Noninvasive test of blood flow response may reveal early coronary disease

Chest pain patients who have abnormal coronary blood vessel function also have less responsive blood vessels in their fingertips, suggesting that a type of fingertip probe could become a useful screening tool, according to a new study in the Dec. 7, 2004 issue of the Journal of the American College of Cardiology.

“This test is a noninvasive and easy-to-perform technique to assess peripheral endothelial function that has the potential to become a valuable tool for cardiovascular risk stratification in daily clinical practice,” said Amir Lerman, M.D., F.A.C.C., at the Mayo Clinic in Rochester, Minn.

The test, reactive hyperemia peripheral arterial tonometry (RH-PAT), uses a probe that measures how the volume of a fingertip changes as blood pulses through it. After a baseline measurement, a blood pressure cuff is inflated to restrict blood flow in the arm for five minutes. The key measurement is how blood vessels in the fingertip respond to the initial rush of blood after the cuff is released.

The researchers, including lead author Piero O. Bonetti, M.D., studied 94 patients with chest pain who had been referred for coronary angiography testing. The patients did not have obstructive coronary artery disease, according to their angiography tests. However, the responsiveness of coronary blood vessel linings (endothelial function) was abnormal in 55 of the patients.

Normally, RH-PAT shows a distinct increase after blood flow is restored in the arms of subjects, but overall the fingertip blood vessels of the patients with abnormal endothelial function showed a more muted response.

“All of the currently available tests for the assessment of endothelial function are more or less invasive or operator-dependent, which precludes their use as a screening tool for endothelial dysfunction in clinical practice. In contrast, RH-PAT is noninvasive, easy to perform and operator independent,” Lerman said. “Various studies demonstrated that the presence of endothelial dysfunction is an independent risk factor for cardiovascular events. Importantly, various interventions, such as treatment of cardiovascular risk factors and certain drugs, including statins, were shown to improve endothelial function in patients with endothelial dysfunction. Thus, early detection of endothelial dysfunction may have both prognostic and therapeutic implications,” he added.

Despite these results showing a correlation between the fingertip test and endothelial function, Lerman said that RH-PAT needs to be tested in a variety of patients. Also, he pointed out that this study just compared the results of different tests, and researchers still need to find out if the fingertip tests can predict important health outcomes, such as coronary artery disease.

Krishna Sudhir, M.D., Ph.D., F.A.C.C., at Stanford University in Palo Alto, Calif., who was not connected with this study, said that since several therapies for coronary artery disease are available, including aspirin, statins and ACE-inhibitors, there is considerable interest in noninvasive methods for assessing people who are at risk.

“Coronary artery endothelial dysfunction has been shown to predict cardiovascular events. This study describes a novel noninvasive approach using a finger probe to measure digital hyperemia; that is, maximum blood flow to the finger, which appears to be a good index of coronary artery endothelial dysfunction. Thus the technique shows promise as a potential noninvasive tool, to diagnose early coronary artery disease,” Dr. Sudhir said.

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