Accrochage is the name given to the phenomenon in which complete heart block masquerades as 2:1 AV block in short recordings. Long recordings will show the variation in PR interval and hence clarify the diagnosis of complete heart block. This occurs when the atrial rate is nearly double that of the escape rhythm in complete heart block.
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In the ECG shown above the atrial rate is double that of ventricular rate. PR interval appears to be fixed , suggesting 2:1 AV block. This pattern can very well be an accrochage, which may be evident only in long recordings. One close scrutiny, the PR interval is shorter than that in lead I. This could be taken as an evidence of complete heart block. But it is also possible that a portion of the P wave in V6 is isoelectric. This possibility can be very well considered as the P wave in other leads is wider than what is seen in V6. The second P wave seen in lead lead II after the T wave of the first QRS is wide and has the appearance of P mitrale. The two simultaneously recorded complexes in V3 and V4 show different PR intervals due to this reason. This is seen well in the second complex of V3 and V4.