Assessment of atherosclerosis in erectile dysfunction subjects using second derivative of photoplethysmogram

Cardiovascular diseases are the main cause of death worldwide. Stiffing of the arterial wall is normally related with the beginning, or the progression of atherosclerosis. Atherosclerosis plays an important role in loss of the elastic properties of arteries walls. Thereby, atherosclerosis might cause harmful damage to arteries which in turn might cause cardiovascular disease and erectile dysfunction. Carotid intima-media thickness (CIMT) is used to measure atherosclerosis in parallel with the recording of Photoplethysmogram (PPG) from samples of erectile dysfunction subjects (68 patients). The results revealed PPG and clinical indices were correlated to CIMT. An index extracted from PPG 2ndderivative (b/a ratio) was found to be a good measure of high-risk of atherosclerosis in parallel with CIMT measurement. In addition, pulse pressure (PP) which is an indicator of arterial stiffness, was found to be positively correlated to CIMT. PP, b/a index and subject’s height (H) were used to predict a high-risk of atherosclerosis by means of a logistic regression model. The developed model showed a sensitivity of 76.4% and specificity of 64.7% in the prediction of high-risk of atherosclerosis. In addition, the Nagelkerke R-square was better in backward logistic regression (0.372) compared to forward logistic regression (0.288). Thus increases in thickness of the intima and media of the carotid artery, as measured by CIMT, are directly associated with a decreased of b/a index values and increased of PP values. Thereby, PPG is recommended to be used as an assistant technique in the prediction of high-risk of atherosclerosis.   Key words: Photoplethysmogram (PPG), carotid intima-media thickness (CIMT), pulse pressure (PP), arterial stiffness and atherosclerosis.