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(Circulation. 1997;95:1686-1744.)
© 1997 American Heart Association, Inc.
Articles |
ACC/AHA Guidelines for the Clinical Application of Echocardiography
A Report of the American College of Cardiology/ American Heart Association Task Force on Practice Guidelines (Committee on Clinical Application of Echocardiography) Developed in Collaboration With the American Society of Echocardiography
Key Words: diagnosis • AHA Medical/Scientific Statements • echocardiography
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Contents |
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Top
Contents
II. Murmurs and Valvular...- Preamble
I. Introduction, General Considerations, and Scope
II. Murmurs and Valvular Heart Disease
- Murmurs
Native Valvular Stenosis
Native Valvular Regurgitation
Repeated Studies in Valvular Heart Disease
Mitral Valve Prolapse
Infective Endocarditis: Native Valves
Prosthetic Valves
Prosthetic Valve Dysfunction and Endocarditis
IV. Ischemic Heart Disease
- Acute Ischemic Syndromes
Chronic Ischemic Heart Disease
- Assessment of Ejection Fraction
Edema and Dyspnea
Regional Left Ventricular Function
Ventricular Dysfunction
Dilated Cardiomyopathy
Hypertrophic Cardiomyopathy
Restrictive Cardiomyopathy
Heart Failure With Normal Systolic Function
Evaluation of the Right Ventricle
- Pericardial Effusion
Cardiac Tamponade
Increased Pericardial Thickness
Pericardial Tumors and Cysts
Constrictive Pericarditis
Congenital Absence of the Pericardium and Pericardial Disease After Open-Heart Surgery
VIII. Diseases of the Great Vessels
- Aortic Dissection
Aortic Aneurysm
Aortic Rupture and Thoracic Aortic Degenerative Disease
The Great Veins
- Pulmonary Thromboembolism
XI. Neurological Disease and Other Cardioembolic Disease
XII. Arrhythmias and Palpitation
- Cardioversion of Patients With Atrial Fibrillation
Syncope
Screening
- Echocardiography in the Trauma Patient
XV. Echocardiography in the Pediatric Patient
- Resource Utilization and Age
Congenital Cardiovascular Disease in the Neonate
Cardiopulmonary Disease
Arrhythmias
Myocardial Disease in the Neonate
Congenital Cardiovascular Disease in the Infant, Child, and Adolescent
Arrhythmias/Conduction Disturbances
Acquired Cardiovascular Disease
Pulmonary Diseases in Pediatric Acquired Cardiovascular Disease
Thrombus/Tumor
Transesophageal Echocardiography
Fetal Echocardiography
Preamble
It is clearly important that the medical profession plays a
significant role in critically evaluation of the use of diagnostic
procedures and therapies in the management or prevention of disease.
Rigorous and expert analysis of the available data documenting relative
benefits and risks of those procedures and therapies can produce
helpful guidelines that improve the effectiveness of care, optimize
patient outcomes, and impact the overall cost of care favorably by
focusing resources on the most effective strategies.
The American College of Cardiology (ACC) and the American Heart Association (AHA) have jointly engaged in the production of such guidelines in the area of cardiovascular disease since 1980. This effort is directed by the ACC/AHA Task Force on Practice Guidelines. Its charge is to develop and revise practice guidelines for important cardiovascular diseases and procedures. Experts in the subject under consideration are selected from both organizations to examine subject-specific data and write guidelines. The process includes additional representatives from other medical practitioner and specialty groups as appropriate. Writing groups are specifically charged to perform a formal literature review, weigh the strength of evidence for or against a particular treatment or procedure, and include estimates of expected health outcomes where data exist. Patient-specific modifiers, comorbidities, and issues of patient preference that might influence the choice of particular tests or therapies are considered as well as frequency of follow-up and cost-effectiveness.
These practice guidelines are intended to assist physicians in clinical decision making by describing a range of generally acceptable approaches for the diagnosis, management, or prevention of specific diseases or conditions. These guidelines attempt to define practices that meet the needs of most patients in most circumstances. The ultimate judgment regarding care of a particular patient must be made by the physician and patient in light of all of the circumstances presented by that patient.
The Committee on Clinical Application of Echocardiography was chaired by Melvin D. Cheitlin, MD, FACC, and included the following members: Joseph S. Alpert, MD, FACC, William F. Armstrong, MD, FACC, Gerard P. Aurigemma, MD, FACC, George A. Beller, MD, FACC, Fredrick Z. Bierman, MD, FACC, Thomas W. Davidson, MD, FAAFP, Jack L. Davis, MD, FACC, Pamela S. Douglas, MD, FACC, Linda D. Gillam, MD, FACC, Richard P. Lewis, MD, FACC, Alan S. Pearlman, MD, FACC, John T. Philbrick, MD, FACP, Pravin M. Shah, MD, FACC, and Roberta G. Williams, MD, FACC.
The committee is composed of both university-affiliated and practicing physicians and those with specific echocardiographic expertise and senior clinicians who use the technique. Two general physicians (one general internal medicine and one family practitioner) also served on the committee.
The document was reviewed by three outside reviewers nominated by the ACC and three outside reviewers nominated by the AHA as well as other individuals from the American Society of Echocardiography, Society of Pediatric Echocardiography, American College of Physicians, and American Academy of Family Physicians.
The executive summary and recommendations are published in the March 15, 1997, issue of Journal of the American College of Cardiology. The full text is published in Circulation. Reprints of both the full text and the executive summary and recommendations are available from both organizations. The document will be reviewed 2 years after publication and yearly thereafter and considered current unless the task force revises or withdraws it from distribution. The document was endorsed by the American Society of Echocardiography.
James L. Ritchie, MD, FACC Chair, ACC/AHA Task Force on Practice Guidelines
I. Introduction, General Considerations, and
Scope
The previous guidelines for the use of echocardiography were
published in December 1990. Since that time there have been significant
advances in the technology of Doppler echocardiography and growth in
its clinical use and in the scientific evidence leading to
recommendations for its proper use.
