ECG Challenge: Wheezing With a Rapid Heartbeat

The correct diagnosis is atrial flutter with 2:1 atrioventricular (AV) block (Figure 2).

Figure 2. Courtesy of Philip J. Podrid, MD.

Discussion

The rhythm is regular at a rate of 150 beats/min. The QRS complex is narrow (0.08 sec) with a normal axis between 0° and +90° (positive QRS complex in leads I and aVF). The QRS complex morphology is normal except for a significant Q wave in leads II, III, and aVF (+), consistent with an old inferior wall myocardial infarction. The QT/QTc intervals are normal (280/440 msec).

An atrial wave occurs before each QRS complex, particularly in leads II, III, aVF, and V4-V6 (*). The wave is negative in these leads and is positive in lead aVR. This is termed a long RP tachycardia. Etiologies for a long RP tachycardia include sinus tachycardia, which is not the case here because the P waves are negative in leads II, aVF, and V4-V6) which leaves:

Atrial tachycardia
Ectopic junctional tachycardia
Atrial flutter with 2:1 AV block
Atypical AV nodal tachycardia (fast-slow)
AV re-entrant tachycardia

A second atrial waveform is superimposed at the end of the QRS complex (↑), resembling an S wave in leads II, III, aVF, and V5-V6 and an R' in aVR (↓). The interval between these two atrial waveforms is regular with a rate of 300 beats/min. Therefore, the rhythm is atrial flutter with 2:1 AV block or AV conduction.

Philip Podrid, MD, is an electrophysiologist, a professor of medicine and pharmacology at Boston University School of Medicine, and a lecturer in medicine at Harvard Medical School. Although retired from clinical practice, he continues to teach clinical cardiology and especially ECGs to medical students, house staff, and cardiology fellows at many major teaching hospitals in Massachusetts. In his limited free time he enjoys photography, music, and reading.

You can follow Dr Podrid on Twitter @PPodrid

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Any views expressed above are the author's own and do not necessarily reflect the views of WebMD or Medscape.

Cite this: ECG Challenge: Wheezing With a Rapid Heartbeat - Medscape - Mar 20, 2023.

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