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Third Degree Block example one



In third degree block, there is no electrical relationship between the atria
and the ventricles.  What we see here is a regular atrial rate (the P-P interval
is 0.72 seconds, so the atrial rate is 83 per minute) and a regular ventricular
rate (the R-R interval is 1.70 seconds, so the ventricular rate is 35 per minute),
but these two rates are not related to one another.  We know this because
the ratio of the two rates is 2.4, not a whole number.  Also notice how no two
P-R intervals are the same.  Based on the rate and the QRS width and shape,
the pacemaker for the ventricles here is probably a bundle branch.