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Transthoracic echocardiography (TTE) affords unique insight into
cardiac structure and function. Two dimensional imaging (2D) defines the
configuration and changing dimensions of the chambers; dynamic cyclic
variation in myocardial thickness; and the associated valvular motions
throughout the cardiac cycle. Superimposition of Doppler velocity
recordings (with volumetric flow calculations) provides an integrated
picture of cardiac structure, function and adaptation to both normal and
abnormal physiology. The proximal great vessels and the pericardium can
also be directly visualized.
The plethora of structural and functional information provided by TTE is
unique among diagnostic testing modalities. The rapid and noninvasive
acquisition of this information has contributed to exponential application;
and to potential over utilization. The National Claims History database
attests to the growth of the application of TTE. In 1994 TTE (4 of 7333 CPT
codes) accounted for 0.5% ($851 million) of the total Medicare expenditure
of $162 billion. This policy addresses the medically necessary and
appropriate application of TTE. Transesophageal echocardiography (TEE) is
the subject of a separate policy statement.
Ventricular Function and Cardiomyopathies
Changes in myocardial thickness (hypertrophy and thinning), derived
parameters of contractility, and in chamber volume and morphology can be
quantified and charted over time by TTE. Cardiac responses to volume
perturbations, chronic pressure excess and therapeutic interventions can be
monitored. Recognition of the relative contributions of myocardial and valvular
functional perturbations to a clinical presentation is facilitated. TTE
aids the recognition of myopathies and their classification into
hypertrophic, dilated and restrictive types and absent clinically
documented, discrete (abrupt change in signs and symptoms) episodes of
deterioration. It is not generally medically necessary to augment clinical
assessments with TTE measurements at more frequent than annual
examinations.
Although TTE is used in the assessment of ventricular diastolic function, reproducible
pathognomonic findings are to well established. In individuals with signs
and/or symptoms suggestive of ventricular dysfunction, the demonstration by
TTE of normal systolic function and/or ventricular hypertrophy may suggest
the presence of diastolic functional abnormalities. Because the TTE
findings suggesting diastolic dysfunction are less well established, this
application of TTE will be expected to be confined to examiners with
published peer review recognition of expertise in ventricular diastolic
functional assessment and treatment.
Hypertensive Cardiovascular Disease
Left ventricular hypertrophy (LVH) correlates with prognosis in
hypertensive cardiovascular disease. Certain antihypertensive medications
have been reported to stabilize and possibly contribute to the regression
of left ventricular hypertrophy and the insidiously progressive development
of left ventricular dysfunction and dilatation. In young individuals and in
individuals with borderline hypertension, the decision to commit to
long-term antihypertensive therapy may be determined by the presence of
left ventricular hypertrophy. TTE may assist with the decision to treat and
the analysis and formulation of a treatment program. Baseline follow-up or
limited study TTE and periodic serial assessment (no more frequently than
annually) would be medically appropriate. More frequent assessment should
have explicit contemporaneous medical necessity documentation.
Acute Myocardial Infarction and Coronary
Insufficiency
TTE can detect ischemic and infarcted myocardium. Regional motion, systolic
thickening perturbations and mural thinning can be quantified and global
functional adaptation assessed. The relative contributions of right
ventricular ischemia and/or infarction can be evaluated. Complications of
acute infarction (mural thrombi, papillary muscle dysfunction and rupture,
septal defects, true or false aneurysm and myocardial rupture) can be
diagnosed and their contribution to the overall clinical status placed in
perspective. Following an initial TTE in the setting of acute infarction,
repetition frequency will typically be dictated by the acute clinical
course. Absent clinical deterioration or unclear examination findings,
repeat assessment typically includes an evaluation at discharge.
Convalescent evaluation at approximately six (6) months and annually
thereafter generally provides adequate supplemental data to a thoughtful
clinical evaluation. The medical record should document the medical
necessity of more frequent TTE assessment.
The role for TTE in the emergency room assessment of individuals presenting
with chest pain is in evolution. Absent supporting clinical findings of
myocardial dysfunction, this application is considered investigational and
will be subjected to medical necessity review.
Exposure to Cardiotoxic Agents
(chemotherapeutic and external)
Measures of myocardial contractility, thinning and dilatation are important
in the titration of therapeutic agents with known myocardial toxicity.
Baseline assessment, bimonthly during and at six (6) months following
therapy is generally considered medically appropriate. Following accidental
exposure to known myocardial toxic agents, absent abrupt change in clinical
signs and/or symptoms, annual assessment would be considered reasonable and
medically necessary.
Cardiac Transplant and Rejection Monitoring
TTE is an integral part of the cardiac donor selection and donor recipient
matching process. Evaluations focus on analysis of ventricular function and
the integrity of valvular performance. TTE is also incorporated into the
management of allograft recipients. Myocardial thickness, refractile
properties, contractile patterns and indices, restrictive hemodynamics, and
the late development of pericardial fluid may alert to a refection episode.
None of these findings has achieved diagnostic sensitivity or specificity.
Typically, TTE is performed weekly for the first four to eight (4-8) weeks
following transplant with decremental frequency subsequently. Absent acute
refection episodes, approximately three (3) TTE examinations are typically
performed yearly in chronic transplant recipients. TTE of cardiac
allografts will most appropriately be performed at transplant centers by
examiners with unique expertise in the management of cardiac allograft
recipients. Other will be expected to provide appropriate medical necessity
documentation.
