Internal Medicine

0521779407-C01 CUNY1086/Karliner 0 521 77940 7 June 4, 2007 20:53

Chronic Bundle Branch Block 313

➣Left ventricular posterior fascicular block (LPFB):

right QRS axis deviation (90◦to 180◦), qR in III and F, rS in I and

aVL, q wave≤40 ms in the inferior leads.

Exclude RVH by echo.

➣Bifascicular block: RBBB+LAFB or LPFB.

■Specific Diagnostic Test

➣Electrophysiology study to measure HQ intervals (not indicated

for this measurement alone) or to assess inducibility of VT with

syncope and bifascicular block.

differential diagnosis

■Secondary 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

■No acute intervention required unless syncope occurs.

General Measures

■Identify and initiate treatment of underlying conditions responsible

for BBB block.

specific therapy

Pacemaker Implantation

■Intermittent third degree or second degree AV block in chronic bi-

or trifascicular block (Class I)

■Syncope when VT is excluded with EP study (Class IIa).

■Incidental finding at EP study of non-physiologic paced induced

infra-Hisian block (Class IIa)

■Incidental finding at EP study of HV interval≥100 ms (Class IIa)

Side Effects & Contraindications

■none

follow-up

■ECG and Holter monitoring if symptoms appear to search for heart

block and ventricular tachyarrhythmias. Pacemaker follow-up after

implantation