Role of Transesophageal Echocardiography in Dissection of the Aorta and Evaluation of Degenerative Aortic Disease

Abstract

The combination of different ultrasound techniques such as transthoracic, suprasternal, subcostal, and TEE has a high sensitivity and specificity in the diagnosis of aortic dissection. Limitations of this combined ultrasound technique are related to the visualization of the ascending part of the aortic arch, which, because of the interposition of the trachea, cannot be visualized completely. The beginning or end of a dissection in this part of the aorta may be misinterpreted. However, false-negative results are rare. False-positive results due to artifacts resulting from reverberations in an ectatic ascending aorta must be taken into account. The most important diagnostic goals in acute or chronic aortic dissection are (1) confirmation of the diagnosis by visualization of the intimal membrane; (2) the differentiation of true and false lumen, depending on visualization of spontaneous echocardiographic contrast, thrombus formation, slow or reduced reversed flow, systolic diameter reduction, and signs of entry jet into the false lumen; (3) detection of intimal tear, demonstrating communication by 2-D or color Doppler echocardiography; (4) determination of the extent of dissection with classification according to DeBakey types I, II, and III, or Stanford types A and B, with differentiation between communicating or noncommunicating dissection and antegrade or retrograde dissection limited to the descending aorta or expanding into the ascending aorta; (5) detection of wall motion abnormalities as a sign of preexisting coronary artery disease or myocardial ischemia due to ostium occlusion by an intimal flap, coronary artery rupture, or collapse of the true lumen during diastole; (6) detection and grading of aortic insufficiency; (7) detection of side branch involvement by suprasternal, subcostal, and abdominal sonography (which will provide information about the choice of the site for cannulation or catheterization of the femoral artery); and (8) detection of pericardial or pleural effusion and mediastinal hematoma as signs of an emergency situation (i.e., suspending rupture). Based on ultrasound diagnostic information, operation can be performed in all acute situations in patients with type A dissection without further investigation. The ability to act decisively in this setting is particularly important in patients with signs suggesting a dire prognosis (i.e., pericardial or pleural effusion or mediastinal hematoma). For follow-up studies, the combination of echocardiography with MR tomography is recommended. With TEE, entry tears can be detected with a higher sensitivity than with MR tomography. This capability may be important for the patient's prognosis. MR tomography, on the other hand, has a better spatial resolution showing the entire aorta, particularly the ascending aortic arch.