Pacemakers are medical devices used to manage bradyarrhythmias by maintaining an adequate heart rate. These devices are typically indicated for patients with sinus node dysfunction, where the sinus rate is too slow, or AV block, where the electrical impulse from the atria does not conduct properly to the ventricles. The pacemaker itself is a subcutaneous device consisting of a battery, computer components, and leads (wires).
The leads are usually transvenous, entering through the subclavian vein and advancing into either the right atrium, right ventricle, or both, depending on the type of pacemaker. There are three primary types of pacemakers:
- Single Chamber Pacemaker: Typically has one lead, either in the right atrium or the right ventricle.
- Dual Chamber Pacemaker: Has two leads, one in the right atrium and one in the right ventricle, allowing for synchronized pacing of both chambers.
- Biventricular Pacemaker (CRT - Cardiac Resynchronization Therapy): Includes a third lead that paces both ventricles, usually to treat heart failure by improving the coordination of ventricular contractions.
Pacemakers serve two main functions:
- Pacing: The device sends electrical impulses to stimulate the heart to contract.
- Sensing: The pacemaker monitors the heart's natural rhythm and decides when to deliver pacing impulses, preventing unnecessary stimulation when the heart is functioning on its own.
