A 64-year-old woman is brought to the emergency department after her husband found her obtunded.  He also found open medication bottle of amitriptyline at her bedside.  She has a long history of chronic lower back pain and insomnia for which she is taking zolpidem, naproxen, and amitriptyline.  Her husband reports that she has appeared depressed recently, but she did not seek any help.  She has no known cardiac history or history of a stroke.  In the emergency department, she is lethargic but arousable.

Her temperature is 36.7 C (98 F), blood pressure is 95/45 mm Hg, and pulse is 106/min.  Her oxygen saturation is 94% on room air.  Heart sounds are normal. Lungs are clear.  She moves all extremities on command.

Which of the following would impact the further treatment of this patient the most?

A.  Amitriptyline blood level [4%]
B.  EEG recording [0%]
C.  PR interval duration on electrocardiogram [15%]
D.  QRS complex duration on the electrocardiogram [78%]
E.  Systolic left ventricular function on echocardiogram [1%]