Cardio-Pulmonary Features of Long COVID: From Molecular and Histopathological Characteristics to Clinical Implications

Long COVID is a persistent post-viral syndrome with the significant involvement of both the cardiovascular and pulmonary systems, often extending well beyond the acute phase of SARS-CoV-2 infection. Emerging evidence has highlighted a spectrum of chronic alterations, including endothelial dysfunction, microvascular inflammation, perivascular fibrosis, and in some cases, the persistence of viral components in the cardiac and pulmonary tissues. At the molecular level, a sustained inflammatory milieu—characterized by elevated pro-inflammatory cytokines such as interleukin 6 (IL-6)—and chronic platelet hyperreactivity contribute to a prothrombotic state. These mechanisms are implicated in microvascular damage, cardiac strain, and impaired gas exchange, correlating with clinical manifestations such as fatigue, dyspnea, chest discomfort, and reduced exercise capacity. In certain patients, especially those who were not hospitalized during the acute phase, cardiac MRI and myocardial biopsy may reveal signs of myocardial inflammation and autonomic dysregulation. These often subclinical cardiovascular alterations underscore the need for improved diagnostic strategies, integrating molecular and histopathological markers during post-COVID evaluations. Recognizing persistent inflammatory and thrombotic activity may inform risk stratification and individualized therapeutic approaches. The interdependence between pulmonary fibrosis and cardiac dysfunction highlights the importance of multidisciplinary care. In this context, molecular and tissue-based diagnostics play a pivotal role in elucidating the long-term cardio-pulmonary sequelae of long COVID and guiding targeted interventions. Early identification and structured follow-up are essential to mitigate the burden of chronic complications in affected individuals.