Uses and abuses of two-dimensional echocardiography

International Journal of Cardiology, Elsevier Biomedical Press

I ( 1982) 22 I-227

Editorial

221

review

Uses and abuses of two-dimensional echocardiography Nathaniel hroninoasroe Department

Laboratory

Cardiovascular

ofMedicine,Universrty

Reichek

*

Section, Hospital of the University of Pennsylvania and the School of Medicine. Philadelphia, PA 19104, U.S.A

of Penngkmnia

The rapid proliferation of new cardiac diagnostic methods during the past decade has inevitably resulted in a number of problems and uncertainties in the assimilation and clinical application of these techniques. Two-dimensional echocardiography is an important example of such a new method which because of its wide applicability, safety and ease of application has grown especially rapidly in its clinical availability and use. This brief review will consider some of the principal ‘uses and abuses’ of two-dimensional echocardiography that have emerged to date.

Uses

Ischemic heart disease Since two-dimensional echocardiography permits extensive tomographic sampling of left ventricular dimensions, shape, segmental wall motion, wall thickening and myocardial reflectance patterns, it is particularly suited to the analysis of the inhomogeneous ventricular anatomy and function produced by ischemic heart disease. Identification of segmental dysfunction, acute and old infarction, ventricular aneurysm and mural thrombus are well described applications for which two-dimensional echocardiography appears to be comparable to, if not superior to, alternative methods such as contrast and radionuclide ventriculography [l-4]. Promising new applications in recent years include early diagnosis of infarction and two-dimensional echocardiography with exercise to detect reversible global or segmental left ventricular dysfunction [5,6]. Areas of ongoing investigation not yet ready for clinical application include: (1) noninvasive assessment of coronary anatomy; (2) recognition of acute or old infarction by ‘tissue signature’: and (3) intraoperative use * Member Editorial Board, International Journal of Cardiology. Reprint requests to: Dr. N. Reichek. Noninvasive Laboratory, Cardiovascular University of Pennsylvania, 3400 Spruce St., Philadelphia, PA 19104. U.S.A.

0167-5273/82/C@OC-0/$02.75

G Elsevier Biomedical

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to assess coronary anatomy and segmental left ventricular function [7-91. In clinical practice, bedside assessment of the patient with complicated acute myocardial infarction [IO] and outpatient assessment of left ventricular function have been especially useful. Recent development of carefully validated methods for computerassisted analysis of segmental wall motion will greatly enhance and simplify the appliction of two-dimensional echocardiography to evaluation of ischemic heart disease [ 111. Congenital heart disease The contribution of two-dimensional echocardiography to the diagnostic assessment of congenital heart disease has been larger than its impact in any other area. The method permits reliable assessment of the anatomy of the great vessels, atrioventricular valves, the size, number and orientation of the cardiac chambers and the presence or absence of septal defects [ 12-151. Thus, the great majority of complex congenital defects can be reliably assessed noninvasively, whether in the critically ill newborn, or the occasional adult who has escaped detection in childhood. The inherent power of the method is further enhanced by use of contrast echocardiography techniques to demonstrate right-to-left and, in certain instances, left-to-right shunts [ 161. As higher frequency systems with higher resolution become available, and Doppler sampling of blood flow direction and velocity improves, quantitative assessment of septal defect size and pulmonary/systemic flow ratios should become practical in some instances. Two-dimensional echocardiography has been especially helpful in the critically ill newborn, where it may eliminate the need for catheterization in the hypoplastic left heart syndrome and many instances of pulmonary disease with or without persistent fetal circulation, and speed recourse to catheterization, balloon septostomy or palliative surgery. Mitral stenosis Although assessment of mitral stenosis was the first major application of M-mode echocardiography, the technique did not permit either a complete inspection of the valve apparatus or reliable quantitation of mitral valve area. Two-dimensional echocardiography meets both of these needs, even in subjects with significant mitral regurgitation, which invalidates the Gorlin formula analysis in the catheterization laboratory [ 17,181. Since other hemodynamic and angiographic variables can be extremely important in clinical decision-making, the determination of valve area may not be a sufficient basis for determining management, but dependence on invasive studies has been greatly decreased. Other echocardiographic variables of value in mitral disease will be considered under mitral regurgitation. Aortic stenosis Two-dimensional echocardiography assessment of aortic valve morphology,

has permitted the refinement of noninvasive aortic root anatomy, left ventricular anatomy