Native Valvular Heart Disease
Detection of mitral stenosis was among the first practical clinical
applications of TTE. TTE is well established as a technique of primary
choice for the evaluation of valvular pathology and its effect upon global
myocardial function. The relative severity of multi valve pathologies can
be quantified. Visualization of the valve and valvular apparatus
facilitates therapeutic decisions when competing therapeutic options exist;
especially interventions for mitral stenosis. Absent acute intervention, or
a discrete change in otherwise stable clinical signs and symptoms, TTE in
chronic valvular disease is used to document course over time. Generally it
is not medically necessary to repeat these examinations more frequently
than annually.
Prosthetic Heart Valves (Mechanical &
Bio-prostheses)
TTE assessment soon after prosthetic valve implant is important in
establishing a baseline structural and hemodynamic profile unique to the
individual and the prosthesis. Size, position, underlying ventricular
function and concomitant valve pathologies all impact this unique profile.
Reassessment following convalescence (36 months) is appropriate.
Thereafter, absent discretely defined clinical events or obvious change in
physical examination findings, annual stability assessment is considered
medically reasonable and appropriate.
Acute Endocarditis
TTE can provide diagnostic information; larger vegatations may be directly
visualized, valvular anatomy, and ventricular function directly assessed.
The complications or sequelae of acute infective endocarditis can be
detected and monitored over time. Acutely, examination frequency is dictated
by the individual clinical course. When the acute process has been
stabilized, the frequency of serial TTE evaluation will be dictated by the
residual pathophysiology and discrete clinical events; analogous to the
serial assessment of chronic valvular dysfunction and/or normally
functioning prosthetic valves. (vide supra).
Pericardial Disease
Detection, and quantitation of the amount, of pericardial effusion were
among the first and remains an important application of TTE. Pericardial
fluid accumulations of as little as twenty (20) milliliters have been
reliably diagnosed by TTE. Cardiac motion and blood flow patterns
demonstrated by TTE characterize the hemodynamic consequences of
pericardial fluid accumulation. A collage of TTE findings have been found
to be reliable indices of cardiac tamponade. TTE can be a valuable adjunct
during the removal of pericardial fluid and creation of pericardial windows
by balloon techniques. Acutely, clinical status will dictate examination
frequency. Absent acute pathophysiology, serial assessment of chronic
stable pericardial effusion by TTE is not usually medically necessary. TTE
is less reliable in the detection of chronic pericardial constriction.
Current echocardiographic findings in constrictive pericarditis lack the
necessary specificity and sensitivity to be reliable diagnostic aids.
Aortic Pathology
TTE can provide valuable information when acute or chronic aortic pathology
is present. However, the posterior window of TEE, coupled with the more
posterior position of the thoracic aorta has rendered TEE a more
determinative study. Noninvasive TTE remains the study of choice for
following chronic aortic pathology when images suitable for serial
quantitation can be obtained. Repetition frequency should be guided by the
pathophysiologic milieu.
Congenital Heart Disease
In children and small adults TTE provides accurate anatomic definition of
most congenital heart diseases. Coupled with Doppler hemodynamic
measurements, TTE usually providers accurate diagnosis and noninvasive
serial assessment. A technically adequate TTE can obviate the need for
preoperative catheterization in select individuals. When the disease
process and therapy are stable, serial assessment by TTE requires
contemporaneous medical necessity documentation, if the frequency exceeds
an annual evaluation.
Suspected Cardiac Thrombi and Embolic Sources
TTE is particularly sensitive in the detection of ventricular thrombi and
potentially embolic material. Limited visualization of atrial interstices
and the more peripheral and superior portions of the atria render TTE less
sensitive than TEE in the detection of atrial thrombus and potentially
embolic material. In individuals with cardiac pathology associated with a
high incidence of thromboembolic (valvular heart disease, arrhythmias,
-especially atrial fibrillation, cardiomyopathies and ventricular
dysfunction). TTE usually provides adequate supplemental therapeutic
decisional data. In those instances where the precise diagnosis and localization
of potentially embolic material is of paramount therapeutic importance
(e.g. younger stroke patients, generally #45 year old) and the information
so obtained will potentially and substantively alter therapy, or the risk
of anticoagulants is inordinately high, consideration should be given to
TEE if TTE provides inadequate decisional information. It merits emphasis
that a negative examination (TTE or TEE) does not exclude a cardiac embolus
and the findings of thrombus or vegetation does not establish a cardiac
embolic source. Absent the definition of, and serial assessment for
regression of, potentially embolic material, repeat examinations are not
generally medically required to direct clinical decisions.
Cardiac Tumors and Masses
Infiltrate and ventricular tumors and masses can be visualized, their
extent quantified and their hemodynamic consequences assessed by TTE. Right
atrial space occupying masses are usually well visualized by TTE. TEE
provides a more detailed view of the left atrium and is more sensitive in
quantifying mass characteristics (solid, cystic, etc.) extensions and
attachments. These acute pathologies are not typically followed serially.
Critically Ill and Trauma Patients
There is a role for echocardiography in the management of critically ill
patients and trauma victims. The cause of a persistent fever may be
elucidated. The diagnosis of suspect aortic or central pulmonary pathology,
cardiac contusion, or a pericardial effusion may be confirmed.
Perturbations of volume status may be more completely defined and
management strategies modified. The frequency of these typically acute
studies will be dictated by the exigencies of the clinical milieu.
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