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Second Degree Block Type Two example one



Notice that two P-waves on this strip are not followed by QRS complexes.  Also notice the
left bundle branch block.   The P-R intervals do not vary, and there is no pattern to the missed beats.
This is a classic example of second degree block type two.  This type of block is more worrisome
than second degree block type one because of its mechanism: with one bundle branch already blocked,
the non-conducted beats are due to an intermittent block in the other bundle branch.  If this
intermittent block were to become continuous, third degree block would result.