Latest Pacemakers Adapt to Changes in Physical Activity

Recent advances in technology have now made it possible for people with heart-rhythm irregularities to use pacemakers that respond to changes in physical activity and are simple to monitor and maintain.

“The latest improvement is rate-adaptive pacing, which helps the pacemaker meet the demand for an increased or decreased heart rate when an individual changes his or her level of physical activity,” said Dr. Sydney Mehl, a cardiologist at New York University Medical Center.

This is particularly valuable for very active people and for those with “sick sinus syndrome,” a condition in which the sinus node, the heart’s natural pacemaker, does not properly initiate the impulse.

“It is also a boon for children who need pacemakers, since it means less interference with their normal levels of play,” Mehl said.

Pacemakers can now be monitored quickly and efficiently over the telephone by a machine in the physician’s office. Necessary adjustments can be made in the office without removing the pacemaker.

A pacemaker is a device that provides a regular electrical impulse to replace an absent or too-infrequent natural one. Pacemakers consist of a lithium-battery-operated pulse generator and one or two insulated wires with electrodes at the tip.

The first model, introduced 30 years ago, was very large and had to be implanted in the chest cavity. Today, pacemaker implantation is much simpler, causes less pain and involves less risk to the patient.

Pacemakers are now placed in a “pocket” under the skin of the chest. The wire is fed to the heart through a vein near the collarbone. Typically, a pacemaker has a useful life of about 10 years. The battery can then be replaced under local anesthesia. The standard pacemaker is set at a fixed rate, usually in the range of 60 to 72 beats per minute, to prevent the heart rate from falling below that level.

Its sensing circuit allows it to be used on demand; it does not compete with the patient’s heart if the heart is beating faster than the pacemaker rate. However, it cannot adapt to changes in activity.

This model can only pace one chamber in the heart. A dual-chamber pacemaker allows stimulation of the heart’s upper chambers, the atria, and the lower ones, the ventricles.