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Echocardiography in surgical assessment of mitral stenosis AS Vengsarkar, DR Kulkarni, DS ParikhDepartment of Cardiology, K.E.M.Hospital, Parel, Bombay-400012, India
Correspondence Address: Source of Support: None, Conflict of Interest: None PMID: 529178
Eighty patients of isolated mitral stenosis were studied echocardiographically to assess the nature of the stenosed mitral valve as this seems to have a significant bearing on the surgical treatment of mitral stenosis. Echocardiographic findings were compared with the surgical observations and correlated with the post-operative results. EF slope did not have significant correlation with surgically estimated mitral valve area. Calcification was found in 21.25% patients. Leaflet echo thickness as a sign of mitral valve calcification has a high sensitivity (88%) though it lacks specificity (42%). A combined echo graphic sign of leaflet echo thickness of greater than 6 mm, and an opening amplitude of less than 16 mm was associated with an adverse outcome (mitral regurgitation) in 41.6% patients, compared to an incidence of 21% in the remaining.
The nature of the diseased mitra valve is what a surgeon strives to know [1],[19] in the management of mitra stenosis and this has been desperately sought after in the clinical signs and roentgenography [3] but not with encouraging returns. [6],[20] Echocardiography introduced in 1954 came to the forefront as it seemed to offer this very knowledge by way of imaging the diseased valve it a non-invasive manner. The technique has subsequently been employed in an attempt to predict the severity of the stenosis [8],[9],[10],[12],[15],[24] and the state of the mitral apparatus in the assessment of its mobility,thickness and calcification. [13],[14],[23] In an earlier communique [27] we have put forth our experience regarding the ultrasonic assessment of surgical mitral stenosis; this has encouraged us to undertake the present study as an extension of the previous work.
Eighty patients with pure isolated mitral stenosis were studied. There were 34 males and 46 females. The age ranged from 10 to 50 years [Table 1]. All patients were studied pre-operatively in a detailed clinical examination, haemogram, chest X-ray, and a 12 lead electrocardiogram. The echoes were recorded with Unirad sonograph machine; a non-focused 2.25 mHz transducer with a diameter of 13 mm was used. The records were photographed with a 400 ASA 120 size roll film on e Graflex No. 107 A Camera. Previously reported recording techniques were used [11],[23] to make the echoes comparable the only control adjusted was the gain, which was lowered till the left side of the interventricular septum was seen clearly. 'The tricuspid valve was recorded in 50 cases. The EF slope was measured along with the opening amplitude (DE), and total amplitude (CE); the echo thickness of the both leaflets was measured in millimeters. The thickness of the systolic segment was measured in millimeters at its widest part. The post-operative echoes were recorded on the 7th day after operation, by the same method. During surgery the following information was obtained directly from the operating surgeon; valve narrowing by finger palpation; [8],[12] associated mitral regurgitation; fibrosis; leaflet calcification; subvalvular crowding and fusion; and all were graded in 3 groups according to the severity. The final orifice size, regurgitation, and mobility were assessed similarly at the end of the procedure. The patients were reassessed clinically on the 7th post-operative day with special attention paid to the apical murmurs and the 3rd heart sound. The murmurs were graded in the conventional manner. The EF slope was correlated with surgically estimated mitral valve area, the leaflet echo thickness with the surgically estimated calcification. The surgical results were classified in 4 groups. (1) Death within 7 post operative days. (2) Mitral regurgitation-when a systolic murmur graded 2 or more was associated with a 3rd heart sound. (3) Residual mitral stenosis when a significant mid diastolic murmur was heard at the apex. (4) The remaining patients had optimum results. These subgroups were correlated with various echographic features such as EF slope, EF thickness and opening amplitude.
