For the past six hours, a 58-year-old man has been experiencing substernal chest discomfort. Upon arrival at your facility, the patient appears uncomfortable but denies pain in his chest; there is no radiation to the neck, back, or arm. He denies palpitations, nausea, vomiting, diarrhea, and constipation. He says he feels more short of breath now than he did earlier, adding that “something just doesn’t feel right.”

His medical history is remarkable for GERD, which was confirmed two months ago by upper endoscopy following several episodes of epigastric pain. He was prescribed a proton pump inhibitor, which he has forgotten to take for the past two days. His last physical, performed one year ago, was normal. Surgical history is remarkable for a tonsillectomy and a left inguinal hernia repair, both during childhood.

His current medication list includes lansoprazole and ibuprofen (as needed for musculoskeletal pain). He does not smoke, and he occasionally has a beer on the weekends. The review of systems is noncontributory apart from his previously detailed symptoms.

Vital signs include a blood pressure of 130/86 mm Hg; pulse, 128 beats/min; respiratory rate, 12 breaths/min-1; and temperature, 97.9°F. His weight is 189 lb and his height, 73 in. The cardiac exam reveals a regular rate of 130 beats/min with no evidence of murmurs or rubs.

A chest x-ray, ECG, and bloodwork are obtained. The ECG reveals a ventricular rate of 128 beats/min; PR interval, 136 ms; QRS duration, 72 ms; QT/QTc interval, 326/475 ms; P axis, 44°; R axis, 40°; and T axis, –47°. The ECG obtained during his physical one year ago showed normal sinus rhythm with nonspecific ST- and T-wave changes but was otherwise normal.