FASCICULAR BLOCKS Flashcards
Right Bundle Branch Block:
CRITERIA
Prolonged QRS (>120 ms)
rSR’ (M Shaped) in early precordial leads (V1-V3)
Wide, slurred S in lateral leads (I, aVL, V5-6)
Leads V1-V3 often have ST-segment depression and inverted T Waves (Appropriate discordance)
ETIOLOGY
Myocarditis
RVH / Cor Pulmonale
Pulmonary Embolus
Ischemic Heart Disease
Cardiomyopathy
Incomplete Right Bundle Branch Block
rSR’ in early precordial leads (V1-V3) (M Shaped)
Wide, slurred S in lateral leads (I, aVL, V5-6)
QRS is NOT Prolonged (>120 ms)
Left Bundle Branch Block
QRS duration > 120ms
Dominant S wave in V1
Broad monophasic R wave in lateral leads (I, aVL, V5-6) with discordant ST depression and T wave inversion
The ST-segments and the T-waves are directed in an opposite direction to the main QRS vector in all leads (the rule of “appropriatediscordance”
Absence of Q waves in lateral leads
Prolonged R wave peak time > 60ms in leads V5-6
DDx: LBBB
Ischaemic heart disease
Anterior MI
Aortic stenosis
Hypertension
Dilated cardiomyopathy
Lenègre-Lev disease: primary degenerative disease (fibrosis) of the conducting system
Hyperkalaemia
Digoxin toxicity
Left Anterior Fascicular Block (LAFB)
Left Axis Deviation
qR complex in leads I and aVL (small Q waves and tall R waves)
rS in II, III and aVF (small R waves and deep S waves)
Prolong R wave peak time in aVL > 45 ms
NO prolonged QRS
Left Posterior Fascicular Block (LPFB)
NO prolonged QRS
Right Axis Deviation
rS complexes in leads I and aVL
qR complexes in leads II, III and aVF
Bifascicular Block: Criteria
RBBB with LAFB manifested as LAD
RBBB with LPFB manifested as RAD
+/- T wave inversions in the inferior leads
+/- qR in lead IIIn