Working Diagnosis:
Post-infectious dysautonomia, specifically Postural Orthostatic Tachycardia Syndrome (POTS), following a viral diarrheal illness.

Treatment:
Cardiology initiated fludrocortisone, midodrine, ivabradine, and nebivolol. She was also treated with aggressive hydration (4-5 L/day), salt loading (4-6 g/day), compression stockings, and graded exercise. The patient reported improved tolerance and functional recovery.

Outcome:
The athlete resumed lacrosse with medication support, pre-game IV hydration, and dietary modifications. Two years post-diagnosis, symptoms had improved though episodic tachycardia (up to 190 bpm), lightheadedness, and presyncope persisted with heavy exertion. She continued gradual conditioning and pursued training for a half marathon.

Author's Comments:
POTS is a form of autonomic dysfunction characterized by excessive tachycardia upon standing without orthostatic hypotension, leading to dizziness, fatigue, and palpitations. Diagnosis requires a greater than or equal to 30 bpm HR rise within 10 minutes of standing and compatible symptoms, best confirmed via tilt-table testing after excluding secondary causes. POTS affects less than 1 percent of the U.S. population, with 28-41 percent of cases following a viral illness. Post-infectious and post-COVID-19 POTS cases have increased in recent years.

Editor's Comments:
Interesting case with many teaching points. POTS predominantly affects women (80-90%), frequently occurs after an inciting event such as a virus, surgery, trauma or pregnancy.
Symptom severity does not correlate with the degree of tachycardia and lowering HR alone often does not relieve symptoms. Leg edema is due to impaired autonomic control of blood vessels leading to blood pooling. It is treated w/ compression stockings, hydration, and salt as in this case
Gait instability in POTS can simply be due to autonomic dysfunction or be related to an underlying hypermobility syndrome, mixed connective tissue disease, or small fiber neuropathy.
Exclusion of other causes should include anemia, hyperthyroidism, pheochromocytoma, and medications such as SNRIs. There was no mention of this patient being on medication for her anxiety. Diagnosis is made with a tilt table test which involves passively tilting a patient at an angle and assessing for symptoms and tachycardia. A provocative tilt table test uses medication such as nitroglycerin to speed up the process. Finally, if this case was Guillian Barre Syndrome, the patient would have ascending weakness and absent deep tendon reflexes. Diagnosis typically involves an LP and EMG.

References:
1. Cheshire WP. Postural tachycardia syndrome. UpToDate. March 2026. Accessed April 12, 2026. https://www.uptodate.com/contents/postural-tachycardia-syndrome
2.Bryarly, M, Phillips, L, Fu, Q. et al. Postural Orthostatic Tachycardia Syndrome: JACC Focus Seminar. JACC. 2019 Mar, 73 (10) 1207�"1228.
https://doi.org/10.1016/j.jacc.2018.11.059

Return To The Case Studies List.