Author + information
- Received March 13, 1996
- Revision received May 9, 1996
- Accepted May 14, 1996
- Published online October 1, 1996.
- VÍCTOR G DÁVILA-ROMÁN*,
- KENNETH J PHILLIPS,
- BILL B DAILY,
- ROSA M DÁVILA,
- NICHOLAS T KOUCHOUKOS and
- BENICO BARZILAI ()
- ↵*Address for correspondence: Dr. Víctor G. Dávila-Román, Cardiovascular Division, Box 8086, Washington University, 660 South Euclid Avenue, Saint Louis, Missouri 63110.
Objectives. This study sought to determine the role of transesophageal echocardiography (TEE) and epiaortic ultrasound in the detection of atherosclerosis of the ascending aorta in patients undergoing cardiac surgery.
Background. Atherosclerosis of the ascending aorta is a major risk factor for perioperative stroke and systemic embolism in patients undergoing cardiac surgery.
Methods. Forty-four patients underwent prospective evaluation of the ascending aorta with two ultrasound techniques—epiaortic ultrasound and biplane TEE—and by palpation. The severity of atherosclerosis was graded on a four-point scale as normal, mild, moderate or severe.
Results. A comparison of results with biplane TEE and those with epiaortic ultrasound yielded a kappa value of 0.12 (95% confidence interval 0 to 0.25), indicating poor correlation between the two. Compared with epiaortic ultrasound, biplane TEE significantly underestimated the severity of ascending aortic atherosclerosis, and this underestimation was more marked in the distal ascending aorta (p < 0.0001). When compared with epiaortic ultrasound and biplane TEE, palpation of the ascending aorta significantly underestimated the presence and severity of atherosclerosis (p < 0.0001 for both).
Conclusions. Epiaortic ultrasound is more accurate than TEE for identification of atherosclerosis of the ascending aorta, but both ultrasound techniques are superior to palpation. Epiaortic ultrasound and TEE provide complementary information regarding thoracic aortic atherosclerosis. Modification of surgical technique on the basis of results of intraoperative epiaortic ultrasound and TEE in elderly patients undergoing cardiac procedures may prevent atheroembolic complications.
Atherosclerosis of the ascending aorta has been recognized as one of the major risk factors associated with perioperative stroke and systemic embolization in patients undergoing cardiac surgery [1–6]. Autopsy studies have shown a strong relation between atherosclerosis of the ascending aorta and atheroembolic events [7, 8]. Approximately 20% of patients ≥50 years old undergoing cardiac surgery have thoracic aortic atherosclerosis, and this percentage increases with age [9, 10]. Thus, identification of atherosclerosis of the ascending aorta before extensive manipulation during cardiac surgery is important to prevent atheroembolic stroke and peripheral embolization.
Our group and others have previously shown [10–17]that evaluation of the ascending aorta with an ultrasound transducer placed directly over the ascending aorta (i.e., epiaortic ultrasound) is a very reliable technique for evaluation of this vessel, and results of ultrasound examinations correlate well with intraoperative or pathologic findings, or both. The use of transesophageal echocardiography (TEE) has been proposed for the identification of disease of the thoracic aorta [18–23], but there have been few studies evaluating the utility of TEE in the detection of atherosclerosis of the ascending aorta, particularly in patients undergoing cardiac surgery [24, 25]. The purpose of the present study was therefore to examine the utility of biplane TEE in the evaluation of the ascending aorta before cardiac surgery. Ultrasound images obtained with TEE were compared with those obtained with epiaortic ultrasound for the detection of atherosclerosis of the ascending aorta.
Patients. Forty-four patients ≥50 years old undergoing a cardiac surgical procedure that required cardiopulmonary bypass were prospectively studied with both biplane TEE and epiaortic ultrasound. The patients were selected on the basis of availability of both equipment and personnel to perform the two studies before cardiac surgery. The study protocol was approved by the Human Studies Committee at the Jewish Hospital of Saint Louis, as was the consent document signed by each patient before his or her operation. A total of 44 patients (28 men, 16 women; mean age 69 years, range 51 to 91) were enrolled. Fifteen patients (34%) were undergoing coronary artery bypass graft procedures (CABG), 11 (25%) CABG and valve surgery, 11 (25%) CABG and another procedure, 5 (11%) valve surgery alone and 2 (5%) other procedures. Thirty-seven patients (84%) underwent CABG surgery alone or in combination with other procedures.
