transesophageal echocardiography in critical care units: henry ford hospital experience and review...

Transesophageal Echocardiography in Critical Care Units: Henry Ford Hospital Experience and Review of the Literature

Mohs in A lam

Transthoracic echocardiography is of limited value in intensive care units primarily because of mechanical ventilators, surgical wounds, and the inability to position the patient to his left side. Imaging from the transesophageal window overcomes these problems, resulting in good-quality study in these patient subsets. We performed both transthoracic and transesophageal echocardiography with color-flow Doppler tests in 121 patients in various critical care units. The transesophageal ultrasound test was valuable in iden- tifying patients with suspected left-sided native and

prosthetic valve vegetations, prosthetic mitral but not aortic valve regurgitation, native mitral and aortic valve pathoogy, and aortic dissection and in determining cardiac etiology of systemic emboli, hypotension, hypoxia, and heart failure. Based on transesophageal echocardiographic findings, additional information was provided in 38 {32%) patients, resulting in appropriate surgery in 22 instances. In conclusion, transesophageal echocardiography is a useful tool in evaluating critically ill patients. Copyright © 1996 by W.B. Saunders Company

C ONVENTIONAL transthoracic echocardiography (TTE) is a useful noninvasive test

in evaluating patients who are critically ill in the intensive care units. However, the TTE test has a number of limitations in these subsets of patients, primarily because of poor quality images associated with mechanical ventilators, inability to position patients, and postoperative wounds. Transesophageal echocardiography (TEE) overcomes most of these problems by virtue of incorporating high-frequency transducers at the tip of a gastroscope. This along with close proximity of the posterior cardiac struc- tures to the esophagus results in superior quality images of the heart.

A number of studies (Table 1) have clearly shown the usefulness and feasibility of perform- ing TEE in critically ill patients and its advantages over TTE in certain disease entities. 1-6 TEE is easy to perform, relatively inexpensive, portable, and can be completed within 15 to 20 minutes. No sophisticated computers are re- quired to evaluate patient studies, and if the clinical situation warrants the test can be re- peated. Furthermore, patients' medication does not interfere with the test, and the use of intravenous contrast agents is not needed.

intensive care units; emergency room; or preoperative suites.

All TEE studies were performed using a 5 MHz trans- ducer with commercially available instrument (Hewlett Packard, Andover, MA). Initial studies were performed using a monoplane, later a biplane, and recently a multiplane transesophageal probe. Twenty-eight (22%) patients were intubated. Whenever possible, the tests were performed with patients positioned in the left lateral decubitus posture. In intubated patients or patients with chest trauma, the test was performed in the supine position. All patients had fasted for 4 to 6 hours and received intravenous Diazepam and/or morphine before the test. In awake patients, local anesthetic spray (Cetacaine; Cetylite Indus- tries, Pennsauken, NJ) was applied to the pharyngeal area. Intravenous antibiotic was administered prophylactically to all patients with prosthetic heart valves. All patients with suspected aortic dissection received sedation and appropriate therapy to control their blood pressure. The electrocar- diographic (ECG) rhythm, blood pressure, and, recently, oxygen saturation by pulse oximetry were continuously monitored. TEE was well tolerated in all 121 instances without any complications.

RESULT AND REVIEW OF THE LITERATURE

T h e ind i ca t i ons fo r T E E in o u r i n t ens ive c a r e

uni t s a r e s u m m a r i z e d in T a b l e 2. M o s t p a t i e n t s

s t u d i e d in t h e m e d i c a l i n t ens ive c a r e un i t w e r e

e x a m i n e d to ru l e o u t i n fec t ive endoca rd i t i s . I n

t h e c o r o n a r y and surg ica l i n t ens ive c a r e uni ts ,

ao r t i c d i s sec t ions and va lve dys func t i on w e r e

t he m o s t c o m m o n ind ica t ions . In t h e n e u r o l o g i c

MATERIAL AND METHODS

Between the years of 1989 and 1994, we performed 123 TEE studies in the intensive care units. In two instances, the TEE probe could not be inserted in the esophagus because of uncooperativeness of the patient. In this study, we retrospectively analyzed the results of 121 TEE and TTE performed in 119 patients in the intensive care units. TTE was performed in all instances within 24 hours of TEE. The patients were located in the coronary, medical, and surgical