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and function and recognition of coexistent valvular, myocardial or ischemic heart disease [19]. Prior to the advent of two-dimensional echocardiography, a major clinical diagnostic problem was the assessment of the elderly patient with cardiac symptoms and a midsystolic murmur. This large population includes individuals falling along a continuum from minimal aortic valve sclerosis, with another cardiac disorder accounting for symptoms, to severe calcific aortic stenosis with typical or atypical symptoms. Unfortunately, in patients over the age of 65 years the ‘classical’ diagnostic features of aortic stenosis are often blunted or distorted by the effects of either age-related decreases in vascular distensibility or development of low cardiac output or right heart failure [20]. M-mode echocardiography provided a reliable method for recognition of left ventricular hypertrophy and aortic valve calcification [21]. However, left ventricular hypertrophy can be due to systolic hypertension and aortic valve calcification may not mean stenosis. With two-dimensional echocardiography direct assessment of the valve leaflet separation has been greatly improved and early reports suggest that either meticulous short-axis imaging or two-dimensional Doppler assessment may permit determination of valve area [22,23]. Mitral regurgitation In patients with mitral regurgitation, two-dimensional echocardiography provides greatly enhanced detail of the mitral apparatus, with resultant enhanced specificity of diagnosis, particularly for papillary muscle dysfunction, chordal rupture and endocarditis [24,25]. It also improves recognition of coexistent tricuspid and aortic disease. Particularly valuable is the improved assessment of cardiac chamber size and motion, relative to M-mode echocardiography, which often underestimates left atria1 and ventricular size in mitral regurgitation due to myxomatous valve with associated thoracic skeletal deformities. Left ventricular size and motion are very useful indices of severity of mitral regurgitation, while left atria1 size is also very helpful. Most important is recognition of the combination of severe mitral regurgitation as judged by left ventricular size and motion, with a relatively small left atrium. This combination means subacute severe mitral regurgitation with severe left atria1 hypertension and large V-waves due to a small maximal atria1 volume, with resultant pulmonary hypertension. Assessment of right heart chamber size and two-dimensional guided contrast echocardiography are invaluable guides to the effects of pulmonary hypertension on right heart function and tricuspid valve competence [26]. Aortic regurgitation In aortic regurgitation two-dimensional echocardiography improves assessment of valve morphology and related aortic root abnormalities. More valuable in chronic aortic regurgitation is the improved assessment of left ventricular size and function, relative to M-mode echocardiography, which tends to overestimate left ventricular systolic function [27]. Extension of quantitative analyses of end-systolic left ventricular size, wall thickness/radius ratio and wall stress to 2-dimensional echocardiography should greatly improve assessment of the left ventricle in aortic regurgitation in the future.

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Disease of the aorta Recognition of aortic root abscess in endocarditis, severity of aortic root dilatation in Marfan’s syndrome and presence and extent of aortic root dissection are all valuable, albeit infrequent applications of two-dimensional echocardiography [28,29]. Left ventricular

size and performance

Continual, slow but steady progress is being made in refining quantitative methods for analysis of left ventricular volume, mass and systolic and diastolic performance [30-321. Usable estimates of volume, ejection fraction and myocardial mass are already available. Future improvements will be largely due to further enhancement of image quality and computer-assisted methods for data analysis, including automated boundary tracking procedures and three dimensional reconstruction [33].

