533 MOBITZ TYPE I AND HIGH-DEGREE ATRIO-VENTRICULAR BLOCK AS LATE SEQUELAE OF ASYMPTOMATIC COVID-19 INFECTION: A CASE REPORT
Authors: Celeski Mihail , Biccirè Flavio Giuseppe , Gatto Laura , Ussia Gian Paolo , Grigioni Francesco , Prati Francesco 
Published: December 2022

Abstract

Background
It is now well-acknowledged that patients with overt COVID-19 are at increased risk of a broad range of acute cardiovascular disorders including myocardial infarction, myocarditis, pericarditis, pulmonary embolism, vasculitis and thromboembolic disease. However, long-term cardiac sequelae of COVID-19 are still poorly understood, especially in young asymptomatic patients.

Case summary
A 40 years-old man, with a history of COVID-19 infection 8 weeks earlier, was admitted to the Emergency Department for detection of type 2 atrio-ventricular block (AVB) Mobitz I at 12-lead ECG during regular medical checkup. The patient was asymptomatic and hemodynamically stable (resting blood pressure 125/75 mmHg). An ECG performed 10 weeks earlier showed no conduction abnormalities. At echocardiographic examination, a preserved left ventricular ejection fraction, no abnormal regional wall motion and no valvular abnormalities were found. Routine laboratory tests showed normal values of blood count, electrolytes, thyroid hormones, C-reactive protein and no elevation in high-sensitivity troponin-I levels. Renal function was preserved. A maximal ECG treadmill test was performed using the Bruce protocol that showed no ectopy during exercise, no ST segment changes during exercise or recovery. During the exercise, the patient remained asymptomatic and the AVB disappeared at stage IV and came back at the end of the test. During in-hospital stay, a paroxysmal high-grade AVB was also detected at ECG telemetry monitoring. The electrophysiological study revealed normal HV conduction and intranodal Wenckebach AVB. A cardiac magnetic resonance (CMR) was performed which revealed myocardial edema and septal fibrosis. At the end, the patient underwent a loop recorder implantation and was prescribed 600 mg of ibuprofen twice a day and dexamethasone 1 mg with progressively decreasing doses for a total of 4 weeks. At 3-month follow-up the patient remained asymptomatic and a persistence of type 2 AVB Mobitz I yet no events of high-grade AVB, were recorded at loop recorder monitoring. In addition, the 3-month follow-up CMR showed no signs of edema or fibrosis.

Discussion
Myocardial injury and conduction disorders have been well-described to complicate the acute COVID-19 infection. However, this is the first report of an atrioventricular conduction block as isolated long-term consequence of COVID-19 in asymptomatic patient. The persistence of AVB during follow-up could be probably explained by microscopic affection of conduction system non detectable at CMR imaging. To date, there is no long-term data to suggest whether such isolated conduction abnormalities are temporary or permanent. The decision of implanting a definitive pacemaker should be based on accurate analysis aimed at evaluating the reversible nature of arrhythmia, especially in young patients. In our case, at 3-month follow-up, CMR showed no macroscopic edema/fibrosis of the myocardium and the high grade AVB disappeared. Serious conduction disorders following asymptomatic or mild COVID-19 may occur and a tailored management is advisable.