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Ann Thorac Surg 2007;83:1279-1284
© 2007 The Society of Thoracic Surgeons
a Department of Cardiac Surgery, Free University of Brussels, Brussels, Belgium
b Department of Cardiovascular Surgery, Montreal Heart Institute, Montreal, Quebec, Canada
c Department of Medicine, Montreal Heart Institute, Montreal, Quebec, Canada
Accepted for publication December 27, 2006.
* Address correspondence to Dr Bouchard, Department of Surgery, Montreal Heart Institute, 5000 Bélanger Est, Montreal, Quebec, Canada H1T1C8 (Email: denis.bouchard{at}icm-mhi.org).
| Adult cardiac surgery:
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Abstract |
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Methods: Using an institutional databank of prospectively collected data, all patients undergoing isolated AVR for aortic stenosis with moderate (2+) to moderate-severe (3+) MR between 1994 and 1996 at the Montreal Heart Institute were evaluated.
Results: Eighty patients with preoperative and postoperative transthoracic echocardiographic follow-up were identified. Preoperative MR was moderate (2+) in 78 patients (97.5%) and moderate-severe (3+) in 2 patients (2.5%). Mitral regurgitation was classified as rheumatic (32%), ischemic (32%), functional (21%), and myxomatous (15%). At 1-year follow-up transthoracic echocardiography, MR improved by 1 or 2 grades in 29 patients (35%), was unchanged in 44 (55%), and worsened in 7 (10%). On multivariate analysis, isolated ischemic and functional MR were the only preoperative factors predictive of MR improvement after AVR (p = 0.01): 54% of ischemic and 44% of functional MR patients showed improvement in MR after AVR compared with 23% of rheumatic and 17% of myxomatous MR patients.
Conclusions: Etiology of MR was a significant prognostic factor for improvement in MR grade. Since there was little improvement in the rheumatoid and myxomatous group, replacement or repair should strongly be considered. For functional and ischemic mitral regurgitation, a surgical correction should be performed on an individual basis.
Aortic valve replacement (AVR) for aortic stenosis is the most frequently performed surgery for valvular heart disease. Mitral regurgitation (MR) is a common finding in patients with aortic valve stenosis, with an incidence as high as 67% reported in the literature [1]. Whether a concomitant mitral procedure should be performed is usually not an issue when MR is mild; most surgeons will not expose the patient to excessive morbidity for grade 1 MR nor let a patient with grade 4 MR leave the operating room untreated. But when MR is moderate, the question is whether a second valve should be replaced or repaired at the same time. In the literature, functional mitral regurgitation appears to have a better prognosis than structural regurgitation after AVR. Because the concurrent replacement of both valves is associated with higher postoperative mortality (5% to 12.5%) and morbidity rates [2, 3], mitral valve surgery could be avoided if it were possible to reliably predict that MR would improve after AVR. In contrast, combined valve surgery would be warranted for patients with significant or progressive MR after isolated AVR.
The purpose of our study was to evaluate in a cohort of patients (1) the changes in MR severity that occur after isolated aortic valve replacement for aortic stenosis for moderate (2+) and moderate-to-severe (3+) mitral regurgitation; (2) the clinical and echocardiographic findings that may be preoperative predictors of MR improvement after aortic valve surgery, focusing on the cause of mitral regurgitation; and (3) the long-term survival benefit of improvement in MR after isolated AVR.
