Beta-blockers, medications that block the action of certain hormones on the heart, can benefit patients with certain serious heart problems such as diastolic heart failure, according to cardiologists at the Keck School of Medicine of the University of Southern California and Loma Linda University Medical Center.
Researchers presented two reports on the use of beta-blockers in patients with chronic severe mitral regurgitation, or MR, and congestive heart failure, CHF, at the American College of Cardiology's 54th Annual Scientific Session on March 7. These patients had a normal ejection fraction, a measure of how well the heart pumps out blood.
"Our findings are encouraging because there are no data on the survival benefit of medical therapy in CHF or severe MR patients with normal ejection fraction. CHF with normal ejection fraction, popularly referred to as diastolic heart failure, makes up nearly 50 percent of all CHF patients-and these patients have very similar mortality and morbidity as those with reduced ejection fraction," says Padmini Varadarajan, M.D., advanced cardiac imaging fellow in the Department of Cardiovascular Medicine at the Keck School of Medicine and the study's lead author.
In their first presentation, researchers showed that using beta-blockers as part of therapy significantly reduced risk of death for patients with chronic severe mitral regurgitation with normal ejection fraction.
The mitral valve separates the heart's left atrium from the left ventricle. With every heartbeat, oxygen-rich blood moves from the left atrium, a holding chamber, to the left ventricle, which squeezes or ejects the blood out to the rest of the body.
When the mitral valve does not close well, blood can flow from the ventricle back into the atrium-a condition called mitral regurgitation. That means blood flow to the rest of the body decreases, and the heart may have to work extra hard to compensate.
Doctors can see how well the left ventricle works by measuring the ejection fraction, which is the percentage of blood squeezed out of the ventricle with each heartbeat. An ejection fraction of 50 percent means the ventricle spurts out half its volume each time it contracts.
Healthy ejection fractions are 50 percent or higher; lower ejection fractions can mean heart disease. But patients may have normal ejection fractions and still have serious heart problems such as severe mitral regurgitation.
In the study, 32 percent of 869 participating mitral regurgitation patients were on a beta-blocker. Beta-blockers reduce the heart rate and the force of muscle contraction, thereby reducing oxygen demand on heart muscle.
The researchers found that beta-blockers increased patients' survival, independent of patients' age, gender, or whether they had coronary artery disease, diabetes, high blood pressure or valve surgery.
In a related poster, researchers showed the drugs' benefits to patients with diastolic heart failure-those with congestive heart failure, or CHF, who have normal ejection fraction.
Researchers studied 2,246 patients with CHF; 1,079 of them had normal ejection fractions. The patients were on a variety of CHF therapy regimens, which might include aspirin, diuretics, digoxin, ACE inhibitors and beta-blockers.
Beta-blockers were once thought risky for heart-failure patients. But the investigators found that after five years, 65 percent of patients treated with beta-blockers were alive, compared to 50 percent of those who received no beta-blockers. Beta-blocker therapy still showed a strong survival benefit after researchers adjusted for patients' age, gender, hypertension, diabetes and coronary artery disease.
Ramdas G. Pai, M.D., professor of clinical cardiovascular medicine at the Keck School and the study's senior author, explained that catecholamines-the hormones released in the body in stress situations such as heart failure and mitral regurgitation-are toxic to the heart muscle. Beta-blockers keep catecholamines from acting.
"For the first time, our large observational studies show that beta-blockers may have large benefit in CHF and severe MR patients with normal ejection fraction. However these findings need to be substantiated further by randomized clinical trials," she says. She and her colleagues are planning further study on the drugs.