BACKGROUND During the past few years, transesophageal echocardiography (TEE) has been increasingly used in clinical cardiology; data concerning the practicability and safety of the technique, however, are rare. METHODS AND RESULTS This report analyzes the experience of 15 European centers performing TEE studies for at least 1 year. At the time of this survey, 10,419 TEE examinations had been attempted or performed in these institutions. These TEE examinations were carried out by 54 physicians, 53.7% of whom had been trained in endoscopic techniques. Within the same time period, 160,431 precordial echocardiographic examinations were performed in the 15 institutions; the ratio between TEE and transthoracic studies averaged 9.03 +/- 6.4% (range of the 15 centers, 1.4-23.6%). Of the 10,419 patients, 9,240 (88.7%) were conscious inpatients or outpatients at the time of the TEE examination; the vast majority of the conscious patients did not receive intravenous sedation before TEE. In 201 cases (1.9%), insertion of the TEE probe was unsuccessfully attempted because of a lack of patient cooperation and/or operator experience (98.5%) or because of anatomical reasons (1.5%). In 90 of 10,218 TEE studies (0.88%) with successful probe insertion, the examination had to be interrupted because of the patient's intolerance of the echoscope (65 cases); because of pulmonary (eight cases), cardiac (eight cases), or bleeding complications (two cases); or for other reasons (seven cases). One of the bleeding complications resulted from a malignant lung tumor with esophageal infiltration and was fatal (mortality rate, 0.0098%). CONCLUSIONS This multicenter survey documents that TEE studies are associated with an acceptable low risk when used by experienced operators under proper safety conditions.

As shown previously, TEE is superior to the transthoracic approach in the diagnosis of ASA. The most common abnormalities associated with ASA are interatrial shunts, in particular patent foramen ovale. In this retrospective study, patients with ASA (especially with shunts) showed a high frequency of previous clinical events compatible with cardiogenic embolism; in a significant subgroup of patients, ASA appears to be the only source of embolism, as judged by TEE. Our data are consistent with the view that ASA is a risk factor for cardiogenic embolism, but thrombi attached to ASA as detected by TEE are apparently rare.

Our fax numbers: 617-739-9864 and 617-734-4457Our e-mail address: letters@nejm.orgWe cannot acknowledge receipt of your letter, but we will notify you when we have made a decision about publication. We are unable to provide prepublication proofs. Please enclose a stamped, self-addressed envelope if you want unpublished material returned to you. Financial associations or other possible conflicts of interest must be disclosed. Submission of a letter constitutes permission for the Massachusetts Medical Society, its licensees, and its assignees to use it in the Journal' s various editions (print, data base, and optical disk) and in anthologies, revisions, and any other form or medium. · Febr uar y 10, 2000The New Eng land Jour nal of Medicine Correspondence Transmyocardial Laser RevascularizationTo the Editor: The placebo effect of surgery for the treatment of angina that is mentioned by Lange and Hillis (Sept. 30 issue) 1 in their editorial on transmyocardial laser revascularization deserves elaboration. In the era before direct coronary revascularization, internal-thoracic-artery ligation was touted as a method to increase myocardial blood flow and relieve anginal symptoms. Initial reports by Ellis et al. 2 and Kitchell et al. 3 indicated that 68 to 75 percent of patients had clinical improvement, including approximately 35 percent who had complete relief and 42 percent with objective improvements, as measured electrocardiographically. These investigators were honest and intelligent but not impartial observers. Double-blind studies conducted later by Cobb et al. 4 and Dimond et al. 5 demonstrated that a sham thoracotomy alone could decrease the need for nitroglycerin and increase exercise tolerance and that it produced subjective improvement in more than 35 percent of patients. These results are similar to the improvement among 34 percent of the patients in the British study of transmyocardial laser revascularization mentioned by Lange and Hillis.When perfusion scans do not correlate in time or magnitude with the patient's clinical improvement, the more subjective data on improvement of symptoms must be approached with great skepticism. As was the case in earlier studies, the thoracotomy incision alone may have an important effect directly or indirectly on the patient's perception of pain. The fact that a patient has already undergone the surgical procedure of last resort has a high likelihood of affecting a physician's choice of treatment plans, and thus study outcome.It may be completely correct that transmyocardial laser revascularization benefits patients with chronic angina. However, given the substantial morbidity and mortality (9 to 15 percent mortality among the patients who were crossed over to transmyocardial laser revascularization in the studies by Frazier et al. 6 and Allen et al. 7 discussed by Lange and Hillis), the potential for a placebo effect must always be remembered.