Ultrasound methods.Transesophageal echocardiography. After induction of general anesthesia, a 5-MHz biplane TEE transducer (Acuson 510B) was inserted into the esophagus of each patient. The TEE study was performed by a cardiologist with expertise in evaluation of the thoracic aorta. Particular attention was given to the optimization of the ultrasound images of the ascending aorta, the aortic arch and the descending aorta in the transverse and longitudinal imaging planes. All studies were recorded on 0.5-in. S-VHS videotape for subsequent off-line evaluation.
Epiaortic ultrasound. After median sternotomy and retraction of the pericardium, the aortic root and ascending aorta (from the aortic root to the origin of the innominate artery) were scanned directly by the surgeon using a 7-MHz ultrasound transducer (Acuson L7384M or V714), as described previously [9–15]. The pericardial cradle was filled with saline to surround the aorta and allow better image quality. The transducer was inserted into a sterile plastic bag filled with ultrasound gel and was placed directly over the aorta. Longitudinal and transverse images were obtained and recorded on 0.5-in. S-VHS videotape for subsequent off-line evaluation.
Ultrasound analysis. For the purpose of analysis, the ascending aorta was divided into two segments: the proximal half (from the aortic root to the level of the right pulmonary artery) and the distal half (from the right pulmonary artery to the proximal aortic arch). The severity of atherosclerosis was graded on a four-point scale (normal, mild, moderate or severe), as described previously [9–15]. In brief, a normal aorta was defined as that having no identifiable intimal thickening; mild atherosclerosis was defined as ≤3.0-mm intimal thickening without intimal irregularities; moderate atherosclerosis as >3.0-mm intimal thickening with diffuse irregularities or calcification, or both; and severe atherosclerosis as ≥5.0-mm intimal thickening in addition to one or more of the following: large protruding atheromatous debris or thrombus, extensive calcification or ulcerated plaques.
Two independent, experienced echocardiographers (V.G.D.-R. and B.B. or K.J.P.) with no knowledge of patient identity, surgical and pathologic findings and clinical outcomes reviewed both studies in random order and graded severity of atherosclerosis as just described. The epiaortic and the TEE studies were recorded on separate videotapes; therefore, the investigators reviewing the tapes could not link them. A total of 264 segments were analyzed: 176 ascending aorta (88 epiaortic and 88 TEE), 44 aortic arch (TEE) and 44 descending aorta (TEE) segments. There was complete agreement between the two observers in 248 (94%) of 264 segments: 167 (95%) of 176 ascending aorta segments, 40 (91%) of 44 aortic arch segments and 41 (93%) of 44 descending aorta segments. Discrepancies in grading between the two observers in the remaining 16 segments were of only one grade and were settled by consensus. Pathologic evaluation was performed on aortic segments that were replaced at the time of operation.
Intraoperative and postoperative protocol. Light palpation of the ascending aorta was performed, and results were recorded by the surgeon (B.B. or N.T.K.) before ultrasound evaluation. By palpation, the aorta was graded as normal or as showing signs of mild atherosclerosis (defined as focal thickening in one segment, without evidence of induration or calcification), moderate atherosclerosis (more diffuse thickening or localized induration/calcification, or both) or severe atherosclerosis (diffuse thickening, or calcification, or both).
The operating surgeon (B.B. or N.T.K.) determined, in conjunction with the cardiologist and as a result of the epiaortic ultrasound findings, whether a modification in surgical technique (e.g., cannula insertion; cross-clamping; or placement of vein grafts or replacement of the ascending aorta, or both) was indicated to avoid dislodgment of atheromatous debris. During the postoperative period, each patient was closely monitored for development of neurologic or peripheral embolic events, or both.
