MEDizzy - Mr. Smith had an ECG at a local hospital, but his records

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THE HEART (II)

Mr. Smith had an ECG at a local hospital, but his records were lost. The ECG technician remembered that the QRS deflection was large and positive in lead II and 0 in aVL. What is his mean electrical axis in the frontal plane?

ExplanationThe patient has a mean electrical axis of 60 degrees because of the large deflection in lead II and zero in lead aVL. The axis of aVL is −30 degrees, which is perpendicular to lead II, and this indicates that the axis must be 60 degrees.