You are called to consult on a 72-year-old man who presented to the emergency department (ED) earlier today with chest pain. He had been mowing the lawn approximately four hours prior to presentation when he felt his heart “go out of whack again.” He says he does not recall feeling this sick with any of his other episodes. The intern in the ED is able to find the patient’s old records. They document multiple admissions in the past for atrial fibrillation, which has been successfully cardioverted to normal sinus on at least four prior occasions. His medication list includes furosemide 40 mg/d, potassium chloride 20 mEq/d, digoxin 0.25 mg/d, and atenolol 50 mg/d. He also admits rather sheepishly that he has “tried a Viagra every once in a while.” When you arrive in the ED, the intern hands this electrocardiogram to you and says, “What’s going on here?” The readout shows a ventricular rate of 36 beats/min; no PR interval; QRS duration, 128 ms; QT/QTc intervals, 494/382 ms; R axis, -34°; T axis, -89°. What is your interpretation of this ECG?