Cardiac injury has been reported as an important manifestation of coronavirus disease 2019 (COVID-19) and arrhythmic events are common. Here, we report a case series of severe sinus bradycardia among patients hospitalized in intensive care units (ICU) with COVID-19.

From January to May 2020, 113 patients were admitted in ICU for severe COVID-19. All these patients underwent continuous monitoring of their cardiac rhythm. Ten patients (9%) presented a bradycardia. A 24-hour Holter-ECG was subsequently performed for 7 patients.

Patients had a median age of 63years. Most of them were men and had severe acute respiratory distress syndrome. All episodes were due to sinus bradycardia with a median heart rate of 36 bpm. Bradycardia was sudden for four patients and required brief resuscitation maneuvers for one. Bradycardia was persistent for the six other patients and required transient continuous isoprenaline infusion for three. Patients had normal baseline ECG and echocardiography. A comprehensive review of patient's files ruled out bradycardia due to drug-drug interactions, myocarditis, hyperkalemia, hypoxia or vagal physical stimulation. Two patients had beta-blockers interrupted several days before bradycardia and one patient received Hydroxychloroquine discontinued 21days before bradycardia. On the Holter-ECG, 3 recordings evoked vagal hyperactivity (low mean heart rate and elevated pNN50/RMSSD, Fig. 1, patient A), 3 others cardiac dysautonomia (SDNN<100ms, Fig. 1, patient B). Amongst these 10 patients, five returned home and five died from COVID-19 associated multiple-organ failure. None of them required temporary or permanent cardiac pacing (Fig. 1).

We hypothesized that bradycardia may be due to an autonomic nervous system injury. The parallel course of COVID-19 and bradycardia suggest that these patients do not have intrinsic sinus node disease and that pacemaker implantation should not be recommended.