Case Report Theophylline in Treatment of COVID-19 Induced Sinus Bradycardia Khalid Sawalha 1, * , Fuad J. Habash 2 , Srikanth Vallurupalli 2 and Hakan Paydak 3   Citation: Sawalha, K.; Habash, F.J.; Vallurupalli, S.; Paydak, H. Theophylline in Treatment of COVID-19 Induced Sinus Bradycardia. Clin. Pract. 2021, 11, 332–336. https://doi.org/10.3390/ clinpract11020047 Received: 25 March 2021 Accepted: 26 May 2021 Published: 1 June 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Internal Medicine Division, White River Health System, Batesville, AR 72501, USA 2 Cardiology Division, University of Arkansas for Medical Sciences, Little Rock, AR 72501, USA; FHabash@uams.edu (F.J.H.); SVallurupalli@uams.edu (S.V.) 3 Electrophysiology Division, University of Arkansas for Medical Sciences, Little Rock, AR 72501, USA; HPaydak@uams.edu * Correspondence: Ksawalha@aol.com; Tel.: +1-984-3641-158 Abstract: This is a retrospective case series of two patients with laboratory-confirmed coronavirus 2 (SARS-CoV-2) infection, presented to the University of Arkansas for Medical Sciences in January 2021. Medical records of these patients were reviewed using the EPIC electronic health record system. Clinical, laboratory, and treatment data were reviewed against periods of bradycardia in each patient. Both of the patients presented with dizziness and presyncope related to sinus bradycardia in which they received treatment with 1 mg of IV atropine and theophylline 200 mg orally. We share these two cases of theophylline treatment in COVID-19 induced sinus bradycardia. The first patient was a 39-year-old female, with a past medical history of polycystic ovarian syndrome, who presented to the emergency department with lightheadedness and dizziness. Two weeks prior to her presentation, she was tested positive for COVID-19 infection that was treated with azithromycin, dexamethasone and aspirin. Upon presentation, her ECG showed sinus bradycardia at a rate of 48 bpm. The second patient, a 21-year-old female with no significant past medical history, presented with presyncope. Three weeks prior to her presentation, she tested positive for COVID-19 infection that was treated symptomatically at her home. Upon presentation, her ECG showed junctional rhythm at a heart rate of 51 bpm. Keywords: bradycardia; COVID-19; theophylline; bradyarrhythmias; junctional rhythm 1. Introduction Sinus bradycardia is a rhythm in which the rate of impulses arising from the sinoatrial (SA) node is lower than expected. The normal adult heart rate, arising from the SA node, is considered historically to range from 60 to 100 beats per minute, with sinus bradycardia defined as a sinus rhythm with a rate below 60 beats per minute. However, the normal heart rate is, in part, the result of the complex interplay between the sympathetic and parasympathetic nervous systems. It is affected by numerous factors and varies in part with age and physical conditioning [1,2]. Evaluation of beat-to-beat heart rate dynamics, as a result of autonomic nervous system function, is of main interest generally as a higher sympathetic activity unopposed by vagal activity promotes arrhythmia in a variety of ways, such as reducing ventricular refractory period and the ventricular fibrillation threshold, promoting triggered activity afterpotentials and enhancing automaticity. Vagal stimulation opposes these changes and reduces the effects of sympathetic stimulation by prolonging refractoriness, elevating the ventricular fibrillation threshold, and reducing automaticity. Furthermore, the fundamental role of the autonomic nervous system in regulating inflammation, believed to underlie many disease processes, is increasingly being appreciated. Increased sympathetic activity promotes inflammation, and increased vagal activity moderates it [3,4]. Clin. Pract. 2021, 11, 332–336. https://doi.org/10.3390/clinpract11020047 https://www.mdpi.com/journal/clinpract