While all types of cardiac pacemakers perform the same basic function, they vary in how that function is performed. Pacemakers are small, battery-operated devices that are surgically implanted into the chest. Once implanted, the pacemaker generates an electrical signal that regulates irregular heartbeats. Pacemakers are used to treat bradycardia--slow heart beat, tachyarrhythmias--fast heart beat, and arrhythmia--irregular heart beat. Cardiac pacemakers can be temporary, sometimes necessary just after major cardiac surgery, or permanent, needed to sustain proper heart operations. Physicians will work with their patients to determine the best type of cardiac pacemaker to use. The decision is based on the type of heart condition the patient has, as well as his lifestyle.
Single-Chamber Pacemakers
The heart has four chambers. The left and right ventricle move blood outside the heart; the left and right atrium move the blood back in. There are also four valves that keep the blood flowing through the heart. Single-chamber pacemakers have just one wire, known as a pacing lead. Once the pacemaker is surgically implanted, the pacing lead extends from the device along a vein. The pacing lead extends through one of the valves before finally attaching to a heart chamber. Since a single-chamber pacemaker can connect to only one chamber, these devices are normally reserved for patients who do not have severe cardiac problems, and only an occasional need to stabilize their heart rates.
Dual-Chamber Pacemakers
Dual-chamber pacemakers have two pacing leads connecting to two heart chambers. Most pacemakers implanted in the United States each year are dual-chamber devices. Dual-chamber cardiac pacemakers more closely mimic the heart’s natural beating than the single-chamber pacemaker. Dual-chamber pacemakers are more expensive than single-chamber pacemakers, but there is some indication that they may actually be more cost effective. In the January 2005 issue of “Circulation,” Dr. David Cohen, director of cardiovascular research at Saint Luke's Mid America Heart Institute in Kansas City, Missouri, writes that while the dual-chamber devices cost $3,000 more initially, the total lifetime cost mirrors that of the single-chamber devices. Patients with dual-chamber cardiac pacemakers are also less likely to be hospitalized for heart failure than patients with single-chamber devices, according to Dr. Cohen.
Triple-Chambered Pacemakers
Triple-chambered pacemakers have three pacing leads, two for each ventricle and one to an atrium. Typically, triple-chambered pacemakers are reserved for patients with congestive heart failure, a condition that arises when the heart experiences difficulty performing its most basic function, pumping blood. These devices help improve blood flow through the heart by properly syncing the ventricles.
Rate-Responsive Pacemakers
Thanks to their special activity and breathing sensors, rate-responsive pacemakers have the ability to self-adjust based on a patient’s current level of physical activity, emotional state and metabolic needs. These devices respond to physiological changes in the body rather than to atrial rate, or heart rhythm.
References
- “Implantable Cardiac Pacemakers and Defibrillators”; Anthony W. C. Chow, M.R.C.P.; March 2006
- “Circulation”; Cost-Effectiveness of Dual-Chamber Pacing Compared With Ventricular Pacing for Sinus Node Dysfunction; David J. Cohen, MD, MSc; January 2005