Statistical analysis. Comparison of TEE and epiaortic assessments of severity of atherosclerosis was by use of the weighted kappa statistic, and 95% confidence intervals were calculated for the odds ratios of the kappa statistic. A kappa value of 1.00 indicates perfect agreement, ≥0.75 indicates good agreement, and 0 indicates random or no agreement. Comparison of severity of atherosclerosis in various segments was performed by simple binomial testing; p < 0.05 was considered statistically significant.
The results of the comparison of findings with the two ultrasound techniques are shown in Table 1Table 2. No TEE images indicated severe atherosclerotic disease, although six epiaortic ultrasound images were graded as such, and these results were confirmed on pathologic examination. The kappa value for the comparison between biplane TEE and epiaortic ultrasound was 0.12 (95% confidence interval [CI] 0 to 0.25), indicating poor correlation between the two.
Proximal versus distal aorta. When results in the proximal and distal segments of the ascending aorta were considered separately, the correlation between findings with the two imaging techniques was poor as well (Table 2). Atherosclerosis was judged to be more severe by epiaortic ultrasound than by TEE in 17 (39%) of 44 proximal segments and 29 (66%) of 44 distal segments. These data confirm that when compared with epiaortic ultrasound, biplane TEE significantly underestimates the severity of atherosclerosis of the ascending aorta and that this underestimation is more marked in the distal ascending aorta. This finding is significant because the distal ascending aorta undergoes the most extensive manipulation at the time of cardiac surgery, and thus the potential for atheroembolism is increased.
Ultrasound versus palpation. A comparison of the severity of atherosclerosis measured by the two ultrasound techniques versus palpation is shown in Table 3. When compared with epiaortic ultrasound and biplane TEE, palpation of the ascending aorta significantly underestimated the presence and severity of atherosclerosis. Thus, intraoperative ultrasound by either of the techniques we studied is superior to palpation for identification of atherosclerosis of the ascending aorta.
Atherosclerosis of ascending aorta versus that of aortic arch and descending aorta. To assess whether atherosclerosis in the aortic arch and the descending aorta (by TEE) is predictive of atherosclerosis of the ascending aorta (by epiaortic ultrasound), the most severe grade in the aortic arch and descending aorta were compared with the most severe grade in the ascending aorta in each patient (Table 4). There was a poor correlation between severity of atherosclerosis in the ascending aorta and that in the aortic arch (kappa 0.43, 95% CI 0.23 to 0.62) or the descending aorta (kappa 0.13, 95% CI 0.12 to 0.50). The severity of atherosclerosis in the aortic arch and descending aorta was similar to that in the ascending aorta in only 54% and 46% of cases, respectively. Thus, atherosclerosis in one segment of the thoracic aorta is a poor predictor of atherosclerosis in another segment.
Intraoperative management and clinical follow-up. As a result of the epiaortic ultrasound findings, modifications in surgical technique were implemented in 11 patients of 44 (25%). These included minor modifications (i.e., alternative placement of cannulas, clamps or vein graft anatomic sites, alone or in combination) in eight patients and major modifications (i.e., replacement of a segment of the ascending aorta for severe atherosclerosis and performance of operation under conditions of hypothermic circulatory arrest) in three patients (two segments per patient). Pathologic evaluation of all three specimens confirmed the presence of severe atherosclerosis in this vessel. The epiaortic ultrasound and TEE findings and pathologic specimen from one of these patients is shown in Fig. 1. All patients survived the cardiac operation, and there was no clinical evidence of perioperative stroke or peripheral embolization during the postoperative period.