The recommendations are based on a Medline search of the English literature from 1990 to May 1995. Echocardiography was cross-referenced with the following terms: antineoplastic agents, aortic or dissecting aneurysm, arrhythmias, athletes, atrial fibrillation, cardioversion, Marfan syndrome, bacterial endocarditis, myocardial infarction, myocardial ischemia, coronary disease, chest pain, cardiomyopathies, cerebrovascular disorders or cerebral ischemia, embolism, heart neoplasms, heart valve disease, heart murmurs, hypertension, mitral valve prolapse, pericarditis, pericardial effusion, cardiac tamponade, pericardium, pulmonary embolism or pulmonary heart disease or cor pulmonale, screening, shock or aortic rupture or heart rupture, syncope, transplantation, unstable angina, congenital heart disease in the adult, specific congenital lesions, arrhythmias in children, pediatric echocardiography, and fetal echocardiography.
The search yielded over 3000 references, which the committee reviewed. This document includes recommendations for the use of Doppler echocardiography in both adult and pediatric patients. The pediatric guidelines also include recommendations for fetal Doppler echocardiography, an increasingly important field. The guidelines include recommendations for the use of Doppler echocardiography in both specific cardiovascular disorders and in the evaluation of patients with frequently observed cardiovascular symptoms and signs, common presenting complaints, or findings of dyspnea, chest discomfort, and cardiac murmur. In this way the guidelines will provide assistance to physicians regarding the use of Doppler echocardiographic techniques in the evaluation of such common clinical problems.
The recommendations concerning the use of Doppler echocardiography follow the indication classification system (eg, Class I, II, and III) used in other ACC/AHA guidelines:
Class I: Conditions for which there is evidence and/or general agreement that a given procedure or treatment is useful and effective.
Class II: Conditions for which there is conflicting evidence and/or a divergence of opinion about the usefulness/efficacy of a procedure or treatment.
IIa: Weight of evidence/opinion is in favor of usefulness/efficacy.
IIb: Usefulness/efficacy is less well established by evidence/opinion.
Class III: Conditions for which there is evidence and/or general agreement that the procedure/treatment is not useful/effective and in some cases may be harmful.
Evaluation of the clinical utility of a diagnostic test such as echocardiography is far more difficult than assessment of the efficacy of a therapeutic intervention, because the diagnostic test can never have the same direct impact on patient survival or recovery. Nevertheless, a series of hierarchical criteria are generally accepted as a scale by which to judge worth.1 2 3
Hierarchical Levels of Echocardiography
Assessment
- Technical capacity
- Diagnostic performance
- Impact on diagnostic and prognostic thinking
- Therapeutic impact
- Health-related outcomes
The most fundamental criterion is technical capacity, including adequacy of equipment and study performance. The next is diagnostic performance, which encompasses much of traditional diagnostic test assessment, including delineation of the range of clinical circumstances in which a test is applicable, as well as test sensitivity, specificity, and accuracy for individual applications. The third criterion is the capability of a test to alter diagnostic and prognostic thinking, ie, to offer added value. This level depends on the context in which the test is performed and is therefore affected by such factors as what is already known, the judged value of confirmatory data, and the importance of reassurance in a particular clinical situation. Impact on diagnostic and prognostic thinking is an important link between test results and patient treatment. Subsequent criteria include therapeutic impact and health-related outcomes. Because there are essentially no randomized trials assessing health outcomes for diagnostic tests, the committee has not ranked the available scientific evidence in an A, B, C fashion (as in other ACC/AHA documents) but rather has compiled the evidence in tables. All recommendations are thus based on either this evidence from observational studies or on the expert consensus of the committee.
Two-dimensional echocardiography can provide excellent images of the heart, paracardiac structures, and the great vessels. Because it depends on satisfactory examining windows from the body surface to the cardiovascular structures, there may be limitations on its use for adult patients. For patients with chronic obstructive pulmonary disease, the interposition of air-filled lung between the body surface and the heart severely limits access, and complete examination may not be possible. Other circumstances limit the use of transthoracic echocardiography (TTE), especially for patients in the intensive care unit. For example, patients on ventilators, those who cannot be rotated into a lateral position, and those with incisions may not have satisfactory precordial or apical windows. TEE may avoid most of these limitations because there is no interposed lung tissue between the transducer and the heart.
The definition of echocardiography used in this document incorporates Doppler analysis, M-mode echocardiography, two-dimensional TTE, and, when indicated, TEE. Intravascular ultrasound is not considered here but will be reviewed in the revised guidelines for coronary angiography (in preparation). Echocardiography for evaluating the patient with cardiovascular disease for noncardiac surgery is considered in the ACC/AHA Guidelines for Perioperative Cardiovascular Evaluation for Noncardiac Surgery.4 The techniques of three-dimensional echocardiography are in the developmental stages and also are not considered here. Intraoperative TEE is not considered in this document because it is the subject of practice guidelines for perioperative TEE.5
New techniques that are still rapidly evolving are also not addressed in this document. Echocardiography-contrast substances that can pass through the pulmonary circulation and opacify the left heart are in development. Echocardiography-contrast injections into the coronary artery to quantitate myocardium at risk and perfusion territories and the second harmonic echocardiogram to enhance echocardiographic contrast also are not addressed.
With the development of Doppler echocardiography and proof that the
modified Bernoulli equation permitted the conversion of instantaneous
velocities of blood flow into instantaneous pressure gradients across
obstructions, it became possible to precisely localize and quantitate
obstruction in the cardiovascular system. This information, when
considered with flow volume information provided by Doppler flow
velocity integrals, allows a plethora of physiological and functional
information to be obtained noninvasively. The differing capabilities of
the several types of available Doppler echocardiographic techniques are
outlined in Table 1
. Recognizing the strengths of each
technique will enable the physician to order the appropriate study.
