These tracings are compatible with
We all love to diagnose the syndrome of right bundle branch block with alternating left anterior and left posterior hemiblock. This is a form of trifascicular block, described by the Argentinian school of electrocardiography. 
However, this combination is extremely uncommon. Left posterior hemiblock is uncommon. In my experience, these tracings more often than not have been due to reversal of left arm and left leg cables. In the book, this is not even mentioned in the differential! Other times.
So following a Bayesian approach, I always try to find something else. The key to diagnosing the reversal is the P in lead I taller than the P in lead II. This cannot happen with a sinus P wave.
Otherwise, I is II, II is I and III is reversed. aVR is the same, aVL and aVF are switched.
@arron_pearce nailed it in the comments here.
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