Internal Medicine

P1: SBT

0521779407-05 CUNY1086/Karliner 0 521 77940 7 June 4, 2007 20:49

200 Atrioventricular Block

P-P interval encompassing the block is twice the regular P-P

interval.

A bundle branch block or intraventricular conduction delay

almost always present

Third-degree (complete) AV block: All P waves fail to conduct

to ventricle.

No relationship between P wave and QRS complexes

Both P-P and R-R intervals are constant.

■Specific Diagnostic Test

➣Holter monitoring

➣Electrophysiology study to diagnose infra or intra-Hisian block

usually not required

differential diagnosis

■Second-degree AV block: from blocked APC

■Third-degree (complete) AV block is a form of AV dissociation. P-P

intervals > R-R intervals in third-degree AV block.

■In 2:1 AV block (either constant or isolated), surface ECG cannot

distinguish Mobitz I from II.

■Evidence for Mobitz II: presence of IVCD or BBB

management

What to Do First

■Vital signs to ascertain hemodynamic effect of AV block

General Measures

■Identify and initiate treatment of underlying conditions responsible

for AV block. Establish relationship between symptoms and presence

of AV block. Review and readjust drug treatment accordingly.

specific therapy

Pacemaker implantation:

First-degree AV block: No pacemaker implantation except when

markedly prolonged PR interval (>0.3 s)

■results in dizziness, lightheadedness and fatigue (Class IIa indica-

tion)

■occurs in patients with LV dysfunction and CHF (Class IIb)

Second-degree AV block:

■Symptomatic bradycardia with second-degree AV block (Class I)

■Asymptomatic Type II second-degree AV block with wide QRS

(Class I)