From the Echo Doppler Laboratory and the Cardiovascular Clinic, Heart and Vascular Institute, Henry Ford Hospital, Detroit, ML

Address reprint requests to Mohsin Alam, MD, Director, Echo Doppler Laboratory, Heart & Vascular Institute, Henry Ford Hospital, 2799 W Grand Blvd, Detroit M148202-2689.

Copyright © 1996 by W.B. Saunders Company 0033-0620/96/3804-000355.00/0

Progress in Cardiovascu/arDiseases, Vol XXXVIII, No 4 (January/February), 1996: pp 315-328 315

316 MOHSIN ALAM

Table 1. TEE in Critical Care Units

Surgery No TEE Additional Additional Based on

Author (Center) Study TEE Abn. (%) Abn. TEE

Font et al 1 (Cleveland, OH)

Foster and Schiller 2 (UCSF, CA)

Chenzbraun et al ~ (Stanford, CA) Oh et al 3 (Mayo Clinic, MN)

Pearson et al 4 (St Louis U, MO) Hwang et al 6 (Taiwan U, China)

112 36 (32) Unknown

83 21 (25) 13

113 51 (45) 9

51 30 (59) 12

62 27 (44) Unknown

78 39 (50) 14

Abbreviations: UCSF, University of California at San Francisco; U, University.

intensive care unit, the potential identification of a cardiac source of emboli was the primary indication to perform the test. In 121 patients studied by TEE and TTE, additional information was provided in 38 (32%) instances by TEE. Based on this result, appropriate surgery was performed in 22 patients.

Infective Endocarditis

We evaluated 36 patients with suspected infective endocarditis in our intensive care units; of these, 26 involved the native valves and 10 involved prosthetic (St. Jude or Bioprosthetic) valves. TEE showed vegetations on 14 native mitral (Fig 1) and aortic valves as compared with 8 shown by TTE. (Table 2) TEE showed

vegetations on 6 St. Jude and Bioprosthetic mitral and aortic valves as compared with none by TTE. Additionally, 2 patients had aortic root abscesses (Fig 2) identified by TEE as compared with 1 by TTE. The presence of vegetations on the native and prosthetic valves were confirmed during surgery or autopsy in 15 instances. All 16 patients with negative TEE for vegetations had infective endocarditis ruled out by serial blood cultures and the subsequent clinical course. In 1 instance, a mass on the mitral valve showed by both TEE (Fig 3) and TTE was initially deemed to be vegetation. This patient had no clinical or laboratory evidence of endocarditis. At surgery, fibroelastoma of the mitral valve was confirmed. Varying degrees of

Fig 1. A TEE study of patients with mitral valve endocarditis. Note the mass echoes of vegetations (arrows) on the valve. LA, left atrium; LV, left ventricle; MV, mitral valve; RV, right ventricle.

TEE IN INTENSIVE CARE 317

Table 2. Indications for TEE in Critical Care Units (HFH)

No. of Diagnostic

Indication Cases TEE "CI-E

Endocarditis 36 Native valve 26 14 8

Prosthetic 10 6 0

Aortic dissection 21 14 5

Cardiac source of emboli 20 8 2

Valve dysfunction 18 Native va lye 10 6 3

Prosthetic valve 8 6 2

Idiopathic hypotension-CHF 9 9 3

Miscellaneous 19

ASD (hypoxia) 1 0

PFO (hypoxia) 2 0

Massive obesity 1 0 Cardiac contusion 2 0

Pulmonary emboli 1 0

Abbreviations: ASD, atrial septal defect; CHF, congestive

heart failure; PFO, patent foramen ovale; HFH, Henry Ford

Hospital.

