January 23, 2016

Sinus rhythm, 2:1 AV block due to Mobitz II

This is a 70 yo pt who was admitted due to weakness. What is your interpretation?

Figure 1 - ECG case

Sinus rhythm, 2:1 AV block due to Mobitz II

Figure 2 - case marked

The sinus (atrial) rate is about 88 bpm and the ventricular rate is about  42 bpm. The QRS has right bundle branch block (RBBB) configuration. There are 2 P's for every 1 QRS. This is termed 2:1 AV block. A 2:1 AV block is a special form of second degree AV block. It can either be second degee type I (Mobitz I or Wenckebach) or second degree type II (Mobitz II). A longer strip is needed to elucidate the mechanism. In this case, this 10 second strip captured 3:2 AV conduction showing a dropped beat with no PR interval prolongation prior to the dropped beat. So, this is second degree AV block type II (Mobitz II) manifesting as 2:1 (predominantly) and 3:2 AV conduction.

Sinus rhythm, advanced heart block

Figure 3 - Advanced Heart Block

This 10 sec strips is minutres after the previous strip. QRS #2 is a conducted beat and after that there is AV dissociation due to accelerated idioventricular rhythm (AIVR). Obvious P waves are marked in read and hidden P waves are marked in green. When the AV conduction ratio s 3:1 or higher, the rhythm is called advanced AV block. This block occurs because of AV node or His-purkijne disease and not retrograde concealment in the AV node or His-Purkije system caused by junctional or ventricular escape complexes. A few minutes later, 2:1 AV blocked recurred (not shown). A permanent pacemaker was eventually placed.


Surawicz B and Knilans TK. 2008. Chou’s Electrocardiography in Clinical Practice. 6th ed. PA. Saunders-Elseiver

Issa Z, Miller J and Zipes D. 2012. Clinical Arrhythmology and Electrophysiology A Companion to Braunwald’s Heart Disease 2nd Ed. PA Saunders

Das and Zipes. 2012. Electrocardiography of arrhythmias : a comprehensive review. Elsevier PA


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