combination devices adds the two-chamber pacing
capability to the defibrillator.
The unit is implanted under the
skin and attached to the heart with leads. Electrical
impulses are then used to correct the arrhythmia or
The heart is essentially two
pumps - the upper chambers called the atria and the lower
chambers called the ventricles. Pumping of the heart is
controlled by electrical impulses from the sinus node, a
group of cells in the right atrium.
If something goes wrong with
the functioning of the sinus node and normal pacing of the
heart is disrupted, a number of arrhythmias may develop.
Some are too fast, others too slow. Still others are
irregular or out of proper sequence.
Defibrillators monitor the
heart's rhythm and when an excessively rapid rhythm occurs,
it delivers a shock to correct it. Pacemakers are typically
used to prevent a slow rhythm or ensure that the chambers
beat in the proper sequence (atrium then ventricle).
Many patients who require an
implantable defibrillator to correct a dangerously fast
heart rhythm also experience slow or out-of-sequence
Unlike the earlier devices, the
combination unit provides pacing of both the atrium and
ventricle, as well as ventricular defibrillation.
Like other defibrillators, the
device records and stores data about the heart's electrical
activity in the form of electrocardiogram (EKG) readings
that the physician can access. However, the Pacemaker
Defibrillator combination unit takes that feature a step
further with electrical information from the atrium as well
as the ventricles.