MitraL-valve surgery Heart's gatekeeper sometimes needs fix

What do the swinging doors of a western movie have to do with mitral-valve surgery? They're the easiest way to describe what's wrong with the heart's valves and what surgical procedure is needed to correct mitral-valve prolapse (MVP). To get a first-hand look, I watched Dr. Tirone David, one the world's great cardiac surgeons, perform this operation at the Toronto General Hospital.

The mitral valve separates the two left chambers of the heart. Each time the heart beats, the valves open, like the swinging doors of a western saloon. But after opening, they firmly close while the heart pumps blood to the body.

The problem is that swinging doors of saloons often develop loose, rusty hinges that don't close well. The mitral valve has the same trouble when the tough, parachute-like cords that attach the valves to the heart's muscle become too loose.

When this happens, some of the ejected blood falls back into the heart's chamber following every beat. This places an extra burden on the heart's muscle.

Before the use of echocardiograms (ultrasound of the heart), doctors believed MVP was present in 17 per cent of women and five per cent of men. Now we know it's less common, affecting about 2.4 per cent of both sexes. But according to a report from Johns Hopkins University, about 25 per cent of Americans older than 55 have some degree of MVP. In addition to aging, genetics may play a role in who develops this condition.

How mitral-valve prolapse is treated depends on several factors. Many patients with MVP have no idea it is present and normally do not need surgery.

Others complain of shortness of breath, palpitations and fatigue. But people without MVP can experience similar symptoms. What often happens is that these symptoms may occur after the diagnosis is made, which triggers anxiety.

Dr. David says several factors must be considered in deciding whether mitral surgery is suggested. One of the most important is the severity of the prolapse and what effect it's having on the heart's muscle.

There's an old saying that "a stitch in time saves nine." In mild cases of MVP, there's no point in prematurely exposing patients to the risk of surgery.

But it also makes no sense to wait until either the patient's symptoms are severe or the muscle of the heart is failing from the extra stress placed on it.

Mitral-valve surgery is not just for incompetent valves. It's also performed when the mitral valve becomes thickened and rigid from aging and the opening becomes as small as a pencil. The extra work of pushing blood through such a tiny opening can also cause heart failure.

Patients with these conditions often have heart murmurs that can be detected by a stethoscope. But an echocardiogram of the heart will determine the severity of these problems and help gauge whether the condition is worsening. Fortunately, in recent years, tremendous advances have been made in surgical technique regarding the treatment of MVP and stenosis.

The morning I watched Dr. David operate, the chest was opened in the same way as if a bypass operation were being done. This patient suffered from severe mitral stenosis and required a new valve.

The majority of cases performed today try to save the old valve. For instance, it is often possible to shorten the parachute-like cords, restoring the valves to their normal position. The other advantage to using the patient's own tissue is there is no chance of its rejection by the body.

In other cases, minimal invasive surgery can be done by working through the femoral artery, the main vessel at the top of the leg. The new valve is guided through the artery using a special catheter tube until it reaches the mitral valve and is inserted.

Dr. David says there's no age limit for mitral-valve surgery as long as the patient doesn't have other problems that would increase risk. He says, "My oldest patient was 96, in remarkably good shape. If he had said he was 76, I would have believed him."

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Republished from the Winnipeg Free Press print edition August 5, 2011 A19