Left bundle branch block (LBBB) with concordant T waves in lateral leads
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LBBB pattern is identified by the slurred positive QRS in I, aVL, V5 and V6. Along with it there are slurred negative QRS complexes in V1 and V2. Initial septal q waves in lateral leads are absent in LBBB because the normal left to right septal activation sequence is reversed in the presence of LBBB. Secondary to the depolarisation abnormality, the repolarisation sequence changes and the ST segment and T wave are opposite in polarity to the dominant QRS in LBBB. This would mean ST depression and T wave inversion in lateral leads in LBBB (discordant). When the ST segment and T wave are in the same direction as the QRS, it is called concordant ST segment and T wave, usually indicating a primary myocardial problem like infarction or ischemia.