LAUSR

An 84-year-old man with a history of ischemic cardiomyopathy and atrial flutter was referred to the electrophysiology clinic for consideration of cardiac resynchronization therapy. He had been found to have symptomatic atrial flutter over a decade earlier, at which time he underwent electrical cardioversion and was started on oral propafenone. He had remained on this medication at a dose of 325 mg twice daily since then without recurrent palpitations or arrhythmias. Six months before the electrophysiology clinic visit, he was found to have ischemic cardiomyopathy with a left ventricular ejection fraction (LVEF) of 32% and received multivessel percutaneous coronary intervention. An echocardiogram on follow-up showed no improvement in his LVEF and the patient continued to have Class II heart failure symptoms despite 3 months of optimal, guideline-directed medical therapy. His ECG in the clinic (Figure 1) demonstrated normal sinus rhythm with a heart rate ≈60 beats per minute and a QRS duration of 196 ms, which is his baseline on the basis of a review of his medical history. What is the cause of the patient’s persistent wide QRS complex, and what is the best next step in management? Please turn the page to read the diagnosis. Michael Jiang, MD Bradley P. Knight, MD Nishant Verma , MD, MPH