Diagnosis and Treatment
����Permanent pacemaker implantation is NOT indicated for:
������ asymptomatic first-degree AV block. (III-B) (See ���Permanent Pacing in Chronic
Bifascicular Block.���)
������ asymptomatic type I second-degree AV block at the supra-His (AV node) level or
that which is not known to be intra- or infra-Hisian. (III-C)
������ AV block that is expected to resolve and is unlikely to recur (eg, drug toxicity,
Lyme disease, or transient increases in vagal tone or during hypoxia in sleep apnea
syndrome in the absence of symptoms). (III-B)
Permanent Pacing in Chronic Bifascicular Block
Key Points
����Bifascicular block refers to ECG evidence of impaired conduction
below the AV node in the right and left bundles.
Alternating bundle-branch block (also known as bilateral bundle-branch block) refers
to situations in which clear ECG evidence for block in all 3 fascicles is manifested on
successive ECGs.
����Patients with first-degree AV block in association with bifascicular
block and symptomatic, advanced AV block have a high mortality rate
and a substantial incidence of sudden death.
����Syncope is common in patients with bifascicular block, but it is not
associated with an increased incidence of sudden death.
Therefore, pacing relieves the neurological symptoms but does not reduce the occurrence of
sudden death.
����Ventricular arrhythmias are common in patients with bifascicular block.
Treatment
����Permanent pacemaker implantation is indicated for:
������ advanced second-degree AV block or intermittent third-degree AV block. (I-B)
������ type II second-degree AV block. (I-B)
������ alternating bundle-branch block. (I-C)
����Permanent pacemaker implantation is reasonable for:
������ syncope not demonstrated to be due to AV block when other likely causes have
been excluded, specifically ventricular tachycardia (VT). (IIa-B)
������ an incidental finding at electrophysiological study of a markedly prolonged ���
His to ventricle interval (���100 milliseconds) in asymptomatic patients. (IIa-B)
������ an incidental finding at electrophysiological study of pacing-induced infra-His
block that is not physiological. (IIa-B)
����Permanent pacemaker implantation may be considered:
������ in the setting of neuromuscular diseases such as myotonic muscular dystrophy, Erb
dystrophy (limb-girdle muscular dystrophy), and peroneal muscular atrophy with
bifascicular block or any fascicular block, with or without symptoms. (IIb-C)
����Permanent pacemaker implantation is NOT indicated for:
������ fascicular block without AV block or symptoms. (III-B)
������ fascicular block with first-degree AV block without symptoms. (III-B)
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