mitral and aortic regurgitation were detected by color-flow Doppler in 20 patients who had vegetative masses on native or prosthetic valves. The TEE color-flow Doppler showed higher grades of mitral but not aortic regurgitation as compared with that for TTE color-flow Dopp- ler. The results of TEE valve regurgitation was substantiated by angiography and/or surgery in all patients who had severe regurgitation. Our

data are confirmed by larger studies of patients with infective endocarditis that showed the sensitivity of TEE for left-sided native valve regurgitation to be 88% to 98% as compared with 58% to 62% by TTE. 7-9 The sensitivity of TEE in diagnosing left-sided prosthetic valve vegetations has been reported to be 77% as compared with 27% by TTE. 7 The role of TEE in evaluating tricuspid valve endocarditis in intravenous drug users showed no difference between TEE and TTE in diagnosing tricuspid valve vegetations, t° TEE has also been shown to be superior to TTE in diagnosing complications of endocarditis including aortic root abscess, fistulae, and ruptured chordae tendonae of the mitral valve.

One drawback of any cardiac imaging including TEE and TTE is differentiating infective from noninfective mass lesions. The noninfective vegetations may result from tumors (as substantiated by 1 of our patients), myxomatous degeneration, marantic endocarditis, lambs ex- crescences, valve thrombus, and suture material in patients with repaired native or prosthetic valves. Our approach is to recommend TEE in critical care units when TTE is of poor quality or is negative and the clinical suspicion for infective endocarditis is high.

Fig 2. A TEE study of a patient with aortic valve endocarditis and aortic root abscess (arrow). A, aorta; LA, left atrium; LV, left ventricle.

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Aortic Dissection

In 21 instances, TEE was performed to rule out aortic dissection. A total of 14 patients had dissection confirmed by TEE, of which 8 were type A diagnosed by TEE as compared with 5 by TTE. There were 6 type B aortic dissections diagnosed by TEE as compared with none by TTE. There was 1 false-positive and no false- negative TEE studies for dissection. All but 1 patient with aortic dissection shown by TEE had additional tests or procedures confirming the diagnosis including aortography, computer tomography (CT), magnetic resonance imaging (MRI), or surgery. The 1 patient with a false- positive TEE for type A dissection had a dilated aorta with a linear echo mimicking an intimal flap. The clinical features, aortography and CT were negative for aortic dissection on this patient. Figures 4 and 5 show classical TEE features of type A and B dissection with dilated aortic root, intimal flap, thrombus in the false lumen, and point of entry identified by color- flow Doppler.

The European Cooperative study showed a 99% sensitivity and 98% specificity of TEE in diagnosing aortic dissection as compared with 83% and 100% with CT and 88% and 94% sensitivity and specificity with aortography. 11

Fig 3, A TEE study of a patient with mitral valve mass (arrows) mimicking vegetations. At surgery, it was confirmed as fibroelastoma. LA, left atrium; LV, left ventricle.

They also observed 2 false-positive studies for type A dissection by TEE in their study. Ballal et a112 reported a 97% sensitivity and 100% specificity of TEE for diagnosing aortic dissection as compared with 67% by CT scanning. Because many of the TEE tests in this study were performed in the operating room, this may have introduced some bias favoring TEE over CT. Nienabar et a113 compared TEE with TTE and MRI scanning. They reported high sensitivity of both TEE and MRI over TTE in diagnosing type A and B dissection. 13 However, 7 of 28 patients in their study had false-positive test results for type A aortic dissection by TEE as compared with none by MRI. All TEE studies were performed by monoplane transducers in this study. Perhaps, with a multiplane TEE probe false-positive studies may have been lower. In view of the potential for false-positive study by TEE for type A dissection, we believe that other imaging tests such as aortography, CT, or MRI should be performed in addition to TEE when the TEE findings are somewhat equivocal and do not fit the clinical picture. Despite this drawback, TEE has a number of advantages over other imaging modalities in diagnosing aortic dissection, including its portability, ease of performance, and avoidance of intravenous