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Patients and Methods |
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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Echocardiographic Analysis
The peak and mean gradients across the aortic valve were calculated using the Bernoulli equation, and the aortic valve area was assessed using the continuity equation. The severity of MR was assessed using several color-flow and spectral Doppler criteria, including MR area, MR/left atrium (LA) area ratio (the area of the regurgitant jet relative to the LA size), antegrade mitral flow velocity, and pulmonary venous flow, together with other two-dimensional criteria of MR severity (left ventricle dimensions and function, LA dimensions, and mitral valve morphology). Attenuation of the systolic component of the pulmonary veins (PV) flow generally resulted in grading the MR as moderate, whereas systolic wave inversion resulted in considering the MR as severe. Two-dimensional and M-mode echocardiography were used to detect the underlying cause of MR. Thickening and calcification of the leaflet tissue and subvalvular apparatus with restricted leaflet motion and commissural fusion combined with mild mitral stenosis and a history of rheumatic fever were criteria retained for rheumatic origin. Myxomatous origin was recognized when the mitral valve met the criteria for classic or nonclassic mitral leaflet prolapse (Carpentier type II): a maximum superior displacement of one or both mitral leaflets of more than 2 mm relative to the line connecting the annular hinge points during systole, whether the leaflet was superior or inferior to 5 mm. When valvular anatomy was normal and MR was caused by failure in coaptation of mitral leaflets because of their restricted motion (Carpentier type IIIb) and there was a history of myocardial infarction, the MR was attributed to an ischemic origin. When none of these criteria was met, the MR was targeted as functional (Carpentier type I).
Mitral regurgitation severity was scored as follows: absent or trace = 0, mild = 1, moderate = 2, moderate to severe = 3, and severe = 4 [5, 6]. A change in MR was considered significant when there was at least a 1 score difference between preoperative and postoperative studies. When no morphologic abnormality was found, the MR was classified as functional. The presence or absence of mitral annulus calcification was determined with two-dimensional parasternal and apical views. The left ventricular end-diastolic diameter and the thickness of the interventricular septum and posterior wall were measured by two-dimensionally–guided M-mode echocardiography using standard American Society of Echocardiography criteria. Left atrial diameter was measured using M-mode in the parasternal view. Left ventricular ejection fraction was determined with the apical views and the modified Simpson formula.
Because changes in MR severity in the immediate and short-term postoperative period may not reflect those in a more stable setting, we elected to focus on the postoperative echocardiogram performed 1 year after isolated AVR.
Statistical Methods
Univariate analysis of preoperative patient history and physical characteristics and echocardiographic findings was performed for the overall group. Student’s t test was used to compare continuous variables and Fisher’s exact test, to compare categorical variables. Univariate analysis was used to determine possible predictors of MR evolution, using a p value of less than 0.05 as a cutoff for significance. Significant factors were then analyzed in a multivariate logistic regression analysis to determine predictors of regurgitation improvement. Survival analysis was done using the Kaplan-Meier method, and statistical significance was obtained using the Breslow test. A p value of less than 0.05 was considered significant. The data were analyzed using the statistical package program SPSS 13 (SPSS, Chicago, Illinois).
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Results |
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Postoperative EOAi (p = 0.68) and concomitant CABG surgery (p = 0.71) had no effect on MR regression after AVR. The etiology of mitral regurgitation before AVR, namely, ischemic, functional, rheumatic, or myxomatous, was independently correlated with MR improvement (p = 0.013).
Survival Analysis
Survival of patients according to etiology of MR (Fig 2)—rheumatic plus myxomatous and ischemic plus functional—was similar at 10 years after isolated AVR (p = 0.867). Patients who showed MR improvement after isolated AVR had a better 10-year survival than did patients who had no changes or had deteriorating MR (p = 0.072; Fig 3).
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Comment |
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TopAbstractIntroductionPatients and MethodsResultsCommentReferences |
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In patients with severe aortic stenosis, concomitant MR either may be caused by morphologic changes of the mitral valve or may be secondary to aortic stenosis and increased afterload and left ventricular dysfunction or a combination of both. The degree of MR depends on the regurgitant orifice and the systolic pressure gradient between the left ventricle and left atrium. The former may be affected by ventricular remodeling after AVR; the latter may be affected by replacing a stenotic aortic valve, thereby lowering the left ventricular systolic pressure [7]. Given the morphologic and physiologic modification after AVR, the degree of MR might improve.
