Echocardiography in Chronic Rheumatic Mitral Valve Disease

ILLUSTRATIVE ECHOCARDIOGRAM Echocardiography in Chronic Rheumatic Mitral Valve

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Charles M. Gross, M.D.;·· Raymond Gramiak, M.D.;t and Navin C. Nunda, M.D.t chronic rheumatic disease, echocardiography has I nproved to be a reliable method for obtaining infor-

mation about the mitral valve which is not as readily available by other methods. Since the surgical approach to mitral valve disease is now commonplace, this technique of preoperative assessment is of enhanced interest.. This paper will set forth some current views on the utility of the echocardiogram in the evaluation of rheumatic mitral valve disease. NORMAL

MITRAL

VALVE

The mitral valve motion pattern contains information relating to the physiologic events of the cardiac cycle. The following nomenclature has been used in designating mitral valve movements (Fig 1): (a) response to atrial contraction, (b) onset of ventricular systole, (c) mitral valve closure, (d) onset of valve opening, (e) maximal valve opening, and (f) end of rapid ventricular filling phase. The f-a interval represents ventricular diastasis.

MITRAL

STENOSIS

Diagnostic Criteria

Mitral stenosis produces a typical constellation of echographic findings (Fig 1). Reduction of the diastolic ef slope of the anterior mitral leaflet, usually below 35 mm/sec, is one of the reliable diagnostic criteria for mitral stenosis. 1 In a patient in sinus rhythm, failure to demonstrate a discrete "an wave may also be considered a useful criterion in the diagnosis of mitral stenosis. Motion of the posterior mitral leaflet parallel to the anterior leaflet in diastole is another indicator of the presence of mitral stenosis- and can be observed in 90 percent of proved cases." Since the leaflets of the mitral valve chronically involved in the rheumatic process are somewhat thickened and/or calcified, the detection of these abnormalities is another helpful sign. The normal mitral valve displays echoes that are thin and discrete. Calcification of the leaflets may be accurately assessed under standard conditions when the ultra-From the Departments of Medicine (Cardiology Unit) and Radiology (Diagnostic Radiology) University of Rochester School of Medicine and Dentistry, Rochester~.NY. - - Instructor in Medicine and Trainee in Cardiology. tProfessor of Radiology. *Assistant Professor of Medicine (Cardiology Unit) and of Radiology. Supported in part by the National Institutes of Health training grant HL 05500 from the National Heart and Lung Institute (Dr. Gross). Reprint requests: Dr. Gramiak, Department of Radiology, Strong Memorial Hospital, Rochester, New York 14642

CHEST, 68: 4, OCTOBER, 1975

sonoscope controls are adjusted so as to obliterate intracavitary echoes while leaving the left side of the interventricular septum as a distinct reflector. Associated Findings

Certain associated findings, often helpful in making the diagnosis of mitral stenosis, may be seen. These include decreased valve mobility (ce amplitude), increased velocity of mitral valve closure (ac slope), and a large left atrium. The ce amplitude measures the extent of anterior leaflet excursion from the c point at the time of valve closure to the e point at the time of maximal anterior leaflet opening during early diastolic filling. Reduction in the ce amplitude of the anterior leaflet below the lower limit of the normal range (20 mm) is commonly seen in mitral stenosis. Such decrease in anterior leaflet excursion, however, is neither pathognomonic for mitral stenosis, nor does relatively normal ce amplitude exclude the diagnosis. An increase in the rate of mitral valve closure (ac slope) has also been presented as a feature of mitral stenosis.' We have found that a slow ac slope in the absence of mitral valve calcification is strong evidence against mitral stenosis. Left atrial size may also be assessed by echocardiography.! and a large left atrium is supporting evidence for the diagnosis of mitral stenosis. Assessment of Severity

The rate of the ef slope is dependent upon the rate of left atrial emptying. This, in tum, is dependent upon many variables, including left ventricular compliance and diastolic pressure. In mitral stenosis, reduction in ef slope is due to obstruction to left atrial emptying caused by the stenotic mitral valve orifice. Conditions that decrease left ventricular compliance may also decrease the ef slope, for example, aortic valve disease and hypertrophic obstructive cardiomyopathy." Reduction in ef slope is often seen in the presence of left atrial myxoma 1 and has also been noted, for reasons that are not clear, in some cases of marked pulmonary hypertension due to a variety of causes. 2,8 The reduction in ef slope has been shown to correlate with the valve area in mitral stenosis, whether calculated from cardiac catheterization data or estimated directly at the time of surgery." Statistical analysis of a large number of cases carried out in our laboratory has indicated that the correlation between ef slope and traditional indicators of the severity of mitral stenosis is poor and not useful for predictive purposes in the individual case.'? The factors responsible for this discrepancy are

ECHOCARDIOGRAPHY IN CHRONIC RHEUMATIC MITRAL VALVE DISEASE 568

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not clear, hut probably include coexistence of left ventricular disease, effects of associated minimal mitral regurgitation. and struct ural disease in the valve leaflet or apparatus, or both.

