ECG Challenge: Tired and Out of Control

Philip J. Podrid, MD

Disclosures

December 06, 2018

Discussion

Figure 2. Courtesy of Dr Podrid.

The diagnosis is normal sinus rhythm, first-degree AV block (prolonged AV conduction), premature ventricular complexes, escape junctional complex, left ventricular hypertrophy with associated ST-T wave changes, and low-voltage limb leads.

The rhythm is irregular, but many of the RR intervals are the same, with a rate of 78 beats/min. Therefore, the rhythm is regularly irregular. All of the QRS complexes have the same morphology, except for the 6th and 10th QRS complexes (*), which are wider and premature. The QRS complexes have a normal duration (0.10 sec) and a normal morphology. However, there is low QRS complex amplitude in the limb leads, defined as an amplitude <5 mm in each limb lead. There is also evidence of left ventricular hypertrophy with an S wave in lead V2 ( [ ) that is 25 mm in depth and an R wave in lead V5 ( ] ) that is 15 mm tall. Therefore, the SV2 + RV5= 40 mm, which meets one of the criteria for left ventricular hypertrophy.

There are also ST-T wave changes in leads I and V4-V6 (^), which are associated with left ventricular hypertrophy and represent chronic subendocardial ischemia. The axis is normal between 0° and +90° (positive QRS complex in leads I and aVF). The QT/QTc intervals are normal (400/455 msec). Although no obvious P waves are seen before most of the QRS complexes, notches of the T waves of many of the QRS complexes (v) are suggestive of superimposed P waves. Importantly, definitive P waves can be seen after the two premature complexes (+). The P waves are obvious as a result of the pause. It can be seen that these P waves are followed by QRS complexes and the PR interval is constant but very long (0.52 sec) (↔), indicating a first-degree AV block or prolonged AV conduction. Using this PR interval, it can be seen that the notches on the T waves (v) are indeed P waves, as they are associated with the same PR interval (↔). Therefore, there is a normal sinus rhythm with prolonged AV conduction.

After the 4th QRS complex there is a pause, followed by a P wave (^) and then a QRS complex (•) having the same morphology as all of the other sinus complexes. However, the PR interval (└┘) is much shorter (0.36 sec) than the baseline PR interval, meaning that the QRS complex is not the result of the P wave—the P wave is not conducted. Rather, this QRS complex (•) is a junctional escape complex. The pause is the result of a nonconducted premature P wave (↓) or a blocked PAC, which can be seen at the end of the 4th QRS complex, altering its morphology. The two early complexes (*), which have a different morphology, are PVCs. Although a P wave is seen before these two PVCs (↑), the PR intervals are very short and hence the QRS complexes are not related to the P wave.

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