A malfunctioning mitral heart valve (a valve that lets blood flow from one chamber of the heart, the left atrium, to another called the left ventricle) often causes or greatly contributes to congestive heart failure in patients with heart disease.

There are two basic categories of leaky mitral valves: degenerative (also known as primary) mitral regurgitation (MR), in which the valvular structure is abnormal and blood leaks through the defects; and functional (also known as secondary), in which the valve itself is normal, but the annulus or supporting ring of the valve is dilated or the left ventricle is enlarged and the cords supporting the valve leaflets pull the leaflets down and apart.

In either type of mitral regurgitation, much of the blood that is supposed to go forward goes backward when the left ventricle contracts, causing fluid to build up in the lungs, resulting in shortness of breath and heart failure.

The favoured treatment of primary MR remains repair rather than replacement with an artificial valve, if a well functioning native valve can result from the operation that will maintains adequate function for the long term. The methods of repair are changing, in that the use of artificial cords are tending to replace the use of leaflet resection and annuloplasty alone. Any of these methods be used to repair the mitral valve and can result in long term success in the elimination of MR.

The surgical treatment of secondary, or functional MR is also controversial and changing. Until recently, the favoured treatment of severe functional mitral regurgitation (MR) was considered to be annuloplasty repair in nearly all cases, and a mitral valve replacement was reserved only when a repair could not be performed.

However, a randomised trial sponsored by the Cardiothoracic Surgery (CTS) Network of the National Heart, Lung, and Blood Institute of the United States, examined the outcome of mitral repair versus replacement for severe functional MR. There was no difference in death, major adverse cardiovascular events, left ventricular end systolic volume index or quality of life between groups at two years follow-up.

However, it was found that recurrence of at least moderate to severe MR occurred in one third of patients within one year of surgery and this difference remained at 2 years.

Another area of controversy is the treatment of moderate functional MR in the setting of coronary artery bypass grafting (CABG). However, CABG with mitral repair was associated with more neurologic events, increased cross clamp and cardiopulmonary bypass time, and longer ICU and hospital lengths of stay.

In addition, minimally access methods with the utilisation of small incisions or a robotic approach are becoming more popular versus the traditional median sternotomy approach.

While methods of surgical repair have improved and surgery can be less invasive with a better cosmetic result, outcomes are generally similar between the different approaches in the hands of skilled cardiac surgeons. Percutaneous approaches to repair and replacement of the mitral valve are currently being developed.

The primary goal of mitral valve surgery should be the short and long term effectiveness, cost, and safety of the procedure. A balanced approach should be taken for the treatment of both degenerative and functional MR, considering long term results of repair versus replacement, costs and risk of complications.

The writer is the Chief of Cardiothoracic Surgery at the Alpert Medical School of Brown University, and Director, Lifespan Cardiovascular Institute, USA.

E-mail: fsellke@lifespan.org