Surgical Intervention The rational approach to surgical correction of mitral stenosis requires, among other things, evaluation of two variables : mitral valve mobility and degree of calcification . Evaluation of mitral valve mobility ordinarily requires angiography, but the mobility can be classified as normal, restricted, or poor (Table 1) more readily and effectively by echocardiography. Mitral valve mobility (ce amplitude) is a function of movement related to left ventricular emptying (cd) , the state of the commissures, fibrotic and /or calcific thickening of the cusps, and derangement of the subvalvular apparatus (de) .I ~ The degree of mitral valve calcification may also be assessed semiquantitatively by echocardiography using stan dard sensitivity settings as previously defined.!" Calcification may reliably be categorized as heavy (thick conglomerate echoes), light (multiple discrete linear echoes), or absent (thin single or duplicate signals) (Fig 2) . Based upon work from this laboratory,U it appears unlikely that multiple or conglomerate echoes are produced by the mild to moderate degrees of fibrosis present in noncalcified and lightly calcified valves. The two mitral valve variables of calcification and mobility have been examined with regard to the question of mitral commissurotomy or replacement. U Indications are that careful evaluation of these two variables in the manner described is of considerable value in preoperative planning. Absence of mitral valve calcification appears to be the echocardiographic finding most closely correlated with the feasibility of commissurotomy, while heavy valve calcification and/or poor mobility

570 GROSS, GRAMIAK, NANDA

FIGURE 1. Upper panel, Echogram of normal mitral valve illu strating nomenclature. Important dimensions are shown by two-headed arrows : ( I ) left ventricular outflow tract, measured from left side of ventricular septum to closure point of mitral valve; and (2) ce amplitude measured as vertical distance from closure point of mitral valve ( c) to point of maximal valve opening (e) . Posterior leaflet demonstrates normal counter motion (thick arrow) . R waves of electrocardiogram are marked by short vertical bars. a, Response to atrial contraction; b, onset of ventricular systole; c, mitral valve closure; d, onset of valve opening; I, end of rapid ventricular 611ing phase. Lower panel, Echogram of mitral valve in typical mitral stenosis. Diastolic ei slope is reduced, leaflets are thickened, "a" wave is absent, and posterior leaflet (arrow) moves parallel to anterior leaflet in diastole. ~1V , Mitral valve; RESP , respiration; PHONO, phonocardiogram.

(c e amplitude less than 15 mm) correlate best with the need for valve replacement. Using these three echocardiographic findings, the method of surgical intervention can be reliably categorized in about two thirds of patients with mitral stenosis . Other echocardiographic findings, such as mobility in the normal range, light calcification or restrieted mobility, appear to be less well correlated with the type of surgical procedure. The evaluation of mitral valve mobility has not been improved by separate consideration of de rather than total ce amplitude (Navin C. Nanda, MD : Unpublished data) . The echocardiogram may also provide other indispensable information in cases where prosthetic mitral Table l-Echocardiographic Mea8urementa in Mi'ral S'eno8i8

ef Slope (mrn /sec) 80-150 Normal 35-80 Indeterminate < 35 Mit rnl stenosis rangtac Slope (rnm /sec ) 125-250 Normal 350-600 :\1it ral stenosis range ce Amplitude (mm) in Mitral St enosis 2 20 Normal 16-1!l Restricted $ 15 Poor LV Outflow Trar-t (rnrn ) in Mitral Stpnosis with Vulve

Replacement > 20 < 20

Caged-hall prosthesis It<'(·pp ta h lp Low-profile prosthesis n-r-ommonded

Left Atrium (rnm /sq M of hody surfur« arpa)' 10-20 Normal 20-30 :\lild enlargement 30-40 Moderate r-nlargemont > 40 Spvprp enlargement

CHEST, 68: 4, OCTOBER, 1975

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FJ(;VHE 2. Evaluation of mitral valve calcification by echocardiography, Calcification may be categorized as absent (thin single or duplicate echoes), light (multiple discrete linear echoes) , or heavy (thick conglomerate echoes). ~lV, Mitral valve; PHO:'\O, phonocardiogram . (From Gramiak R: Echocardiography in acquired heart disease. In Diagnostic Ultrasound [King DL ed] . St. Louis, CV Mosby Co, 19i4) .

