ECG Challenge: An 80-year-old woman with a history of hypertension, being treated with amlodipine and a β-blocker, presents to her primary care physician for a routine physical examination. Her blood pressure is controlled and her physical examination is unremarkable. Her pulse is noted to be slow and a 12-lead ECG is obtained.
The rhythm is irregular, but the long intervals are the same (↔) and the short intervals (┌┐) are the same. There is 1 premature QRS complex seen (↑). Therefore, the rhythm is regularly irregular. The QRS complexes are narrow (0.08 s) and have a normal morphology and normal axis between 0° and +90° (positive QRS complex in leads I and aVF). The average rate is 42 bpm. The QT/QTc intervals are normal (440 ms/370 ms). P waves are seen before the first, third, fifth, and eighth QRS complexes (+). The PR interval is constant although slightly prolonged (0.22 ms). A P wave is also seen after the second, fourth, and seventh QRS complexes (*), although it is at the very end of the seventh QRS complex and, hence, less obvious. The P waves are positive in leads I, II, aVF, and V4 through V6. Hence, there is an underlying normal sinus rhythm, and there is a first-degree atrioventricular block (or conduction delay) when there is intact atrioventricular conduction (ie, first, third, fifth, and eighth QRS complexes). Although the PP intervals are not regular, several of the PP intervals are the same at a rate of 52 bpm (└┘). Following the first and third QRS complex, there is a negative P wave (^), which is premature. This is a nonconducted premature atrial complex. As a result, there is resending of the sinus impulse, accounting for the irregular PP intervals. Following the nonconducted premature atrial complex, there is a narrow normal QRS complex that is not preceded by a P wave; there is a P wave (*) that follows this QRS complex. This is an escape junctional complex, a result of the long pause resulting from the nonconducted premature atrial complex. The sixth QRS complex is premature (↑) and is wider and has a different morphology. This is a premature ventricular complex, and it is also followed by an escape junctional complex as a result of the long pause. As already stated, there is an on-time sinus P wave at the very end of this complex.
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- © 2016 American Heart Association, Inc.