Stroke after cardiac surgery is a major cause of morbidity and mortality [1–6]. Although there has been a decline in the overall mortality from cardiac surgery, the perioperative stroke rate has not changed substantially and may in fact be increasing as a result of the number of patients of advanced age who are undergoing cardiac surgical procedures . Advanced age is clearly the most important risk factor associated with an increased incidence of perioperative stroke. In a series of 5,070 patients undergoing cardiac surgery, Loop et al. showed that the incidence of perioperative stroke in patients >65 years old was greater than 2.4%, and this number was more than twice the incidence in patients <65 years old. Gardner et al. showed, in a series of 3,279 patients undergoing isolated CABG surgery, that patients >75 years old had an incidence of perioperative stroke of 7.1%. Preexisting cerebrovascular disease, atherosclerosis of the ascending aorta and prolonged cardiopulmonary bypass time have also been identified as significant risk factors [6, 7, 10–12, 14, 15, 26–31]. There is a very strong relation between age and incidence of significant atherosclerotic disease of the ascending aorta that increases from <10% in patients <60 years old to >32% in patients >80 years old [9, 10]. Two recent autopsy studies [7, 8]showed a strong correlation between age, aortic atherosclerosis and atheroembolism. Because extensive manipulation of the ascending aorta (cannula insertion, aortic cross-clamping and vein graft attachment) occurs during cardiac operations, identification of significant atherosclerosis allows modification of the surgical technique to decrease the risk of embolization.
Our group and others [9–17]have previously shown that epiaortic ultrasound is a highly accurate technique for determination of the extent and severity of atherosclerosis of the ascending aorta. The correlation of results of epiaortic ultrasound with intraoperative and with pathologic findings has been excellent. In addition, we and others [11, 14, 15, 24]have shown that palpation of the ascending aorta, which is the traditional method for identification of aortic atherosclerosis at the time of operation, yields a significant underestimation of extent and severity of disease. With epiaortic ultrasound, visualization of the entire wall and lumen of the ascending aorta in transverse and longitudinal imaging planes can be achieved in <10 min after the chest is opened. The technique is safe: We have documented no untoward effects associated with the test in >2,500 patients studied over the past 7 years. By incorporating epiaortic ultrasound as part of a surgical strategy, we have achieved a reduction in the incidence of perioperative strokes compared with that when this test is not done and that in historical control subjects [10, 12]. Because the cost associated with perioperative strokes in terms of mortality, disability and expense is high, use of relatively simple strategies like intraoperative ultrasound to reduce the incidence of this devastating complication appear to be cost-effective.
In the present study, we showed conclusively that the presence and severity of aortic atherosclerosis are significantly underestimated by biplane TEE versus epiaortic ultrasound and that this difference is more marked in the distal half of the ascending aorta. Kondstadt et al. made similar observations when they compared biplane TEE with epiaortic ultrasound in 14 patients undergoing cardiac surgery. They found that even though epiaortic ultrasound demonstrated atheromatous plaques that were >3 mm in the distal third of the ascending aorta in 5 of 14 patients, biplane TEE failed to identify disease in any segment.
In another study, using intraoperative TEE, Ribakove et al. studied the aortas of 97 patients undergoing cardiac surgery; modifications of the surgical technique were based on the TEE findings. They found that patients with the most severe atherosclerotic changes had a higher likelihood of postoperative stroke. These findings indicate that severe atheromatous disease of the ascending aorta is associated with strokes, that the incidence of strokes appears to be reduced with appropriate modification of the surgical technique and that TEE is useful for identification of atherosclerosis of the aortic arch, but that disease limited to the ascending aorta may be missed by this technique.
Transesophageal echocardiography has been shown [32–38]to be extremely useful in the preoperative and postoperative evaluation of patients undergoing cardiac surgery. In the identification of diseases of the aorta, such as thoracic aortic dissection and intramural hematoma, TEE has been shown [39, 40]to yield results comparable to those of computerized tomography and magnetic resonance imaging. However, visualization of the distal ascending aorta is suboptimal with TEE because air in the trachea and major bronchi obscure a portion of this segment [41, 42]. Because atheromatous disease can be focal, it can be missed by TEE, particularly if present in the ascending aorta. Epiaortic ultrasound is superior to biplane TEE in the detection of atherosclerosis of the ascending aorta for a number of reasons. The epiaortic transducer used has a higher frequency (7 MHz) than the TEE transducer (5 MHz), and because ultrasound attenuation is eliminated by placing the transducer directly over the aorta, image resolution is optimized. With epiaortic ultrasound, multiple views of the entire ascending aorta can be obtained, but with biplane TEE only a thin slice of the ascending aorta is seen in the longitudinal plane; in the transverse plane, even though good images are obtained in the proximal half of the ascending aorta, in the distal portion visualization is obstructed by air in the trachea and major bronchi. Thus, because each technique offers unique and important information in patients undergoing cardiac surgery, epiaortic ultrasound (to evaluate the ascending aorta) and TEE (to evaluate the aortic arch and descending aorta) should be considered complementary techniques in the evaluation of the thoracic aorta.