Fig 4. A TEE test of a patient with classic type A dissection involving the ascending aorta. Note the intimal flap (arrows) in a dilated aorta, with possible thrombus in the false lumen. Note the patient, in addition, has a bicuspid valve, AV, aortic valve; FL, false lumen; TL, true lumen.

contrast agents. Furthermore, the ability to detect dissection into the proximal coronary arteries; pericardial or mediastinal hematoma/ effusion; the presence, severity, and mechanism of concomitant aortic valve regurgitation; thrombus in the false lumen; and communication site between the false and true lumen are additional features identified by TEE and color-flow Dopp- ler. Intraoperatively, the adequacy of surgical repair of the dissection can be assessed by TEE. Recently, Mohr-Kahaly et a114 showed the ability of TEE in diagnosing intraluminal aortic hematoma. The investigators showed this feature in 15 of 114 patients studied with TEE. They postulate that these patients had rupture of vasovasorum in the wall of the aorta resulting in hematoma contained within the wall of the aorta without a break in the intima. Of these 15 patients, 5 subsequently developed a full-blown picture of dissection and 4 had rupture of the aorta over the course of time. The TEE test in these patients showed greater than 7-ram thickening of the wall of the aorta, without an intimal flap or point of entry. Because the dissection is contained within the walls of the aorta, aortography most likely would have limitations in diagnosing this entity. Even with TEE, the thickening/lucency in the wall of the aorta may

be a subtle finding and sometimes difficult to differentiate from thickening caused by atheromatous plaque.

Cardiac Source of Emboli

We performed 20 TEE and TTE tests in the intensive care units to evaluate patients with systemic emboli presenting with strokes, transient ischemic cerebral attacks, and systolic emboli to the lower extremities or viscera. The TEE test showed left atrial appendage thrombi (Fig 6) in two patients that were not detected or were equivocal by TTE. In one patient, a mobile mass (Fig 7) was detected in the ascending aorta. This patient presented with transient ischemic cerebral attacks. This patient had a small atrial myxoma (Fig 8) that had embolized to the ascending aorta. The atrial myxoma and emboli in transit in the aorta was missed by the TTE study. A number of studies comparing TEE and TTE in patients with strokes and/or transient ischemic cerebral attacks have shown that TEE can detect more cardiac abnormalities that may be contributing to the strokes. ~5,16 In a group of patients with stroke Pearson et a115 showed 58% cardiac abnormalities by TEE that may have contributed to the embolic event as compared with only 15% by TTE study. These

320 MOHSIN ALAM

Fig 5. TEE study with color-flow Doppler of a patient with classic type B aortic dissection involving the descending thoracic aorta. Note the intimal flap separating the true lumen from the false lumen and the two points of entry (arrows) by color-flow Doppler. FL, false lumen; TL, true lumen.

abnormalities include atrial thrombi, tumors, valve vegetations, atheromatous plaques in the aorta, atrial septal aneurysm with or without patent foramen ovale, and atrial septal defect. Most likely, atrial thrombi, myxoma, valve vegetations, and mobile atheromatous plaque (Fig 9) may well have been the cardiac source of systemic emboli. The role of atrial septal aneurysm with or without patent foramen ovale and of mitral valve prolapse as potential sources of emboli is more difficult to evaluate in patients

Fig 13. The TEE color-flow Doppler of patient whose two dimensional study is shown in Fig 12. Note the severe mitral bioprosthetic regurgitation (arrows). LA, left atrium; LV, left ventricle; MR, mitral regurgitant jet,

with strokes. This is especially true when some of these entities are commonly seen in the general population without systemic emboli. In our practice, when patent foramen ovale is detected in patients with systemic emboli, we perform Doppler study of the lower extremities to rule out deep venous thrombosis. If deep venous thrombus is detected, the patients are placed on anticoagulation therapy. There are no studies available to address the dilemma of patients who have patent foramen ovale and

Fig 11. TEE with color-flow Doppler of the patient with ruptured mitral chordae tendonae. Note the severe mitrai regurgitation (arrows) jet. I.A, left atrium; LV, left ventricle.

