LBBB with Northwest Axis

Report:

Atrial fibrillation with ventricular response 98/min

Left bundle branch block

Axis approx. +240o

Comment:

The S wave in lead 1 makes the axis extreme right or left (no man’s land); this seems to have the same significance as right axis deviation with LBBB: congestive cardiomyopathy, often primary. In atrial fibrillation arm leads reversal may produce this pattern. Other tracings should be sought, preferably in sinus rhythm (below, with marked LAA). Left or normal axis with LBBB are not reportable; RAD or NW axis are, for their connotation of severe myocardial disease.

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