Left bundle branch block

Left bundle branch blockCreated OnApril 19, 2020Last Updated OnOctober 28, 2020byadmin You are here: Main ECG Left bundle branch block < All Topics Table of Contents A differential of poor R wave progression ECG features: QRS duration of > 120 ms Dominant S wave in V1 Broad monophasic R wave in lateral leads (I, aVL, V5-V6) Absence of Q waves in lateral leads (I, V5-V6; small Q waves are still allowed in aVL) Appropriate discordance: the ST segments and T waves always go in the opposite direction to the main vector of the QRS complex Poor R wave progression in the chest leads Left axis deviation Incomplete LBBB is diagnosed when typical LBBB morphology is associated with a QRS duration < 120ms QRS Morphology in the Lateral Leads The QRS complex in V1 may be either: Rs complex (small R wave, deep S wave) QS complex (deep Q/S wave with no preceding R wave) The R wave in the lateral leads (I, aVL, V5-V6) may be either: ‘M ‘-shaped Notched Monophasic RS complex

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