Submitted by Dr. Yasser Mokhtar, MD. Dept. of internal
medicine. School of medicine, University of South Dakota.
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 (Mügge 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 (Mügge 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.
H. Others
-
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).
-
Ruptured chordae tendinae:
TTE
is limited in
providing accurate visualization, whereas TEE detects a ruptured chorda
in 100% of cases compared to 65% of patients when using
TTE
(Shyu
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).
The indications of TEE continue to expand and the
preceding discussion is meant to emphasize well established applications
of TEE.
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