Generally a complete transthoracic echocardiogram and Doppler study is
called for unless otherwise specified.
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When faced with a patient needing cardiovascular evaluation and testing, the clinician must choose among available tests. Echocardiography, nuclear testing, magnetic resonance imaging (MRI), and positron emission tomography can yield overlapping if not identical information, often with similar or comparable accuracy. Decisions concerning which technique to use must then be based on such factors as local expertise in performance and interpretation, test availability, cost, and patient preference. Therefore, it is impossible in this document to judge competing tests or recommend the use of one over another.
TTE is associated with little if any patient discomfort, and no risks with this procedure have been identified. Moreover, the use of TTE with exercise or vasoactive drugs such as dipyridamole or dobutamine involves the minimal risks of arrhythmia, ischemia, and hypotension seen with exercise and the aforementioned drugs. In TEE, the echocardiographic transducer is mounted on a flexible endoscope and passed into the esophagus and stomach. This involves some discomfort and minimal but definite risk of pharyngeal and esophageal trauma and even rarely esophageal perforation. Rare instances of infective endocarditis have been associated with the use of TEE. An occasional patient has a reaction to either the sedative or the local anesthesia used.
The ability of Doppler echocardiography to provide unique noninvasive information with minimal discomfort or risk without using contrast material or ionizing radiation, coupled with its portability, immediate availability, and repeatability, accounts for its use in virtually all categories of cardiovascular disease. However, two-dimensional Doppler echocardiography is best used after a careful history, physical examination, appropriate electrocardiogram (ECG), and chest radiograph have been obtained so that the appropriate questions can be asked. Indiscriminate use of echocardiography or its use for "screening" is not indicated for two principal reasons. First, the cost of echocardiography is not trivial. Second, the current Doppler echocardiographic techniques reveal details of structure and function such as filamentous strands on valves, valvular prolapse, and jet velocities representing minimal and at times transient valvular insufficiency that could generate unnecessary further testing or inappropriate and potentially detrimental therapy.
These guidelines contain recommendations concerning not only indications for the use of these techniques but also specific circumstances when Doppler echocardiography adds little or nothing to the care of the patient and is therefore not indicated. An example is the evaluation of the patient with a clearly innocent murmur in the opinion of a qualified, knowledgeable examining physician. Another example is the use of echocardiography in diagnosing mitral valve prolapse (MVP) in a patient with chest pain or premature ventricular contractions in the absence of clinical findings consistent with MVP. Because there is no evidence that such patients have an increased risk of endocarditis beyond the general population which does not have "echo-only" MVP, echocardiography is generally not indicated in this situation.
An echocardiographic study is not indicated when the pathology and/or systolic ventricular function have been adequately defined by other techniques, making the echocardiographic study redundant. Furthermore, echocardiography should be performed by laboratories with adequately trained physicians and cardiac sonographers where patient volume recommendations are met as previously described.3
These guidelines also address recommendations about the frequency with which a Doppler echocardiographic study is repeated. If the frequency with which studies are repeated could be decreased without adversely affecting the quality of care, the economic savings realized would likely be significant. With a noninvasive diagnostic study and no known complications, the potential for repeating the study unnecessarily exists. It is easier to state when a repeat echocardiogram is not needed then when and how often it should be repeated, since no studies in the literature address this question. An adult patient with hemodynamically insignificant aortic regurgitation almost certainly does not need a repeat echocardiogram unless there is a change in the clinical picture. The asymptomatic patient with hemodynamically severe aortic regurgitation probably needs repeat echocardiography to monitor left ventricular function. How often this should be done depends on the individual patient and must be left to the judgment of the physician until evidence-based data addressing this issue are available.
The use of two-dimensional Doppler echocardiography in establishing cardiac diagnoses and making therapeutic decisions is well established. Examples include the demonstration of an acquired ventricular septal defect in a patient with an acute myocardial infarction. In the past this diagnosis required catheterization; now the definitive diagnosis can be made in most cases with Doppler echocardiography. At times the Doppler echocardiogram can enable cardiac surgery to proceed without a comprehensive catheterization. Examples of this are the finding of severe aortic stenosis or mitral or aortic regurgitation in the symptomatic young patient or the finding of a left atrial myxoma.
The use of repeated Doppler echocardiographic studies in following patients is illustrated in adult patients with moderate aortic stenosis who have a change in symptoms. Similarly the follow-up evaluation of ventricular function in the patient with chronic aortic or mitral valvular insufficiency lesions can help determine the timing of valvular surgery.
This document assumes that Doppler echocardiographic studies are performed and interpreted in accordance with the statements for clinical competence in echocardiography set forth by the Joint Task Force of the American College of Physicians/American College of Cardiology/American Heart Association. Optimal training for such studies is set forth by the American Society of Echocardiography, the American College of Cardiology, and the Society of Pediatric Echocardiography.
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II. Murmurs and Valvular Heart Disease |
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Echocardiography is extremely useful in the assessment of cardiac murmurs, stenosis and regurgitation of all four cardiac valves, prosthetic valve function, and patients with infective endocarditis. Echocardiography provides valuable information regarding diagnosis, valvular morphology, etiology of valve disease, identification and quantification of lesions, detection and evaluation of associated abnormalities, delineation of cardiac size and function, and assessment of the adequacy of ventricular compensation. Echocardiography readily detects structural abnormalities such as fibrosis, calcification, thrombus, or vegetation, and abnormalities of valvular motion such as immobility, flail or prolapsing leaflets, or prosthetic valve dehiscence. A full echocardiographic evaluation should provide prognostic as well as diagnostic information, allow for risk stratification, establish baseline data for subsequent examinations, and help guide and evaluate the therapeutic approach.