Fig 18, A TEE study of a patient with traumatic transection of the descending thoracic aorta. Note the hematoma/ thickening in the wall of the aorta (arrows). A, descending thoracic aorta; H, hematoma.


Fig 6. A TEE study of a pa- t ient wi th a large left atrial appendage thrombi (arrows). A, aorta; LA, left atrium.

systemic emboli despite warfarin therapy. Surgi- cal closure of the patent foramen ovale may be one option in these patients. However, its role is yet to be defined in the literature. Patients with atrial septal aneurysm, mitral prolapse, and

atheromatous plaque in the aorta should be treated with antiplatelet agents such as aspirin. The role of surgery in the treatment of mobile atheromatous plaque especially in the descending thoracic aorta is unclear.

Fig 7. A TEE test of a patient with a mobile mass in the ascending aorta (arrows). This was confirmed to be tumor (myxoma) emboli in transit. A, aorta; LV, left ventricle,

322 MOHSlN ALAM

Fig 8. The TEE echo of the patient in Fig 8. Note the small mass in the atrial septum (arrows) showing remnants of atrial myxoma after it embolized. A, aorta; I.A, left atrium; RA, right atrium.

A good-quality TTE is as useful as TEE in detecting left ventricular thrombi and wall motion abnormalities. We believe that TTE should be performed in all patients with strokes and systemic emboli. There is controversy whether, in addition, all these patients should have TEE

study. In our practice, we take a modified approach to the algorithm suggested by De Rook et a116 for patients with nonhemorrhagic strokes. We would perform TTE in all patients with systemic emboli. If TTE is unrevealing, especially in a y o u n g ~ r ~ e n t (less than 50

Fig 9. A TEE study of a patient with systemic emboii to the toes and multiple mobile athero- sclerotic plaques (arrows) in the aorta, DA, descending thoracic aorta,


years of age), we will perform TEE along with saline contrast injection in a peripheral vein to rule out patent foramen ovale. In patients over the age of 50 years, if TTE is completely normal, we would perform TEE only if the carotid and neurologic work-ups are unrevealing and the neurologist feels that emboli is most likely the etiology of the stroke or transient ischemic attack. Alternatively, we would not perform TEE if the decision has already been made to administer anticoagulant therapy in a patient with atrial fibrillation or if bleeding problems preclude anticoagulation use.

Valve Function

We performed TEE in 18 patients in the intensive care units primarily for evaluation of native mitral and aortic valve regurgitation and aortic valve stenosis. All these patients had congestive heart failure and no evidence of infective endocarditis. The etiology of mitral regurgitation, whether primary or secondary to heart failure, was unknown before TEE. The TEE study showed the presence of ruptured chordae tendonae (Fig 10) and severe mitral regurgitation (Fig 11) in 4 patients. None of these patients had ruptured chordae tendonae as shown by TTE, but they did have moderate to severe mitral regurgitation as shown by TTE

and color-flow Doppler. In 2 instances in which TTE was inadequate to show the severity of aortic stenosis, TEE was useful in determining the valve orifice and gradients across the aortic valve. In 1 instance, TEE showed the etiology of stenosis to be because of a bicuspid aortic valve that was not evident by the TTE study. In 3 patients, both TTE and TEE were of equal value in detecting and quantifying the severity of aortic regurgitation. In 10 critically ill patients, TEE was performed to rule out St. Jude and bioprosthesis mitral and aortic valve dysfunction caused by spontaneous degeneration and rupture of the bioprosthetic cusps (Fig 12) and severe paravalvular regurgitation of St. Jude valves. All these patients had congestive heart failure. The TEE with color-flow Doppler and angiography showed severe paravalvular St. Jude and bioprosthetic mitral regurgitation (Fig 13) in 4 instances and aortic regurgitation in 2 instances. The TTE with color-flow Doppler test underestimated the mitral regurgitation as mild or absent in all 4 patients, but it correctly estimated the severity of prosthetic aortic valve regurgitation in both instances. In 4 other patients, the prosthetic valves were normal with physiological valve regurgitation and poor left ventricular function by both TEE and TTE. Our data are supported by larger patient studies in

Fig 10. A TEE study of a patient with ruptured and flail mitral chordae tendonae (arrows). LA, left atrium; LV, left ventricle.