Whether the mitral valve should be repaired or replaced during the same operation in patients with severe aortic stenosis undergoing AVR is controversial when considering patients with moderate (2+) or moderate-to-severe (3+) MR. Because the concurrent replacement of both valves is associated with higher postoperative mortality (5% to 12.5%) and morbidity [2, 3], mitral valve surgery could be avoided if it were possible to reliably predict in which circumstances MR would improve after AVR. In contrast, combined valve surgery would be warranted for patients with unchanged but significant or progressive MR after isolated AVR. Thus, it is crucial to predict which are the preoperative clinical and echocardiographic factors influencing the improvement or deterioration of MR in patients undergoing AVR.
In our study, we had a significant change in the distribution of MR severity before and after AVR toward improvement: 36% of patients improved by 1 or 2 on the scale of MR at 1 year. This finding is consistent with other reports in the literature including all types of MR. Tunick and associates [8] studied MR evolution at a mean of 58 days after AVR. Half of the patients had structural valve lesions, and of the 44 patients studied, 11 had moderate MR. In those 11 patients, 10 showed an improvement of MR after AVR [8]. In contrast, Adams and associates [9] had only 4 patients improving in the sample of 16 patients with moderate MR at a mean of 176 days after surgery. Given the sample size, they could not identify prognostic factors. More recently, Brasch and associates [10] studied 27 patients, 16 of them having grade 2 or 3 MR, and 9 (44%) of those experienced an improvement of MR. Larger left ventricular mass was the only significant prognostic of MR improvement when considering the whole group at mean follow-up of 2.2 months [10]. Etiology of MR was not reported, but 96% had mitral calcifications and 33% had thickening of the leaflets. Bareirro and coworkers [11] reported 80% improvement in the functional group and 50% improvement in the myxomatous group, but of the 70 patients studied, only 37 had a postoperative echography.
We showed that the most significant prognostic factor was the etiology of MR: ischemic and functional MR improved at echocardiographic analysis 1 year after isolated AVR whereas rheumatic and myxomatous disease remained stable or deteriorated. Although etiology was a strong prognostic factor, we had also 5 of 26 patients (23%) improved in the rheumatoid group and 2 of 12 (17%) in the myxomatous group.
The MR amendment has been more extensively studied in the literature in the functional group [12–14]. Seven patients (7 of 16, 43%) in our study with functional MR improved, as shown by Moazami and associates [15] after a mean 818 days of follow-up. This figure was confirmed by Absil and colleagues [16] (40 patients of a cohort of 58 patients with grade 2 or 3 improved) and by Ruel and associates [17]. Ruel showed that functional MR improved in 68.4% of patients with moderate MR and no additional identified risk factors (left atrial diameter >5 cm, atrial fibrillation, mean aortic gradient >40 mm Hg), in 63.5% if one risk factor was present, and in 44.4% if two risk factors were present.
In our study, the most important improvement was seen in the ischemic group, occurring in 14 patients (14 of 26, 54%). Christenson and associates [18] specifically assessed this issue, showing improved MR in 19 of 21 patients (90%) with AVR and CABG-associated procedure and improved MR in 12 of 19 patients (63%) in the AVR only group [18]. Patients with MR improvement after isolated AVR seemed to have a better 10-year survival compared with patients with stable or deteriorating MR. This observation did not reach statistical significance (p = 0.072), and other confounding variables such as left ventricular ejection fraction were not assessed; however, it is consistent with other reports in the literature in which the burden of MR, even mild, is an independent prognostic factor for worse long-term survival as seen in the setting of ventricular dysfunction [19] or ischemic mitral regurgitation [20].
In conclusion, our patients undergoing isolated AVR for aortic stenosis with significant MR before surgery showed that MR improved in ischemic and functional MR whereas MR deteriorated in rheumatic and myxomatous etiology at 1-year echographic follow-up. The decision to repair or replace the mitral valve at the time of AVR remains difficult, but preoperative echocardiographic analysis of the mitral valve morphology gives the surgeon the most important prognostic factor for the change in MR severity: the etiology of MR. Functional or ischemic MR will likely improve after isolated AVR, whereas rheumatic or myxomatous MR will most likely remain stable or even deteriorate.
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