Diseases involving the aorta can present a challenge to both surgeons and anesthesiologists. Aortic dissection and rupture are life threatening, require rapid and accurate diagnosis, and need definitive medical and/or surgical management due to their high risk of morbidity and mortality.1,2 A key ingredient in the efficient management of these patients is imaging of the thoracic aorta. Transesophageal echocardiography (TEE) has become an essential noninvasive diagnostic modality for acute thoracic aortic pathologies, and is a standard part of the echocardiographer's armamentarium in the operating room.3–6 It is important for the echocardiographer to quickly and accurately verify the diagnosis, distinguish true pathology from the many common confounding artifacts, and clearly communicate precise echocardiographic findings of the aorta and related cardiac anatomy to the surgeon in order to guide intervention. The following text reviews aortic anatomy and pathology and associated echocardiographic features that assist with imaging during aortic surgery.
In order to truly appreciate the invaluable role that TEE plays in the assessment for diseases of the aorta, a detailed understanding of the aorta and surrounding anatomic structures is crucial. The thoracic aorta can be divided into three anatomic segments: ascending thoracic aorta, aortic arch, and descending thoracic aorta (Figure 16–1). The ascending thoracic aorta originates at the level of the aortic valve annulus. As previously described in Chapter 9, the aortic valve comprises three crescent-shaped leaflets that coapt to form three commissures. Immediately distal to the aortic valve apparatus is a short and dilated aortic segment—the sinus of Valsalva—which is subdivided into the noncoronary, left coronary, and right coronary sinuses. As the nomenclature suggests, the left and right coronary arteries each originate from their respectively named sinus. Distal to the sinus of Valsalva, the aorta slightly narrows, forming the sinotubular junction (STJ). From this point, the ascending aorta crosses beneath the main pulmonary artery, then courses in an anterior, cranial, and rightward direction over the origin of the right pulmonary artery.
Anatomic course of the thoracic aorta. The relationship with the esophagus is particularly important with regard to orientation of the probe and the aorta in each of its thoracic sections: the ascending aorta, aortic arch, and descending aorta. The interposition of the trachea makes portions of the ascending aorta and arch either completely invisible or partially visible.
The ascending aorta terminates and continues as the aortic arch at the origin of the brachiocephalic (innominate) artery. The aortic arch then proceeds to curve in a posterior and leftward direction with cranial convexity. Three arteries arise from the aortic arch: the brachiocephalic, left common carotid, and left subclavian arteries. It is often difficult to visualize the distal ascending thoracic aorta and proximal aortic arch with TEE because the trachea is positioned between the esophagus and aorta, effectively preventing ultrasound transmission. Immediately beyond the origin of the left subclavian artery, at the point ...