Assessment of vasoactive agents and vascular aging by the second derivative of photoplethysmogram waveform

The paper that defined the second-derivative aging index (b−c−d−e)/a. In 39 patients, d/a from the fingertip PPG tracked drug-induced changes in ascending-aortic pressure augmentation (r≈0.8 with augmentation indices). In 600 health-check subjects, the aging index rose with age (r=0.80) and was higher in people with diabetes, hypertension, hypercholesterolemia or ischemic heart disease than in age-matched controls.

• Form factor: finger

—To evaluate the clinical application of the second derivative of the fingertip photoplethysmogram waveform, we performed drug administration studies (study 1) and epidemiological studies (study 2). In study 1, ascending aortic pressure was recorded simultaneously with the fingertip photoplethysmogram and its second derivative in 39 patients with a mean±SD age of 54±11 years. The augmentation index was defined as the ratio of the height of the late systolic peak to that of the early systolic peak in the pulse. The second derivative consists of an a, b, c, and d wave in systole and an e wave in diastole. Ascending aortic pressure increased after injection of 2.5 μg angiotensin from 126/74 to 160/91 mm Hg and decreased after 0.3 mg sublingual nitroglycerin to 111/73 mm Hg. The d/a, the ratio of the height of the d wave to that of the a wave, decreased after angiotensin from −0.40±0.13 to −0.62±0.19 and increased after nitroglycerin to −0.25±0.12 ( P P r =0.79, P r =0.80, P y ) increased with age ( x ) ( r =0.80, P y =0.023 x −1.515). The second derivative aging index was higher in 126 subjects with any history of diabetes mellitus, hypertension, hypercholesterolemia, and ischemic heart disease than in age-matched subjects without such a history (−0.06±0.36 versus −0.22±0.41, P P <0.01). The b-c-d-e/a ratio may be useful for evaluation of vascular aging and for screening of arteriosclerotic disease.

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