April 23, 2005
Pacemakers Continue to Prove Their Worth
21st century twists improve performance, experts say
HealthDay News -- It may be nearly a half-century old, but the cardiac pacemaker just keeps on ticking, pepping up desultory hearts quietly and efficiently. The advent of the implantable battery-powered pacemaker is considered one of the singular medical achievements of the 20th century.
But it's not your father's pacemaker any more. Almost without notice, the little device to regulate the heart rate has gotten some zip from 21st century electronic wizardry. These days, the newest versions of the pacemaker keep the heart beating at just the right speed with electronic leads placed on both the organ's upper chambers (the atria) and one of the lower chambers (the right ventricle). The older versions generally did their work via a single electrode placed on the right ventricle, occasionally the right atrium.
Why is this important, you may ask. It all has to do with the electrical activity of the heart and how, when it goes awry, to best mimic the natural physiology artificially with a battery-operated stimulator. Easy to say, hard to do.
For some time now, the atrial version of the pacemaker, known as the dual-chamber device, has taken over the market for the 600,000 or so patients who get a device implanted every year. Cardiologists assumed that the newer device's more physiological approach had a variety of advantages -- among them reducing the risk of heart failure and stroke and improving quality of life. They also assumed it extended life.
In fact, several large studies suggested a modest benefit for all these and others, except that life expectancy was essentially unchanged. But as the dual-chamber pacemaker was about $3,000 more expensive, the question arose as to whether the modest clinical improvements were worth the extra money.
Now, for at least one major reason that people are given pacemakers, the answer appears to be yes, as measured by a complicated formula called quality-adjusted life years gained. This problem is called sick sinus syndrome. It refers to the sinus node, the bundle of specialized cells in the right atrial wall that form the body's natural pacemaker.
The cost-benefit study was published in the Jan. 4 issue of Circulation, the journal of the American Heart Association. It found that the dual-chamber device had a greater cost-benefit advantage than a number of other interventions in cardiology. Over a projected lifetime, particularly beyond four years, it actually saved money in hospitalization and other medical costs compared with the single-chamber device.
Meanwhile, a small study published in The Lancet suggested that pacemakers could help epileptics with a high risk of sudden death, a rare outcome of epilepsy.
Twenty patients with severe epilepsy were monitored for 22 months with implanted devices that recorded heart rates. Sixteen had frequent episodes of abnormally rapid heart rates, though they were not life-threatening. The other four patients, however, had bouts of abnormally slow heart rates, which were dangerous. Those four were given pacemakers.
Although the practicality of finding those with epilepsy who are at risk of sudden death was not clear, neurologists were intrigued by the possibilities. About one in every 1,000 persons with epilepsy dies each year of what is called SUDEP, sudden unexplained death in epilepsy, and the incidence of sudden death increases with the severity of the condition. For patients whose epilepsy is severe enough to require surgery, the annual SUDEP death rate is 1 percent.
Finally, there was a byte of good news for the three million Americans living with pacemakers. The devices appear to be standing up well to the wireless age, according to a Mayo Clinic study.
Doctors there undertook the study to avoid risking danger to patients with an implanted pacemaker. They wanted to make sure that wireless networks they set up at the clinic were not affecting the sophisticated pacemaker circuitry with electromagnetic interference. All systems were "go."
To learn more about pacemakers, visit the American Heart Association.