Echocardiography often provides a definitive diagnosis and may obviate the need for catheterization in selected patients. Patients' acceptance of this noninvasive technique for initial and reevaluation observation is high.6 7 8 MRI has the capability to detect the presence of stenotic and regurgitant lesions9 10 and has several advantages. However, MRI instrumentation is substantially more expensive and not as widely available.
Murmurs
Cardiac auscultation remains the most widely used method of
screening for heart disease. Heart murmurs are produced by turbulent
blood flow and are often signs of stenotic or regurgitant valve disease
or acquired or congenital cardiovascular defects. In valvular and
congenital forms of heart disease, a murmur is usually the major
evidence of the abnormality, although some hemodynamically significant
regurgitant lesions may be silent.11 12 However, many
murmurs in asymptomatic people are innocent and of no functional
significance. Such murmurs are defined as having the following
characteristics: a systolic murmur of short duration, grade 1 or 2
intensity at the left sternal border, a systolic ejection pattern, a
normal S2, no other abnormal sounds or murmurs, no evidence
of ventricular hypertrophy or dilation, no thrills, and the absence of
an increase in intensity with the Valsalva maneuver. Such murmurs are
especially common in high-output states such as
pregnancy.13 14 When the characteristic findings of an
individual murmur are considered together with other patient
information and clinical data from the physical examination, the
correct diagnosis can usually be established.15 In
patients with ambiguous clinical findings, the echocardiogram may be
the preferred test because it can provide a definitive diagnosis,
rendering a chest radiograph and/or ECG unnecessary. In some patients
the Doppler echocardiogram is the only noninvasive method capable of
identifying the cause of a heart murmur.12 16
In the evaluation of heart murmurs, the purposes of performing a Doppler echocardiogram are to
- Define the primary lesion and its etiology and judge its severity.
- Define hemodynamics.
- Detect coexisting abnormalities.
- Detect lesions secondary to the primary lesion.
- Evaluate cardiac size and function.
- Establish a reference point for future observations.
- Reevaluate the patient after an intervention.
As valuable as echocardiography may be, the basic cardiovascular
evaluation is still the most appropriate method to screen for cardiac
disease and will establish many clinical diagnoses.17
Echocardiography should not be used to replace the cardiovascular
examination but can be helpful in determining the etiology and judging
the severity of lesions, particularly in pediatric and elderly
patients.15 17 18 19
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Native Valvular Stenosis
Two-dimensional and Doppler echocardiography reliably identify and
quantitate the severity of stenotic lesions of both native and
prosthetic valves. Mitral stenosis is accurately quantified by
planimetry of transthoracic or transesophageal two-dimensional images,
Doppler measurement of transvalvular gradients, and estimation of valve
area by the pressure half-time or continuity methods.20 21 22 23
Prognostic information is obtained from assessment of the hemodynamic
response to exercise24 and/or delineation of morphological
characteristics,25 which in turn help guide the selection
of therapeutic interventions.26
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TEE has also been useful in guiding balloon valvuloplasty procedures.27
Although tricuspid stenosis is readily detected and assessed hemodynamically, the accuracy of Doppler echocardiographic determinations is less well validated but still preferred over other methods.28
Aortic stenosis is accurately quantified by Doppler measurements of instantaneous and mean transvalvular gradients, estimation of valve area by the continuity method, or determination of aortic valve resistance.29 30 31 In patients with reduced LV function, gradient measurements may appear falsely low, while valve area and resistance measurements will more reliably predict the severity of stenosis. Dobutamine perturbation with Doppler assessment of gradients may also be of use.32 Pulmonic valve gradients are similarly quantified. While still experimental, contrast injection may allow more accurate recording of stenotic jet velocities and therefore transvalvular gradients.33
Native Valvular Regurgitation
Doppler echocardiography is the most sensitive technique available
for detection of native valve regurgitation; care must be taken to
distinguish physiological phenomena from pathological lesions. Mild
retrograde flow disturbances are frequently detected in normal
subjects34 35 and if trivial should be identified as being
within the expected normal range and not suggestive of the presence of
valvular heart disease. On the other hand, significant regurgitation
may be silent on auscultation, most often, but not always, in unstable
symptomatic patients.36 Because the finding of clinically
silent valvular regurgitation in an asymptomatic patient carries an
unknown significance, performance of Doppler echocardiography to
exclude valvular heart disease in an asymptomatic patient with a normal
physical examination is not indicated.
Precise assessment of the severity of regurgitant valvular lesions is difficult using any invasive or noninvasive technique, and no gold standard is available to judge relative accuracy.7 Doppler methods for detection of regurgitation are similar for all four native valves and prosthetic valves. Methods include assessment of regurgitant jet characteristics (length, height, area, and width at the vena contracta), effective regurgitant orifice area, and measurement of regurgitant flow volume using the proximal isovelocity surface area.7 37 38 39 40 41 42 43 44 45 The severity of semilunar valve regurgitation is also assessed by the rate of decline in regurgitant gradient as measured by the slope of diastolic flow velocity envelope.46 47 The severity of atrioventricular regurgitation is also reflected by reduction or reversal of the systolic components of venous inflow.48 Finally, in isolated valve disease, regurgitant fraction may be assessed by comparison of stroke volumes at the regurgitant valve and an uninvolved valve.
