraction, this trial establishes that there’s no indication that routine use of beta blockers is beneficial.”

The REBOOT study also underscores the need for gender-specific treatment.

Older heart research, Dr. Martinez explains, was done mostly on men and “from there it was assumed it applied to women.” We now know that’s not necessarily true.

Women have smaller hearts and are more sensitive to blood pressure medications. In addition, heart disease manifests itself differently in women. Women, for example, are likely to store plaque buildup in the heart’s smaller blood vessels. Their heart attack symptoms tend to be back pain, shortness of breath and indigestion. Men, on the other hand, have plaque buildup in their major arteries. They also display the more typical chest pain as a sign of a heart attack.

“We are moving toward treatment that is more specific both in gender and ethnicity,” she explains. One-size-fits-all medicine misses the mark, and “by directing research and treatment it has been shown that we can improve outcomes.”

Written by Ana Veciana-Suárez, a regular contributor to the University of Miami Health System. She is an acclaimed author and journalist who has worked for The Miami Herald, The Miami News, and The Palm Beach Post.

Tags: Beta Blocker Side Effects, Cardiovascular Gender Differences, Claudia Martinez-Bermudez, Women and Heart Disease