Abnormalities of the Mitral Valve and Related Anomalies

20 Abnormalities of the Mitral Valve and Related Anomalies

With Anne Geoffray

Definition and Classification

Various anatomic lesions result in obstruction to flow from the left atrium to left ventricle.

Congenital mitral stenosis is a malformed valve of variable morphology, including hypoplasia of the annulus, fusion of leaflets, double orifice valve, shortened or thickened chordae tendineae, and abnormal papillary muscles.

Cor triatriatum versus supramitral stenosing ring (Fig. 20.1):
- • Cor triatriatum is an intraatrial membrane with one or more potentially restrictive ostia dividing the left atrium into a distal chamber containing the left atrial appendage (LAA) and mitral valve, and a proximal chamber that receives the pulmonary veins.
- • Supramitral stenosing ring is a circumferential membrane arising from the left atrial wall overlying the mitral valve. The atrial appendage is above and behind the membrane, and therefore belongs to the proximal chamber.
Shone’s syndrome is the concurrence of both left ventricular inflow and outflow tract obstructions. The left ventricular inflow obstructions include supravalvar mitral ring, mitral arcade, and parachute mitral valve. The left ventricular outflow obstructions include subvalvar stenosis, bicuspid aortic valve, and aortic coarctation.
Mitral regurgitation can rarely be due to a congenitally dysplastic mitral valve.

Fig. 20.1 Comparison of cor triatriatum and supramitral stenosing ring. LA, left atrium; LAA, left atrial appendage; LV, left ventricle; RA, right atrium; RV, right ventricle.