MITRAL REGURGITATION (MR) in patients undergoing aortic valve replacement (AVR) for aortic stenosis (AS) is a common finding, and reported incidence varies from 61% to 90%.
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Although most reported MR is functional (ie, in the absence of a structural abnormality), significant MR (≥grade 2/4) has been reported in almost 13% of such cases.2
The presence of concomitant coronary artery disease, fluid overload, and structural changes in the left ventricle (LV) also are believed to contribute to concomitant mitral valve dysfunction in patients with critical AS. Additionally, chronic left ventricular outflow tract obstruction as seen in AS can cause permanent geometric changes in left ventricular shape and structure, which eventually result in reduced mitral leaflet coaptation and significant MR.1
It is obvious that the pathophysiology of this condition is more complicated than MR because of the structural abnormalities of leaflets.The indications of AVR for AS are straightforward and are based on the calculation of the geometric aortic valve area (AVA) and the measurement of peak and mean transvalvular gradients. However, the verbatim application of such “rigid” guidelines may not be the most prudent management plan in this particular situation. Because AVA and transaortic valvular gradient are flow dependent, the presence of significant MR and the reduction in the “forward” flow adds another level of complexity. This is based on the notion that AVA varies with a transvalvular flow, and it may be possible to “improve” the AVA with increased stroke volume.
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Furthermore, it is very difficult to accurately measure the AVA via the continuity equation in the presence of arrhythmias (atrial fibrillation) when there is beat-to-beat variation in LV stroke volume.1
The patient presented by Subramaniam et al
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in the present E-Challenge also had significant MR in addition to severe AS, and the authors were faced with the challenge whether to surgically address the MR or manage it medically. After an AVR, there is a significant reduction in afterload, which can have beneficial effects on the severity of coexistent MR, favoring the conservative approach. There is also a significant reduction in transmitral pressure gradient after AVR, which is different from the acute afterload reduction achieved with vasodilator therapy when the transmitral pressure is maintained.5
Whether the reduction in MR severity after AVR is caused by altered loading conditions or geometric changes in LV geometry is not decided conclusively. It may be quite possible that immediate improvement in MR severity may be caused by the reduction in the transmitral pressure gradient, whereas favorable changes in LV geometry may be more important determinants in the long-term benefits of AVR. In either case, the addition of a mitral valve procedure to AVR may add to the risk of the procedure.6
Which patients with significant MR with AS will improve after AVR alone is not well established. Other than the degree of the preoperative severity of MR, there are no universally accepted predictors of improvement in MR grade after AVR alone. Although most studies do not include patients with severe MR, data from 40 patients with severe MR suggested that a majority had an improvement of their MR by at least 2 grades.
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The etiology of MR is also a strong predictor of postoperative MR improvement. Although patients with functional or ischemic MR have shown the greatest degree of improvement, myxomatous and rheumatic diseases showed minimal improvement,7
strengthening the case for surgery in these patients with structural abnormalities of the leaflets. Thus, ruling out myxomatous or rheumatic disease is an important part of the echocardiographic challenge in these patients. Other adverse predictive factors of outcome after AVR for patients with AS and concomitant functional MR include functional MR ≥2+ with either a left atrial diameter of >5 cm, a preoperative peak AV gradient <60 mmHg, or atrial fibrillation.2
The illustrated case by Subramanian et al
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highlights many of these challenges encountered in this situation. The initial difficulty in this case was to establish the severity of AS, which is quite tricky in patients with severe MR caused by reduced forward flow as was the grading of the severity of MR. The decision to change the procedure to AVR and mitral valve replacement hinged on an accurate assessment of mitral valve dysfunction. Also, it was important to appreciate the contribution of LV remodeling to the severity of MR and the reduction in transmitral valvular gradient and the expected improvement in MR after AVR. The surgical risk of a combined procedure, particularly in a patient with a heavily calcified mitral annulus, is another very important consideration in this decision-making process. Therefore, the decision to replace/repair the mitral valve is not just based on a single variable (eg, size of the vena contracta or the regurgitant orifice area) but on an assessment based on the context of the complete clinical scenario. Therefore, the severity of MR is only one of the factors to be considered in this situation and not the only one. Although proposed diagnostic algorithms have been devised,1
these patients require an individualized and tailored approach based on their operative risk and their echocardiographic and clinical predictors of improvement in MR after AVR surgery.References
- Mitral regurgitation in patients with aortic stenosis undergoing valve replacement.Heart. 2010; 96: 9-14
- Natural history and predictors of outcome in patients with concomitant functional mitral regurgitation at the time of aortic valve replacement.Circulation. 2006; 114: I541-I546
- Intraoperative dobutamine stress echocardiography to assess aortic valve stenosis.J Cardiothorac Vasc Anesth. 2006; 20: 862-866
- Fate of mitral regurgitation after aortic valve replacement for aortic stenosis.J Cardiothorac Vasc Anesth. 2011; 25: 885-886
- The mechanism of decrease in dynamic mitral regurgitation during heart failure treatment: importance of reduction in the regurgitant orifice size.J Am Coll Cardiol. 1998; 32: 1819-1824
- Long-term results of mitral-aortic valve operations.J Thorac Cardiovasc Surg. 1998; 115: 1298-1309
- Effect of aortic valve replacement for aortic stenosis on severity of mitral regurgitation.Ann Thorac Surg. 2007; 83: 1279-1284
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Published online: August 12, 2011
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© 2011 Published by Elsevier Inc.
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- Fate of Mitral Regurgitation After Aortic Valve Replacement for Aortic StenosisJournal of Cardiothoracic and Vascular AnesthesiaVol. 25Issue 5
- PreviewA 75-YEAR-OLD MAN with dizziness and shortness of breath underwent a balloon valvuloplasty performed for critical aortic stenosis. After experiencing minimal symptomatic relief, the patient presented to the authors' tertiary care center with worsening symptoms 2 weeks after the procedure. The patient's history was significant for congestive heart failure, type-2 diabetes mellitus, coronary artery disease, chronic atrial fibrillation, and hypertension, and he had undergone a coronary artery bypass graft procedure in 1992.
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