324 MOHSIN ALAM

which TTE was shown to either miss or severely underestimate the severity of St. Jude and bioprosthetic mitral but not aortic regurgitation.l%19

Hypotension and Congestive Heart Failure

Nine patients were evaluated for hypotension or congestive heart failure of undetermined

Fig 12. ATEEs tudy of a pa- t ient with degenerated thick- ened and flail (arrow) bioprosthetic mitral valve. LA, left atrium; LV, left ventricle.

etiology. Three patients had sustained an acute myocardial infarction and had new systolic mur- murs. The TEE showed a ruptured papillary muscle (Fig 14), with severe mitral regurgitation in two instances and intact papillary muscle structure with severe mitral regurgitation in the third instances presumably because of papillary muscle dysfunction. The TTE test was equivocal

Fig 14. TEE study of a patient with ruptured, f lail papil lary muscle (arrow) after an acute myocardial infarction. LA, left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle.


for papillary muscle rupture in one patient and did not show this phenomena in the other patient. In a series of 18 patients, with myocardial rupture after an acute myocardial infarction, TEE was shown to be superior to TTE in detecting papillary muscle rupture, z° However, TTE with color-flow Doppler was superior to TEE in detecting ventricular septal rupture located near the apex. This may have been related to the foreshortened view of the left ventricle obtained by TEE in which the apex of the ventricle and the septum may have been missed. Cardiac rupture elsewhere in the sep- turn and free wall of the left ventricle including pseudoaneursym was diagnosed equally well both by TEE and TTE in the study.

In one of our patients who was hypotensive after aortic valve replacement and one-vessel coronary bypass graft surgery, the TEE showed a pericardial hematoma compressing the right atrium (Fig 15) and accounting for cardiac tamponade. This feature was not detected by the limited TTE study. The prosthetic aortic valve and left ventricular function of this patient were normal by both TEE and rITE study. After surgical evacuation of the hematoma, the patient was able to be weaned from the intra- aortic balloon pump and intravenous inotropic

agents and did very well. In another hypotensive patient who sustained an acute inferior wall myocardial infarction after failed balloon angio- plasty of the right coronary artery, the TTE test showed inferior wall akinesis with good overall left ventricular function and an ejection fraction of 50% to 55%. The etiology of shock and hypotension was not determined by TTE. The TEE showed very poor function of the right ventricle that could not be visualized by TTE, thus confirming severe right ventricular infarction as the etiology for hypotension and shock. In a morbidly obese (over 550 lb), intubated patient with hypoxia and hypotension, the TEE study showed marked right ventricular, right atrial, and pulmonary artery dilatation with poor right ventricular function (Fig 16). The pulmonary artery of this patient was markedly dilated, thus suggesting pulmonary hypertension; left ventricular function was normal. This confirmed the diagnosis of chronic corpulmonale and pulmonary hypertension probably resulting from upper airway obstruction. The TTE study of this patient was of poor quality and was practically unreadable. In two other patients with unexplained hypotension, both the TEE and TTE studies showed the ventricles to be of small size, with hyperdynamic motion compat-

Fig 15. TEE study of a patient with hypotension and pericardial hematoma (M} compressing the right atrial wall (arrows). RA, right atrium; RV, right ventricle; LA, left atrium,

326 MOHSIN ALAM

Fig 16. ATEEstudy of a patient with corpulmonale with markedly dilated right atrium and right ventricle. RA, right atrium; RV, right ventricle; LV, left Yen- tricle.

ible with hypovolemia. Both of these patients responded to intravenous fluid therapy.

