DK2985_C000 1..28 - AlSharqia Echo Club

Aorta 277(A)(B)AoLATVRAFL TLPVRV(C)FALSE LUMENFigure 12.26 A 59-year-old woman with sudden onset of severe chest pain while swimming was admitted after the diagnosis of aorticdissection was made with computed tomography scan and confirmed intraoperatively. (A, B) The aortic dissection involved the proximalascending aorta and all the rest of the aorta down to the iliac arteries. (C) Intraoperative view. Note the false lumen (FL) (Ao, aorta;LA, left atrium; PV, pulmonic valve; RA, right atrium; RV, right ventricle; TL, true lumen; TV, tricuspid valve). (Photo C courtesyof Drs. Nicolas Noiseux and Raymond Cartier.)the diagnosis of dissection. In a report by Adler et al. (20),the sensitivity, specificity, positive, and negative predictivevalues for CT scanning were 83%, 100%, 100%,and 86% respectively. Corresponding values for aortographywere reported to be at 88%, 94%, 96%, and 84%.While Nienaber et al. (30) reported a sensitivity of 100%for both TEE and MRI, the specificity of TEE was lower(68%) than that of MRI (100%). Nevertheless, TEE hasthe advantage of being more easily accessible at thebedside for hemodynamically unstable patients and mayalso be performed intraoperatively. This allows unstablepatients to be monitored and treated in a safe environment.As mentioned previously, a complete evaluation of theentire ascending Ao with TEE may sometimes be impossibledue to the trachea and/or the right mainstem bronchusinterfering with the visualization of the mid and distalascending aortic segments. Dissections discretely limitedto these blind areas could therefore be missed despitecareful TEE examination (31). An erroneous diagnosiscan also occur when there is increased aortic diameter(.5 cm), which is associated with a higher incidence oflinear artifacts (32). Other linear artifacts may also originatefrom pulmonary artery catheters (Fig. 12.22) andpericardial effusions (Fig. 12.23).The diagnosis of aortic dissection is based on the identificationof an intimal flap dividing the Ao into two separatechannels, the true and the false lumen (Figs. 12.24–12.27).Determining which lumen is the false one may sometimesbe difficult. Nevertheless, blood should not flow freelythrough the false lumen if it is a blind pouch. On 2Dimaging, the pulsatile lumen could represent the truelumen, while smoke-like or twirling spontaneous echo contrastsuggests sluggish or absent flow in the false lumen(Fig. 12.21). Color flow imaging and pulsed-wave (PW)Doppler may also confirm decreased flow in the blindfalse lumen (Fig. 12.25). However, these criteria may alsobe misleading in certain settings: indeed if the false lumenhas a proximal entry and a distal exit site, blood may flowfreely both in the false and true lumen. Epiaortic scanningcan be helpful to localize the site of intimal rupture.D. Associated ComplicationsIn addition to identifying the location and extent of dissection,evidence of associated complications must also besought. Aortic regurgitation may result from bothannular dilation of the aortic root and direct geometric disruptionof the support by the false lumen. The extent and