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 signal and attenuate (acoustic shadowing) structures in the distal field until contrast concentrations drop to a proper level. In addition, distinguishing small enhancing differences between structures is not possible, given that the upper limit of dynamic range (grayscale) of the equipment has been exceeded. 128 One way of highlighting different enhancing levels caused by contrast in a structure is to adjust the dose of contrast to allow adequate opacification, without blurring or attenuation, and increase the dynamic range of the equipment. In turn, low doses will not reach the opacification level desired. 8.3. Indications for Contrast in Vascular Ultrasound Table 28 lists the main indications for microbubble contrast agents in US studies of different vascular systems (consensus of the European Federation of Societies for Ultrasound in Medicine and Biology, published in 2011). 129 The levels of evidence, based on multicenter and/or single-center studies, were classified as A (good), B (moderate), and C (recommended by expert consensus). 8.4. Preparation, Application, and Dose of Microbubble Contrast SonoVue ® is a kit that includes: a vial with 25 mg of lyophilized powder in an atmosphere of sulfur hexafluoride; a syringe filled with 5 ml of sodium chloride 9 mg/ml (0.9%) solution; a transfer system. The contrast is easy to prepare at the bedside, following the manufacturer’s instructions. After transferring the content of the syringe to the vial with powder, shake it for 20 seconds to create microbubbles and transform the saline solution into a milky suspension (indicating homogeneous microbubble distribution). In this state, the suspension can be stored for up to 6 hours. If microbubbles accumulate on the surface during rest, shake the solution again, so the microbubbles regain homogeneous distribution before use. The usual route of administration is by intravenous bolus injection in a vessel with caliber suitable for puncture with a needle of 20G in diameter (preferably in the antecubital fossa) . Administer a small initial volume, followed by a flush of 5 ml of saline solution at 0.9% to push the contrast agent into the central vein (which happens in seconds). In most publications, the recommended dose for a single injection in VUS studies is 2.4 ml, ranging from 1 to 4.8 ml, according to the organ studied, the probe used, and the sensitivity of the equipment available (always remembering that probes with higher frequencies need higher doses, in this case, 4.8 ml). 7 The first 10 to 40 seconds after bolus injection correspond to the contrast enhancement curve (wash-in and wash-out) and should be continuously recorded for later analysis. In some specific situations, such as the study of late endoleaks, the period of evaluation can reach 5 minutes; in these cases, shorter videos can be recorded. Bear in mind that the higher the MI, the greater the destruction of bubbles, and shorter the duration of contrast. After the bubbles burst, the lungs quickly (2 minutes) and fully eliminate the sulfur hexafluoride (Anvisa). SonoVue ® is a safe agent, with a low complication rate. Reports of anaphylactic reaction correspond to < 0.002% of cases. Table 28 – Indications for contrast agents in vascular ultrasound System Application Level of evidence Probe Carotids Occlusion or subocclusion In-stent stenosis Dissection Plaque neovascularization B B C B Linear Aorta Dissection, extension of the flap to branches, false lumen patency, re-entry points, and perfusion level of branches that originate from false lumen C Convex abdominal or sector cardiac Differentiation between an inflammatory aneurysm and contained rupture Endoleak B A Intracerebral vessels Signal increase in unsatisfactory basal study Perfusion in ischemic CVA A C Sector cardiac Complications in vascular accesses Arteriovenous fistulas Pseudoaneurysms, hematomas C C Linear or convex abdominal or sector cardiac Kidney Signal increase in the renal artery Renal perfusion C C Convex abdominal or sector cardiac Lower limbs Obstructive atherosclerotic disease (assessment of collateral circulation and microcirculation) Deep venous thrombosis (signal improvement and inflammatory reaction in perithrombus) C C Linear or convex abdominal CVA: cerebrovascular accident. 843