**1. Introduction**

### **1.1 Post-acute COVID-19 syndrome introduction**

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the pathogen responsible for coronavirus disease 2019 (COVID-19), has caused morbidity and mortality at an unprecedented level worldwide [1]. Scientific interest is progressively shifting from the acute phase toward the subacute and long-term consequences of COVID-19, which can affect many organ systems [2]. As replication-competent

SARS-CoV-2 has not been isolated after 3 weeks, literature defined post-acute COVID-19 syndrome (PACS) as "persistent symptoms and/or delayed or long-term complications of SARS-CoV-2 infection beyond 4 weeks from the onset of symptoms" [3], which can be further divided into two categories:


A large constellation of symptoms has been associated with PACS, of which the most common include fatigue (53.1%), dyspnea (43.4%), joint pain (27.3%), and chest pain (21.7%) [3]. Moreover, more than half of patients experiencing three or more symptoms [7]. Long COVID was the first term used to describe the range of signs and symptoms that can appear suddenly and last for months to years after SARS-CoV-2 infection [8]. The patient community as a whole coined this phrase in the spring of 2020 [9], and others such as post-COVID-19 condition, post-acute sequelae of SARS-CoV-2 infection, and post-COVID syndrome soon followed. Patients-researchers with long COVID, later known as the Patient-Led Research Collaborative, wrote the first article on prolonged symptoms of COVID-19, and long COVID continues to be the term of choice for patients [10]. As a result, the diagnostic criteria and outcomes employed vary greatly. The WHO, the UK National Institute for Health and Care Excellence, and the US Centres for Disease Control and Prevention are just a few organizations that have developed their own terminologies and definitions [11, 12]. It is noteworthy that long COVID is still frequently used by researchers as a fairly general word covering persistent signs and symptoms that remain or emerge after acute SARS-CoV-2 infection for any amount of time, while other names have much more specific definitions [13]. This highlights how, although long COVID is not always caused by viral persistence, it is difficult to determine with precision when acute COVID-19 ends [13]. Moreover, data about the length of long-term viral persistence are limited, a further item leading to lack of concordance between researchers. **Table 1** summarized different terms used to describe post-COVID-19 sequelae.

Since there is a lack of universally accepted diagnostic criteria, the exact epidemiology of PACS is still not known, and the prevalence rates are extremely different between COVID-19 severity, different world area, different pandemic waves or viral variants as well as between different samples. For these reasons, differences in prevalence data of PACS may range from 30 to 90% of patients [3]. **Figure 1** shows different post-COVID-19 nomenclatures and typical postacute COVID-19 symptoms arranged within the shape of SARS-CoV2.

### **1.2 Post-acute COVID-19 syndrome and cardiovascular disease introduction**

The first case of SARS-CoV-2 was discovered on December 31, 2019, in Wuhan, China. In March 2020, the COVID-19 pandemic's epicenter began to shift to Latin America, Europe, and the United States. Cardiac symptoms, such as chest pain, fatigue, shortness of breath, and palpitations, might last for months in some SARS-CoV-2 patients [14]. Myocardial injury and involvement have been seen in both

*Perspective Chapter: Cardiovascular Post-Acute COVID-19 Syndrome – Definition, Clinical... DOI: http://dx.doi.org/10.5772/intechopen.109292*


#### **Table 1.**

*Post-COVID-19 nomenclature.*

symptomatic and asymptomatic individuals [14]. This evidence has been seen in both laboratory and imaging studies, and patients hospitalized for COVID-19 have been shown to have a variety of cardiac testing abnormalities (such as electrocardiographic abnormalities and elevated cardiac biomarkers), as well as a variety of cardiovascular complications (such as myocardial damage, thrombosis, and arrhythmia) [15–18]. The literature is starting to define the specific types of Cardiovascular disease (CVD), such as myocardial injury, arrhythmias, heart failure (HF), vascular dysfunction, and thromboembolic disease, that appear to be a consequence of severe infection. Comorbid CVD has been linked to a more severe course and increased mortality of COVID-19, according to numerous studies [19–22]. A meta-analysis by Figliozzi et al. revealed that having a history of CVD tripled the odds of developing a severe course of COVID-19, which was defined as death, severe COVID-19 infection, hospitalization in an intensive care unit (ICU), use of mechanical ventilation, or disease progression [23]. Congestive HF was discovered as a potential outcome of a COVID-19 as

#### **Figure 1.**

*Different post-COVID-19 nomenclatures and typical post-acute COVID-19 symptoms arranged within the shape of SARS.*

well as a risk factor for a more severe course and greater mortality [24]. Moreover, in comparison with CVD, CV risk factors are linked to a higher probability of a more severe course and a higher mortality. Different studies reported how diabetes mellitus, chronic kidney disease, and hypertension are linked to COVID-19 and PACS [25–28]. However, prognostic factors of COVID-19 severity still represent a scientific challenge, since even subjects with the same genotype and infected by the same virus may show marked difference in disease severity [29].
