Pacemaker Insertion

Excerpt

Pacemakers are adjustable artificial electrical pulse generators, frequently emitting a pulse with a duration between 0.5 and 25 ms with an output of 0.1 to 15 V at a frequency of up to 300/min. The cardiologist or pacemaker technologist will be able to interrogate and control the pacing rate, the pulse width, and the voltage, whether the device is temporary or permanent. Pacemakers are typically categorized as temporary and permanent. Temporarily, pacemakers are almost always placed to stabilize the patient temporarily or facilitate some surgical procedure. The implantable pacemakers are usually permanent and often significantly more complex than temporary pacemakers.

The true beginning of the concept of a pacemaker began over 200 years ago. In the late 1700s, Luigi Galvani discovered that he could cause the contraction of a frog's heart simply by passing an electrical current through the heart. This concept was further realized nearly 100 years later with the first successful resuscitation of a child by Guilliame de Boulogne using electricity. He accomplished this by introducing an electrical current to the patient's chest with a return electrode on the leg after a drowning. After this feat, many successful resuscitations were reported, leading to Dr. Hyman's term "artificial cardiac pacemaker" in 1932.

Pacemakers are one cardiac implantable electronic device type (CIED). This broad category also includes implantable cardioverter-defibrillators (ICDs). This group of devices was introduced in the 1950s, shortly after the advent of the transistor. As technology has improved, so has the pacemaker device. The first implantable ICD was developed in 1980. Since then, it has become more challenging to differentiate between pacemakers and ICDs because every ICD currently implanted has an antibradycardia pacing function. The patient and any clinician should understand which device has been implanted to prevent unnecessary ICD therapy, which is most likely to occur with any electromagnetic interference and could lead to device activation with an ICD. Most types of CIED use several insulated lead wires with non-insulated tips that are implanted in the heart, either by percutaneous vein insertion or directly by a cardiac surgeon. Cardiac pacemakers comprise the pulse generator and the leads or electrodes.

The North American Society of Pacing and Electrophysiology and the British Pacing and Electrophysiology Group jointly developed a generic pacemaker code utilized worldwide that would allow clinicians and manufacturers to describe the device's characteristics, which was last updated in 2002 (see Image. Pacemaker Table). The first letter in the code indicates which chamber is paced; the second letter indicates which chamber is being sensed by the device; the third letter indicates if there is a response to sensing; the fourth position indicates whether the device will modulate or change the programmed rate independent of the patient's cardiac activity, for example, with exercise; the fifth and last letter of the code indicates additional multisite pacing. The last 2 letters of the code (in the fourth and fifth position) are rarely used in typical nomenclature. The latest generation of pacemakers has many capabilities. The simplest settings are AAI and VVI. The AAI mode paces and senses in the atrium, and each sensed event triggers the generator to fire within the P wave. The VVI mode paces and senses the ventricle and is suppressed by a sensed ventricular event.