Data analyzed for the article of Evaluating photoplethysmography-based pulsewave parameters and composite scores for assessment of cardiac function: A comparison with echocardiography

The study involved healthy volunteers (n=37, 21 female, 16 male, mean age 37.0, standard deviation: 11.4)), who claimed themselves healthy by filling out a detailed questionnaire, had normal BMI (18 - 25 kg/m2), had no history of smoking, and denied drinking alcohol regularly. Those who had been diagnosed with or had received treatment for diabetes or any CV disease were excluded from the study. Further exclusion criteria involved: pregnancy, previous cancerous disease, wearing false nails; SARS-CoV-2 infection in the last 6 months before the exam. The measurements were conducted at Semmelweis University's Városmajor Heart and Vascular Clinic. The study was approved by the Regional and Institutional Committee of Science and Research Ethics at Semmelweis University (Budapest, Hungary) (approval number 120/2018-3). Protocol In this study, we employed simultaneous recordings to capture and compare data from photoplethysmography (PPG) and echocardiography, ensuring synchronized measurement across both methodologies. PPG parameters were calculated by averaging measurements from each heartbeat during continuous recordings over a two-minute period. Concurrently, echocardiographic parameters were derived by averaging the data from 1-3 heartbeats, allowing for a direct comparison of cardiac function assessments between the two techniques, by the following. Echocardiography Blood pressure (BP) was measured thrice using an automatic sphygmomanometer before conducting a cardiac ultrasound scan. During the scan, the participant lay on the examination bed with the upper body undressed, positioned on the left side. 2D echocardiography examinations were performed with a GE Vivid E95 system with a 4Vc-D phased-array transducer (GE Vingmed Ultrasound, Horten, Norway). LV focused, ECG-gated datasets were obtained from parasternal long and short axis, apical four-chamber, apical three-chamber and apical two-chamber views at a minimum rate of 50 frames per second. Offline analyses of these datasets were performed after selecting the optimal heart cycle using commercially available software (Autostrain LV, TOMTEC Imaging Systems GmbH, Unterschleissheim, Germany). The algorithm automatically generated the endocardial contours of the cavities, which were manually corrected throughout the entire cardiac cycle. Speckle tracking technique was used for the deformation analysis. The assessed parameters can be found in Error! Reference source not found. PPG measurements During the cardiac ultrasound, a pulse waveform was recorded for 140 seconds using a special pulse oximeter on the patient's right index finger, with a 200 Hz sampling frequency (Shanghai Berry Electronic Tech Co., Ltd., Shanghai, China). The patient lay on their side, staying still. The oximeter, wirelessly connected to the SCN4ALL mobile app (E-Med4All Europe Ltd, Budapest, Hungary), sent the anonymized data in real time to a secure online database. The SCN4ALL software analyzed the signals, its proprietary algorithm identifies points of interest on the pulse wave from which it calculates over 30 morphological and pulse rate variability parameters online. Previous studies have provided insights into the system's reliability, repeatability, and detailed descriptions of its architecture and signal processing. [11], [12] (The SCN4ALL parameters assessed in this study are found in – List of echocardiographic and PPG parameters, with abbreviations and definitions.Table 1) Besides “conventional” PPG parameters, already known from the literature, composite parameters, called “Scores” were also analyzed. The different “Scores” are constructed using different combinations of parameters, each of which is assigned a value based on specific cutoff values along a monotonous or U-shaped Likert scale. The scores, with a maximum of 100, indicate health levels for evaluated aspects. Their actual reliability and validity in clinical practice are evaluated based on the current and upcoming studies. The exact constituents of the Scores are a proprietary secret, kept confidential at the manufacturer’s discretion.