Doppler echocardiography is also the test of choice in the reevaluation
of regurgitant lesions and in determination of the timing of operative
intervention.49 50 51 Echocardiographically obtainable
information about the severity of regurgitation and associated
structural and functional changes are all important to this therapeutic
decision. The choice between mitral valve repair and replacement is
greatly aided by TTE and TEE; intraoperative assessment of valve repair
is essential to optimal surgical practice, while intraoperative
determination of prosthetic valve seating and function is also
useful.52
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Repeated Studies in Valvular Heart
Disease
A routine follow-up echocardiographic examination is not indicated
after an initial finding of minimal or mild abnormalities in the
absence of a change in clinical signs or symptoms. Patients with more
significant abnormalities on the initial study may be followed
echocardiographically even in the absence of such changes, with the
frequency determined by the hemodynamic severity of the lesion and the
extent of ventricular compensation noted on initial and subsequent
studies. Marked changes in the echocardiographic findings, which may
indicate an alteration in management even in the absence of changes in
clinical signs and symptoms, should be confirmed by reevaluation at a
shorter interval. (See "Indications for Echocardiography in Valvular
Stenosis," "Indications for Echocardiography in Native Valvular
Regurgitation," and "Indications for Echocardiography in
Interventions for Valvular Heart Disease and Prosthetic
Valves.")
Mitral Valve Prolapse
The physical examination remains the optimal method of diagnosing
MVP, because echocardiography may detect systolic billowing of the
leaflets not representing clinically relevant disease. The etiology of
the auscultatory finding of systolic clicks may be defined (as valvular
or chordal), valvular thickening assessed, and the presence, timing,
and severity of regurgitation determined.49 53 In patients
with a nonejection click and/or murmur, an echocardiogram is useful for
diagnosis and risk stratification, particularly by identifying leaflet
thickening and LV dilation (Table 2).54 55 56 57 58 59
Routine repeated studies are of little value unless there is
significant (nontrivial) mitral regurgitation or a change in symptoms
or physical findings.
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Echocardiography to diagnose MVP is of no use in the absence of
physical findings unless there is supportive clinical evidence of
structural heart disease or a family history of myxomatous valve
disease.
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Infective Endocarditis: Native
Valves
Echocardiography is useful for the detection and characterization
of the hemodynamic and pathological consequences of infection,
including valvular vegetations, regurgitant lesions, ventricular
function, and associated abnormalities such as abscesses, shunts, and
ruptured chordae.60 TTE is less sensitive in detecting
vegetations than TEE.61 62 Because of the possibility of a
false-negative examination (or the absence of a vegetation) or a
false-positive study (Lambl's excrecenses, noninfective vegetations,
thrombi), echocardiography should not supplant clinical and
microbiological diagnosis. Echocardiography may be useful in the case
of culture-negative endocarditis63 or in the diagnosis of
a persistent bacteremia whose source remains unidentified after
appropriate evaluation.
Controversy remains as to whether the echocardiographic characteristics
of vegetations are of use in predicting embolization,64 65
although vegetation size and mobility, identification of the involved
valve(s), and especially diagnosis of myocardial involvement are
important for risk stratification and prognosis (Table 3).66 67 68 These features, along with
clinical characteristics such as persistent fever, infecting organism,
etc, may help guide decision making regarding repeated studies and even
valve replacement.
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In most cases TEE is not indicated as the initial examination in the
diagnosis of native valve endocarditis. When the valvular structure or
pathology is well visualized by TTE, there is no indication to perform
TEE. Indications for routine TEE in established endocarditis are
unclear because the clinical importance of the possible additional
information obtained is unproved.69 However, TEE should be
performed when specific questions are not adequately addressed by the
initial TTE examination or in cases where TEE is clearly superior to
TTE. Clinical situations in which TEE is indicated include instances
when the TTE is diagnostically inadequate due to poor quality or
limited echocardiographic windows, when the TTE is negative despite
high clinical suspicion, when a prosthetic valve is involved, when
there is high suspicion such as staphylococcus bacteremia, or in an
elderly patient with valvular abnormalities that make diagnosis
difficult.70
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Prosthetic Valves
Valve replacement is a palliative procedure that carries a
subsequent risk of valve degeneration, development of regurgitation or
stenotic lesions, thrombosis, and endocarditis. Different prostheses
carry different risks for these events so that subsequent evaluations
must be tailored to the patient's clinical situation and type of
prosthesis.
Because the evaluation of prosthetic valves is difficult even in the
best of circumstances, obtaining baseline postoperative studies can be
useful for comparison with future evaluations and assessment of changes
in ventricular function and hemodynamics in response to surgery.
However, the need for routine follow-up echocardiography in the patient
with unchanged clinical signs and symptoms is controversial. In some
patients with known prosthetic valve dysfunction, reevaluation is
indicated even in the absence of a changing clinical situation, as in
some cases reoperation may be dictated by echocardiographic findings
alone.
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Prosthetic Valve Dysfunction and
Endocarditis
Echocardiography is the preferred modality for definition of
abnormalities of poppet motion, annular motion, the presence of
thrombus or fibrin, or prosthetic leaks or stenoses. Because TEE is
often necessary to provide adequate visualization,77 the
necessity for previous performance of a transthoracic study has been
questioned. However, because a great deal of additional information can
be obtained regarding cardiac function and hemodynamics by TTE that may
not be otherwise available and/or may help guide the transesophageal
examination, sequential examinations, starting with TTE, are the
preferred approach.
Assessment of prosthetic valve stenosis is best performed by a combined echocardiography-Doppler technique. However, the Doppler examination may be problematic because eccentric jets may cause recording of falsely low velocities, especially in valves with central occluders. On the other hand, elevated transvalvular velocities may be seen in some prosthetic valves due to pressure recovery and may not accurately represent the hemodynamic gradient. Transvalvular gradients will vary with valve type and size even in the normally functioning prosthesis; individual valve flow characteristics must be considered in the diagnosis of obstruction.78 Reevaluation may be particularly useful in the individual patient.
