#4500 IMPLEMENTATION OF A NEW GENERATION DIGITAL STETHOSCOPE FOR ARTERIOVENOUS FISTULA MONITORING IN HEMODIALYSIS PATIENTS

Abstract Background and Aims The management of complications of arteriovenous fistula (AVF) for hemodialysis, principally stenosis, remains a major challenge for clinicians with a substantial impact on health resources. Stenosis not infrequently preludes to thrombotic events with the loss of AVF functionality. A frequent monitoring with physical examination is at the basis for an appropriate clinical care. It includes a regular inspection, palpation and auscultation of the arm. A normally functioning AVF, when listened by a stethoscope, has a continuous systolic-diastolic low-frequency murmur while with stenosis the frequency of the murmur increases and the duration of diastolic component decreases, disappearing in severe stenosis. These evidences are strictly subjective and dependent from operator skill and experience. New generation digital stethoscopes are able to record sound and subsequently dedicated software allows to extract quantitative variables (amplitude and frequency) that characterize the sound in an absolutely objective and repeatable way. The aim of our study was to analyze with an appropriate software listenable sound from AVFs taken by a commercial digital stethoscope and to investigate the potentiality to develop an objective new monitoring system to detect stenosis. Method Between September 2022 and January 2023, we screened forty-eight patients from two hemodialysis centers in Catanzaro (Italy). Patients were screened from two blinded experienced examiners for recognized criteria for stenosis by doppler ultrasound (DUS). We recorded the sound coming from the AVFs using a 3M™ Littmann® CORE Digital Stethoscope 8570 (Figure 1-A), in standardized sites: on the anastomosis chamber, at a distance of 5 and 10 cm from it, on the site of stenosis and immediately after. The sound waves were transformed into quantitative variables (amplitude and frequency) using a sound analysis software. Results Based on doppler evaluation, 14/48 patients (29%) were classified as stenotic of which three were hemodynamically significant. The sounds detected in the stenosis sites had a significant higher average frequency compared to non-stenotic sites (Figure 1-B). Characteristics of sound waves were significant different for stenotic and non-stenotic patients in term of average power, mean amplitude and mean frequency. Analysis of waves permitted us to determine peculiar shape for stenosis and another for normal AVF (Figure 1-C,D). Conclusions The analysis of sound waves by a digital stethoscope permitted us to distinguish between stenotic and no stenotic AVFs. The standardization of this technique and the introducing of data in a deep learning algorithm could allow an objective and fast method for a frequent monitoring of AVF.