Biomedical Engineering Reference
In-Depth Information
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Nonhospitalized
patients
awaiting
cardiac
6.2
Implantable Cardioverter-De fi brillator
Implantation Indications
transplantation
Patients with Brugada syndrome who have had syncope
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Patients with Brugada syndrome who have documented
ICDs are intended to provide ventricular antitachycardia pac-
ing and ventricular defibrillation shocks for automated treat-
ment of life-threatening ventricular arrhythmias. Indications
for ICD implants are based on results of large randomized
clinical trials, which approved the effectiveness of this therapy
for the secondary as well as the primary prevention of SCD
[36, 37]. An overview of the most important clinical trials is
provided below. However, ICD implantation is not indicated
for patients whose VT may have a transient cause (acute myo-
cardial infarction, electrocution, drowning) or a reversible
cause (digitalis intoxication, electrolyte imbalance, hypoxia,
sepsis) or patients who have a unipolar pacemaker [70].
According to ACC/AHA/HRS 2008 Guidelines for
Device-Based Therapy of Cardiac Rhythm Abnormalities
[34, 35], the indications (class I and class IIa) for ICDs are
described in the following paragraphs.
Survivors of cardiac arrest due to ventricular fibrillation
VT that has not resulted in cardiac arrest
Patients with catecholaminergic polymorphic VT who
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have syncope, documented sustained VT, or both while
receiving
-blockers
Patients with cardiac sarcoidosis, giant cell myocarditis,
b
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or Chagas disease
Recommendations for Implantable Cardioverter-
Defibrillators in Pediatric Patients and Patients with
Congenital Heart Disease
Survivors of cardiac arrest after evaluation to define the
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cause of the event and to exclude any reversible causes
Patients with symptomatic sustained VT in association
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with congenital heart disease who have undergone hemo-
dynamic and electrophysiologic testing; catheter ablation
or surgical repair may offer possible alternatives in care-
fully selected patients
Patients with congenital heart disease with recurrent syn-
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or hemodynamically unstable sustained VT after evalua-
tion to define the cause of the event and to exclude any
completely reversible causes
Structural heart disease and spontaneous, sustained VT,
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cope of undetermined origin in the presence of either ven-
tricular dysfunction or inducible ventricular arrhythmias
during electrophysiologic testing
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whether hemodynamically stable or unstable
Syncope of undetermined origin with clinically relevant,
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6.2.1
Signi fi cant Clinical Studies of ICDs
hemodynamically significant sustained VT or ventricular
fibrillation induced during electrophysiologic testing
LV ejection fraction (LVEF) less than 35 % due to prior
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Clinical studies deal with assessing the long-term clinical
effect of treatment. In the early days of use of device therapy
with ICDs, it was necessary to compare the effect of this new
treatment with the existing medical therapy. Here, descrip-
tion of significant clinical studies will be divided into those
investigating secondary and primary prevention. Interpretation
of study endpoints and results is not possible here without
major simplification because additional meta-analyses were
performed for many studies, and clinical efficacy for various
specific indications was observed.
Clinical studies in medicine are divided according to the
following properties [ 38 ] :
myocardial infarction in patients who are at least 40 days
after the event and are in New York Heart Association
(NYHA) functional class II or III
Patients with nonischemic dilated cardiomyopathy who
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have an LVEF less than or equal to 35 % and who are in
NYHA functional class II or III
LV dysfunction due to prior myocardial infarction in
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patients who are at least 40 days after the event, have an
LVEF less than 30 %, and are in NYHA functional class I
Nonsustained VT due to prior myocardial infarction,
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LVEF less than 40 %, and inducible ventricular fibrillation
or sustained VT during electrophysiologic testing
Unexplained syncope, significant LV dysfunction, and
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Controlled/uncontrolled study
A controlled study involves assessment of treatment efficacy
in comparison with an untreated group or a group treated
with another drug or method. This group is referred to as
the control group, and it significantly increases the informa-
tive value of the study. Placebo, another type of treatment,
or results of standard therapy can all be used as controls.
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nonischemic dilated cardiomyopathy
Sustained VT and normal or near-normal ventricular
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function
Patients with hypertrophic cardiomyopathy who have one
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or more major risk factor for SCD
Prevention of SCD in patients with arrhythmogenic right
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Randomized/nonrandomized study
In a controlled study, it is necessary to ensure that patients
as clinically similar as possible be represented in the
groups. This is achieved by randomization of patients into
treatment and control groups. In multicenter studies, it is
ventricular dysplasia/cardiomyopathy who have one or
more risk factors for SCD
Long-QT syndrome in patients who are experiencing
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syncope, VT, or both while receiving
b
-blockers
