Con: Epiaortic scanning is not routinely necessary for cardiac surgery

Con: Epiaortic Scanning Is Not Routinely Necessary for Cardiac Surgery John W. Ostrowski, MD and Marc S. Kanchuger, MD

TROKE IS A devastating complication of cardiac surgery and remains a major cause of morbidity. Despite many advances in cardiac surgery over the last 30 years, improvement in neurologic outcome has been lacking because stroke still has an incidence of 1% to 5%. 1-3 Atheromatous disease of the ascending aorta, aortic arch, and descending thoracic aorta is a risk factor for stroke in medical patients and especially cardiac surgery patients. 1,3-6 A great deal of effort has been spent in identifying patients with aortic atheroma (AA) in hopes of decreasing the incidence of adverse neurologic outcomes, with altered operative interventions. Large-scale prospective studies supporting these interventions are lacking. A retrospective analysis of 3,279 consecutive patients having isolated coronary artery bypass graft (CABG) surgery over 10 years (1974-1983) found that stroke rate rose over time, as did the mean patient age, Age (63 years old v 57 years old, p < 0.0001), previous cerebrovascular disease (20% v 8%, p < 0.03), severe atherosclerosis of the ascending aorta (14% v 3%, p < 0.005), protracted cardiopulmonary bypass (CPB) time (122 minutes v 105 minutes, p < 0.005), and severe perioperative hypotension (23% v 4%, p < 0.0001) were all correlated with perioperative strokes. 7 Roach et al I reported a rate of adverse neurologic outcomes of 6.1% in a large prospective observational study of 2,104 patients at 24 centers. Type 1 neurologic outcomes, defined as a focal injury or stupor or coma at discharge, were found to have the following predictors: proximal aortic atherosclerosis, a history of neurologic disease, and older age. Proximal atherosclerosis in this study was identified by palpation, which would tend to falsely decrease the incidence of atherosclerosis in this population. This study as well as others 8 have pointed out the need for precise identification prospectively of patients with severe atherosclerosis of the aorta because they are at increased risk for stroke. Early attempts to define AA were based on palpation; subsequent work brought the use of ultrasound to the forefront of atheroma detection. Even before the advent of echocardiography, surgeons were aware that AA was unrecognized because they would unexpectedly discover atheroma during a procedure. 6,9-1l Ultrasonography of the thoracic aorta, by transesophageal echocardiography (TEE) and epiaortic scanning, has been used extensively in the diagnosis of AA; however, the routine use of either technique has not been shown in a large prospective randomized trial to reduce stroke. In 1989, Barzilai et a112 first reported on the use of epiaortic ultrasonography as a guide to select cross-clamp and aortic cannula sites in 33 patients. Eighteen patients had significant atherosclerotic disease, and the planned cannulation site was changed in eight. They reported no strokes. In 1989, 50 patients were studied using epiaortic scanning of the ascending aorta. Surgical palpation did not identify significant plaques 29% of the time. Epiaortic scanning changed operative management 24% of the time. 13 In 1993, Wareing et a114 extended their analysis to 1,200 patients. They found a stroke rate of 1.1% in the group (969 patients) with none to mild disease (<3 mm plaques) and a 6.3% stroke rate in 111 patients with moderate-to-severe disease (plaques >3 ram) who had

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minor interventions. They also reported on the prevalence of moderate-to-severe ascending AA and found 9% of patients younger than 59 years old to have it, whereas 33% of patients older than 80 years old had significant disease. In the same group of 1,200 patients, the same authors determined which factors would place patients at risk for having moderate-tosevere ascending AA. They found that smoking (p < 0.0001) and a history of peripheral vascular disease (p < 0.0001) are the most impoitant risk factors other than increasing age) Davila-Roman et a115 performed epiaortic scanning in 100 patients and found that age and diabetes mellitus were significant independent predictors of ascending AA. Epiaortic scanning provided excellent visualization of the ascending aorta. In 1990, Tunick and Kronzon4 at New York University first reported the finding of mobile atheromas in the aortic arches of three patients referred for TEE to rule out a cardiac source for cerebral embolization. A case-control study of 122 patients referred for TEE to identify a source of embolization in patients with a history of unexplained stroke, transient ischemic attack, or peripheral embolizationdemonstrated the presence of protruding atheromas related to embolic symptoms with an odds ratio of 3.2, p < 0.001 using matched logistic regression. 9Amerenco et al 1° prospectively studied 250 patients admitted to the hospital for ischemic stroke with TEE of the aortic arch and matched them to 250 controls. Of the stroke patients, 14.4% had aortic plaques greater than 4 mm thick as compared with 2% of controls (odds ratio, 9.1;p < 0.001). In 1992, Katz et a111reported a stroke rate of 2% in patients with none to moderate arch atheromas (<5 mm thick) and a stroke rate of 25% in patients with mobile atheromas of the aortic arch as seen with TEE. The authors' group studied 258 patients using TEE of the thoracic aorta and aortic arch to look for atheromatous disease and compared TEE with chest radiograph and cardiac catheterization as traditional methods of assessing the presence of AA. Neither chest radiograph nor cardiac catheterization could predict the presence of atheromatous disease of the aortic arch as seen by TEE. Patients with severe disease of the aortic arch (>5 mm thick or with a mobile component) had a stroke rate of 9.4% versus 1% to 2% in patients in the normal or moderately diseased group (p < 0.01). Aortic arch disease was also associated with descending thoracic aortic disease, but thoracic disease did not correlate with stroke. 6 Hartmau et al5 showed in a prospective study that atheromatous disease of the descending aorta was a univariate predictor of stroke after CABG surgery. A stroke rate of 45.5% (5 of 11 patients) was found in patients with severe atheromatous disease of the thoracic aorta.