Determination of prosthetic valve regurgitation is often hampered by prosthetic shadowing, particularly in the mitral position. The transesophageal approach may be particularly useful in this case. Care must be taken to differentiate between the normal, central regurgitation of many mechanical prostheses and pathological paravalvular leaks.79 80 Contrast injection may enhance the spectral recording of both right-sided regurgitant velocities as well as the extent of the regurgitant jet.81 82
Diagnosis of prosthetic valve endocarditis by the transthoracic technique is more difficult than diagnosis of endocarditis of native valves because of the reverberations, attenuation, and other image artifacts related to both mechanical valves and bioprosthesis. Particularly in the case of a mechanical valve, TTE may be helpful only when there is a large or mobile vegetation or significant regurgitation. Thus, the technique cannot be used to exclude the presence of small vegetations. These limitations are diminished with the use of transesophageal recording techniques because of the superior imaging quality and posterior transducer position. Thus, transesophageal techniques have enhanced echocardiographic assessment of prosthetic valve infective endocarditis, especially of the mitral valve and of both mitral and aortic annular areas for abscesses.
Doppler techniques offer important information about the functional
consequences of endocarditis of prosthetic valves, such as the
existence of paravalvular leaks. It should be noted, however, that
paravalvular leaks are not specific for endocarditis. Importantly,
echocardiography may identify vegetations on native valves in patients
with suspected prosthetic endocarditis.
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III. Chest Pain |
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Chest pain can result from many cardiac and noncardiac causes. In mature adults the most common clinical cardiac disorder presenting as chest pain is coronary artery disease (see section IV, "Ischemic Heart Disease"). Other cardiovascular abnormalities that frequently cause chest pain, including hypertrophic cardiomyopathy, valvular aortic stenosis, aortic dissection, pericarditis, MVP, and acute pulmonary embolism, produce distinctive and diagnostic echocardiographic findings (see sections II, IV through VI, VIII, and IX).
In patients with chest pain known to be of noncardiac origin,
further cardiac testing is usually unnecessary. In patients for whom
the character of chest pain or the presence of risk factors raises
concern about possible coronary artery disease, the role of
echocardiography has grown over the last 5 years. Echocardiography can
be performed when possible during chest pain in the emergency room; the
presence of regional systolic wall motion abnormalities in a patient
without known coronary artery disease is a moderately accurate
indicator of an increased likelihood of acute myocardial ischemia or
infarction by pooled data with a positive predictive accuracy of about
50%. The absence of regional wall motion abnormalities identifies a
subset of patients unlikely to have an acute
infarction83 84 85 with a pooled negative predictive accuracy
of about 95%. In a patient with previous myocardial infarction (either
clinically evident or silent), the resting echocardiogram can confirm
that event and evaluate its functional significance.
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IV. Ischemic Heart Disease |
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Echocardiography has become an established and powerful tool for diagnosing the presence of coronary artery disease and defining its consequences in patients with acute ischemic syndromes and those with chronic coronary atherosclerosis. Transthoracic imaging and Doppler techniques are generally sufficient for evaluating patients with suspected or documented ischemic heart disease. However, TEE may be needed in some patients, particularly those with serious hemodynamic compromise but nondiagnostic TTE studies. In these circumstances TEE can distinguish among extensive infarction with pump failure, mechanical complications of infarction, or hypovolemia and can guide prompt therapy.86 87 88 89 Stress echocardiography is useful for evaluating the presence, location, and severity of inducible myocardial ischemia as well as risk stratification and prognostication.
Acute Ischemic Syndromes (Acute Myocardial Infarction and
Unstable Angina)
Echocardiography can be used to rapidly diagnose the presence of
regional contraction abnormality resulting from acute myocardial
infarction, evaluate the extent of associated regional dysfunction,
stratify patients into high- or low-risk categories, document serial
changes in ventricular function, and diagnose important complications.
Some patients with acute chest pain have unstable angina; in these
individuals, echocardiography can also be helpful in diagnosis and risk
assessment.
Diagnosis
The use of echocardiography for diagnosis of acute myocardial
infarction is most helpful when the clinical history and ECG findings
are nondiagnostic.
Segmental LV wall motion abnormalities are characteristic of myocardial
infarction. Their location correlates well with the distribution of
coronary artery disease and pathological evidence of
infarction.83 90 91 92 93 94 95 96 97 However, regional wall motion
abnormalities also can be seen in patients with transient myocardial
ischemia, chronic ischemia (hibernating myocardium), or myocardial
scar. Segmental wall motion abnormalities can also occur in some
patients with myocarditis or other conditions not associated with
coronary occlusion. Table 4 summarizes the utility of TTE in
the diagnosis of acute myocardial infarction. In patients presenting
with chest pain, segmental LV wall motion abnormalities predict the
presence of coronary artery disease but can diagnose an acute
myocardial infarction with only moderate certainty, because acute
ischemia may not be separable from myocardial infarction or even old
scar.83 84 85 90 98 99 100 101 102 However, the absence of segmental
abnormalities (ie, the presence of either normal wall motion or diffuse
abnormalities) has a high negative predictive value. Although it may
not be easy to distinguish acute ischemia or necrosis from
previous myocardial infarction, preservation of normal wall thickness
and normal reflectivity suggest an acute event. Prompt initiation of
treatment to achieve reperfusion can reduce mortality, morbidity, and
patient care costs.103 104 105 106 Hence, early echocardiography
is particularly useful in patients with a high clinical suspicion of
acute myocardial infarction but a nondiagnostic ECG.
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Significant obstructive coronary artery disease is usually present in patients with unstable angina. These patients generally are identified by clinical history, and reversible ECG abnormalities may be recorded during episodes of chest pain. When the clinical history and ECG are unavailable or not reliable and an adequate echocardiographic study can be performed during an episode of chest pain, documentation of reversible segmental wall motion abnormalities confirms the diagnosis of unstable angina.
