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 compression indicates obstruction between the compression site and the location of the sample flow. Retrograde flow occurs when there is valve damage. Thus, valve regurgitation is a pathological sign, which can warn to the presence of previous thrombosis, and valve agenesia or venous reflux secondary to hyperflow should be ruled out. Table 22 describes VUS characteristics that assist in the identification of stages of venous thrombosis. Valsalva and inspiration and expiration maneuvers help and add information (Table 23). 6.3. Rethrombosis High risk of recurrent venous thromboembolic disease persists after DVT treatment, with a cumulative incidence of these complications close to 30% in eight years of follow-up; among them, mortality reaches 30%, mainly due to malignant diseases. 100,101 Relevant predictive factors for risk of recurrence are male gender, thrombus location, and D-dimer. 102 Other less known risk factors are residual thrombus occupying 50% of the vessel lumen diameter after treatment and failure in normalization of compression with VUS. 101 As the non-invasive diagnosis of recurrence is difficult, some ultrasound criteria can be used, such as: • Measurement of the residual thrombus mass. • Abnormalities in the thrombus extension. • Ultrasound characteristics of the thrombus – low echogenicity, slight compressibility, presence of tail, adhesion to the wall, and increase in venous diameter (≥ 2 times the contralateral vein, or compared to the diameter of the adjacent artery). 100,101,103 Table 22 – Characteristics of different stages of deep venous thrombosis observed in vascular ultrasound Stage Acute Intermediate (subacute) Chronic Event time Up to 14 days 14 to 28 days > 28 days Vessel caliber Dilated Still dilated, normal, or slightly reduced Usually reduced Incompressibility Total or partial Total or partial Partial or absent Thrombus aspect Hypoechoic Isoechoic Hyperechoic Parietal irregularities Fibrotic residues Residual thrombus: caliber > 2 mm after maximum compression in 6 months or > 3 mm in two consecutive examinations Flow Absent or partial Flow channels permeating the thrombotic mass Can have microfistula Multiple flow channels permeating the thrombus Complete lumen filling Presence of collaterals Continuous flow or reduced amplitude spectrum Can have orthostatic reflux 6.4. Examination Technique Some protocols assess only the proximal segment (femoropopliteal) or the compression VUS of two points (common femoral vein and popliteal vein). These protocols, known as point of care, facilitate the examination by emergency physicians and are proving to be an alternative in the emergency room. 106 However, evaluating the entire venous system is important for a proper DVT diagnosis, better assessment in case of recurrence, and to assist in the differential diagnosis with other pathologies. This guideline recommends always performing a full examination. 107,108 In lower limbs, the patient should be in a comfortable supine position with the torso and head elevated up to 30°, close to the edge of the bed, on the same side of the examiner, with a slight lateral rotation of the hip and slight knee flexion. In upper limbs, the patient should be in the supine position, with the limb stretched alongside and slightly away from the body. Examine the deep venous system starting with the inguinal fold, gently compressing the veins with the transducer, using transverse planes. 85,104,105 The goal is to confirm the absence Table 23 – Venous flow variation according to the phase of the respiratory cycle Flow Inspiration Expiration Lower limbs ↓ ↑ Upper limbs ↑ ↓ Subclavians ↑ ↓ 837