ECG Challenge Response ECG Response: April 8, 2014 ECG Challenge: A 65-year-old woman with a history of hypertension for which she is taking a β-blocker and angiotensin-converting enzyme inhibitor is admitted to the hospital because of a cerebrovascular accident. While on telemetry, she is noted to have a significant bradycardia and an ECG is obtained.

The rhythm is irregular, but there some RR intervals that are similar to each other (↔, ┌┐). Therefore the rhythm is regularly irregular. The average rate is 36 bpm. P waves are seen (+) at a regular rate of 56 bpm. The P waves are positive in leads I, II, aVF, and V4 to V6 with a constant PP interval. Therefore, this is a sinus bradycardia. The P wave is broad and prominently notched in leads II, aVF, and V3 to V4 (P mitrale), consistent with left atrial hypertrophy or abnormality. There is a P wave before each QRS complex, but the PR interval is not constant. The PR intervals associated with complexes 2, 5, and 6 are the same (0.20 s), but the PR intervals of the third and fourth QRS complexes show progressive lengthening (from the baseline PR interval of 0.20 s to 0.28 and 0.40 s, respectively) (↑). The P wave after the fourth QRS complex is nonconducted (o). Hence, this

Correspondence to Philip J. Podrid, MD, West Roxbury VA Hospital, Section of Cardiology, 1400 VFW Pkwy, West Roxbury, MA 02132. E-mail [email protected] (Circulation. 2014;129:1538-1539.) © 2014 American Heart Association, Inc. Circulation is available at

DOI: 10.1161/CIRCULATIONAHA.114.009858

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ECG Challenge Response   1539 is a second-degree atrioventricular block with a pattern of 4:3 Wenckebach or Mobitz type I. The first QRS complex is preceded by a P wave and a PR interval of 0.44 s. After this complex, there is a nonconducted P wave (↓); hence, this QRS complex represents the end of a Wenckebach cycle. Following the fifth QRS complex, it can be seen that there is another nonconducted P wave (▲) (ie, a pattern of 2:1 atrioventricular block [or atrioventricular conduction] that is 2:1 Wenckebach). The QRS complexes have 2 different morphologies. Complexes 1, 3, and 4 (▼) are wide (0.12 s) with a right bundle-branch pattern with a broad terminal S wave in lead I and an R′ in aVR. Complexes 2, 5, and 6 have a normal duration (0.08 s) and morphology. The voltage is increased in lead V5 (R wave= 40 mm; }), and, along with the S wave in lead V2 (20 mm; {), the criteria for left ventricular hypertrophy are met (ie, S wave V2 + R wave V5 = 60 mm). There is J-point and ST-segment elevation (^) in leads V3 to V5, consistent with early repolarization, which is often seen with left ventricular hypertrophy or tall QRS complex amplitude. The T waves are also tall and appear to be peaked. However, they are asymmetrical in morphology (upstroke slower than downstroke), and, hence, the T waves are normal. Prominent and tall peak P waves may be seen with left ventricular hypertrophy or tall QRS voltage. The QT/QTc intervals are normal (480/370 ms). It can be seen that the QRS complexes with a right ­bundle-branch block are associated with a shorter RR interval. Therefore, the right ­bundle-branch block is rate related. Please go to the journal’s Facebook page for more ECG Challenges: Challenges are posted on Tuesdays and Responses on Wednesdays.

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ECG Response: April 8, 2014 Circulation. 2014;129:1538-1539 doi: 10.1161/CIRCULATIONAHA.114.009858 Circulation is published by the American Heart Association, 7272 Greenville Avenue, Dallas, TX 75231 Copyright © 2014 American Heart Association, Inc. All rights reserved. Print ISSN: 0009-7322. Online ISSN: 1524-4539

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ECG Response: April 8, 2014.

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