A pacemaker sends electrical impulses to the heart muscle to maintain a suitable heart rate and rhythm. Leads may be placed on the atria and ventricles. A pacemaker may be inserted for fainting spells (syncope), congestive heart failure, tachybradyarrhythmias, and hypertrophic cardiomyopathy.
The pacemaker has two parts: the leads and a pulse generator. The pulse generator houses the battery and a tiny computer, and resides just under the skin of the chest. The leads are wires that are threaded through the veins into the heart and implanted into the heart muscle. They send impulses from the pulse generator to the heart muscle as well as sense the heart’s electrical activity. Biventricular pacers use three leads: one placed in the right atrium, one placed in the right ventricle, and one placed in the left ventricle (via the coronary sinus vein). The provider programs the minimum heart rate. When the patient’s heart rate drops below that set rate, the pacemaker generates (fires) an electrical impulse that passes through the lead to the heart muscle. Overdrive pacing may be set as well to control the ventricular rate of tachyarrhythmias.