Abuses Excessive

use

Many of the abuses of two-dimensional echocardiography that commonly occur where it is readily available fall under this heading. Neither this nor any other imaging procedure is a substitute for or negates the obligation to perform a careful clinical evaluation of the patient. By performing two-dimensional echocardiography in the absence of such an evaluation, one does a profound disservice to the patient and loses the invaluable opportunity to relate the echocardiographic findings to other data to produce a whole that is greater than the sum of its parts. Moreover. since two-dimensional echocardiography often reveals minor morphologic and functional abnormalities that are not clinically apparent, there is ample opportunity to create spurious disease. When this occurs in a patient with a typical innocent murmur who is, therefore, labeled with a cardiac diagnosis, the morbidity of this ‘harmless’ procedure becomes very great indeed. Also in this category is the phenomenon of reflexive resort to two-dimensional echocardiography in stroke patients to ‘rule out a cardiac source of emboli’. There is now ample evidence that the yield in this setting is vanishingly low in the absence of clinical heart disease [34]. Furthermore, incidental two-dimensional echocardiographic abnormalities, which are particularly common in the elderly, may lead to a mistaken diagnosis of ‘embolic stroke’ and to inappropriate therapy which may have substantial morbidity. In my judgement, the use of two-dimensional echocardiography to seek evidence of mitral prolapse in the absence of other clinical signs thereof, or based on misinterpretation of innocent midsystolic murmurs, also often falls in this category. Since the significance of two-dimensional echocardiographic evidence of prolapse in the absence of M-mode or auscultatory signs is unknown, the result is of doubtful utility and, again, may offer the opportunity to create spurious disease.

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Inadequate

use

In a number of important clinical populations, M-mode and two-dimensional echocardiography are often not used, even where readily available. A prime example is the elderly patient with a systolic murmur and cardiac symptoms, who all too often is found to have aortic stenosis or hypertrophic cardiomyopathy if the studies are done. A related population is that with congestive heart failure, assumed due to ‘atherosclerotic heart disease’. In this setting, use of M-mode and two-dimensional echocardiography often results in recognition of ventricular aneurysm, significant valvular disease, hypertensive heart disease or hypertrophic, congestive or restrictive cardiomyopathy. Use of two-dimensional echocardiography as a screening procedure in selecting patients for cardiac catheterization is also too infrequent in many centers. There is often little justification for catheterizing the patient with asymptomatic mitral valve disease, asymptomatic aortic regurgitation, congestive cardiomyopathy, heart failure due to hypertensive heart disease, hypertrophic cardiomyopathy or atria1 myxoma. Furthermore, where either limited catheterization resources or a situation imposing increased risk of catheterization in a given patient exists, it is abundantly clear that most straightforward patients with valvular heart disease can safely undergo corrective surgery based on echo data alone [35,36]. Misuse The most important abuse in this category is performance and interpretation of two-dimensional echocardiography by unqualified individuals. Despite its apparent simplicity and safety, two-dimensional echocardiography is not an easy procedure to perform well. Moreover, reliable two-dimensional echocardiographic interpretation must cope with many pitfalls and be based on a broad and deep understanding of cardiology as a whole. Missed diagnoses and mistaken diagnoses both pose significant hazards to patients. In general, it is desirable to have two-dimensional echocardiography performed by dedicated well-trained echocardiography technicians or physicians who are themselves formally trained and devote a major portion of their time to echocardiography analysis. Minimal physician training recommendations are available from the American Society of Echocardiography. * A second misuse of two-dimensional echocardiography is to seek to use it to obtain information it cannot provide: ‘Is the patient in heart failure?’ is a good example. Since heart failure remains a clinical description of a constellation of signs, symptoms and hemodynamic correlates, two-dimensional echocardiography can never answer this question. ‘Is the patient in tamponade?’ poses similar problems. Although echocardiography is the method of choice for recognition of pericardial effusion, the echocardiographic manifestations of tamponade are not sufficiently

* Address: C/O Walter Drive South, Orange.

Henry, M.D., Division CA 92668, U.S.A.

of Cardiology,

University

of California.

Irvine,

101 City

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specific to give a completely reliable answer in many instances. Despite the large number of potential abuses it shares with other new diagnostic techniques, two-dimensional echocardiography has proved itself an invaluable clinical test which, when used appropriately and performed and interpreted well, can have a profound impact on clinical decision-making.

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