2:1 and Mobitz Type II Atrioventricular Block: A Common Fallible Diagnosis

Abstract

A patient with Wenckebach phenomenon followed by runs of 2:1 atrioventricular (AV) block, labeled as Mobitz type II AV block by the referring physician, was referred for permanent pacemaker implantation. Apropos with this case and similar publications with this fallible diagnosis, the correct diagnosis of second degree AV block is revisited. It is pointed out that an ECG diagnosis of 2:1 AV block is by no means synonymous to Mobitz type II AV block, as two successive PR intervals are required to make a distinction between Mobitz type I and type II, which is never the case with a constant 2:1 AV block recording. On the other hand, the correct diagnosis can only be made by association. When longer ECG recordings are available and at least two consecutive PR intervals are seen, as in the present case, and one can discern a definite pattern of Mobitz type I (with progressive PR prolongation) or type II block (with stable PR intervals), then one can conclude that the 2:1 AV block is a consequence of one of the two types. Rhythmos 2018;13(2): 35-37.