Miscellaneous

TEE performed in our intensive care units for indications other than those listed previously are as follows. A patient with deep venous thrombosis and bilateral pulmonary emboli by perfusion-ventilation lung scan had TEE performed to evaluate the etiology of cardiomegaly and continued dyspnea. The TEE showed right ventricular and right atrial dilatation, with a large serpingious mass in the right atrium (Fig 17). This was probably a large thrombus that had embolized from the lower extremities. Part of this mass was noted in the main pulmonary artery. Within 1 hour of the TEE study, the patient was rushed to the operating room for surgical removal of the thrombus. While being prepped in the presurgical holding area, the patient, who was otherwise stable, had a cardiac arrest. The patient was rushed into the operating room where the right atrium was opened and no thrombus was detected. The main pulmonary artery was immediately explored and large mass of thrombus that had embolized from the right atrium to the pulmonary artery was re- moved. The patient did well after pulmonary

artery embolectomy and was ultimately sent home. Few studies have shown the feasibility of TEE in diagnosing emboli in the main pulmonary artery and proximate right pulmonary trunk. 21 Because distal pulmonary arteries and the left pulmonary arteries are not visualized by TEE, it is not a good test for diagnosing pulmonary emboli. Nonetheless, the main pulmonary artery and proximal right pulmonary artery should always be imaged in all critically ill patients who have unexplained dyspnea, hypoxia, shock, or heart failure to rule out emboli in these vessels.

TEE was performed on two patients with chest wall trauma sustained after an automobile accident. CT had shown transection of the descending thoracic aorta. The TEE finding not only confirmed (Fig 18) this, but also showed poor right and left ventricu!ar function probably because of cardiac contusion. The limited TTE test had shown only a poorly functioning left ventricle in this patient. This confirmed previ- ous larger studies alluding to the value of TEE in these patients, especially when TTE is limited or of suboptimal quality. 22

In five patients, TEE was performed to evaluate hypoxia of unknown etiology. A sinus venous atrial septal defect was detected in one


Fig 17. A TEE study of a patient with a large right atrial thrombi (arrows) and pulmonary emboli. Note the dilated right atrium and right ventricle. RA, right atrium; RV, right ventricle.

instance in which it was missed by TTE. In two other patients, patent foramen ovale was detected only by TEE, with abnormal saline contrast echoes noted in the left atrium after injection in a peripheral vein (Fig 19). All three patients had TI 'E tests of technically poor

quality. In two other patients, both TEE and TTE failed to detect the etiology of hypoxia.

In conclusion, TEE is a valuable adjunct to TTE in critically ill patients. This test should be routinely performed in selected individuals in the intensive care units.

Fig 19. TEE with contrast injection in a patient with patent foramen ovale. Note the presence of abnormal contrast echoes in left atrium (arrow). A, aorta; LA, left atrium; LV, left ventricle; RA, right atrium.

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13. Nienaber CA, Spielmann RP, Kodolitsch VY, et al: Diagnosis of thoracic aortic dissection. Magnetic resonance imaging versus transesophageal echocardiography. Circula- tion 85:434-447, 1992

14. Mohr-Kahaly S, Erbel R, KearneY P, et al: Aortic intramural hemorrhage visualized by transesophageal echocardiography: Findings and prognostic implications. J Am Coil Cardio123:658-664, 1994

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16. DeRook FA, Comess KA, Albers GW, et al: Trans- esophageal echocardiography in the evaluation of stroke. Ann Int Med 117:922-932, 1992

17. Nellessen U, Schnittger I, Appleton CP, et al: Trans- esophageal two-dimensional echocardiography and color Doppler flow velocity mapping in the evaluation of cardiac valve prostheses. Circulation 78:848-855, 1988

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19. Alam M, Serwin JB, Rosman HS, et al: Transesopha- geal color flow Doppler and echocardiographic features of normal and regurgitant St. Jude medical prostheses in the aortic valve position. Am J Cardio166:873-875, 1990

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