#4524 TRIBOELECTRIC EVALUATION OF ARTERIOVENOUS FISTULA FOR HAEMODIALYSIS: A PILOT STUDY
Authors: Presta Pierangela , Oliva Giuseppe , Musolino Michela , Fabiano Giuseppe , Carullo Nazareno , Armeni Annarita , Chiarella Salvatore , Andreucci Michele , Fiorillo Antonio , Bolignano Davide , Pullano Salvatore , Coppolino Giuseppe 
Published: June 2023

Abstract

Background and Aims
Determination of stenosis in an arteriovenous fistula (AVF) for hemodialysis is an essential step in the management of patients with end-stage kidney disease. Stenosis, or narrowing of the blood vessels, can significantly reduce blood flow and ultimately lead to thrombosis and dysfunction of the AVF. Therefore, accurate and frequent surveillance is crucial for detection of stenosis and for the proper management of AVF. Surveillance of AVF is based on direct methods including ultrasound imaging and magnetic resonance angiography both dependent from examiner availability and not ever regularly repeatable. The triboelectric effect refers to the phenomenon where certain materials become charged after coming into contact with another material. In blood vessels the rubbing of erythrocytes against each other and arterial and vein wall generates a negative triboelectric charge and an electric potential range directly related to flow rate. The aim of our study was firstly to investigate the potential reliability of a wearable device able (Figure 1A) to record this constant potential and consequently evaluating the aptitude of waveforms generated to detect AVF stenosis in comparison to standard doppler evaluation.

Method
Between September 2022 and January 2023, we screened forty-eight patients from two hemodialysis centers in Catanzaro (Italy) Patients were divided in two groups basing on the assessment from two blinded experienced examiners for recognized criteria for stenosis: 2 major criteria (reduction of vessel size greater than 50% and a ratio between systolic peak velocity (SPV) in the stenotic region and SPV in pre-stenotic region major of 2 (&gt;2)) and a supplementary finding like drop of the access flow [QA] below 500ml/min or drop of QA&gt;25% as compared to the previous measurements in FAV with QA&lt;1000ml/min or residual diameter &lt;2mm). Patients were then evaluated using the PVDF/Kapton triboelectric sensor placed in contact with the skin on the lower surface, and with the thumb in contact with the upper surface to close the circuit and graphically recording typical pattern waveform generated. AVFs were analyzed considering the following acquisition sites: the chamber which corresponds to the site where surgery anastomosis was performed, a site located 5 cm from the chamber, and finally at the level of the humeral artery.

Results
There was an almost perfect (R = 0.97) correlation between the blood flow measured at the humeral artery level and the maximum-time derivative equation computed for each patient (Figure 1B). Based on doppler evaluation, 14/48 patients (29%) were classified as stenotic. Of these, 13 patients (93%) presented a typical wave pattern (B-point) with a ‘Notch’ shape (Figure 1D) which, conversely, was found in only 1 patient out of 34 without evidence of stenosis. The presence of Notch reflected the presence of stenosis with a Sensitivity of 92,8% (95%CI 66,1 to 99,8%), a specificity of 97% (95%CI 84,7 to 99,9%), holding an overall accuracy of 95,8% (95%CI 85,7% to 99,5%). Patients without stenosis assumed a different waveform (Figure 1C).

Conclusions
In chronic hemodialysis patients, the evaluation of AVF by a biosensor based on triboelectric potential measurement might represent an accurate and easy-to-perform surrogate of standard eco-doppler method for a quick and reliable evaluation of AVF functioning and, particularly, for a rapid risk stratification of patients with high suspect of AVF stenosis.