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Chapter 2
•
Cardiovascular Care
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Implantable Cardioverter Defibrillators
A Look at an ICD
An ICD typically consists of a programmable pulse generator and an
electrode. Most new ICDs can act as both pacemakers and defibrillator.
The subcutaneous implantable cardioverter defibrillator (S-ICD), which
is being implanted throughout the world, was approved for use in the
United States in September of 2012.
The S-ICD can be implanted without the use of fluoroscopy by using
anatomic landmarks to guide proper positioning.
Left
subclavian
access line
Leadwire
Pulse
generator
Types of ICD Therapies
VF is a common cause of sudden cardiac death (SCD) and is sometimes
preceded by monomorphic or polymorphic ventricular tachycardia (VT).
While cardiopulmonary resuscitation, including chest compressions and
assisted ventilation, can provide temporary circulatory support for the patient
with cardiac arrest, the only effective approach for terminating VF is electrical
defibrillation. Development of the ICD was first implanted in humans in the 80s,
which lead to the success and survival of patients with VF/VT.
Therapy
What It Does
Antitachycardia
pacing
A series of small, rapid, electrical pacing pulses are used to
terminate ventricular tachycardia (VT) and return the heart to its
normal rhythm.
Cardioversion
A low- or high-energy shock is timed to the R wave to terminate VT
and return the heart to its normal rhythm.
Defibrillation
A high-energy shock to terminate ventricular fibrillation and return
the heart to its normal rhythm.
Bradycardia
pacing
Electrical pacing pulses are used when the heart’s natural electrical
signals are too slow. Most ICD systems can pace one chamber (VVI
pacing) of the heart at a preset rate. Some systems sense and pace
both chambers (DDD pacing).