Resha Reya Ganthan MD^1,, Fadi Yacoub MD², Asher Gorantla MD², Nidal Isber MD FACC FHRS^{3, 4}

The long-term effects following a COVID-19 infection vary widely, with that including inappropriate sinus tachycardia as a manifestation. Herein we report the case of a middle-aged woman with a history significant for a COVID-19 infection 2-years prior, following which she developed brief episodes of palpitations, otherwise controlled with Metoprolol Succinate. She presented to the hospital after a 1-week history of worsening palpitations far worse in severity from prior episodes, associated with shortness of breath and pre-syncope. ECG on admission demonstrated sinus tachycardia with a significantly elevated heart rate. Multiple repeat ECGs demonstrated periods of sinus tachycardia when symptomatic alternating with a normal sinus rhythm when asymptomatic. Continuous telemetry monitoring while inpatient reported similar findings, with no other tachyarrhythmias present. Multiple other diagnostic tests were performed to rule out a more malignant cause of autonomic instability, which ultimately yielded negative results. The patient was however additionally diagnosed with orthostatic hypotension, which posed a potential confounding factor in the steadfast diagnosis of inappropriate sinus tachycardia. This case highlights the multiple simultaneous manifestations of post-covid syndrome with significant symptom overlap, leading to a missed diagnosis.

Inappropriate sinus tachycardia (IST), Intrinsic heart rate (IHR), Electrocardigram (EKG), Orthostatic hypotension, Post-Covid syndrome (PCS), Postural orthostatic tachycardia syndrome (POTS), Sinoatrial node (SAN), Transthoracic echocardiography (TTE), Tilt-table test (TTT)