Experimental study of a new method for early detection of vascular access stenoses: pulse pressure analysis at hemodialysis needle.

Hemodialysis vascular access (VA) stenosis remains a frequent complication. However, early detection is challenging and costly. The aim of this in vitro study was to assess a new detection method based on pulse pressure analysis at the hemodialysis needle. A silicon model of a radiocephalic arteriovenous fistula was built in a mock loop. Pressure profiles were measured at the arterial hemodialysis needle and in the proximal feeding artery. Stenoses (50 and 25% diameter reduction) were created proximal to the anastomosis (proximal artery) and distal to the arterial needle (distal vein and proximal vein). The pulse pressure (PP) at the needle was divided by the PP at the feeding artery to obtain a dimensionless ratio, %PP. Experiments were conducted at different blood flow (500-1200 mL/min) and heart rates (60-90 beats/min) to test this new index over a wide range of hemodynamic conditions. In the control model (no stenosis), %PP was 20.26 +/- 4.55. A proximal artery 50% stenosis significantly decreased %PP to 7.69 +/- 2.08 (P < 0.0001), while the presence of 50% stenosis in the distal (36.20 +/- 2.12) and proximal (32.38 +/- 2.17) vein led to significantly higher values of %PP (P < 0.0001). For stenosis of 25% diameter reduction in the proximal artery, the %PP decreased to 15.45 +/- 2.13 (P = 0.0022) and the %PP increased with a 25% stenosis in the distal vein to 26.71 +/- 3.01 (P = 0.0003) and in the proximal vein to 26.53 +/- 2.67 (P = 0.0004). This in vitro study shows that the analysis of the PP at the dialysis needle is useful for early detection and localization of hemodialysis VA stenosis, independent of heart rate and flow level.