DEAR DR. DONOHUE: I am an active man, 73 years old. I had a treadmill stress test, and the doctor said I did well. He also said I should see his partner, who is a specialist in electrophysiology and pacemaker implantation. This doctor said I had a problem of a slow heartbeat when under stress. He thought I should consider a pacemaker. He said that if I develop shortness of breath or lightheadedness to see him right away. What does implanting a pacemaker entail? – J.T.

ANSWER: The normal heart beats 60 to 100 times a minute when a person is resting. When a person is active, the heartbeat can come close to doubling, in order to provide exercising muscles with the additional blood they need.

If a person’s heart is unable to speed up during activity, then that person can be subject to spells of dizziness and episodes of breathlessness. The brain and body aren’t getting enough oxygen.

The trouble often lies in the heart’s normal pacemaker, a tiny island of special heart cells that generates an electric signal.

You were examined by an electrophysiologist, a heart specialist with special training in diagnosing and treating heartbeat problems and problems that arise from the faulty generation and transmission of electrical signals. He gave you good advice. If you develop the symptoms he mentioned, get to him right away. An artificial pacemaker can correct the malfunction. It’s a gadget, about the size of a half dollar, that’s put under the skin below the collarbone. Wires from it are threaded to the heart through a vein. The procedure is done with a local anesthetic. You go home the same day. You can resume most of your activities immediately, but you have to limit a bit the use of the shoulder and arm on the side of the pacemaker for a couple of weeks.

The heartbeat booklet deals with the common heartbeat ills, such as atrial fibrillation, but not with pacemakers. Readers can obtain a copy by writing: Dr. Donohue – No. 107, Box 536475, Orlando, FL 32853-6475. Enclose a check or money order (no cash) for $4.50 U.S./$6.50 Can. with the recipient’s printed name and address. Please allow four weeks for delivery.

DEAR DR. DONOHUE: I have a hiatal hernia that causes acid reflux. I have been diagnosed with osteoporosis. It is my understanding that I cannot take any osteoporosis medicine due to my hiatal hernia and reflux. Is that the case? – K.G.

ANSWER: No, that’s not the case. Perhaps you are thinking about the most popular and effective osteoporosis drugs – bisphosphonates. They stop bone from being broken down by slowing the action of bone-eating cells – osteoclasts. If they lodge in the esophagus, they can irritate it. That would make heartburn (acid reflux) worse. However, when people take these medicines with a full glass of water and do not lie down for 30 minutes after taking them, the chances of their getting stuck in the esophagus are small. Furthermore, Actonel and Fosamax, the two most widely used of these drugs, each come in a once-a-week tablet that makes taking them even easier. Your hiatal hernia and acid reflux won’t stop you from using either one.

Vitamin D and calcium are essential for bone health. Your conditions don’t preclude their use.

DEAR DR. DONOHUE: My 8-month-old daughter has just been discovered to have cystic fibrosis. Has any cure been found for it? – C.M.

ANSWER: There is no cure, but there are excellent treatments for cystic fibrosis, and affected children live much longer and have much more active lives than they did only a decade or so ago. Chest physical therapy clears their lungs of the thick secretions that settle in breathing tubes. Pneumatic vests compress the chest and can provide the same effect. Antibiotic mists keep lung infections, a common cystic-fibrosis consequence, to a minimum. If the stage of lung failure is reached, lung transplantation is an option.

Contact the Cystic Fibrosis Foundation – 1-800-344-4823, or www.cff.org – for the wealth of information and help it can provide.

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.