Friendly Advice Goes Awry

You have been following a 57-year-old man for gastroesophageal reflux disease (GERD). He presents for routine follow-up stating that his reflux has subsided; you presume this is a result of the 14-day course of a proton pump inhibitor that you prescribed. However, the patient confesses that, for about three months, he’s taken his omeprazole at twice the dose—because a friend told him that OTC medications are half the dose of the prescription versions. His primary concern today is that his heart has started flip-flopping in his chest for brief periods at bedtime. The symptoms typically last for 30 to 60 minutes and recur when he wakes in the morning—particularly if he is startled by his alarm clock. They began approximately a week ago, and he reports that they start and stop abruptly. The patient denies chest pain, dyspnea, and syncope or near-syncope, but he does note that it feels like something is “sticking in his throat.” His active medical problems include GERD, hypertension, and obesity. Surgical history is remarkable for repair of bilateral ankle fractures and a left femur fracture sustained in a motorcycle accident six years ago. Current medications include omeprazole, metoprolol, furo­semide, and potassium chloride. He says he ran out of his potassium about a month ago and hasn’t refilled it yet. He also reports that he hasn’t taken his metoprolol in more than six months, because it makes him lethargic. He has no known drug allergies. The patient, who works as a welder, is married and has one son. He drinks approximately one six-pack of beer per week and smokes half a pack of cigarettes per day. He uses marijuana recreationally once or twice a month but denies use of any other illicit or naturopathic drugs. Review of systems is remarkable for a smoker’s cough, which clears with coughing. He also states his right eye twitches uncontrollably, and he feels weak and washed out. He denies nausea, vomiting, diarrhea, and constipation. While you are conducting the review, he states, “It just started again.” You immediately check the patient’s pulse; it is 110 beats/min and irregular. Additional vital statistics include a blood pressure of 124/74 mm Hg; respiratory rate, 14 breaths/min; O2 saturation, 96% on room air; and temperature, 98.4°F. His weight is 245 lb and his height, 72 in. Pertinent physical findings include inspiratory and expiratory crackles that change with coughing, an irregularly irregular rhythm without evidence of a murmur or rub, a soft abdomen, and no evidence of jugular venous distention or peripheral edema. Laboratory values are within normal limits, with the exception of the potassium (2.8 mmol/L; normal range, 3.6-5.2 mmol/L) and magnesium (0.9 mg/dL; normal range, 1.8-2.6 mg/dL). An ECG reveals a ventricular rate of 108 beats/min; PR interval, not measured; QRS duration, 78 ms; QT/QTc interval, 352/471 ms; no P axis; R axis, –64°; and T axis, –58°. What is your interpretation of this ECG?