ECG FINDINGS(SEEFIGURE2.3)
■ Normal QRS duration
■ Leftward QRS axis of > −30°
■ Small Q wave in Lead I and S wave in Lead III (Q 1 S 3 )
TREATMENT
■ Treat underlying condition.
LEFTPOSTERIORFASCICULARBLOCK(LPFB)
LPFB results from damage to the L posterior fascicle of the L bundle.
CAUSES
Causes are similar to LBBB.
ECG FINDINGS(SEEFIGURE2.4)
■ Normal QRS duration
■ Right axis deviation
■ S wave in Lead I and Q wave in Lead III (S 1 Q 3 )
TREATMENT
■ Treat underlying condition.
BIFASCICULARBLOCK
Bifascicular block occurs when any two of the three major infranodal path-
ways (R bundle branch, L anterior fascicle, L posterior fascicle) are blocked.
CARDIOVASCULAR EMERGENCIESFIGURE 2.3. Left anterior fascicular block.
(Reproduced, with permission, from Tintinalli JE, Kelen GD, Stapczynski JS. Emergency Medicine:
A Comprehensive Study Guide, 6th ed. New York: McGraw-Hill, 2004:195.)
LAFB = Q 1 S 3
LPFB = S 1 Q 3