Biomedical Engineering Reference
In-Depth Information
6
Indications for Implantable System
Treatment
Implantation of pacing or defibrillation systems is a serious
medical intervention. From this reason, patients have to
fulfill certain medical criteria - called
indications
- before
they undergo an implant. Indications are a complex of diag-
nostic and clinical symptoms presenting within the patient
and indicate the suitability of an implantable system accord-
ing to recent scientific knowledge. According to the indica-
tions it is determined which implantable system the patient
needs; health insurance companies approve payment for
implantation based on the fulfillment of indication criteria.
Before each implant, risks and benefits for the given
patient are evaluated. The main criteria are life expectancy,
quality of life, and patient prognosis. Recent recommenda-
tions use standard recommendation categorizations accord-
ing to classes (Table
6.1
) and three levels of evidence
(Table
6.2
) [ 33 ] . This classifi cation enables easier decision
making by the clinician .
Indication criteria can be generally divided into two cate-
gories: primary preventive (prevention before an event) and
secondary preventive (prevention after an event). This divi-
sion is most often associated with indications for use of
implantable cardioverter-defibrillator (ICD) systems. The
means of primary and secondary prevention are frequently
the same.
The aim of primary preventive indications is to identify
high-risk patients and implant an appropriate system even in
them before first arrhythmic incident. Clinical trials have
evaluated the risks and benefits of the ICD in the prevention
of sudden cardiac death (SCD) and results have shown
improved survival in multiple patient populations. Prospective
registry data offer recommendations for ICD implantation in
select other patient populations, such as those with hypertro-
phic cardiomyopathy, arrhythmogenic right ventricular dys-
plasia/cardiomyopathy, and long-QT syndrome. In less
common conditions (e.g., Brugada syndrome, catecholamin-
ergic polymorphic ventricular tachycardia (VT), cardiac sar-
coidosis, left ventricular (LV) noncompaction), clinical
reports and retrospectively analyzed series provide less rig-
orous evidence in support of current recommendations for
ICD use, but this constitutes the best available evidence for
these conditions [ 34, 35 ] . For speci fi cation of arrhythmia
classification, electrophysiology study is used. Its aim is to
induce VT and determine its characteristics. The positive
electrophysiology study stands for increased risk of future
malignant arrhythmia. In addition, other risk factors such as
family history or age are applied in primary prevention.
Secondary prevention refers to prevention of SCD in
those patients who have already survived a prior sudden car-
diac arrest or sustained arrhythmic episode, including hemo-
dynamically unstable monomorphic VT, polymorphic VT, or
ventricular fibrillation. The aim is to prevent the repetition of
a risky situation.
6.1
Pacemaker Implantation Indications
Pacemakers generally are indicated for treatment of the fol-
lowing clinical conditions [ 32 ] :
Symptomatic paroxysmal or permanent second- or third-
•
degree atrioventricular (AV) block
Symptomatic bilateral bundle branch block
•
•
Symptomatic paroxysmal or transient sinus node dysfunc-
tion with or without associated AV conduction disorders
(e.g., sinus bradycardia, sinus arrest, sinoatrial block)
Bradycardia-tachycardia syndrome and to prevent symp-
•
tomatic bradycardia or some forms of symptomatic
tachycardia
Neurovascular (vasovagal) syndromes or hypersensitive
•
carotid sinus syndromes
Adaptive-rate pacing is indicated for patients who may
benefit from increased pacing rates concurrent with increases
in minute ventilation (MV), level of physical activity, or
both. Dual-chamber and atrial tracking modes also are indi-
cated for patients who may benefit from maintenance of AV
synchrony. Dual-chamber modes are indicated specifically
for treatment of the following:
