Eur J Cardiothorac Surg 1999;16:240-242
© 1999 Elsevier Science NL
The formation of two layers detectable by intraoperative echocardiography is a reliable predictor of late thrombosis within the false lumen of a dissected aorta
Masahiro Yoshida,
Yutaka Okita,
Motomi Ando,
Soichiro Kitamura
Department of Cardiovascular Surgery, National Cardiovascular Center, 5-7-1 Fujishirodai, Suita, Osaka 565, Japan
Corresponding author. Tel.: +81-6-68335012; fax: +81-6-68727486
e-mail: yokita{at}hsp.ncvc.go.jp
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Abstract
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The subjects consisted of one patient with chronic type A and three patients with chronic type B aortic dissection, who underwent replacement of an aorta obliterating distal false lumen. After the repair, the formation of two layers was detected by direct scanning echocardiography within the false lumen even during heparinization. In all cases, postoperative computed tomography confirmed complete thrombosis of the false lumen. The formation of two layers was considered to be a reliable predictor of late thrombosis.
Key Words: Echocardiography • Thrombosis • Aortic dissection
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1. Introduction
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Intraoperative transesophageal echocardiography or direct scanning echocardiography is a useful diagnostic modality to interpret hemodynamic change within the cardiac chambers and great arteries [1]. In this report, we describe the formation of two distinct layers demonstrated by intraoperative direct scanning echocardiography in a false lumen of an aortic dissection, where exclusion from the blood stream could predict late thrombosis. We call it ‘niveau formation’ referring back to the ileus sign in radiography.
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2. Case report
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Patient no. 1 was a 45-year-old male presenting with lumbago. His physical examinations and laboratory tests were unremarkable. Computed tomography (Fig. 1a) demonstrated a huge chronic type A aortic dissection extending from the ascending aorta to the bilateral common iliac arteries. A wide intimal tear was detected in the arch. The maximum diameters of the ascending aorta, arch, upper descending aorta, lower descending aorta, infrarenal abdominal aorta, and common iliac artery were 65 mm, 80 mm, 75 mm, 82 mm, 68 mm, and 45 mm, respectively. Urgent surgery was performed because of persistent back pain. Transesophageal intraoperative and direct scanning echocardiography (Hewlett Packard Co. Ltd.; 5.0/3.5 MHz; Aloka Co. Ltd.; 5 MHz) disclosed that all the aortic branches, including the brachiocephalic artery, left common carotid artery, left subclavian artery, common trunk of the celiac and superior mesenteric artery, and right and left renal arteries, were arising from the true channel and that no intimal tear existed in the descending aorta until the level of the diaphragm. Under deep hypothermia with retrograde cerebral perfusion, total replacement of the ascending aorta and aortic arch was performed. Distal to the left subclavian artery, the descending aorta was transected, and a collagen-impregnated woven Dacron graft (Hemashield, 20 mm in diameter and 12 cm in length; Meadox Inc., Oakland, NJ) was inserted into the true lumen of the descending aorta as an ‘elephant trunk’. The proximal stump of the descending aorta, including the elephant trunk, was anastomosed with the arch graft. After weaning from the cardiopulmonary bypass, the infrarenal aorta was replaced with a bifurcated albumin-coated Dacron knitted graft (DeBakey, 20x10 mm; C.R. Bard, Inc., Billerica, MA). Intraoperative echocardiography through the median laparotomy demonstrated the formation of two layers including an upper clear layer and a lower dense layer, in the false lumen of the descending aorta (Fig. 1b). No Doppler flow signal was detected within the false lumen. The postoperative course was uneventful, and computed tomography showed a complete thrombosis of the false lumen of the descending aorta down to the diaphragm (Fig. 1c,d). The digital subtraction angiography showed a complete repair of the aortic dissection that meant no flow in the false lumen (Fig. 1e).
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Fig. 1. (a) Preoperative computed tomography of case 1. A huge chronic type A aortic dissection extending from the ascending aorta to the bilateral common iliac arteries. (b) Intraoperative direct scanning Doppler echocardiography. The formation of two layers between an upper clear liquid layer and a lower dense layer in the false lumen of the descending aorta. Blood flow was detected only in the true lumen (*). (c) Postoperative computed tomography of case 1: complete thrombosis of the false lumen of the descending aorta. (d) Postoperative computed tomography of case 1: complete thrombosis of the false lumen that was almost the same portion of (b). (e) Postoperative digital subtraction angiography shows no flow in the false lumen.
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Patients nos. 2–4 (Table 1) had chronic type B aortic dissection and underwent graft replacement of the descending aorta obliterating the distal false lumen. All cases revealed similar formations of two layers in the distal false lumen after aneurysm repair and postoperative computed tomography confirmed complete thrombosis of the false lumen.
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3. Discussion
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It has been shown that intraoperative echocardiography, either transesophageal or by direct scanning, is an indispensable diagnostic modality for assessing instantaneous intra- or postoperative hemodynamics [1]. In aortic surgery, intraoperative echocardiography provides precise mapping not only of the deceptive anatomical relationship between the true and false lumens of the aortic dissection, but also of lesions of the aortic wall such as calcification, atherosclerotic ulcerations or plaque, and mural thrombi in the aortic aneurysm [1]. In this report, the formation of two layers detected by intraoperative direct scanning echocardiography in the excluded false lumen of the aortic dissection is described as a characteristic feature predicting late thrombosis. Generally, two layers are formed in a boundary between two layers of different physical nature, such as a gas and a liquid [2]. In present cases, the blood confined within the aortic false lumen after exclusion from the blood stream was separated by gravity into two distinct parts, an upper clear liquid layer and a lower dense layer, the former representing the cell free plasma components and the latter, the cell components. This phenomenon never occurs where active movement of the blood contents exists. The resultant thrombosis was confirmed by postoperative computed tomography or angiography. No report that describes such a sign has been found in the published literature.
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References
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Takamoto S., Kyo S., Yokote Y., Omoto R. Decision-making by transcutaneous and transesophageal Doppler color flow mapping followed by intraoperative direct scanning in dissecting aortic aneurysm. In: Minami K., Korfer R., Wada J., eds. . Amsterdam: Elsevier, 1992 pp. 103–114.
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Gregg E.C., Palogallo G.L. Acoustic impedence of tissue. Invest Radiol 1969;4:357-363.[Medline]
Received November 10, 1998;
received in revised form April 19, 1999;
accepted April 28, 1999.
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Abstract
1. Introduction
