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 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 3 rd degree AV block Trifascicular block—as above, with 1 st 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

RBBB EKG findings

RBBB

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

LBBB causes CAD Cardiomyopathy Myocarditis LVH Anatomic malformations Neuromuscular disease Hemochromatosis Aortic valve endocarditis RHD Perinatal exposure to HIV-I

LBBB PE What heart sound changes will you hear on auscultation? –Absent or diminished S1, reverse split S2

LBBB EKG findings

LBBB EKG

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

EKG

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

EKG

Tough scenarios with BBB RVH LVH MI

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

EKG smorgasbord

EKG smorgasbord cont’d

Questions ?