ECG Challenge: Sudden-Onset Palpitations in a Young Woman

Philip J. Podrid, MD

Disclosures

December 06, 2017

Discussion

The diagnosis is atrial fibrillation, WPW, and a pseudo inferior wall infarction.

Figure 2. Courtesy of Dr Podrid.

The rhythm is irregularly irregular; the average rate is 90 beats/min. There are only three supraventricular rhythms that are irregularly irregular. They are:

  • Sinus arrhythmia (one P-wave morphology and stable PR interval);

  • Multifocal atrial rhythm with a rate <100 beats/min and multifocal atrial tachycardia with a rate >100 beats/min (three or more different P-wave morphologies and PR intervals without any P wave morphology being dominant); and

  • Atrial fibrillation in which there are no organized P waves.

Therefore, this is atrial fibrillation. The QRS complexes have two different widths and morphologies. The two narrow QRS complexes (+) have a normal duration (0.08 sec) and morphology, although there is an R' in lead V1 (←) and a tall R wave in lead V2 (→), consistent with early transition or counterclockwise rotation. This is an electrical axis shift in the horizontal plane, determined by imagining the heart as if viewed from under the diaphragm. With counterclockwise rotation, the left ventricular forces develop earlier and are seen in the right precordial leads. The QT/QTc intervals are normal (320/390 msec). The wide QRS complexes (0.16 sec) have an LBBB morphology, although the widening of the QRS complex is primarily at the base, while the rest of the QRS complex is narrow. Noted is a slurring in the upstroke of the QRS complex (↑), which is consistent with a delta wave and a WPW pattern. Further support for WPW is the lack of a relationship between QRS complex width and heart rate (or RR intervals). Noted are narrow QRS complexes at faster rates or shorter RR intervals (┌┐) and wider QRS complexes at slower rates or longer RR intervals (↔). This is not the pattern in rate-related aberrations, in which wider or aberrated QRS complexes are seen at faster rates. This pattern is typical for WPW. It can be noted that the WPW complexes have a QS morphology in the inferior leads (^), consistent with a pseudo inferior wall myocardial infarction. The Q wave in aVF is not present when the complex is narrow. Abnormalities of the left ventricle cannot be reliably diagnosed in the presence of WPW because initial activation is directly through the myocardium and not through the normal His-Purkinje system. This is a pseudo inferior wall infarction pattern, which is consistent with a posteroseptal (or inferoseptal) bypass tract.

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