ABC | Volume 112, Nº6, June 2019

Statement Vascular Ultrasound Statement from the Department of Cardiovascular Imaging of the Brazilian Society of Cardiology – 2019 Arq Bras Cardiol. 2019; 112(6):809-849 Figure 13 – Types of polytetrafluoroethylene (PTFE) grafts. (A) Straight PTFE graft between the basilic vein and radial artery. (B) Loop PTFE graft between the basilic vein and radial artery. (C) Curved PTFE graft between the brachial artery and vein. (D) Loop PTFE graft between the great saphenous vein and femoral artery. 5.4.2. Protocol after Procedure 77,79,81 • Measurements of artery, vein, and anastomosis; - Ideal venous or arterial diameter: elbow – 4 mm; wrist – 3 mm - Minimum functional diameter: 2 mm • Flow volume: to obtain the effective flow volume through an AVFH, measure the diameter of the drainage vein by its inner edges (in cm), preferably with a transverse plane, to calculate its radius (R) and, consequently, its area (in cm²). Take this measurement farther from the anastomosis site of the fistula, where the color flow imaging shows no flow turbulence, usually 2 to 5 cm from the anastomosis. Find the flow in the same place of the vein where the diameter was assessed with pulsed wave Doppler. Locate the sample volume in the center of the vessel and correct the Doppler flow angle to up to 60°. Determine the mean flow velocity (V MEAN ) in cm/s with pulsed wave Doppler. Calculate the mean of 3 to 5 cardiac cycles. Apply the following formula: Mean flow (ml/min) = V MEAN (cm/s) × R 2 (cm 2 ) × π × 60 (s) The values below are used for normal flow volume of homologous and heterologous AVFH: • Brescia-Cimino fistula (radiocephalic) =614±242ml/min. • PTFE = 464 ± 199 ml/min. • Mean normal value = 514 ml/min. Fistulas with flow volume < 450 ml/min have a high risk of thrombosis in 2 to 6 weeks. The minimum functional flow volume for AVFH in the elbow is ≥ 200 ml/min, and in the wrist is ≥ 150 ml/min. Hyperflow is considered when the flow volume is > 3,000 ml/min. • Maturation protocol: 73,74,77 AVFH maturation consists of an increase in caliber and flow of the vessels used. Assess vessel diameter and structure (≥ 6 mm), flow volume (≥ 600 ml/min), and the distance between the vein and skin surface ≤ 6 mm. Wait at least 14 days; the ideal scenario is individualization with follow-up for each patient and interval superior to 30 days. If possible, wait 60 or even 90 days before the first canalization. Table 19 summarizes the main objectives of VUS findings. 832