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ECG Challenge: A 34-year-old man with a history of atrioventricular nodal reentrant tachycardia being treated with a β-blocker and verapamil presents to the emergency department with complaints of fatigue and a slow heartrate. A 12-lead ECG is obtained.
The rhythm is irregular as a result of 2 premature QRS complexes (↓). Therefore, the rhythm is regularly irregular. The other QRS complexes are occurring at a regular interval and a rate of 42 bpm. These regular QRS complexes are …