(A) Measurements: The EF slope ranged from 0 to 50 mm/sec., the normal range employed in this laboratory being 60 to 210 mm/sec. There were only 2 patients with an EF slope above 30 mm/ sec. Both these patients were operated as the symptoms indicated significant cardiac decompensation. The opening amplitude ranged from 7 mm to 20 mm. 56 of 80 (70%) patients had opening amplitude greater than 16 mm. The leaflet echo thickness ranged from 2 mm to 10 mm. Posterior leaflet was recorded in each case and a normal posterior leaflet movement was found in 2 patients. (B)Correlations: The EF slope did not have a significant correlation with the surgically estimated mitral valve area (See [Figure 1] below). Calcific deposits were found in 17 patients (21.25%). 15 of 39 patient (38.4%) with leaflet echo thickness of more than 6 mm had calcification while only 2 of 41 (4.9%) patients with leaflet echo thickness of less than 6 mm had calcification. The number of- patients with calcification and the total number of patients in each leaflet thickness group are shown in [Figure 2]. A pre-operative grade I mitral regurgitation was found at surgery in 6 patients (7.5%); in none of these did it increase post-operatively. These cases did not belong to the group of patients who developed mitral regurgitation postoperatively. The surgical outcome in 80 patients was as follows-(i) Death-4 patients (5%), (ii) Mitral regurgitation-21 patients (26.25%), (iii) Residual mitral stenosis-3 patients (3.75%), (iv) 52 patients (65%) had optimum results. In a combined consideration of excessively thick leaflet echoes (more than 6 mm) and severely reduced opening amplitude (less than 16 mm) (See [Figure 3] on page 200 A) plotted against the incidence of post-operative mitral regurgitation it was observed that 5 of 12 (41.6%) patients with such echoes had post-operative mitral regurgitation; 16 of the remaining 68 patients (23.5%) without such echoes (See [Figure 4] on page 200 B) had mitral regurgitation. In 10 (12.5%) patients a normalization of the posterior leaflet was observed post-operatively (See [Figure 5] on page 200 B). Tricuspid valve abnormality was not detected in any patient.
The abnormally low diastolic closing rate of anterior mitral leaflet (less than 30 mm) is the cardinal feature of surgical mitral stenosis. [11] The lower limit of normal EF slope is 60 mm/sec. at Many authors have discussed the determinants of the 'EF' slope of the mitral valve echo; in this regard the size, the duration of transmitral pressure gradient, [16] left ventricular filling rate [18] , ventricular compliances [5] , mitral ring motion, [31] peak inflow velocity [28] have all been considered; but the issue remains to be clarified. In its genesis, the EF slope is a complex phenomenon with many of these factors playing a varying role in a patient with mitral stenosis; [17] to consider it alone as an index of severity of mitral stenosis would therefore seem an over simplification. This is borne out by the poor correlations observed in this and other series. [2] The favourable early reports [8],[10],[12] included mild mitral stenosis and normals as well. Though the diastolic opening amplitude is partially contributed to by annular movement [31] it mostly reflects the mobility of valve cusps. Despite a severe orifice narrowing it may be normal if the chordo-papillary apparatus is intact; [30] it is diminished with subvalvar fibro-calcific disease. [29] A severely diminished opening amplitude specially when considered along with leaflet echo thickness, was thought a possible predictor of adverse surgical outcome after commissurotomy. [29] In cases with opening amplitude of less than 16 mm and a standardized leaflet echo thickness greater than 6 mm there was a higher incidence post-operative mitral regurgitation (42%) as compared to the remaining cases (21%). The destroyed leaflets become the seat of fibrosis and calcification [4] in a significant number of cases. Rarely other components of mitral valve also get calcified [4],[26] Leaflet echo characteristics do not appear to provide useful clues which may influence surgical management by detection of calcification in mitral stenosis. [22] Multilinear and coalescent echoes [23] independent of thickness were reported by one of the authors [27] not to be specific for calcification. Excessively thick leaflet echoes (more than 6 mm) as a sign of calcification employed in this series also lacked specificity (42%) (See [Figure 2] on page 203), possibly due to the unknown variable of valve interface characteristics; the sign, however, had a high sensitivity (88%) for leaflet calcification. Patients with thick leaflet echoes and reduced opening amplitude appeared to have higher incidence of post-operative mitral regurgitation (41.6%) as compared to the incidence (23.5%) of the remaining patients without such echoes; this subject is therefore being studied at these institutions in a larger number in regard to its predictive value as related to the surgical outcome in mitral commissurotomy. Posterior mitral leaflet moves anteriorly during diastole in mitral stenosis [7] but ocasionally it moves posteriorly (See [Figure 6] on page 200 B) which is explained by selective involvement of the anterior leaflet; relative predominance of the posterior leaflet and the annular movement has also been considered; if the latter predominates normal leaflet movement becomes possible [18] . The posterior leaflet was normal pre-operatively in only two patients (2.5%); one patient had an EF slope of 50 mm/sec. These two findings suggested mild mitral stenosis though the symptoms or surgical findings did not corroborate this. The other patient had EF slope of 20 mm/sec and the anterior mitral leaflet was moderately thickened, suggesting moderate mitral stenosis, which was confirmed at surgery. Normal posterior leaflet motion in mitral stenosis has been reported in upto 10% [18] The posterior leaflet exhibited a normal movement post-operatively in 10 patients (12.50%). As a group they had a near normal opening amplitude (19.6 mm. mean) and 7 of them had leaflet thickness less than 6 mm. No specific factors have been reported as being contributory to the normalization of posterior mitral leaflet post-operatively.
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]
[Table 1]
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