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Bundle Branch Blocks. J. Huffman, PGY-4 July 2, 2009. Outline. LBBB RBBB Hemiblock PRACTICE!. Physiologically. On ECG. Unblocked ventricle. R. R’. Blocked ventricle. Two QRS’s out of ‘sync’. Single, wide QRS. LBBB. RBBB. RBBB. RBBB. LBBB. LBBB. “WiLLiaM MoRRoW”. LBBB. LBBB.
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Bundle Branch Blocks J. Huffman, PGY-4 July 2, 2009
Outline • LBBB • RBBB • Hemiblock • PRACTICE!
Physiologically On ECG Unblocked ventricle R R’ Blocked ventricle Two QRS’s out of ‘sync’ Single, wide QRS
ECG Changes: • Hemiblock (unlike a full LBBB or RBBB) does not widen the QRS complex. • Main effect is a change in the QRS axis: Left anterior fascicular block results in marked left axis deviation (-30° or more) QISIII pattern Left posterior fascicular block produces marked right axis deviation (+120° or more) SIQIII pattern
Anterior Hemiblock aVL I III II Posterior Hemiblock aVF
Axis? Between -30 and -90 deg LAD
Bifascicular Block (RBBB & LAFB)
V1 & V2 have the best “view” of the RV • V5 & V6 look at the LV • Look for the RR’ pattern in those pairs of leads • Incomplete = <120ms but meets morphology criteria • Hemiblocks: look at the axis!