A simple blood test that can be completed in 15 minutes can show whether a patient presenting with congestive heart failure has restrictive cardiomyopathy or constrictive pericarditis, according to an article in the June 7 issue of the Journal of the American College of Cardiology.

In the study, American researchers found significantly higher levels of the cardiac hormone, brain natriuretic peptide, in the blood of patients with restrictive cardiomyopathy versus constrictive pericarditis.

“This is an important discovery because, while the symptoms are similar for both types of heart failure, the diagnosis, treatment and prognosis are very different,” said lead author Fred Leya, MD. “By examining the brain natriuretic peptide level in congestive heart failure patients, we can quickly determine whether they have restrictive cardiomyopathy or constrictive pericarditis. As a result, we can provide the appropriate treatment much sooner.”

The test is based on the fact that myocardium releases excessive amounts of brain natriuretic peptide in response to heart failure. Therefore, as expected, patients with both types of failure have higher levels than patients with normal hearts. Yet, patients with restrictive cardiomyopathy have significantly elevated levels compared with patients with constrictive pericarditis.

“The reason for this is because constrictive pericarditis patients have a rigid or scarred pericardium ? the sac-like membrane covering the heart,” said Leya. “As a result, the chambers of the heart are “restrained,” and cannot expand and fill with blood to function normally. When this happens, the heart muscle wall cannot stretch as much and release brain natriuretic peptide.”

For the study, Leya and colleagues measured hormone levels in 11 patients suspected of having constrictive or restrictive heart failure. Five patients had restrictive cardiomyopathy and six had constrictive pericarditis confirmed by hemodynamic assessment. “The mean plasma brain natriuretic peptide levels of the restrictive cardiomyopathy group were four times that of the constrictive pericarditis group (825 pg/mL vs. 128 pg/mL, respectively),” said Leya, who is developing a registry of patients to further expand the study.