Patient selection for percutaneous mitral valvuloplasty in mitral stenosis

Mitral stenosis is a valvular heart disease in which the mitral valve, located between the left atrium and left ventricle of the heart, becomes narrowed resulting in obstruction of the blood flow between the left atrium and the left ventricle. The size of a normal mitral valve orifice is 4 - 6 cm². Significant obstruction is present when the mitral valve area becomes less than 2 cm².  Depending on the mitral valve area, mitral stenosis can be classified as mild (2 - 1.5 cm²), moderate (1.5 – 1 cm²) and severe (< 1cm²).

Mitral stenosis

Mitral stenosis can occur due to the following causes –

• Rheumatic fever
• Congenital mitral valve stenosis
• Severe mitral annular calcification
• Systemic Lupus Erythematosus
• Rheumatoid arthritis
• Cor triatriatum
• Infective endocarditis with large vegetation
• Left atrial myxoma

Therapy for mitral stenosis has undergone a reorientation following the introduction of percutaneous mitral valvuloplasty. Percutaneous mitral valvuloplasty is indicated in symptomatic patients of mitral stenosis with the following characteristics –

• Moderate or severe mitral stenosis
• Valve morphology that favors percutaneous intervention
• No thrombus in the left atrium or moderate or severe mitral regurgitation.

Percutaneous intervention for mitral stenosis is associated with some risks and hence is not indicated for asymptomatic patients except –

• Patients with severe mitral stenosis who require other major noncardiac surgery
• Young women who wish to become pregnant
• Patients at high risk of thromboembolism

The immediate outcome of percutaeneous mitral valvuloplasty is predicted by an echocardiographic scoring system called the Wilkins scoring system.

Grade	Mobility	Subvalvar thickening	Thickening	Calcification
1	Highly mobile valve with only leaflet tips restricted	Minimal thickening just below the mitral leaflets	Leaflets near normal in thickness (4-5 mm)	A single area of increased echo brightness
2	Leaflet mid and base portions have normal mobility	Thickening of chordal structures extending up to one third of chordal length	Mid-leaflets normal, considerable thickening of margins (5-8 mm)	Scattered areas of brightness confined to leaflet margins
3	Valve continues to move forward in diastole, mainly from the base	Thickening extending to the distal third of the chords	Thickening extending to the entire leaflet (5-8 mm)	Brightness extending into the mid-portion of the leaflets
4	Brightness extending into the leaflets in diastole	Extensive thickening and shortening of all chordal structures extending down to the papillary muscles	Considerable thickening of all leaflet tissue (>8-10 m)	Extensive brightness throughout much of the leaflet tissue

A score of 8 or less is predictive of a good result with percutaneous mitral valvuloplasty.

Guérios EE, Bueno R, Nercolini D, Tarastchuk J, Andrade P, Pacheco A, Faidiga A, Negrao S, & Barbosa A (2005). Mitral stenosis and percutaneous mitral valvuloplasty (part 1). The Journal of invasive cardiology, 17 (7), 382-6 PMID: 16003027

Wilkins GT, Weyman AE, Abascal VM, Block PC, & Palacios IF (1988). Percutaneous balloon dilatation of the mitral valve: an analysis of echocardiographic variables related to outcome and the mechanism of dilatation. British heart journal, 60 (4), 299-308 PMID: 3190958