valve replacement is to be undertaken. A left ventricular outflow tract of less than 20 mm in width makes the insertion of a Starr-Edwards caged-ball prosthesis inadvisahle, because a low output state may be caused by outflow-tract obstruction produced by the cage and ball in the dosed position projecting into the left ventricular outflow tracty··1H In cases where mitral valve replacement is necessary and the outflow tract measures less than 20 mm, the use of a low-profile valve is advisable, as there is very little encroachment upon the left ventricular outflow tract (FigS).

Other Useful Information

detected in certain cases ." It is to he emphasized that echocardiography cannot as yet absolutely exclude left atrial thrombi. The presence or absence of pulmonary hypertension in the patient with mitral stenosis is of considerable practical importance. Clinical evaluation of this factor may be exceedingly difficult. In our laboratory, echograms of the pulmonary valve, which can be recorded in roughly 65 percent of patients, have proved useful in the diagnosis and assessment of the severity of pulmonary hypertension. I .'-~" Echocardiography may also aid in the evaluation of postcommissurotomy patients suspected of having mitral restenosis. Following successful commissurotomy, the ef slope returns toward normal. When restenosis occurs, the slope again decreases in comparison to the postoperative baseline value.~()·~1 Patients with mitral prostheses may also be followed echocardiographically in comparison to a postoperative baseline examination. However, the

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FIGURE 3. Measurement of left ventricular outflow tract in mitral stenosis by echocardiography. Both valves demonstrate calcification and restricted mobility, but outflow tract dimensions differ markedly. Insertion of caged-ball prosthesis in case at left should be well tolerated. Narrow outflow tract in case at right calls for low-profile prosthesis. LVO, Left ventricular outflow tract; ~IV, mitral valve; PHO:\O, phonocardiogram . (From Gramiak R : Echocardiographv in acquired heart disease. In Diagnostic Ultrasound ([KinR; DL ed]. 51. Louis, CV Mosby Co ., 1974) .

CHEST, 68: 4, OCTOBER, 1975

ECHOCARDIOGRAPHY IN CHRONIC RHEUMATIC MITRAL VALVE DISEASE 571

echocardiographic evaluation of prosthetic valves has yet to become a 6nnly established capability. The mitral echogram may be particularly useful in the clinical setting of aortic regurgitation, regarding the presence or absence of coexisting mitral stenosis. A normal mitral recording showing only the fine diastolic flutter associated with aortic regurgitation can reliably exclude mitral stenosis as an associated lesion.

MITRAL Diagnostic Criteria

REGURGITATION

The diagnosis of rheumatic mitral regurgitation cannot be reliably made by echocardiography. There are, however, some clues to its presence; a systolic intracavitary echo pattern appearing in the left atrium, believed to be produced by the regurgitant jet, has been noted in the presence of mitral regurgitation but is not specific for rheumatic disease;" Roughly 70 percent of patients demonstrating this pattern will prove to have significant mitral regurgitation (Navin C. Nanda, M.D., unpublished data). Often the chronic rheumatic mitral valve demonstrates mixed stenosis and regurgitation. In this situation, it has been found that the early diastolic slope may be rapid but that there is a slower late diastolic component. 24 In our experience with mixed lesions, the mitral stenosis pattern -is seen more frequently even when the stenosis is minimal. We have found a loose positive association between the degree of calcification as demonstrated on the echocardiogram and the presence of mitral regurgitation. Therefore, the echocardiogram may demonstrate the features of mitral stenosis, while the patient evinces clinical and/or hemodynamic evidence of predominant mitral regurgitation. 25 CONCLUSION

In summary, echocardiography is of great usefulness to the clinician in evaluation of patients with mitral valve disease. This noninvasive examination, done with proper skills, can provide a definite diagnosis of rheumatic mitral valve disease. From further analysis of the mitral valve echo gram , the mobility and degree of calcification of the valve may be judged and the size of the left ventricular outflow tract evaluated for the preoperative planning of surgical intervention. We believe, therefore, that echocardiography is an indispensable tool in the evaluation of patients with rheumatic mitral valve disease. ACKNOWLEDGMENTS: The authors wish to express their appreciation to Miss Sharon Frederick for secretarial assistance and to Miss Michelle Berdych and Mr. Ernest B. Emerson for assistance with illustrations. REFERENCES

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572 GROSS, GRAMIAK, MAMDA

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