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Mitral valve disease, atrial fibrilllation and surgical repair

The mitral valve is one of four valves in the heart. It guards the left atrium (upper chamber) and the left ventricle (the main pumping chamber) of the heart. The valve closes when the left ventricle contracts at systole and opens when the left ventricle relaxes at diastole.

Mitral valve disease can be as a result of narrowing (stenosis) or leaking (regurgitation). Mitral stenosis (MS) is most often caused by rheumatic heart disease which is on the decline in Singapore and therefore incidence of MS in this country is very low. The cases of MS seen in Singapore are mostly from neighbouring countries.

Mitral valve regurgitation (MR) is more common. MR can be caused by degenerative valve disease like mitral valve prolapse and flail leaflets, infective endocarditis and ischemic heart disease. This results in backflow of blood to the left atrium whenever the left ventricle beats.

There are four grades of regurgitation, none, mild, moderate, severe.

When the grade is severe, there will be excess pressure and volume of blood into the left atrium. This can result in heart failure, causing shortness of breath, fluid retention, fluid in the lung fields.

Over time, the left atrium enlarges and stretched. The left ventricle also enlarges, when there is too much volume per heart cycle. 

MR or MS is diagnosed with an echocardiography or echo for short. A typical echo report will tell the doctor, the severity of the MS or MR, the sizes of the chambers of the heart and any other abnormality in the heart.

When left atrium enlarges, it may go into an abnormal rhythm called atrial fibrillation. This makes the heart beat fast at rates up to 120-130 beats per minute. This condition is easily diagnosed with an electrocardiogram (ECG). Long term atrial fibrillation may result in clot formation in the left atrium and result in strokes. Thus this condition needs to be treated medically or in certain cases by a surgical technique called maze procedure.

Mitral valve regurgitation due to degenerative disease may be repaired (not replaced) and maze procedure done at the same setting to correct atrial fibrillation. This restores normal heart function and corrects the heart rhythm back to normal sinus rhythm.

Mitral valve surgery and maze procedure are open heart surgery and most crucially must be performed almost perfectly.

Risk of mitral valve surgery is 2 % mortality, 1% stroke. Success rates for mitral repair is 98% and for maze procedure is 90%. 

Hospital stay is approximately 7 days.