**Abstract**

Although the infection with the severe acute respiratory syndrome (SARS-CoV-2) virus affects primarily the respiratory system, it became evident from the very beginning that the coronavirus disease 2019 (COVID-19) is frequently associated with a large spectrum of cardiovascular involvements such as myocarditis/pericarditis, acute coronary syndrome, arrhythmias, or thromboembolic events, explained by a multitude of pathophysiological mechanisms. Individuals already suffering of significant cardiovascular diseases were more likely to be infected with the virus, had a worse evolution during COVID-19, with further deterioration of their basal condition and increased morbidity and mortality, but significant cardiac dysfunctions were diagnosed even in individuals without a history of heart diseases or being at low risk to develop such a pathology. Cardiovascular complications may occur anytime during the course of COVID-19, persisting even during recovery and, potentially, explaining many of the persisting symptoms included now in terms as subacute or long-COVID-19. It is now well accepted that in COVID-19, the occurrence of cardiovascular impairment represents a significant negative prognostic factor, immensely rising the burden of cardiovascular pathologies.

**Keywords:** COVID-19, inflammation, cytokine storm, myocardial injury, heart failure, thromboembolic events, arrhythmias

### **1. Introduction**

Since the end of 2019, when the first cases were documented in Wuhan (China), the corona virus disease 2019 (COVID-19), a zoonotic infection caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has spread rapidly and rampantly, raising major concerns regarding public health, while applying an unprecedented, continuous strain, on the global medical infrastructure. COVID-19 was officially declared a pandemic by the World Health Organization on 11 March 2020 [1], and since then it has affected over 400 million people worldwide, with a cumulative

mortality rate of under 2% [2] and recent alleviation of clinical outcomes due to the development and widespread implementation of efficient vaccination. Taking into account the extreme polymorphism of clinical presentations, ranging from asymptomatic to severe systemic effects, mainly involving the respiratory and cardiovascular systems, and fatal, rapidly progressing, acute respiratory distress syndrome (ARDS), the containment of transmission, at least in the pre-vaccination era, and the therapeutic management of COVID-19 and its systemic complications, has proven to be quite a challenge for clinicians, especially in the case of high-risk patients [3].

A novel member of the β-coronavirus genus, group 2, the enveloped, positivesense RNA single-stranded SARS-CoV-2, has established itself as the third emerging, highly pathogenic coronavirus, to infect humans and cause a large-scale outbreak since the early 2000s, after severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV) [4]. Even though mortality rates are lower for SARS-CoV2 than for previous related coronavirus outbreaks (>35% for MERS-CoV and > 10% for SARS-CoV), contagiousness is much higher (MERS-CoV and SARS-CoV had only 10000 cumulative cases between them), as transmission is mainly airborne (via respiratory droplets), with multiple alternative mechanisms being reported (aerosols, direct contact with contaminated surfaces, and fecal-oral transmission [4]).

From a genomic viewpoint, SARS-CoV-2 shares ~80% sequence identity with SARS-CoV and ~ 50% with MERS-CoV, encoding 16 nonstructural proteins (that make up the replicase complex), 9 accessory proteins, and 4 structural proteins – spike (S), envelope (E), membrane (M), and nucleocapsid (N). The SARS-CoV-2 life cycle revolves around the envelope S protein. Direct contact between the Spike receptor-binding domain and the innate cellular receptor (angiotensin-converting enzyme 2 – ACE2), if provided adequate cleavage of the viral Spike S1/S2 polybasic cleavage site by host-cell proteolytic enzymes, will ensure Spike activation in endosomes and virus-cell membrane fusion (cell surface and endosomal compartments), allowing viral RNA to be released into the host-cell cytosol. Viral replication ensues, with subsequent expulsion into the intercellular space [4]. In fact, the S gene of SARS-CoV-2 represents the distinguishing genomic feature from SARS-CoV, sharing <75% nucleotide identity [4].

The main tissue tropism of SARS-CoV-2 is pulmonary, targeting high ACE2 expression cells (airway/alveolar epithelial cells, vascular endothelial cells, and alveolar macrophages) [5]. Even so, higher levels of ACE2 messenger RNA expression can be found in many extra-pulmonary tissues as well and nearly undetectable amounts of ACE2 still support viral host-cell entry. Therefore, additional, underappreciated, cell-intrinsic factors must also be involved in host-cell entry [4]. Noteworthy, a subpopulation of human type II alveolar cells has been documented, which manifest abundant ACE2 expression, and concomitant high levels of messenger RNA, specific to certain cellular proviral genes (coding elements of the, SARS-CoV-2 cell entry facilitating, and endosomal transport system) [6]. Also, ACE2 expression regulation must be considered, as, during viral infection, ACE2 gene expression in human airway epithelial cells is upregulated by type I and II interferons [5].

Considering the multitude of the medical literature written on the topic of multisystem impairment occurred during the infection with the SARS-CoV-2 virus, the purpose of our research was to summarize the opinions of experts concerning the cardiovascular alterations associated with COVID-19, and for this aim we reviewed the most significant articles published on PubMed, Medline, and Research gate on these topics and provided individualized summaries of expert opinions.
