12 Lead ECGs: Bundle Branch Blocks & Hemiblocks :12 Lead ECGs: Bundle Branch Blocks & Hemiblocks EMS Professions Temple College


Hemiblocks & Bundle Branch Blocks :Hemiblocks & Bundle Branch Blocks Value Help to identify patients at high risk for complete heart block Hemiblocks, Bundle branch blocks and AV blocks are precursors to complete heart block You are Alert & Better Prepared!!!


Anatomy Review :Anatomy Review Anatomy Bundle of His Left Bundle Branch Anterior fascicle long, thin; only blood supply from LAD Posterior fascicle shorter, thick; blood supply from RCA and LCX Right Bundle Branch


Definitions :Definitions Hemiblock Also called fascicular blocks block in one of the two fascicles of the left bundle branch Bundle Branch Block block of the entire left or right bundle branch


Hemiblocks :Hemiblocks Posterior fascicle Much more difficult to have block  greater disease Less common but more concerning Supplies majority of inferior wall of LV If blocked, results in right axis deviation


Hemiblocks :Hemiblocks Anterior fascicle Easier to have block; More common Supplies superior wall of LV If blocked, results in pathologic left axis deviation


Hemiblock Identification :Hemiblock Identification Left Anterior Hemiblock Pathologic Left Axis Deviation small q wave in lead I small r wave in lead III Normal QRS or RBBB Left Posterior Hemiblock Right Axis Deviation small r wave in lead I small q wave in lead III Normal QRS or RBBB usually does have RBBB “absence of right ventricular hypertrophy”


Precursors to Complete Heart Block :Precursors to Complete Heart Block Any Type II AV Block Anyone with disease of both bundles Anyone with two or more of any blocks Examples: Prolonged P-R & anterior hemiblock RBBB & anterior hemiblock RBBB & posterior hemiblock Prolonged P-R with anterior hemiblock & RBBB


Precursors to Complete Heart Block :Precursors to Complete Heart Block If recognize precursors to CHB, then: Have high index of suspicion for CHB Have TCP ready (standby mode) Patient may need a pacemaker Administration of Lidocaine and other ventricular antidysrhythmics may result in CHB Lidocaine contraindicated in patients with precursors to CHB unless TCP in place and ready


Bundle Branch Block :Bundle Branch Block Can be pre-existing condition Can be caused by ACS If AMI caused 60-70% associated with pump failure 40-60% mortality w/o reperfusion


Bundle Branch Block :Bundle Branch Block May Produce ST elevation ST depression Tall T waves Inverted T waves Wide Q waves May Hide ST elevation ST depression Tall T waves Inverted T waves Wide Q waves Can Mimic or Hide Evidence Needed to Identify AMI


BBB Problem :BBB Problem BBB Problem Critical to reperfuse patients with BBB produced by ACS ACS “harder” to identify on ECG when BBB present New or presumably new BBB is an indication for thrombolytic therapy


BBB Recognition :BBB Recognition Forget About the Notch!


BBB Recognition :BBB Recognition Fundamental Criteria Wide QRS > 100 ms (or, 0.10 sec) Supraventricular rhythm


BBB Recognition :BBB Recognition


Normal Ventricular Conduction :Normal Ventricular Conduction Normal Conduction fibers of LBB begin conduction impulse travels across interventricular septum from left to right towards + electrode creates small r wave travels across ventricles causing depolarization of both simultaneously LV contributes most to complex impulse travels away from + electrode creates primarily negative complex


RBBB :RBBB RBBB in V1 no change in initial impulse travel small r wave impulse depolarizes LV by itself since RBBB RV depolarized by impulse thru muscle it now contributes to complex travels toward + electrode creating positive deflection R-S-R´


LBBB :LBBB LBBB in V1 initial deflection altered since travels right to left now Q wave or small q wave RV depolarizes unopposed may produce small r wave travels across septum to depolarize LV deep S wave


BBB Recognition :BBB Recognition Terminal Force in V1 direction of deflection prior to J point J point


BBB Recognition :BBB Recognition Use V1 Find Terminal force Identify direction of terminal force Downward  LBBB Upward  RBBB Picture a Steering Wheel Right turn  turn signal goes up Left turn  turn signal goes down


BBB Recognition Practice :BBB Recognition Practice


BBB Recognition Practice :BBB Recognition Practice