DEAR DR. DONOHUE: I had a double heart bypass done seven years ago. I have emphysema.

Now I have three out of four heart valves that are bad.

My doctor says I need surgery, but he wants to put it off as long as possible because of my health. I have had many surgeries, but for the first time in my life, I am scared of surgery.

What is the function of heart valves? What causes them to go bad? What types of replacement valves are available? – J.B.

The four heart valves keep blood flowing in the right direction from one heart chamber to the next, and finally out of the heart.

Serious valve problems can happen to any of the four valves, but the two valves most often affected are the aortic valve and the mitral valve. The aortic valve prevents blood from flowing back into the heart after the left ventricle pumps it out. The mitral valve prevents blood from flowing back into the left atrium after it has filled the left ventricle.

Rheumatic fever used to be the No. 1 cause of valve malfunction. Aging is a big reason why valves fail.

Calcification of valves – something that happens throughout life – is another reason for valve trouble. Congenital valve anomalies, often silent until late in life, are responsible for valve breakdown, as are valve infections.

Valves can become too narrow – stenosis – which makes it difficult for blood to flow through and out of the heart. Or they can become leaky – regurgitant – which causes blood to flow back into the chamber it just left.

Early on, medicines can often compensate for what damaged valves cause in impairing blood flow and heart emptying.

As the condition worsens, then mechanical procedures are necessary to repair the injured valve. Sometimes a catheter with a balloon can be passed through a blood vessel to a narrowed valve. Once there, the balloon is inflated to expand the valve.

Quite often, however, surgical repair or replacement of the valve is the only option.

Replacement valves are mechanical, man-made devices; those fashioned from pig or cow tissue; or ones constructed from a patient’s own tissues. The decision of which is better is based on a patient’s age and the patient’s particular symptoms.

Valve surgery is major surgery. Most do quite well. You should too.

DEAR DR. DONOHUE: How effective is niacin at reducing cholesterol? What are its side effects? I can’t take statins. – F.W.

In small doses, niacin is a B vitamin. In large doses, niacin lowers LDL cholesterol (bad cholesterol), raises HDL cholesterol (good cholesterol) and brings down triglycerides, fats that contribute to artery plugging.

It’s a good medicine, especially for people like you, who can’t tolerate statins.

Niacin can cause flushing, itching and headache, especially when a person first starts it.

Such symptoms are most common with crystalline niacin, the kind that’s rapidly absorbed.

With controlled-release niacin, the kind that’s slowly absorbed, those reactions are less frequent, but controlled-release niacin can damage the liver and raise blood sugar and uric acid. Uric acid is the stuff that triggers gout.

A third form of niacin, intermediate-release niacin, has fewer side effects than either of the other two preparations but is more expensive and requires a prescription. A brand name for the intermediate-release variety is Niaspan.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475. Readers may also order health newsletters from

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