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.