An intracardiac pacemaker is a miniaturized medical device implanted directly inside the heart to manage an abnormally slow or irregular heartbeat, known as an arrhythmia. Often called a leadless pacemaker, this self-contained unit monitors the heart’s electrical rhythm. When it detects a problematic slowdown, it delivers a controlled electrical pulse to restore a normal pace.
This technology is an evolution in cardiac rhythm management. Unlike traditional systems that require a surgical pocket in the chest and wires running to the heart, the entire intracardiac device is housed within a single capsule. This design consolidates the battery, circuitry, and pacing electrode into one component. The device is delivered directly into the heart for the duration of its operational life.
Core Function and Design
The defining characteristic of an intracardiac pacemaker is its all-in-one, leadless construction. The device is about the size of a large vitamin capsule, making it approximately 90% smaller than a conventional pacemaker’s generator. This compact unit contains a battery, a pulse generator, and an electrode, eliminating the need for the connecting wires, or “leads,” used in traditional pacing systems.
To secure its position, the pacemaker is affixed directly to the inner wall of the heart, typically within the right ventricle. Fixation is achieved through small, flexible tines that grip the heart muscle, or a small screw-in helix mechanism that attaches to the tissue. This direct contact allows the device to efficiently sense the heart’s intrinsic electrical signals and deliver corrective electrical pulses.
Once implanted, the device continuously monitors the heart’s electrical activity. If the heart rate drops below a predetermined threshold, the pacemaker delivers a small, painless electrical impulse. This stimulus causes the heart muscle to contract, creating a heartbeat. Advanced models also contain sensors, such as accelerometers, that detect physical activity and adjust the pacing rate to meet the body’s changing metabolic demands.
Candidate Selection
A thorough evaluation of a patient’s cardiac condition, anatomy, and overall health determines their suitability for a leadless pacemaker. The device is primarily indicated for individuals who require single-chamber ventricular pacing. This includes patients with persistent slow heart rates (bradycardia) or those with atrial fibrillation who also experience slow ventricular rates.
A leadless pacemaker is an advantageous choice for certain patients. Ideal candidates may include individuals with:
- Blocked or unsuitable veins in the upper chest and arms, which would normally be used to thread pacemaker leads.
- A need to preserve venous access in the upper body for treatments like hemodialysis.
- A history of complications from traditional pacemakers, such as lead fractures or infections.
- A high risk of infection due to other health issues.
- Congenital heart disease or structural abnormalities of the heart that make navigating wires difficult.
The Implantation Procedure
The implantation of an intracardiac pacemaker is a minimally invasive procedure that avoids open-chest surgery. Performed under local anesthesia with sedation, the process begins with a small incision in the groin to access the femoral vein. This large vein serves as a direct pathway to the heart, allowing the physician to maneuver the device into place.
A specialized delivery system, a steerable catheter, is inserted into the femoral vein. The pacemaker, attached to the tip of this catheter, is guided through the venous system and into the right ventricle of the heart. The physician uses real-time imaging, such as fluoroscopy (a type of X-ray), to visualize the catheter’s journey and position the device.
Once the optimal location is identified, the pacemaker is deployed from the catheter and secured to the heart muscle. The physician then performs tests to ensure the device is firmly attached and functioning correctly, confirming stable electrical measurements. After successful testing, the delivery catheter is removed, and the small incision in the leg is closed. The entire procedure takes between 20 to 45 minutes.
Device Management and Longevity
The battery in a leadless pacemaker is designed to last from 5 to 15 years, depending on how frequently the device needs to pace the heart. This longevity is comparable to that of traditional pacemakers. Regular follow-up appointments are scheduled to check the pacemaker’s function and remaining battery life.
Remote monitoring is a component of ongoing management. Many modern leadless pacemakers can transmit data wirelessly to the patient’s healthcare team. This allows for continuous oversight of the device’s performance and the patient’s heart rhythm from home, reducing the need for frequent in-person clinic visits.
When the battery nears depletion, the original unit is often left in place and deactivated. A new leadless pacemaker is then implanted alongside the old one, as there is typically sufficient space within the right ventricle. In some situations, retrieval of the old device may be performed using a specialized catheter. Modern leadless pacemakers are also designed to be safe for use during magnetic resonance imaging (MRI) scans under specific conditions.