The cardiogram shows a (likely) recent inferior MI. Note the deep Q waves in the inferior leads 2,3, and aVF. There is a mm or so of ST elevation still present, suggesting that this occurred within the past few days-week (although some low-level ST elevation may persist for longer). The Q wave in aVF means the axis is shifted upward in the frontal plane, to the left upper quadrant - therefore left axis deviation.
Put another way, loss of electrically active myocardium in the inferior wall causes the axis to be shifted upward. Inferior MI, together with left anterior fascicular block and LVH constitute the three main causes of left axis deviation. Each of these latter two entities have characteristics that distinguish them from an inferior MI, although sometimes it can be hard to tell if the complex in aVF is a QS (as here) or a rS as in LAFB.
NOTE: EKG's are for internal educational purposes of the University of Massachusetts Department of Family Medicine. Please do not forward without permission from Dr. Golding!
