A new study by researchers from Larkin Community Hospital, Florida-USA has uncovered that heart block is another common cardiovascular occurrence among many COVID-19 patients or those that had been deemed as ‘recovered’ or were even asymptomatic and never knew that they had been infected with the SARS-CoV-2 coronavirus.
The aim of the study was to review various case reports detailing the new onset of heart block in COVID-19 patients and to summarize the clinical course of these patients.
The study team systematically reviewed all reports published and indexed in PubMed, Scopus, and Embase between March 2020 to May 2021, analyzing the relation between the demographics of the patients, pre-existing comorbidities, and the progression of heart block in patients infected with COVID-19.
The COVID-19-Heart Blocks study team identified and included in this study 30 relevant articles describing 49 COVID-19 patients with heart block. Among them, 69.3% (n=34) of patients suffered from at least one comorbidity. 36.73% (n=18) of the patients showed spontaneous resolution of the heart block. Conversely, 63.26% (n=31) of the patients had persistent heart block, out of which 16.33% (n=8) and 42.86% (n=21) were implanted with a temporary and permanent pacemaker respectively. The reported mortality rate was 22.45% (n=11) during hospitalization.
The study findings found that 45.45% (n=5) of the patients who died had complete heart block.
Interestingly 24.49% (n=12) of the patients in the studies the study team reviewed were suspected of having myocarditis. However, none were confirmed with MRI or cardiac biopsy.
The study findings show that heart block is another common cardiovascular occurrence among COVID-19 and Post-COVID patients and in some cases, leads to fatal events.
The study team suggest that additional research is necessary to unearth the mechanism of development of heart block in COVID-19 patients as well as its implications on the clinical course and prognosis.
Importantly doctors must be aware of the importance of monitoring patients hospitalized for COVID-19 for arrhythmias including heart blocks, especially in the presence of comorbidities. Early detection can improve the prognosis of the patient.
The study findings were published on a preprint server and are currently being peer reviewed.
Every day brings about a new discovery about the pathogenesis and clinical manifestations of COVID-19. According to the fast-growing availability of scientific literature on this topic, the heart appears to be one of the elective targets of the virus. It is known that SARS-CoV enters into human cells via Angiotensin-Converting Enzyme 2 (ACE-2) receptors which are found in alveolar epithelial cells and endothelium of arteries and veins.
Multiple hypotheses have been made to explain the mechanism of heart blocks in COVID-19 infection. In autopsy studies, SARS-CoV-2 virus and inflammatory infiltrate have been found in the myocardium, which implies direct viral invasion of the heart. ACE-2 downregulation decreases the action of angiotensin 1–7 leading to increased synthesis of inflammatory mediators like TNFα, CRP, and TGFβ which produces a cytokine storm. TGFβ induces interstitial fibrosis, which damages
cardiac architecture. Troponin elevation and contractility dysfunction occur in the setting of severe hypoxia due to inflammatory damage or hypercoagulability. These phenomena initiated by the virus can occur in parallel with direct viral damage and interact with each other, enhancing their effect 8,42.
In our study, only 24.49% of the patients were suspected of myocarditis. However, none were confirmed with MRI or cardiac biopsy. Kir et al. reported one patient with no evidence of myocardial involvement indicated by normal levels of cardiac enzymes and no findings on ECG, who developed a self-resolving 3rd-degree heart block.
It is postulated that COVID-19 triggered subclinical myocarditis may have given rise to high-degree AV block in this patient 30. The mechanism of heart block in other cases is poorly understood. In our review, all the patients who died after developing heart block were on mechanical ventilation in the intensive care unit.
Deterioration of any pre-existing diseases in the conduction system such as AV node disease, bundle branch blocks, or His-Purkinje system disorder can cause new advanced blocks, leading to poor clinical outcomes 34. Another big role in COVID-19 progression is played by comorbidities and risk factors.
Cardiovascular diseases, hypertension, diabetes mellitus, renal disease, liver disease, cerebrovascular disease, obesity, hyperlipidemia, and smoking history have a crucial impact on disease progression and complications 8. In our review, hypertension and diabetes mellitus were present in the majority of patients who passed away due to heart block during COVID-19 infection. Since many of these risk factors are modifiable, lifestyle changes, early diagnosis, and management of comorbidities must be considered for better outcomes in COVID-19 patients.
Pathophysiological, histological, and imaging data 8,43 indicate that SARS-CoV-2 could induce tissue damage, which would predispose patients to recurrent cardiac issues long-term after discharge. However, the long-term impact of COVID-19 induced heart blocks on late cardiac manifestations are not well studied, thus leading to poor clinical guidance regarding remote cardiac follow-up after discharge.