Among the 230 patients studied, 188 patients (82%) underwent TEE to rule out a spontaneous AD, while the remaining 42 patients (18%) were examined for a suspected TDA after sustaining severe blunt chest trauma. The TEE findings are summarized in Figure 2.
Frequency of Aortic Flaps and Linear Artifacts: In the 81 patients with proven AD (Stanford type A, n = 36; Stanford type B, n = 45), an intimal flap was visualized within the ascending (Fig 3, top left, A) and the descending thoracic aorta (Fig 3, top right, B) in 36 patients and 72 patients, respectively (Fig 2). Traumatic disruption of the aortic isthmus was diagnosed by the presence of a medial flap within the proximal descending aorta in 11 victims of violent deceleration accidents (Fig 2, 3, bottom left, C).
Linear artifacts were observed in the ascending and descending segments of the thoracic aorta in 59 of 230 patients (26%) and 17 of 230 patients (7%), respectively. Of patients with reverberant images within the ascending aorta, 42 of 59 patients (71%) had a normal thoracic aorta. In contrast, no evidence of associated AD or TDA was found in patients with linear artifacts located in the descending thoracic aorta. Of these, four patients (2%) with an otherwise normal thoracic aorta exhibited a linear artifact in both the ascending and descending thoracic aorta. In 13 of 45 patients (29%) with confirmed Stanford type-B aortic dissection and 4 of 11 patients (36%) with proven traumatic disruption of the aortic isthmus, a linear artifact was also evidenced in the ascending aorta (Fig 3, bottom right, D).
Diagnostic Criteria Associated With Linear Artifacts: TEE parameters predictive of the presence of a linear artifact within the ascending aorta using univariate analysis are presented in Table 1. Linear artifacts were thicker than aortic flaps (3.9 ± 1.6 mm vs 2.6 ± 1.2 mm; p < 0.001) and consistently appeared nearly horizontal in the aortic lumen in the transversal view (Fig 4, top left, A, and top right, B), as reflected by a larger angle between the linear image and the ascending aortic wall (91 ± 10° vs 72 ± 39°; p < 0.001). None of the patients in whom a linear artifact was noticed within the ascending aorta had an associated pericardial effusion or evidence for an entry tear. In the presence of an intimal flap in the ascending aorta (Fig 4, bottom left, C), the flap had different orientations within the aortic lumen and overimposition of blood flow was never observed using color Doppler echocardiographic mapping (Fig 4, bottom right, d). Using the logistic regression model, the following criteria were selected as independent predictors of the presence of linear artifact in the ascending aorta: (1) displacement of the linear image parallel to aortic walls (odds ratio, 7.2; CI, 1.3 to 40.0; p = 0.02); (2) similar blood flow velocities on both sides of the linear image (odds ratio, 47.6; CI, 3.4 to 500.0; p = 0.004); (3) thickness of the linear image > 2.5 mm (odds ratio, 4.8; CI, 0.9 to 26.2; p = 0.06); and (4) an angle between the linear image and the aortic wall > 85° (odds ratio, 5.9; CI, 1.1 to 32.2; p = 0.04).
Figure 2. Flow chart summarizing the TEE findings obtained in protocol A. * = more than one linear image may be observed in a single patient (see text for details); ** = intimal flaps refer to spontaneous ADs; *** = medial flaps refer to TDAs.
Figure 3. TEE longitudinal views of the thoracic aorta obtained in four distinct patients with intraluminal linear images (white arrows). The intimal flap associated with type-A AD (top left, A) appears thinner than the linear artifact observed in the ascending aorta (bottom right, D). The medial flap associated with subadventitial traumatic disruption of the aortic isthmus (bottom left, C) also appears thicker than the intimal flap of the type-B AD (top right, B). Note that the medial flap is almost perpendicular to the aortic walls, as opposed to the intimal flap that remains rather parallel to the walls.
Figure 4. Two-dimensional TEE (top left, A; bottom left, C) and color Doppler echocardiographic mapping (top right, B; bottom left, D) of the ascending aorta in a patient with an intraluminal linear artifact (top left, A; top right, B), and in a patient sustaining a type-A AD (bottom left, C; bottom right, D), for comparison. The linear artifact (top left, A, arrow) appears thicker than the intimal flap of the dissection (bottom left, C, arrow), near horizontal, and exhibited movement parallel the aortic walls in real time. Using color Doppler echocardiography, blood flow velocities appear similar on both sides of the artifact, laminar, and overimposed on the linear image (top right, B). In contrast, high-velocity and turbulent blood flow that does not appear overimposed on the intimal flap of the proximal AD is observed within the true lumen, while the false lumen is not circulating (bottom right, D).
Table 1—Univariate Analysis of TEE Parameters Used To Distinguish Between Intraluminal Linear Artifacts and Flaps of Ascending Aorta
|Variables||Artifact (n = 59)||Flap (n = 36)||Odds Ratio||95% CI||p Value|
|Displacement parallel to aortic walls||55 (93)||8 (22)||47.6||13.3-166.7||< 0.001|
|Poorly defined borders||35 (59)||6 (17)||7.3||2.6-20.0||< 0.001|
|Image not confined to aortic lumen||35 (59)||6 (17)||7.3||2.6-20.0||< 0.001|
|Similar blood flow velocities on both sides||58 (98)||10 (28)||142.8||18.2-1000.0||< 0.001|
|Absence of blood flow turbulence||52 (88)||11 (31)||16.9||5.8-47.6||< 0.001|
|Absence of significant aortic regurgitation||54 (82)||19 (53)||9.7||3.1-29.4||< 0.001|
|Thickness > 2.5 mm||44 (75)||12 (33)||7.0||2.7-18.1||< 0.001|
|Angle > 85°||36 (61)||9(25)||5.2||2.0-13.2||< 0.001|