ECG Challenge: 'I Feel Like I'm Going to Pass Out'

Philip J. Podrid, MD


March 01, 2019

The diagnosis is NSR, first-degree AV block, 3:1 AV block, Mobitz type II, and high-degree AV block.

Figure 2. Courtesy of Dr Podrid


The rhythm is regular with a rate of 30 beats/min. The QRS complex duration is normal (0.08 sec) and there is a normal morphology, although there is a narrow R' in lead V1. This has often been termed an incomplete right bundle branch block but this is not appropriate, as conduction through the bundles is all or none and it not incomplete. This pattern is consistent with an intraventricular conduction delay (IVCD) to the right ventricle. This has often been called a "crista pattern." The axis is approximately +90° (biphasic QRS complex in lead I and positive in lead aVF). The QT/QTc intervals are normal (600/425 msec). There is a P wave before each QRS complex (+) with a stable but prolonged PR interval (0.24 sec). The P waves a re positive in leads I, II, aVF, and V4-V6 and hence there is a sinus rhythm. Two additional P waves (*) are seen between each QRS complex. These P waves are not followed by a QRS complex (ie, they are nonconducted). The PP intervals are constant (↔) and the atrial rate is 90 beats/min.

This is, therefore, NSR with a first-degree AV block (prolonged AV conduction). There is also a second-degree AV block with a pattern of 3:1 AV conduction or AV block. This is Mobitz type II. With Mobitz type I there is only one nonconducted P wave, but there may be more than one nonconducted P wave with Mobitz type II. When there is more than one nonconducted P wave, it is often called high-degree AV block.

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