Respiratory Stress Test Quickly Detects Coronary Artery Disease

A novel, noninvasive respiratory modulation response (RMR) test quickly and accurately detects the presence of significant coronary artery disease (sCAD).

Researchers at the Rabin Medical Center (Petah Tikva, Israel) tested a proprietary respiratory stress test based on pulse oximetry photoplethysmograph (PPG) readings on 97 consecutive patients referred for coronary angiography to exclude sCAD; mean patient age was 62, and most were men (77%). The PPG reading measured blood flow in the finger after 20 seconds of spontaneous breathing, followed by 70 seconds of paced breathing at 0.1 Hz; the data was captured and recorded immediately, and then processed using a spectral analysis algorithm that determined the RMR in a percentage value. Coronary angiography was performed on all subjects and analyzed by cardiologists who were blinded to the RMR results; coronary lesions with diameter stenosis of over 50% that required revascularization were classified significant.

The researcher found that patients in the study with sCAD had a lower RMR compared to patients with nonsignificant CAD, regardless of individual risk factors or previous clinical history of angina, myocardial infarction (MI), or angioplasty. Using receiver operating characteristic analysis, the researcher identified an RMR value lower than 30% to be the optimal cutoff for predicting significant CAD. There were no significant differences between patients with sCAD and those with non-sCAD with respect to the risk factors, apart from the fact that patients with sCAD had more incidences of recent (MI), while patients without sCAD did not. No side effects were reported. The study was published in the February 2010 issue of Euro Intervention Journal.

"Identifying significant coronary artery disease through noninvasive testing is very challenging,” said coauthor Ran Kornowski, M.D., director of the department of interventional cardiology.” This study shows that the Spirocor test is a simple and noninvasive test that independently predicts significant coronary artery disease in patients referred for a coronary artery evaluation.”

The proprietary respiratory stress test system was developed by Spirocor (Tel Aviv, Israel). The noninvasive PPG finger probe is 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 and determination of the RMR. A report is automatically generated and made available on a password secured Web site for the cardiologist to review and make a decision regarding future diagnostic and therapeutic steps.

Related Links:
Rabin Medical Center
Spirocor