"What is causing this Sinus Tachycardia?"

A 31-year-old female with past medical history of active tobacco use, presented to her PCP's office for a post hospitalization follow up visit after being hospitalized for Guillain-Barre syndrome (GBS).Her symptoms of weakness of the upper and lower extremities from GBS had improved significantly, and she reported no other symptoms.Her pulse was noted to be high at 102 beats per minute and on review of her recent medical record her heart rate was found to be as high as 121 beats per minute a few days prior to her admission to the hospital, as shown in the ECG (Figure 1).Her complete blood count, basic metabolic profile, chest x-ray and