While COVID-19 is considered a "respiratory virus", it manifests through the entire body. Cardiovascular complications have been well-documented in acute COVID-19 infection, and recent research is showing that it also causes significant cardiovascular manifestations in the post-acute phase of the disease.
A February 2022 study published in Nature Medicine analyzed medical records from the United States Department of Veteran's Affairs medical system to estimate risks and 1-year burdens on a set of specific cardiovascular outcomes. The researchers found that, "beyond the first 30 days after infection, individuals with COVID-19 are at increased risk of incident cardiovascular disease. These risks and burdens were evident even among individuals who were not hospitalized during the acute phase of the infection and increased in a graded fashion according to the care setting during the acute phase (non-hospitalized, hospitalized and admitted to intensive care)."
The Cardiovascular COVID Registry published in December 2022 in PLOS One a large international retrospective cohort study of nearly 4,500 patients. Data were obtained from electronic records, and clinical follow-up was performed at 1-year. The primary outcome was CV death at 1-year. Secondary outcomes included arterial thrombotic events (ATE), venous thromboembolism (VTE), and serious cardiac arrhythmias. The team found that "at 1-year, patients with COVID-19 experienced an increased risk of all-cause death and adverse CV events, including ATE, VTE, and serious cardiac arrhythmias, but not CV death."
Several histopathological findings have been identified among COVID-19 autopsy cases, including severe peripheral lung tissue damage tissue. The most commonly reported histological pattern of lung injury was diffuse alveolar damage (DAD) with two identifiable stages; an acute stage, and a more organized stage of lung collapse.
According to a meta-analysis of COVID-19 inpatients, 14.8% developed acute respiratory distress syndrome (ARDS). DAD has long been considered the hallmark histologic finding in acute ARDS. Pulmonary fibrosis (PF) subsequent to ARDS is well-recognized and with the relatively high incidence of ARDS in among COVID-19 patients, it is not surprising there is an increase incidence of pulmonary fibrosis.
It is proposed that a subset of patients post-ARDS develop long-lasting symptoms with decreased lung function, a form of progressive interstitial lung disease (ILD). This post-COVID interstitial lung disease (PC-ILD) is not directly correlated to severity of initial COVID-19 infection. Many patients with only moderate acute infection had a higher burden of respiratory symptoms including cough in the long-term follow up compared to those with severe acute infections.
Pulmonary function abnormalities are seen as early as 2 weeks post-discharge of an acute SARS-CoV-2 infection, with decreased inspiratory vital capacity and forced vital capacity. Several studies have shown persistent lung function abnormalities at 3 and 4 months follow-up. Longitudinal follow-up has shown that lung function impairments improve over time. However, even after a year post-COVID-19, a proportion of patients will continue to have lung function impairment, raising the suspicion of long-term pulmonary complications such as the development of PF.
Persistent symptoms, lung function, and radiological abnormalities have been reported post-COVID-19. Several studies have demonstrated the gradual resolution of these findings over time including improvements in lung function impairment and radiological abnormalities. However, approximately 20-25% of these patients continued to exhibit ongoing radiological abnormalities and lung dysfunction at 12 months post-infection.
There remain several unanswered questions regarding PC-ILD. There is little doubt that a cohort of individuals have residual fibrotic changes at 12 months ranging from 1 to 29% in studies, however, pathologically whether that is related to fibrosis promoted by coronavirus itself or sequelae of severe infection and mechanical ventilation remains to be determined.