The most appropriate surgical management of patients with severe atherosclerosis of the ascending aorta is a matter of controversy, but several techniques have been proposed, including use of the innominate or internal mammary artery to place the proximal vein anastomosis [43, 44], endarterectomy, patch aortoplasty or graft replacement of the ascending aorta during hypothermic circulatory arrest [14, 45]and the use of hypothermic fibrillatory arrest to obviate the need for cross-clamping of the ascending aorta . Using these techniques in patients with the most severe disease, Wareing et al. achieved a perioperative stroke rate of 0% and a 30-day mortality rate of only 3.7%. In the present study, modifications were made to the surgical technique on the basis of the epiaortic ultrasound findings. Although none of our patients had any complications (i.e., no stroke or peripheral embolism), the number enrolled was too small to reveal statistically significant effects.
Because of the relatively low overall incidence of stroke in patients undergoing cardiac surgery, a large prospective, randomized trial will be necessary to determine the optimal surgical techniques for decreasing the risk of atheroembolism. The data available from the present study and others seem to indicate, however, that simple modifications of the surgical methods on the basis of ultrasound information appear to decrease rates of perioperative stroke.
Limitations of the study. In the present study, we used biplane rather than multiplane TEE for logistic reasons. Even though in theory multiplane TEE offers additional imaging windows , we have observed that for the evaluation of the ascending aorta, and in particular in the distal ascending aorta, it is not superior to biplane TEE. However, a trial comparing multiplane TEE with epiaortic ultrasound will be necessary to address this issue.
Conclusions. Atherosclerosis of the ascending aorta is a significant risk factor for perioperative stroke or peripheral embolism, or both, in patients undergoing cardiac surgery. Identification of this abnormality is possible with intraoperative ultrasound, and modification of the surgical technique on the basis of ultrasound findings is often useful in the prevention of atheroembolism. Epiaortic ultrasound is more accurate than TEE for identification of ascending aortic atherosclerosis, but both ultrasound techniques are superior to palpation. Intraoperative ultrasound evaluation of the ascending aorta should be performed in elderly patients undergoing cardiac surgical procedures to decrease the risk of atheroembolic complications.
A.1 Abbreviations and Acronyms
CABG = coronary artery bypass grafting
CI = confidence interval
TEE = transesophageal echocardiography
↵1 This study was supported in part by a Minority Scientist Development Award from the American Heart Association, Dallas, Texas, to Dr. Dávila-Román.
- Received March 13, 1996.
- Revision received May 9, 1996.
- Accepted May 14, 1996.
- THE AMERICAN COLLEGE OF CARDIOLOGY
- ↵Gilman S. Cerebral disorders after open-heart operations. N Engl J Med 1965;272:489–98.
- Price DL, Harris J. Cholesterol emboli in cerebral arteries as a complication of retrograde aortic perfusion during cardiac surgery. Neurology 1970;20: 1209–14.
- McKibbin DW, Bulkley BH, Green WR, Gott VL, Hutchins GM. Fatal cerebral atheromatous embolization after cardiopulmonary bypass. J Thorac Cardiovasc Surg 1976;71:741–5.
- Furlan AJ, Breuer AC. Central nervous system complications of open heart surgery. Stroke 1984;15:912–5.
- Parker FB, Marvasti MA, Bove EL. Neurologic complications following coronary artery bypass: the role of atherosclerotic emboli. J Thorac Cardiovasc Surg 1985;33:207–9.
- ↵Gardner TJ, Horneffer PJ, Manolio TA, et al. Stroke following coronary artery bypass grafting: a ten-year study. Ann Thorac Surg 1985;40:574–81.
