Discussion
Cardiac arrhythmia related to many viral infections including influenza virus,1 Zika virus,2 Epstein–Barr virus,3 human immune-deficiency virus,4 and others have been reported several times.5 A case also exists of a high-degree AV block caused by the H1N1 influenza virus impacting the cardiac conduction system.6 Several types of tachyarrhythmia and bradyarrhythmia have been reported in severe acute respiratory syndrome and Middle East respiratory syndrome outbreaks that occurred before COVID-19.7,8 As a mechanism of cardiac arrhythmia, virus infection can induce myocardial injury, and damage to the conduction system can consequently trigger cardiac arrhythmias.9 In addition, systemic infection, hypoxemia, pre-existing cardiac diseases, comorbidities, and advanced age affect the development of cardiac arrhythmia.
Various tachyarrhythmia and bradyarrhythmia have also been reported in COVID-19 patients.10,11 In a report from China, cardiac arrhythmia was observed in 16.7% and 44.4% of patients hospitalized for COVID-19 and patients admitted to the intensive care unit, respectively.12 In COVID-19 patients, high degree AV block such as complete AV block is rare. However, some cases have been reported.13,14 It is speculated that cardiac arrhythmia may be caused by the aforementioned mechanisms and causes even in COVID-19 patients. So, first, the conduction disturbances due to the injury of the myocardium after COVID-19 infection can be considered. However, in the case of this patient, cardiac enzyme, troponin I (<0.015 ng/mL) was within the normal range at the time of the development of the paroxysmal complete AV block. In addition, it was difficult to clinically find evidence of myocardial injury. Therefore, the possibility of paroxysmal complete AV block due to damage to the conduction system is considered to be relatively low.
Second, the medication used in the patient possibly induce cardiac arrhythmia. In the patient of this study, piperacillin/tazobactam and azithromycin were used as antibiotics when inducing paroxysmal complete AV block. In addition, antiviral agent was not used due to elevated liver enzyme levels. Antimalarial drugs such as chloroquine and hydroxychloroquine have not been used in patients. It is known that piperacillin/tazobactam rarely causes hypokalemia and has the potential to develop Torsade de Pointes (TdP).15 However, evidence concerning the association with AV block is lacking. Azithromycin induces QRS widening and QRS prolongation, and it is known to induce serious ventricular arrhythmia such as TdP.15,16 However, finding a correlation with the complete AV block was difficult.
Third, a mechanical ventilator was used in our patient for the treatment of severe hypoxia and hypercapnia when paroxysmal complete AV block developed. As aforementioned, the PEEP was applied to the patient and a high respiratory rate was maintained for correction of hypoxia and hypercapnia. The application of PEEP has the potential to increase intrathoracic pressure.17 In addition, the high respiratory rate applied simultaneously with PEEP induces dynamic hyperinflation of the lungs.18 Activation of the pulmonary C and J receptor occurs if the lungs are hyperinflated, which can lead to vagal stimulation.19 Moreover, excessive vagal stimulation causes a decrease in heart rate and blocks the conduction of the heart at the AV node. In consideration of this possibility, the PEEP and the tidal volume were reduced from 10 to 8 cmH2O and 340 to 320 ml per inspiration, respectively. Thereafter, paroxysmal complete AV block disappeared. No further occurrences were observed.
Finally, various types of arrhythmia have been reported in the treatment course of COVID-19 patients. However, the relationship between COVID-19 and arrhythmia still lacks objective evidence and an understanding of its mechanism. Paroxysmal complete AV block may also be associated with COVID-19 infection but can be caused by the patient’s conditions, comorbidities, and medications. Therefore, the aforementioned contents should be checked first if complete AV block occurs during the treatment of COVID-19 patients. Moreover, amendments for correctable factors should be made in advance. Temporary cardiac pacing or permanent pacemaker implantation should be considered even after these measures if complete AV block persists or if the patient has severe hemodynamic impairment or severe bradycardia symptoms.