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Doppler duplex ultrasonography (DDU) is used in arteriovenous fistula (AVF) monitoring to measure AVF access flow volume (Qa) and detect stenosis in real-time. However, there has not been a standardized protocol on the sites of Qa monitoring in AVFs. In theory, the outflow vein of the AVF should be an ideal site for Qa monitoring as it is punctured during dialysis, but the measured Qa may be imprecise as vein can be tortuous with turbulent flow, easily compressed by the transducer placement and may not have uniform diameter for precise cross-sectional area calculation. Conversely, the brachial artery does not collapse easily, has uniform diameter with laminar flow and may be the preferred site for measuring Qa. This study aims to determine the correlation between the brachial artery and outflow vein Qa estimated with DDU in AVFs.
This is a multi-center, longitudinal study of patients who underwent DDU assessment of AVF for surveillance post-angioplasty. All DDUs were performed by trained vascular technologists. Qa values were estimated at the mid-brachial artery and outflow vein while access circuit percent stenosis was measured by subtracting the diameters of the narrowest segment from the healthy segment of AVF x100%. Presence of >50% stenosis determined by DDU was considered significant anatomic stenosis. Pearson correlation was performed between Qa values estimated at the brachial artery and outflow vein of each case.
255 surveillance scans were conducted for 167 patients over 12 months. Of which, 55.1% were radiocephalic AVF, 29.9% were brachiocephalic AVF and 15.0% were brachiobasilic AVF. The correlation coefficient of brachial artery Qa to outflow vein Qa over all scans was 0.894 (p<0.001). Correlation coefficients of radiocephalic, brachiocephalic and brachiobasilic AVFs were 0.837 (p<0.001), 0.913 (p<0.001) and 0.902 (p<0.001) respectively. Subgroup analysis of AVFs with significant anatomic stenosis demonstrated correlation coefficient of 0.862 (p<0.001), while those without significant stenosis was 0.931 (p<0.001).
Conclusions
The results suggest that the brachial artery can be used reliably to estimate AVF access flow volume. Additional studies are needed specifically to validate the diagnostic sensitivity of brachial artery site selection in the detection of clinically significant AVF dysfunction.