- ↵Blauth CI, Cosgrove DM, Webb BW, et al. Atheroembolism from the ascending aorta: an emerging problem in cardiac surgery. J Thorac Cardiovasc Surg 1992;103:1104–12.
- Amarenco P, Duyckaerts C, Tzourio C, Hénin D, Bousser MG, Hauw JJ. The prevalence of ulcerated plaques in the aortic arch in patients with stroke. N Engl J Med 1992;362:221–5.
- ↵Dávila-Román VG, Barzilai B, Wareing TH, Murphy SF, Schechtman KB, Kouchoukos NT. Atherosclerosis of the ascending aorta: prevalence and role as an independent predictor of cerebrovascular events in cardiac patients. Stroke 1994;25:2010–6.
- ↵Wareing TH, Dávila-Román VG, Daily BB, Murphy SF, Barzilai B, Kouchoukos N. Strategy for the reduction of stroke incidence in cardiac surgical patients. Ann Thorac Surg 1993;55:1400–8.
- ↵Barzilai B, Marshall WG Jr, Saffitz JE, Kouchoukos N. Avoidance of embolic complications by ultrasonic characterization of the ascending aorta. Circulation 1989;80 Suppl I:I-275–9.
- Wareing TH, Dávila-Román VG, Barzilai B, Murphy SF, Kouchoukos NT. Management of the severely atherosclerotic ascending aorta during cardiac operations. J Thorac Cardiovasc Surg 1992;103:453–62.
- Barzilai B, Saffitz JE, Miller JG, Sobel BE. Quantitative ultrasonic characterization of the nature of atherosclerotic plaques in human aorta. Circ Res 1987;60:459–63.
- ↵Marshall WG Jr, Barzilai B, Kouchoukos NT, Saffitz J. Intraoperative ultrasonic imaging of the ascending aorta. Ann Thorac Surg 1989;48:339–44.
- Dávila-Román VG, Barzilai B, Wareing TH, Murphy SF, Kouchoukos NT. Intraoperative ultrasonographic evaluation of the ascending aorta in 100 consecutive patients undergoing cardiac surgery. Circulation 1991;84 Suppl III:III-47-53.
- Ohteki H, Itoh T, Natsuaki M, Minato N, Suda H. Intraoperative ultrasonic imaging of the ascending aorta in ischemic heart disease. Ann Thorac Surg 1990;50:539–42.
- Hosoda Y, Watanabe M, Hirooka Y, Ohse Y, Tanaka A, Watanabe T. Significance of atherosclerotic changes of the ascending aorta during coronary bypass surgery with intraoperative detection by echography. J Cardiovasc Surg 1991;32:301–6.
- ↵Pop G, Sutherland GR, Koudstaal PJ, Sit TW, de Jong G, Roelandt JRTC. Transesophageal echocardiography in the detection of intracardiac embolic sources in patients with transient ischemic attacks. Stroke 1990;21:560–5.
- Tunick PA, Perez JL, Kronzon I. Protruding atheromas in the thoracic aorta and systemic embolization. Ann Intern Med 1991;115:423–7.
- Karalis DG, Krishnaswamy C, Victor MF, Ross JJ, Mintz GS. Recognition and embolic potential of intraaortic atherosclerotic debris. J Am Coll Cardiol 1991;17:73–8.
- Rubin DC, Plotnick GD, Hawke MW. Intraaortic debris as a potential source of embolic stroke. Am J Cardiol 1992;15:819–20.
- Dávila-Román VG, Westerhausen D, Hopkins WE, Sicard GA, Barzilai B. Transesophageal echocardiography in the detection of cardiovascular sources of peripheral vascular embolism. Ann Vasc Surg 1995;9:252–60.
- ↵Ribakove GH, Katz ES, Galloway AC, et al. Surgical implications of transesophageal echocardiography to grade the atheromatous aortic arch. Ann Thorac Surg 1992;53:758–63.
- ↵Konstadt SN, Reich DL, Quintana C, Levy M. The ascending aorta: how much does transesophageal echocardiography see? Anesth Analg 1994;78: 240–4.
