Cardiac Respiratory Stress Test Detects Significant Coronary Artery Disease

Testing a patient's cardiac respiratory stress response (RSR) can quickly and accurately detect the presence of significant coronary artery disease (S-CAD), according to new study.

Researchers at Washington Hospital Center (WHC; DC, USA) conducted a prospective observational cohort study involving 153 consecutive patients (referred for coronary angiography with symptoms or signs suggestive of CAD) who underwent the cardiac RSR test. A pulse oximetery photoplethysmography (PPG) device was used to measure blood flow in the finger in response to paced breathing over a 90 second time period; the data were immediately captured and analyzed using a proprietary algorithm to determine cardiac RSR. Coronary angiography was performed on all subjects and analyzed by one cardiologist blinded to the subject's clinical data and RSR, using a validated quantitative coronary angiography (QCA) algorithm.

The results showed that a valid RSR was obtained in 150 patients (98%); 36 patients (24%) were found to have S-CAD, of whom 31 had single-vessel disease and five had multi-vessel disease. The mean RSR was significantly reduced in patients with S-CAD, regardless of age, gender, the existence of risk factors, and medical treatment, suggesting RSR is a strong indicator for the disease. The researchers found that when compared to QCA-- using a receiver operating characteristic curve analysis--the test results were highly accurate, with a sensitivity of 86% and a specificity of 81%. No adverse events were reported. The study was published in the January 2010 issue of Cardiovascular Revascularization Medicine.

"It is always challenging to detect significant coronary artery disease in patients at the physician's office and often required a physical stress test, including nuclear imaging and often cardiac catheterization,” said lead investigator Ron Waksman, M.D., associate director of the division of cardiology at WHC. "The RSR test is simple and fast to perform in a doctor's office without the need for significant expense and hardship to the patient, and the results of the study support its accuracy to detect significant coronary artery disease. We believe it could be a useful diagnostic option.”

The RSR test features a noninvasive PPG finger probe connected to a computer with analyzing software residing on a central server, accessed via the Internet. The patient performs a controlled breathing exercise, which consists of inhaling and exhaling seven times. The PPG signal is automatically captured and the data transmitted for analysis; a RSR report is then automatically generated and made available on a password secured website for the cardiologist to review and make a decision regarding the next diagnostic and therapeutic step.

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