A pacemaker is a medical device that helps regulate the heartbeat by generating electrical impulses to stimulate the heart muscles to contract. There are several types of pacemakers designed to address different heart rhythm abnormalities and patient needs. Here are the main types of pacemakers:

1. Single-Chamber Pacemaker: This type of pacemaker has one lead (electrode) placed in either the atrium (upper chamber) or the ventricle (lower chamber) of the heart, depending on the location of the abnormal rhythm. The device then sends electrical signals to that chamber to regulate its rhythm.
1. Atrial Pacemaker (AAI): It’s used when the natural pacemaker of the heart (the sinoatrial node) is functioning properly, but the electrical signals are not conducting properly to the atria. The pacemaker senses the heart’s natural atrial rhythm and only delivers impulses when needed.
2. Ventricular Pacemaker (VVI): This is used when the atria are functioning properly, but the ventricles are not receiving the electrical signals properly. It stimulates the ventricles to maintain an appropriate heart rate.
2. Dual-Chamber Pacemaker: This type has two leads, one placed in the atrium and one in the ventricle. It coordinates the electrical signals between the two chambers to maintain a more natural heart rhythm.
1. Dual-Chamber Atrioventricular (DDD): It senses the electrical activity in both the atria and ventricles. This type of pacemaker is used when both the atria and ventricles are not conducting electrical impulses properly.
3. Biventricular Pacemaker (Cardiac Resynchronization Therapy – CRT): This pacemaker is used for patients with heart failure and ventricular dyssynchrony, where the ventricles do not contract simultaneously. It has three leads: one in the right atrium, one in the right ventricle, and a third in the left ventricle. By stimulating both ventricles at the same time, it improves the heart’s pumping efficiency.
4. Rate-Responsive Pacemaker: This type adjusts the heart rate based on the body’s physical activity level. It includes sensors that detect changes in activity, body temperature, or other factors to adapt the heart rate accordingly. This mimics the natural response of the heart to physical exertion.
5. Implantable Cardioverter Defibrillator (ICD) with Pacemaker Functions: An ICD is primarily used to treat life-threatening ventricular arrhythmias by delivering a shock to restore normal rhythm. Some ICDs also incorporate pacemaker functions. They monitor the heart’s rhythm and only deliver shocks when needed, but they can also function as a pacemaker to prevent bradycardia (slow heart rate).
6. Leadless Pacemaker: Unlike traditional pacemakers, which require leads threaded through veins to the heart, leadless pacemakers are directly implanted into the heart chamber without leads. They are typically placed in the right ventricle and are ideal for patients who cannot undergo traditional lead placement.

These are the primary types of pacemakers, each designed to address different heart rhythm disorders and patient needs. The choice of pacemaker type depends on factors such as the specific rhythm problem, the patient’s overall health, and the desired functionalities. Cardiologists work closely with patients to determine the most suitable pacemaker for their condition.