Submitted by Dr. Yasser Mokhtar, MD. Dept. of internal medicine. School of medicine, University of South Dakota.
Indications of TEE
I. Cardiac examination:
A. Detection of a suspected source of embolism
TEE is superior to TTE for visualization of left atrial appendage, atrial septum, thoracic aorta and prosthetic valves. It generally affords superior resolution of cardiac and aortic anatomy and pathologic lesion such as masses and thrombi compared to transthoracic approach (Black et al., 1991).
Since TTE has been consistently shown to have a poor yield in patients with intracardiac source of embolism, TEE is being used with increased frequency for evaluating suspected intracardiac source of embolism (Pearson et al., 1991).
B. Infective endocarditis
There is no debate about TEE being the procedure of choice in the evaluation of suspected endocarditis or its complications. TEE has been clearly shown to be superior to TTE in the diagnosis of vegetations and complications of endocarditis such as an abscess and fistula formation (M?ge et al., 1989, Klodas et al., 1989 and Daniel et al., 1991).
C. Valvular heart disease
1. Native valve
TEE provides excellent characterization of valvular pathology. It is valuable in evaluation of valvular regurgitation and characterization of regurgitation jet by two dimensional ultrasound examination and pulsed, continuous and color-coded Doppler echocardiography (Stewart et al., 1988 and Zamorano et al., 1991).
It also provides clinically relevant information affecting patient management such as repair versus replacement of the valve (Stewart et al., 1990 and Castello et al., 1991).
2. Prosthetic valve
It is very useful in diagnosis of prosthetic valve dysfunction especially in the mitral position (Khandheria et al., 1991).
D. Detection of intracardiac masses
An intracardiac mass may be either a thrombus or neoplastic tissue and it may be associated with obstruction or systemic embolization (Aschenberg et al., 1986 and Faletra et al., 1992).
TEE has been found invaluable in the characterization and localization of intracardiac masses such as thrombus, myxoma and other neoplasms (M?ge et al., 1991).
TEE is particularly helpful when TTE is inconclusive such as with small tumors and thrombi, laminated thrombi and thrombi limited to the left or right atrial appendages or poor images. TTE can be inconclusive in diagnosing a mass especially in the presence of prosthetic valve (Aschenberg et al., 1986).
TEE overcomes this dilemma by having imaging ability posterior to the mechanical device and in the left atrial appendage. Left atrial thrombus may be seen in patients with mitral stenosis or atrial fibrillation. Spontaneous contrast as a prelude to formation of a thrombus is seen with TEE but not with TTE (Reader et al., 1991 and Vinga et al., 1993).
E. Congenital heart disease and intracardiac shunts
Conditions such as atrial septal defect, atrial septal aneurysm, patent foramen ovale, anomalous pulmonary venous connection, cor triatriatum, Ebstein?s anomaly and postoperative procedures are all readily recognized by TEE (Stumpor 1991 and Stumpor et al., 1991).
The estimates of the prevalence of PFO defined by postmortem studies is 25-35% (Hagan et al., 1984).
Detection of PFO by contrast imaging using agitated saline with TEE is far superior to that of TTE (Staddard et al., 1993).
A Valsalva maneuver enhances the value of this microbubble test. This is particularly important in assessing cardiac patients and individuals unexplained strokes. Hausmann and his colleagues detected a PFO in 50% of patients who were younger than forty years and who had an unexplained ischemic stroke (Hausmann et al., 1992).
F. Evaluation of left atrium and left atrial appendage before cardioversion of atrial fibrillation
TEE evaluation may be considered to preclude a thrombus in patients who are in an ICU, have acute onset AF and are to be cardioverted. TEE visualized atrial thrombi in 13% of patients who had recent onset AF and who were scheduled for elective cardioversion (Manning et al., 1993).
G. Ischemic heart disease
TEE allows the visualization of proximal coronary arteries and even non-physiologic stress testing. It has also been used to detect regional wall motion abnormalities.
TEE can also facilitate multiple invasive interventional procedures such as transseptal catheterization (Jaarsma et al., 1990), balloon valvuloplasty, radiofrequency ablation of arrhythmogenic pathways (Goldman et al., 1992) and myocardial biopsy.
Postoperative diagnosis of cardiac tamponade especially if caused by loculated pericardial effusion. TEE is superior to TTE in this situation because of the dressings, subcutaneous emphysema, pneumothoraces, obesity and chronic obstructive pulmonary disease (Berge et al., 1992).
Pulmonary embolism: A high index of suspicion for pulmonary embolism exists if TEE shows right ventricular dilatation or hypokinesia, decreased left ventricular dimensions and increased right ventricle to left ventricle diameter ratio, abnormal septal position and paradoxical systolic motion, unusual pulmonary or tricuspid regurgitation or pulmonary artery dilatation (Come 1992).
II. Examination of the thoracic aorta
TEE has a high degree of success in evaluation of disease of thoracic aorta such as aortic dissection, aortic atherosclerosis and its complications. It is the procedure of choice for diagnosis and follow up of patients with aortic dissection. It is superior to other imaging modalities in assessment of atherosclerotic intra-aortic debris, a significant potential source of systemic embolism (Erbel et al., 1989, Mohr-Kahaly et al., 1989, Karalis et al., 1991, Khandheria et al., 1992 and Coy et al., 1992).
III. Intraoperative monitoring
Detection of intracardiac air in neurological operations in the upright posture and other procedures with risk of air embolism (e.g. laparoscopy).
Serial assessment of global and segmental left ventricular function.
The indications of TEE continue to expand and the preceding discussion is meant to emphasize well established applications of TEE.
A. Absolute contraindications:
Esophageal diverticula (e.g. Zenker?s diverticulum).
B. Relative contraindications:
Large diaphragmatic hernia may significantly hinder TEE imaging because of lack of transducer mucosal approximation.
Atlantoaxial disease and severe generalized cervical arthritis: TEE should never be performed if there is any question about stability of cervical spine.
Patients who received extensive radiation to the mediastinum: this can cause significant difficulty in probe manipulation within the esophagus and is a relative contraindication if the anatomy of the esophagus is not known.
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