From the Department of Anesthesiology, New York University Medical Center, New York, NY Address reprint requests to Marc S. Kanchuger, MD, Division of Cardiac Anesthesia, Department of Anesthesiology, New York University Medical Center, 560 First Ave, New York, NY 10016. Copyright © 2000 by W.B. Saunders Company 1053-0770/00/1401-0021510. 00/0 Key words: echocardiography, epiaortic scanning, cardiac surgery, neurologic complications

Journal of Cardiothoracic and Vascular Anesthesia, Vo114,No 1 (February),2000:pp 91-94

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In 1994, the authors' group reported on 71 patients who had both TEE of the aortic arch and ascending aorta and epiaortic scanning of the ascending aorta. TEE of the arch predicted ascending aortic atheromatous disease with a sensitivity of 0.97, a specificity of 0.36, and a false-negative rate of 0.07. Older patients were found to have a higher prevalence of severe ascending aortic disease, greater than 40% in patients older than 80 years. 2 Surgical palpation was found to be unreliable in detecting ascending AA, which has been reported elsewhere. 16A7 The sensitivity of palpation was 0.57, but the specificity was 0.917. The predictive value of palpation was 0.869, the false-positive rate was 0.13, and the false-negative rate was 0.31. It was also shown that when palpation of the ascending aorta and aortic arch TEE were both negative for atheroma, the false-negative rate was 0%. Biplane or omniplane TEE was inferior to epiaortic scanning in visualizing the entire ascending aorta; only 15% of TEE scans could obtain excellent images of the ascending aorta, defined as visualizing greater than 75% of the ascending aorta intima clearly, whereas epiaortic scanning resulted in excellent images in 93% of the patients. 18 A comparison of actual aortic length with measured TEE ascending aortic length was made in 27 patients. The average length of ascending aorta visualized by TEE was 7.4 cm _+ 1.1 cm as compared with a mean of 8.9 cm -+ 1.3 cm from direct measurement. As much as 42% (4.5 cm of 10,7 cm) was not visualized by TEE. It was possible to visualize the aortic cannula with TEE in only 1 of 27 patients. TEE also was unable to visualize severe ascending atheroma in five patients. 19 TEE has been shown to have limited ability to visualize the ascending aorta as a result of several factors: (1) Presence of a pulmonary artery catheter in the right pulmonary artery may create an artifactual echo, (2) it is difficult to define the exact location of atheroma with TEE, and (3) the trachea or fight mainstem bronchus also blocks echo penetration of the ascending aorta. Davila-Roman et a116 prospectively evaluated the ascending aorta using TEE, epiaortic scanning, and palpation in 44 patients. There was a poor correlation between biplane TEE and epiaortic scanning (K = 0.12). Palpation significantly underestimated the degree of atherosclerosis as compared with either of the ultrasound modalities. Alterations in clinical management occurred in 25% (11 of 44) of patients as a result of epiaortic ultrasound findings. 16 This study failed to analyze the utility of TEE as a screening test for ascending AA. Sylivris et a117 also looked at TEE, epiaortic scanning, and palpation in 100 consecutive patients. Age greater than 70 years and hypertension were found to be significant risk factors for ascending AA. Palpation was able to detect atheroma only in 16% of patients, whereas ultrasound found atheroma in 90%; of these, 35% had severe disease. TEE was found to be equal to epiaortic scanning in atheroma detection in the proximal ascending aorta, but epiaortic scanning was superior in the mid and distal segments (p < 0.0001). A significant association was found between the presence of severe descending atheroma and severe ascending atheroma. Konstadt et al2° performed TEE and epiaortic scanning on 81 patients undergoing cardiac surgery. Fourteen of 81 patients

