Question

After wearing a Holter monitor for 24 hours my doctor said I might need a heart defibrillator. What heart problem would be causing this? What is the actual device, and how is it inserted into the heart?

Answer

We assume you mean an implantible defibrillator (it's sometimes called "the box", as they used to be fairly large and were implanted in the abdomen). Defibrillators have been shown to save lives in patients who have certain abnormal heart rhythms.

The box is implanted because of potentially dangerous heart rhythms arising from the main pumping chambers.

These abnormal rhythms can sometimes cause sudden death - what happened to someone who just collapsed on the street. Short runs of these rhythms are not necessarily dangerous, but prolonged ones can be.

If you have what is called 'ventricular tachycardia' it is usally just watched, but if you have had episodes of 'ventricular fibrillation' they should be treated more vigorously. Either way, you apparently have enough on your Holter monitor record to make your doctor concerned about sustained runs.

These rhythms more often occur in patients with weakened hearts, heart disease, or a prior heart attack, but they can also occur with some other processes.

The next step will probably be a heart catherization to see if you have any significant heart disease caused by poor blood supply to the heart muscle. If so, that is usually treated before implanting the box, as lack of oxygen might be reaponsible for the abnormal rhythm runs.

After any potential heart disease is addressed, the next step may be an electrophysical study (eps) which tests the electrical system of your heart to see if the abnormal rhythms can be reproduced. If the rhythms can be produced by electrical stimulation, (or if the Holter result was very troublesome), the box will need to be implanted.

Today, such a box is the size of a small pager and is implanted under the collar bone. Two small wires are then led into the heart and fastened in place. The surgery is done under general anesthesia. The device is tested to be sure it stops anabnormal rhythm before you are sent home. You won't go home the same day, but usually the next day or so.

The box monitors your heart rhythm, and if it detects that one of the dangerous rhythms is occurring, it tries to stop it before you feel symptoms. It first tries to 'pace' the heart out of the rhythm, but if this isn't successful, it sends a small electrical jolt to the heart (it defibrilates it). You don't feel the pacing, but you would feel the jolt.

This information should give you some idea on what may happen, before you talk with your physician or the cardiologist.

Links

• The Essence of the Heartbeat Changes with Aging - Part VI