Severity of Disease/Risk Assessment/Prognosis
In patients with acute myocardial infarction, segmental wall
motion abnormalities can be seen not only in the zone of acute
infarction but also in regions of prior infarction and areas with
ischemic "stunning" or "hibernation" of myocardium that is
nonfunctional but still viable.90 91 94 107 108 109 The sum of
these segmental abnormalities reflects total ventricular functional
impairment, which may overestimate true anatomic infarct size or
perfusion defect.109 Thus, echocardiographically derived
infarct size90 correlates modestly with thallium 201
perfusion defects,94 peak creatine kinase
levels,91 100 hemodynamic changes,90 findings
on ventriculography95 and coronary
angiography96 and pathological findings.108
However, it does predict the development of early110 and
late111 complications and mortality.90 112 In
a given patient with acute myocardial infarction, global and regional
ventricular function as well as clinical status may improve (especially
after reperfusion therapy) or can occasionally deteriorate. As a
noninvasive technique that can be performed at the patient's bedside,
initial and late follow-up echocardiograms are excellent for evaluating
these changes in patients with a large myocardial infarction.
Table 5 summarizes the prognostic value of segmental wall
motion abnormalities detected early in the course of acute myocardial
infarction. In general, more extensive abnormalities denote an
increased risk of complications, including death, recurrent infarction,
pump failure, and serious ventricular dysrhythmias or heart block, even
in patients who appear well
clinically.83 84 91 98 99 110 113 Patients with more
extensive wall motion abnormalities do not invariably develop
complications but do merit careful observation. Relatively mild and
localized wall motion abnormalities indicate a low risk of
complications.
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Assessment of Complications
Echocardiography can be used to evaluate, at the bedside when
needed, virtually any complication of acute myocardial infarction.
1. Acute mitral regurgitation. Development of acute mitral regurgitation following acute myocardial infarction denotes a significantly worsened prognosis.114 Significant regurgitation can result from acute rupture of a papillary muscle head,115 acute ischemic dysfunction of the papillary muscle and associated free wall,116 late fibrosis and shortening of the papillary muscle apparatus,117 altered mitral closure dynamics due to systolic ventricular impairment,118 or annular dilation. All of these different mechanisms can be identified and regurgitant severity evaluated using echocardiographic imaging and Doppler flow studies.
2. Infarct expansion and LV remodeling. Following acute myocardial infarction, development of infarct expansion commonly precedes myocardial rupture (including ventricular septal defect) and denotes a worsened prognosis.119 A follow-up echocardiogram is excellent for identifying infarct expansion120 in patients with a large myocardial infarction and differentiating it from infarct extension as well as subsequent LV remodeling characterized by progressive chamber dilation and further deterioration in global systolic function.
3. Ventricular septal rupture. Both two-dimensional and color Doppler echocardiography can be used to locate and visualize postinfarction ventricular septal defects121 122 123 and to demonstrate left-to-right shunting. Doppler techniques in particular provide an accurate means of distinguishing a ventricular septal defect from mitral regurgitation121 or tricuspid regurgitation that is either preexisting or the result of RV infarction.
4. Free wall rupture. Antemortem diagnosis of free wall rupture in patients with acute myocardial infarction is relatively infrequent. However, free wall rupture is not inevitably fatal,124 and the diagnosis can be made using echocardiographic imaging and Doppler flow studies. Patients who survive free wall rupture often develop a pseudoaneurysm that has a characteristic echocardiographic appearance.125 126 Echocardiography also can help define the presence or absence of associated tamponade physiology and determine the timing of surgical intervention.
5. Intracardiac thrombus. Echocardiography is the definitive test for detecting intracardiac thrombi.127 128 129 130 131 132 133 LV thrombi are most often detected in patients with anterior and apical infarctions127 131 132 133 ; their presence denotes an increased risk of both embolism128 and death.130 The need for serial echocardiography in patients with ventricular thrombi remains controversial.
6. RV infarction. In approximately one third of patients with inferior myocardial infarction, associated RV infarction also occurs.134 This can have significant hemodynamic consequences and implications for patient treatment. Characteristic echocardiographic features of RV infarction have been described.135
7. Pericardial effusion. Pericardial effusion may accompany transmural infarction; its presence does not necessarily imply free wall rupture. The role of echocardiography in evaluating pericardial effusion is discussed in section VI, "Pericardial Disease."
Assessment of Therapy
Given the frequent use of reperfusion therapy (involving either
thrombolytic agents or primary angioplasty) in patients with acute
myocardial infarction, assessment of myocardial salvage is an important
clinical issue. Serial echocardiographic studies can be used to assess
recovery of regional myocardial function from initial stunning.
In patients with unstable angina who undergo revascularization (by angioplasty or surgery), the completeness of revascularization and the functional significance of residual lesions can be determined using exercise or pharmacological stress echocardiography techniques. These applications in unstable angina patients are similar to those in patients with chronic ischemic heart disease discussed below.
Predischarge Evaluation Using Stress Echocardiography
Graded stress echocardiography using intravenous dobutamine can
help in assessing myocardial viability early after myocardial
infarction.136 137 138 Available data suggest that carefully
performed pharmacological stress echocardiography using a gradual
protocol and beginning at low doses of dobutamine appears to be
feasible and reasonably safe when performed 2 to 10 days after acute
myocardial infarction. Myocardial stunning may occur when acute
ischemia is followed by restoration of adequate blood flow and may last
for days to months. Reperfusion-salvaged, stunned (but not functioning
at rest) myocardium can respond to inotropic
stimulation.139 140 As summarized in Table 6,
wall segments that show hypokinesia or akinesia at rest but
improved function during low-dose dobutamine infusion often recover
function136 137 138 (suggesting that these segments are
"stunned"). However, when segments with hypokinesis or akinesis
at rest show no improvement during dobutamine infusion, functional
recovery is less common (suggesting that most of these segments are
infarcted). Segments with initial improvement during low-dose
dobutamine infusion but deterioration of function with higher doses
frequently are supplied by arteries with significant residual stenoses.
Continuing augmentation of systolic wall thickening with higher doses
of dobutamine denotes preserved viability and implies the lack of
critical stenosis in the infarct-related artery.
