ECG Challenge: A 21-year-old male college student without any known cardiac problems presents to his college health service with concerns of intermittent palpitations that occur sporadically. They generally last only for a few minutes, although he did have 1 more prolonged episode 1 week before. This episode also terminated spontaneously. The results of his physical examination are unremarkable. An ECG is obtained.
There is a regular rhythm at a rate of 64 bpm. There are P waves seen before each QRS complex (+), and the P wave is positive in leads I, II, aVF, and V4 through V6. Hence, there is a normal sinus rhythm. The QRS complexes have 2 different morphologies. There are 2 narrow QRS complexes (*) with a normal duration (0.08 s). They appear to have a normal morphology, but because they are only seen in leads II and V1 through V3, this is not certain. The QT/QTc intervals of these complexes are normal (380/390 ms). The PR intervals associated with these 2 complexes are the same and are normal (0.20 s). The remaining QRS complexes are wide (0.16 s) with a morphology suggestive of a left bundle-branch block with a deep QS complex in lead V1 (←) and a broad R wave in leads I and V5 to V6 (→). The QRs complex widening is a result of a very slow (slurred) upstroke of the QRS complex (^). In addition, the PR interval associated with these complexes is constant but is different from the narrow complexes (despite the same sinus P wave preceding them). The PR interval is short (0.10 s). The short PR interval and widened QRS complex with a slurred upstroke is characteristic of Wolff-Parkinson-White pattern. The slurred upstroke is called a delta wave. In this case, the Wolff-Parkinson-White pattern is intermittent, alternating with conduction that is normal.
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- © 2015 American Heart Association, Inc.