An 52 year old female underwent total thyroidectomy due to thyroid cancer. Her post-operative course was complicated by pneumonia for which she is being treated with moxifloxacin. Post-operateve day 5 she passed out briefly while walking in the hallway. Immediately afterwards her temperature is 37.0 C (98.6 F), blood pressure is 120/80, heart rate 70, respirations 16. Physical examination is unremarkable. Her ECG is below.
What most likely caused her syncope?
A. Vasovagal syncope
B. Polymorphic ventricular tachycardia
C. Atrial fibrillation
D. Ventricular septal defect