###### Abstract  
Telemonitoring systems equipped with photoplethysmography-based contour analysis of the digital arterial volume pulse (DVP) can be optimal tools for remote monitoring of cardiovascular patients; however, the method is known to be sensitive to errors. We aimed to show that DVP analysis is a reliable method to track cardiovascular status. We used our proprietary SCN4 ALL telemedicine system and analyzed nine parameters derived from the DVP and its second derivative (SDDVP). First, we assessed the repeatability of system measurements by detecting artificial signals. Then test-retest reliability of human measurements was evaluated in healthy individuals under standardized conditions. The SCN4 ALL system analyzed each parameter with high accuracy (coefficients of variation (CVs) \(<\) 1%). Test-retest reliability of most parameters (stiffness index, reflection index, left ventricular ejection time index, b/a, heart rate) was satisfactory (CVs \(<\) 10%) in healthy individuals. However, aging index and d/a ratio derived from the SDDVP were more variable. Photoplethysmography-based pulse contour analysis is a reliable method to monitor cardiovascular status if measurements are performed with a system of high accuracy. Our results highlighted that SDDVP parameters can be interpreted with limitations due to (patho)physiological variations of the DVP. We recommend the evaluation of these parameters only in measurements where all inflections of SDDVP are detected reliably. pulse wave analysis; photoplethysmography; telemedicine; test-retest reliability; pulse contour +
Footnote †: journal:and not least provides clinically relevant information about the current cardiovascular status of the patient. The detection and analysis of digital arterial volume pulse (DVP) recorded by the photoplethysmographic (PPG) method is a perfect option as it fits all these requirements. In fact, the DVP tracks the changes of vessel diameter and blood volume in the arteries which occur due to arterial pulsation [3; 4], and hence its shape is identical to the digital arterial pulse wave. Mechanistically, the arterial pulse wave is a pressure wave that is initiated by cardiac ejection and runs through the arterial system. It is an invaluable source of information about the cardiovascular status of the patient, as its amplitude and contour are influenced by the dynamics of cardiac function, the elasticity of the arteries, and also by the pressure augmentation caused by the superimposing reflected pressure wave [5], which is highly affected by the tone of the resistance vessels. Moreover, all these factors are dependent on the current status of the autonomic nervous system. Not surprisingly, altered cardiovascular conditions (both physiological and pathological) cause well-defined characteristic changes in the shape and propagation velocity of the pulse wave [6; 7; 8; 9; 10; 11]. Therefore, by detecting the changes in pulse wave contour, it is possible to establish the cardiovascular status of the patient. Mathematical analysis of the pulse wave and DVP is well established in the literature [4; 12; 13; 14]. Several cardiovascular indices, termed pulse contour parameters, derived from the raw curve and from its first and second derivatives have been identified as measures of various elements of cardiac and vascular function (Figure 1). Alterations of these indices have been associated with cardiovascular pathologies such as arterial stiffness, atherosclerosis, hypertension, aging, diabetes, coronary heart disease, and heart failure [12; 13; 14; 15; 16; 17; 18; 19]. Undoubtedly, these scientifically well-established characteristics of PPG-based detection and analysis of DVP make this method an optimal tool for remote cardiovascular monitoring. Despite this, it has not gained ground in clinical practice so far.