A 65-year-old man complains of several episodes of abdominal pain in the past 12 hours. He awakened several times last night with pain in the epigastric area and right lower quadrant of his abdomen. He had a normal meal at 6 pm yesterday and has not eaten since.

At its worst, the pain is described as an 8 out of 10 “stabbing sensation” that seems to come in waves and has an abrupt onset and termination without precipitation. He has never experienced this before. His last bowel movement was three days ago, and he has not noticed blood in his stool or black, tarry stools. He denies nausea, vomiting, diarrhea, urinary retention, chest pain, syncope, or near-syncope.

His medical history is remarkable for paroxysmal atrial fibrillation. After two unsuccessful attempts at catheter ablation of his atrial fibrillation, he was placed on warfarin and amiodarone. His other medications include clonazepam for anxiety and simvastatin for mild hypercholesterolemia. He has no known drug allergies, does not smoke, and drinks one or two cocktails each evening. 

His vital statistics include a temperature of 37.8°C; blood pressure, 102/64 mm Hg; pulse, 132 beats/min and irregular; respiratory rate, 18 breaths/min; and O₂ saturation, 97% on room air. The lungs are clear in all fields.

The cardiovascular exam reveals an irregular rate of 130 beats/min, which abruptly changes to a regular rate of 45 beats/min. There are no murmurs or rubs; there is no jugular venous distention and no peripheral edema. The abdomen is soft, with diffuse tenderness over the right lower quadrant. The abdomen is not distended, and bowel sounds are present in all quadrants. Peripheral pulses are 2+ and equal bilaterally.

Given a history of paroxysmal atrial fibrillation, as well as the abrupt change in heart rate during the examination, an ECG is obtained and shows the following: a ventricular rate of 45 beats/min; PR interval, 194 ms; QRS duration, 100 ms; QT/QTc interval, 568/491 ms; P axis, 62°; R axis, 46°; and T axis, 66°. What is your interpretation of this ECG—and what explanation can you give for the change noted during the physical exam?

ANSWER

The ECG reveals marked sinus bradycardia with a prolonged QT interval. Sinus bradycardia occurs at heart rates below 60 beats/min, with marked bradycardia occurring at rates below 50 beats/min. Because the QT interval is affected by rate, Bazett’s formula (corrected QT = QT Interval / square root of the RR interval) is used to correct the QT interval (QTc) for the heart rate (normal QTc, 440 ms or lower). The corrected QT interval on the ECG is 491 ms, consistent with a prolonged QT interval. 

Patients with paroxysmal atrial fibrillation may experience postconversion bradycardia—particularly in the setting of conduction disease or with medication use (amiodarone in this case), which affects cardiac conduction. The examiner happened to be in the right place at the right time and heard the conversion from atrial fibrillation to marked bradycardia as it occurred. CT of the abdomen and laboratory testing identified an inflamed appendix, and the patient underwent a successful laparoscopic appendectomy.