Pacemaker
Heart pacemaker
A pacemaker is a small device that’s placed in the chest or abdomen to help control abnormal heart rhythms. This device uses electrical pulses to prompt the heart to beat at a normal rate. Pacemakers are used to treat arrhythmias (ah-RITH-me-ahs). Arrhythmias are problems with the rate or rhythm of the heartbeat.
Applications :
Artificial pacemakers can be used in order to help with and/or treat these conditions:
- Sinus node dysfunction – when the sinoatrial node does not fire properly to contract the heart.
- Bifascicular block, trifascicular block, or third-degree AV block.
- Stokes – Adams attack involving disruption of conduction between the sinoatrial node and the atrioventricular node.
1) Transcutaneous Pacing :
Transcutaneous pacing (TCP) also called external pacing, is recommended for the initial stabilization of hemodynamically significant bradycardias of all types. The procedure is performed by placing two pacing pads on the patient’s chest, either in the anterior/lateral position or the anterior/lateral position.
The rescuer selects the pacing rate, and gradually increases the pacing current (measured in mA) until electrical capture (characterized by a wide QRS complex with a tall, broad T wave on the ECG) is achieved, with a corresponding pulse. Pacing artifact on the ECG and severe muscle twitching may make this determination difficult. External pacing should not be relied upon for an extended period of time. It is an emergency procedure that acts as a bridge until transvenous pacing or other therapies can be applied.
2) Transvenous Pacing :
Transvenous pacing, or temporary internal pacing, is an alternative to transcutaneous pacing. A wire is placed under sterile conditions via a central venous catheter. The proximal tip of the wire is placed into either the right atrium or the right ventricle. The distal tip of the wire is attached to the pacemaker generator, outside of the body. Transvenous pacing is often used as a bridge to permanent pacemaker placement. Under certain conditions, a person may require temporary pacing but would not require permanent pacing. In this case, a temporary pacing wire may be the optimal treatment option.
3) Pacemakers :
Permanent pacing with an implantable pacemaker involves the placement of one or more pacing wires within the chambers of the heart. One end of each wire is attached to the muscle of the heart. The other end is screwed into the pacemaker generator. The pacemaker generator is a hermetically sealed device containing a power source and the computer logic for the pacemaker.
Most commonly, the generator is placed below the subcutaneous fat of the chest wall, above the muscles and bones of the chest. However, the placement may vary on a case by case basis.
The outer casing of pacemakers is so designed that it will rarely be rejected by the body’s immune system. It is usually made of titanium, which is very inert in the body.
Modern pacemakers usually have multiple functions. The most basic form listens to the heart’s original electrical rhythm, and if the device doesn’t sense any electrical activity within a certain time period, the pacemaker will stimulate the ventricles of the heart with a set amount of energy.
Advancements in Pacemaker Function :
When first invented, the pacemaker controlled only the rate at which the heart’s two largest chambers, the ventricles, beat. Many advancements have been made to enhance the control of the pacemaker once implanted. Many of these enhancements have been made possible by the transition to microprocessor controlled pacemakers. Pacemakers that control not only the ventricles but the atria as well have become common. Pacemakers that control both the atria and ventricles are called dual-chamber pacemakers. Although these dual-chamber models are usually more expensive, timing the contractions of the atria to precede that of the ventricles improves the pumping efficiency of the heart and can be useful in congestive heart failure.
Rate responsive pacing allows the device to sense the physical activity of the patient and respond appropriately by increasing or decreasing the base pacing rate via rate response algorithms. Another advancement in pacemaker technology is left ventricular pacing. A pacemaker wire is placed on the surface of the left ventricle, with the goal of more physiological pacing than available in standard pacemakers. The extra wire is implanted to improve symptoms in patients with severe heart failure.