Definition
Mitral valve stenosis
Narrowing above, below or at the level of the valve ring. The mitral valve is divided anatomically into the anterior and posterior leaflets, which re divided from the anterolateral to the posteromedial commissure into A1, A2, A3 (anterior leaflet) and P1, P2, P3 (posterior leaflet) (Mitruka classification, 2000).
- supravalvular stenosis (type I): supramitral ring (left atrial appendage lies above)
- valvular stenosis (type II):
type IIA: annular hypoplasia
type IIB: leaflet defects - cleft, double orifice valve - subvalvular stenosis (type III):
type IIIA: abnormal chordae
type IIIB: abnormal papillary muscles: parachute valve (space between chordae obliterated, chordae shortened or non-existent), hammock valve (all chordae pull towards a single posterior papillary muscle) - mixed stenosis (type IV).
Mitral insufficiency
Regurgitant mitral valve or differing cause. Carpentier classification:
- type I: lack of coaptation, annulus dilatation, cleft, mitral valve defect
- type II: leaflet prolapse, chordae elongated or ruptured
- type III: leaflet restrictive: insufficiency or stenosis is the result.
Indication
Mitral stenosis
- infants/children
symptoms: signs of heart failure, dyspnea, failure to thrive, secondary right heart strain. Echocardiography: elevated gradients across the mitral valve, enlargement of the left atrium, secondary right ventricular strain, tricuspid valve insufficiency → elevated right ventricular pressure. - teenagers/adults
mitral opening area <1cm², orthopnea, atrial fibrillation, embolizatin, NYHA class 3-4
Mitral regurgitation
- infants/children
symptoms: signs of heart failure, dyspnea, failure to thrive, secondary right heart strain.
Echocardiography: high-grade mital valve insufficiency, broad jet reaching to the pulmonary veins, enlargement of the left atrium, secondary right ventricular strain, tricuspid valve insufficiency → elevated right ventricular pressure. - teenagers/adults
Diameter: ESD >50mm (norm 40mm), ESV >90ml/m² (norm 30ml/m²) → no normalizatin of LV function after correction.
Diagnosis
- by transthoracic echocardiography: localization and morphology of the stenosis/regurgitation jets, morphology of the mitral valve and subvalvular apparatus. LA size, LV/RV function, tricuspid valve insufficiency, RV pressure
- by magnetic resonance imaging: volumetry (LVESV)
- by heart catheterization: in special cases.
Operation
Access is by median sternotomy. The heart-lung machine is employed and the heart arrested with cardioplegia. The left atrium is opened directly or through the interatrial septum and the mitral valve is inspected.
Reconstruction
- for stenosis: commissurotomy, thinning of the leaflets, division of the papillary muscles.
- for insufficiency: plasty of the annulus and commissures, patch augmentation of the leaflets. Ross II operation (Kabbani et al.): pulmonary autograft is sewn into a synthetic prosthesis and then implanted into the mitral valve annulus. Disadvantage: lack of growth potential → only in adults.
Mitral valve replacement
Mechanical prosthesis with minimal diameter of 16 mm (aortic valve reversed); biological prosthesis minimally 23 mm.
Possible Complications in the Long Term
The prognosis for patients with this heart defect in the mid-term is good. In the further course recurrent stenosis or mitral valve insufficiency Children will gradually outgrow a small prosthesis, so that relative stenosis occurs, making replacement by a larger prosthesis necessary.