An innovative noninvasive respiratory stress test indicates significant coronary artery disease

Respiratory maneuvers can uncover manifestations of myocardial ischemia. Some pulse wave characteristics are strongly associated with significant coronary artery disease (S-CAD). An innovative test using the respiratory stress response (RSR) has been developed for the detection of S-CAD. It is based on spectral analysis of finger pulse wave oscillations measured by photoplethysmography during deep, paced breathing at a rate of six breaths per minute (0.1 Hz) over 70 s.

RSR was assessed, prior to the procedure, in 150 consecutive patients referred for coronary angiography. It was calculated by analyzing the relative spectral power of the respiratory peak area at 0.1 Hz, using proprietary software. The coronary angiograms were analyzed by quantitative coronary angiography by 1 cardiologist who was blinded to the RSR results. S-CAD was defined as luminal stenosis >70% of > or = 1 coronary artery with a diameter > or = 2 mm, or left main stenosis >50%. A valid RSR was obtained in 150 of 153 patients (98%) with a mean age of 58.7 + or - 10.6 years (67% males).

S-CAD was found in 36 patients (24%). S-CAD patients had significantly lower RSR compared to patients without S-CAD (6.7% + or - 5.1 vs. 17.4% + or - 10.6; P<.001, respectively). Multivariate logistic regression analysis, adjusted for known CAD risk factors, showed that RSR is a strong independent indicator of S-CAD (odds ratio 41.2, 95% CI 12.2-139.3; P<.001).

The innovative RSR test is a simple, noninvasive bedside or office-based tool for the detection of S-CAD.