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EKG Rounds. Rebecca Burton-MacLeod R4, Emerg Med July 20 th , 2006. EKG Case . Conduction anatomy . AV node Bundle of His Branching bundle Bundle branches Purkinje fibers Myocardial cells. Bundle branch blocks. RBBB—transmission is delayed or fails to conduct along right bundle branch
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EKG Rounds Rebecca Burton-MacLeod R4, Emerg Med July 20th, 2006
Conduction anatomy • AV node • Bundle of His • Branching bundle • Bundle branches • Purkinje fibers • Myocardial cells
Bundle branch blocks • RBBB—transmission is delayed or fails to conduct along right bundle branch • LBBB—transmission is delayed or fails to conduct along left bundle branch • LAFB—most common type of intraventricular conduction defect • LPFB—very rare!
Terminology • Bifascicular block—conduction defect in RBB and either LAF or LPF • Does not include RBBB and LBBB combination, as this is termed 3rd degree AV block • Trifascicular block—as above, with 1st degree AV block (prolonged PR)
Conduction • Consequence of BBB is that ventricle must await depolarization by opposite ventricle • Activation proceeds on cell-to-cell basis • Results in much slower activation along normal pathways
RBBB • Causes: • In children—surgical repair of VSD’s is most common cause; cardiomyopathy, myocarditis, CHF, hereditary causes (Brugada syndrome), muscular dystrophy • In adults—normal variant, RVH or strain (ex: PE), CAD
RBBB PE • What will you hear on physical examination? • Persistently split S2
EKG criteria • QRS >0.1sec • rSR’ or rR’ pattern in V1-3 • Wide S in leads I, V6 • May have normal axis, or right or left deviation • Usually inverted T in V1-2, in other leads T is directed opposite to terminal portion of QRS
CAD Cardiomyopathy Myocarditis LVH Anatomic malformations Neuromuscular disease Hemochromatosis Aortic valve endocarditis RHD Perinatal exposure to HIV-I LBBB causes
LBBB PE • What heart sound changes will you hear on auscultation? • Absent or diminished S1, reverse split S2
EKG findings • QRS >0.12sec • No Q in I, aVL, V6 • Prominent QS pattern in V1 (+/- small R wave) • Tall, wide, notched R in I, aVL, V6
LAFB • EKG findings: • Normal QRS width • QRS axis is from –30 to –90degrees • Q present in I, aVL • Major QRS direction in aVF is negative • Slurred S wave in left precordial leads • Late R wave in aVR (>0.045sec) • Terminal R in aVL is slurred
LPFB Ddx • Must first exclude other causes of right axis!!! • Cor pulmonale • Pulmonary heart disease • Pulmonary hypertension, etc.
LPFB • EKG findings: • Duration of QRS is usually normal • Q wave present in II, III, aVF • QRS axis is +120 to +180degrees • S wave present at end of QRS in I and aVF
Tough scenarios with BBB • RVH • LVH • MI
Sgarbossa criteria • STE >1mm concordant with QRS (5pts) • STD >1mm in V1-3 (3pts) • STE >5mm discordant with QRS (2pts) • >3pts =AMI Sgarbossa et al. NEJM. 1996