Assessing AVF Dysfunction with Access Stenosis Using Smartphone Videos

Kidney Week 2020

Among patients receiving hemodialysis using arteriovenous fistulas (AVF), hemodynamically relevant stenosis in the AVF are associated with a reduction in access flow rate. Lin-Chun Wang, MS, and colleagues conducted a study to test the hypothesis that the changes in blood flow patterns may be detectable in video recordings done with commercially available smartphones.

Results of the study were reported during a virtual poster session at ASN Kidney Week 2020. The poster was titled Assessment of Arteriovenous Fistula Dysfunction with Access Stenosis in Hemodialysis Patients Using Smartphone Videos.

The study cohort included patients on hemodialysis with AVF dysfunction requiring balloon angioplasty. One-minute video recordings of the skin above the AVF and access flow rate measurements were performed using an iPhone 6S prior to and following the intervention. Access flow rate was measured by HVT100 Transonic flowmeter. Angiography was used to assess the degree of stenosis.

Frame-to-frame pixel changes in video images were amplified; time-domain data were transformed into the frequency-domain signals. Per each 1-minute video, 50 random 10-second segments were sampled; the researchers determined the frequency with the lowest magnitude in each sample. The average frequency magnitude was examined for its association with the degree of stenosis.

The study cohort included 90 hemodialysis patients. Of those, mean age was 63 years and mean hemodialysis vintage was 4.1 years. Post-intervention access flow rate (1638 mL/min) was, on average, 1.23-fold higher than preintervention access flow rate (1373 mL/min), P<.01, paired t-test).

Participants were categorized by degree of stenosis. There was an association between higher degree of stenosis and increase in access flow rate from before to after the intervention. The degree of AVF stenosis was also positively related to the change in frequency magnitude from before to after the intervention.

In conclusion, the researchers said, “Smartphone video recordings of AVF appear to contain frequency-domain information that correlates with hemodynamic changes caused by AVF stenoses. While the frequency magnitude metric employed in our analysis is not ideal, these results should encourage the quest for other parameters that exhibit higher correlations with vascular access dysfunction, allowing timely referrals and avoidance of emergency interventions.”

Source: Wang L-C, Zhu F, Thwin O, et al. Assessment of arteriovenous fistula dysfunction with access stenosis in hemodialysis patients using smartphone videos. Abstract of a poster presented at the American Society of Nephrology virtual Kidney Week 2020 (PO1344), October 22, 2020.