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Because echocardiographic images obtained during graded exercise demonstrate the location and approximate size of the ischemic territory, they will provide useful information in identifying high-risk patients after acute myocardial infarction.141 142 143 144 145 146 There are few data on long-term event rates in patients studied by predischarge stress echocardiography after an acute myocardial infarction in both those who have and those who have not undergone thrombolytic or other reperfusion therapy. Prospective natural history studies are difficult to accomplish because many clinicians now perform angiography and recommend revascularization in patients with an ischemic response. Nonetheless, when coronary anatomy is unknown, patients who have had an acute myocardial infarction should undergo predischarge functional testing for risk assessment. In those patients unable to exercise because of deconditioning, neurological, or orthopedic limitations, pharmacological stress echocardiography is a valuable alternative for graded testing.
In patients with unstable angina but no myocardial infarction, echocardiography is most helpful for answering specific unresolved clinical questions. When ECG changes of ischemia are obscured by baseline abnormalities (such as chronic left bundle branch block, ventricular pacing, or chronic repolarization changes), reversible segmental wall motion abnormalities during pain can document not only the presence of transient ischemia but also the coronary territory involved and the size of the area at risk. The sensitivity of echocardiography for detecting transient wall motion abnormalities resulting from acute ischemia diminishes the longer the time between resolution of chest pain and acquisition of echocardiographic images. When myocardial viability is uncertain because of persistent impairment of ventricular function in the absence of chest pain (which could be due to "silent" ischemia, myocardial stunning, prior infarction, or cardiomyopathy), the response to carefully graded dobutamine infusion can be clinically useful. However, large-scale studies of this latter question have not been reported.
The indications for echocardiography in acute myocardial ischemic
syndromes are summarized
below.
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Chronic Ischemic Heart Disease
In patients with chronic ischemic heart disease, echocardiography
is useful for a range of indications, including diagnosis, risk
stratification, and clinical management decisions. Quantitative indexes
of global and regional systolic function (including fractional
shortening, fractional area change, ejection fraction, and wall motion
score) are valuable in describing LV function, determining prognosis,
and evaluating the results of therapy. Doppler techniques are also
extremely valuable for evaluating both systolic and diastolic
ventricular function in patients with chronic ischemic heart disease
(see section V, "Cardiomyopathy and Assessment of Left Ventricular
Function").
Diagnostic Accuracy of Echocardiographic Techniques in Chronic
Coronary Artery Disease
1. TTE (at rest). Chronic ischemic heart disease often
results in impaired systolic LV function. The extent and severity of
regional and global abnormalities are important considerations in
choosing appropriate medical or surgical therapy. Abnormal diastolic
ventricular function, which frequently accompanies impaired systolic
function but may also occur when global systolic function is normal,
also can be evaluated (see section V, "Cardiomyopathy and Assessment
of Left Ventricular Function").
Other structural and functional alterations can complicate chronic ischemic heart disease. Mitral regurgitation may result from global LV systolic dysfunction,118 regional papillary muscle dysfunction,116 scarring and shortening of the submitral chords,117 papillary muscle rupture,115 or other causes. The presence, severity, and mechanism of mitral regurgitation can be detected reliably using transthoracic imaging and Doppler echocardiographic techniques. Potential surgical approaches also can be defined. In patients with heart failure or significant ventricular arrhythmias, the presence or absence of ventricular aneurysm can be established.147 148 When an aneurysm is demonstrated, the function of the nonaneurysmal portion of the left ventricle is an important consideration in choosing medical or surgical therapy.149
2. Stress echocardiography. As currently practiced (with
the aid of digital acquisition and storage of relevant images), stress
echocardiography is both sensitive and specific for detecting inducible
myocardial ischemia in patients with intermediate to high pretest
probability of coronary artery disease. A variety of methods can be
used to induce stress; exercise (treadmill, upright or supine bicycle)
and pharmacological techniques (using either adrenergic stimulating or
vasodilator agents) are most often used. The accuracy of stress
echocardiography is summarized in Tables 7 and 8.
As with other noninvasive methods, sensitivity is
higher in patients with multivessel disease than in those with
one-vessel disease, in those with prior infarction, and those with
>70% stenosis compared with those with more moderate
lesions.150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 Compared with standard treadmill exercise
testing, stress echocardiography is of significant additive clinical
value for detecting and localizing myocardial ischemia.
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In patients with a significant clinical suspicion of coronary artery disease, stress echocardiography is appropriate when standard exercise testing is likely to be nondiagnostic. Examples include conditions likely to reduce the validity of ST-segment analysis, such as the presence of resting ST-T wave abnormalities, left bundle branch block, ventricular paced rhythms, LV hypertrophy/strain, or digitalis treatment. When a noncardiac limitation precludes adequate exercise testing, pharmacological stress echocardiography is an appropriate alternative. Dobutamine stress echocardiography has substantially higher sensitivity than vasodilator stress echocardiography for detecting coronary stenoses.150 183 184 Treadmill stress echocardiography may have lowered sensitivity if there is a significant delay from the end of exercise to the acquisition of postexercise images.152 164 Sensitivity can also be diminished if all myocardial segments are not adequately visualized.160 This shortcoming occurs quite variably but is not insignificant. In an asymptomatic patient with prior infarction, stress echocardiography may be helpful in assessing the presence, distribution, and severity of inducible myocardial ischemia and thereby determining the need for cardiac catheterization. However, in certain circumstances it may be difficult to detect residual ischemia within a zone of infarction that exhibits akinetic wall motion.161
Special Issues With Regard to Stress Echocardiography for the
Diagnosis of Coronary Artery Disease
1. The influence of Bayes' theorem. In using any
testing method, it is important to consider the pretest likelihood of
the disorder being sought. With specific regard to stress
echocardiography, the diagnostic value is greatest in patients in whom
the pretest probability of clinical coronary artery disease is
intermediate. Subsets of patients with an intermediate pretest
likelihood wou