- Loop FD,
- Lytle BW,
- Cosgrove DM,
- et al.
- Lynn GM, Stefanko K, Reed JF III, Gee W, Nicholas G. Risk factors for stroke after coronary artery bypass. J Thorac Cardiovasc Surg 1992;104: 1518–23.
- McKibbin DW, Bulkley BH, Green WR, Gott VL, Hutchins GM. Fatal cerebral atheromatous embolization after cardiopulmonary bypass. J Thorac Cardiovasc Surg 1976;71:741–5.
- Mills NL, Everson CT. Atherosclerosis of the ascending aorta and coronary artery bypass. J Thorac Cardiovasc Surg 1991;102:546–53.
- Truman KJ, McCarthy RJ, Najafi H, Ivankovich AD. Differential effects of advanced age on neurologic and cardiac risks of coronary artery operations. J Thorac Cardiovasc Surg 1992;104:1510–7.
- ↵Lazar HL, Plehn J. Intraoperative echocardiography. Ann Thorac Surg 1990;50:1010–8.
- Stewart WJ, Currie PJ, Salcedo EE, et al. Intraoperative Doppler color flow mapping for decision-making in valve repair for mitral regurgitation. Circulation 1990;81:556–66.
- Sheikh KH,
- Bengtson JR,
- Rankin JS,
- DeBruijn NP,
- Kisslo J
- Kyo S, Takamoto S, Matsumura M, et al. Immediate and early postoperative evaluation of cardiac surgery by transesophageal two-dimensional Doppler echocardiography. Circulation 1987;76 Suppl V:V-113–21.
- Kochar GS, Jacobs LE, Kotler MN. Right atrial compression in post-operative cardiac patients: detection by transesophageal echocardiography. J Am Coll Cardiol 1990;16:511–6.
- Barzilai B, Dávila-Román VG, Eaton MH, et al. Transesophageal echocardiography predicts successful withdrawal of ventricular assist devices. J Thorac Cardiovasc Surg 1992;104:1410–6.
- Dávila-Román VG, Waggoner AD, Hopkins WE, Barzilai B. Right ventricular dysfunction in low output syndrome after cardiac surgery: assessment by transesophageal echocardiography. Ann Thorac Surg 1995;60:1081–6.
- ↵Erbel R, Daniel W, Visser C, Engerding R, Roelandt J, Rennollet H, and the European Cooperative Study Group for Echocardiography: echocardiography in diagnosis of aortic dissection. Lancet 1989;1:457–61.
- Adachi H, Omoto R, Kyo S, et al. Emergency surgical intervention of acute aortic dissection with the rapid diagnosis by transesophageal echocardiography. Circulation 1991;84 Suppl III:III-14–9.
- ↵Seward JB, Khandheria BD, Edwards WD, Oh JK, Freeman WK, Tajik AJ. Biplanar transesophageal echocardiography: anatomic correlations, image orientation, and clinical applications. Mayo Clin Proc 1990;65:1193–213.
- Mohr-Kahali S, Erbel R, Kearney P, Puth M, Meyer J. Aortic intramural hemorrhage visualized by transesophageal echocardiography: findings and prognostic implications. J Am Coll Cardiol 1994;23:658–64.
- ↵Weinstein G, Killen DA. Innominate artery-coronary artery bypass graft in a patient with calcific aortitis. J Thorac Cardiovasc Surg 1980;79:312–3.
- Murphy DA, Hatcher JR. Coronary revascularization in the presence of ascending aortic calcification: use of an internal mammary artery-saphenous vein composite graft. J Thorac Cardiovasc Surg 1984;87:789–91.
- ↵Akins C. Noncardioplegic myocardial preservation for coronary revascularization. J Thorac Cardiovasc Surg 1984;88:174–81.
- ↵Roelandt JRTC, Thomson IA, Vletter WB, Brommersma P, Bom N, Linker DT. Multiplane transesophageal echocardiography: latest evolution in an imaging revolution. J Am Soc Echocardiogr 1992;5:361–7.