OSTROWSKI AND KANCHUGER

(17%) were found to have significant ascending atherosclerosis by epiaortic scanning, whereas 41 of 81 patients (51%) were found to have significant atherosclerosis of the thoracic aorta by TEE. Comparison of TEE of the entire thoracic aorta and epiaortic scanning was found to be 100% sensitive and 60% specific. There were no false-negative results in this study. TEE of the thoracic aorta was demonstrated to be a sensitive but not specific screening tool for predicting ascending AA, but it was specific for ruling out disease. 2° Another study compared epiaortic scanning with palpation in 89 patients. Palpation was found to have a sensitivity of 0.46 and a specificity of 0.96, and predictive power of a negative test was 0.88. All patients who were judged to have a normal aorta based on palpation did not require an alteration in the operative plan based on epiaortic scan. Palpation was falsely negative in 38 aortic segments. This study suggests that palpation is a reasonable screening tool for selective application of epiaortic scanning. Ascending atherosclerosis was found to be more severe in older patients and smokers. 21 The aforementioned studies when analyzed together indicate that palpation and TEE when used together may be a valid screening test for ascending AA, which the authors have also reported. 18 Palpation alone or aortic arch TEE alone is only moderately reliable at predicting the presence of ascending AA. When palpation by the surgeon and TEE are combined, the value of a negative test is excellent and can be used to rule out the likelihood of finding disease of the ascending aorta (Fig 1). The prevalence data confirm previous findings: Older patients are more prone to have disease of the aorta, and patients older than age 60 and especially those older than age 70 have a high prevalence of severe disease in all parts of the aorta. 18Epiaortic scanning is superior to TEE in viewing the ascending aorta, although omniplane TEE did slightly improve the ability to obtain an excellent image. Based on data collected so far, the authors have devised an algorithm for the use of epiaortic scanning. All patients older than age 65, patients with calcified aortas on chest radiograph, patients with a history of cerebrovascular disease or peripheral vascular disease, and heavy smokers should have TEE assessment of the aorta during cardiac surgery. If there is significant disease found on the aortic arch and

Surgical Palpation

Arch TEE

Palpation & Arch TEE Combined

False Positive Rate

12.7%

40.3%

40.1%

True Positive Rate

87.3%

59.7%

61.3%

False Negative Rate

26.8%

3.8%

0%

True Negative Rate

73.2%

96.2%

100%

Sensitivity

67.9%

98.8%

100%

Specificity

89.9%

31.6%

29.4%

Fig 1. Use of palpation and aortic arch transesophageal echocardiography (TEE) to screen for ascending aortic atherosclerosis, (Reprinted with permission from Kanchuger M, Marschall K, ]issot M, et al: Epiaortic ultrasonography is superior to biplane transesophageal echocardiography or surgical palpation in detecting aortic atherosclerosis. Anesthesiology 81 :A 110, 199478)

PROAND CON

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Age>65 I P.V.D.C.V,D. Ca~ Aortic Knob on CXR

Fig 2. Algorithm for use of epiaortic scanning. Abbreviations: PVD, peripheral vascular disease; CVD, cerebrovascular disease; Ca ++, calcified; CXR, chest x-ray; TEE, transesophageal echocardiography.

[--

I Arch Cannula

~pi Aortic Scan q

+

--] i

Routine Case

I

-

|

Arch Cannula I

descending aorta or the surgeon suspects disease in the ascending aorta, epiaortic scanning should be considered to guide surgical technique (Fig 2). Epiaortic scanning is the optimal method of determining ascending AA, but its routine use is excessive and timeconsuming. There is also clear evidence of risk factors for AA, which allows for preoperative screening of patients at high risk for AA. The algorithm in Fig 2 is an efficient and appropriate

way to screen patients for AA. TEE is a relatively common practice and does not interfere with the surgical procedure. When TEE is combined with palpation, it is a useful screening tool for the identification of ascending AA. Epiaortic scanning interrupts the operative procedure and requires additional training and equipment. There has yet to be a large-scale prospective study to support the use of routine epiaortic scanning to improve outcomes in cardiac surgery.

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to both transesophageal echocardiography and direct palpation. J Cardiothorac Vasc Anesth 11:704-707, 1997 18. Kanchuger M, Marschall K, Tissot M, et al: Epiaortic ultrasonography is superior to biplane transesophageal echocardiography or surgical palpation in detecting aortic atherosclerosis. Anesthesiology 81:Al10, 1994 19. Konstadt SN, Reich DL, Quintana C, Levy M: The ascending

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aorta: How much does transesophageal echocardiography see? Anesth Analg 78:240-244, 1994 20. Konstadt SN, Reich DL, Kahn RR, Viggiani RF: Transesophageal echocardiography can be used to screen for ascending aortic atherosclerosis. Anesth Analg 81:225-228, 1995 21. Nicolosi AC, Aggarwal A, Almassi GH: Intraoperative epiaortic ultrasound during cardiac surgery. J Card Surg 11:49-55, 1996