Summary
Although mitral stenosis is mostly due to rheumatic fever, other etiologies, such as degenerative, congenital, drug- or radiotherapy-induced mitral stenosis, are emerging and need to be recognized in order to decide the best therapeutic options. This pictorial review describes the echocardiographic features of these different anatomical types and the additional value of three-dimensional echocardiography.
Résumé
Bien que le rhumatisme articulaire soit de loin l’étiologie la plus fréquente du rétrécissement mitral, les autres étiologies comme les formes dégénératives, congénitales, secondaires à la radiothérapie ou à certains médicaments voient leur incidence augmenter et doivent être reconnues de manière à permettre un traitement approprié. Dans le présent article, nous décrivons les différentes formes échocardiographiques de rétrécissement mitral en insistant sur la valeur additionnelle de l’échographie tridimensionnelle.
Background
Echocardiography plays a major role in the evaluation and decision-making process in patients with mitral stenosis (MS), allowing for confirmation of diagnosis, evaluation of severity and choice of best therapeutic option (feasibility of a percutaneous mitral commissurotomy [PMC] or surgical valve replacement) . MS is mostly due to rheumatic fever but other aetiologies are emerging and should be recognized, as these forms are usually not suitable for PMC. This review aims to present the different aetiologies of MS, their echocardiographic characteristics and the potential value of three-dimensional (3D) echocardiography ( Table 1 ).
| Etiology | Commissures | Mobility | Calcification |
|---|---|---|---|
| Rheumatic mitral stenosis | |||
| Native valve | Fused | Restrictive motion of the posterior valve | 0 to +++ (Possible) |
| Restenosis due to commissural refusion | At least partially fused | Restrictive motion of the posterior valve | 0 to +++ (Possible) |
| Restenosis due to valve rigidity | At least one commissure completely open | Restrictive motion of the posterior valve | 0 to +++ (Possible) |
| Degenerative mitral stenosis | Both commissures open | Normal mobility of the tip of both leaflets | +++ Important calcifications of the mitral annulus and the base of both leaflets |
| Post-radiation mitral stenosis | Both commissures open | Absence of restrictive motion of the posterior valve | + to +++ Highly suggestive calcifications of the mitral aortic membrane |
| Congenital mitral stenosis | Not applicable (absence of commissure) | Normal | Usually not |
Rheumatic mitral stenosis
Rheumatic MS is a frequent cause of valve disease in developing countries and remains a significant problem in Western countries despite the striking decrease in the prevalence of rheumatic fever, as the consequence of immigration from developing countries. Thus, according to the Euro Heart Survey, MS still accounted for 12% of native valvular heart disease . Commissural fusion is the main mechanism of rheumatic MS. Associated lesions are chordal shortening and fusion, and leaflet thickening. Mobility of the posterior valve is almost always reduced whereas mobility of the anterior valve is often preserved. Later in the disease course, superimposed calcification may contribute to the limitation of leaflet motion.
Commissural splitting is the main mechanism by which the mitral valve area (MVA) increases after PMC. Commissural opening should be evaluated in parasternal short-axis and has been shown to be an important predictor of long-term functional outcome after PMC . The achievement of a complete – ideally bilateral – commissural opening is thus a major goal during PMC. Our group has previously shown that 3D echocardiography provides a better assessment of the degree of commissural opening . Fig. 1 presents different forms of rheumatic MS with no, unilateral and bilateral commissural opening in two-dimensional (2D) transthoracic (TTE) and corresponding 3D transoesophageal echocardiography (TEE) views.
In addition, real-time 3D-TTE has provided accurate MVA measurements similar to 2D-TTE and, more importantly, has improved the accuracy of planimetry when performed by non-experienced operators . 3D-TEE also provides accurate and reproducible MVA measurements, similar to 2D planimetry performed by experienced operators, and could be considered as a second-line alternative tool for the evaluation of MS severity in patients with poor echocardiographic windows or for teams less accustomed to evaluating MS patients .
After a successful PMC, late clinical deterioration may eventually occur, with a 40% rate of anatomical deterioration at 10 years . Late anatomical deterioration – or restenosis – may result from commissural refusion or valve rigidity with persistent commissural opening. Distinction between these two features is of crucial importance, as a new PMC may be attempted in case of restenosis with commissural refusion with good mid-term results in selected patients , whereas PMC is of no use in case of valve rigidity with persistence of commissural opening. Echocardiography – most specifically 3D echocardiography – plays a major role in the assessment of the degree of commissural opening ( Fig. 2 ).
