Non-invasive evaluation of coronary heart disease in patients with chronic kidney disease using photoplethysmography

Background: Chronic kidney disease (CKD) patients have an increased risk for coronary artery disease (CAD) and myocardial infarction. Therefore, there is a need to identify CKD patients at high risk of CAD. Coronary angiography, the gold standard for detecting CAD, carries a risk of serious adverse events.

Methods: Here, we assessed the validity of a novel non-invasive reflectance mode photoplethysmography (PPG) sensor for the evaluation of CAD in patients with advanced CKD. PPG signals were generated using green and infrared wavelengths and recorded from fingers of 98 patients. The detected signal has the shape of the pulse wave contour carrying information about the vascular system, that is, arterial stiffness. We studied four patient groups: (i) controls-patients without CKD or CAD; (ii) CKD alone; (iii) CAD alone (confirmed by coronary angiography); and (iv) CKD and CAD combined.

Results: With advancing age, we observed a steeper ascending signal during systole and greater signal decline during diastole (infrared wavelength: Slopes 4-6, P = 0.002, P = 0.003 and P = 0.014, respectively; green wavelength: Slopes 2-3, P = 0.006 and P = 0.005, respectively). Presence of CAD was associated with a slower signal decline during diastole in CKD patients compared with those without CAD (infrared wavelength: Slope 1, P = 0.012). CKD was associated with lower blood volume amplitude during each cardiac cycle compared with those without CKD (R-value, P = 0.022).

Conclusions: PPG signal analyses showed significant differences between our groups, and it may be a potentially useful tool for the detection of CAD in CKD patients.