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.
|Methods of 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.
|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 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.
|Permanent pacing with an implantable pacemaker involves
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 heart with a set amount of energy.
|Advancements in Pacemaker Function:
|When first invented, pacemaker controlled only the
rate at which the heart’s two largest chambers, the ventricles,
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.