Pulmonary vascular abnormalities in Long COVID: a radiological perspective

Abstract Background Post-COVID-19 condition (Long COVID) has emerged as a major public health challenge, with survivors frequently reporting persistent dyspnea, fatigue, and exercise intolerance. While initial radiological research focused on parenchymal lung disease, a paradigm shift has identified pulmonary vascular abnormalities—specifically endotheliitis, microthrombosis, and maladaptive angiogenesis—as critical drivers of the Long COVID phenotype. Main Body The disease is characterized by “endotheliitis,” where direct viral entry via ACE2 receptors precipitates a pro-coagulant state and the formation of in situ microthrombi. This is further complicated by immunothrombosis involving neutrophil extracellular traps (NETs) and the presence of amyloid-like fibrin microclots that are resistant to natural breakdown. Additionally, structural remodeling through intussusceptive angiogenesis and “vascular pruning” (the loss of distal capillaries) reduces the effective surface area for gas exchange. Conventional CT pulmonary angiography (CTPA) often fails to detect these microvascular changes, despite patients exhibiting severe symptoms. However, advanced modalities provide deeper insights. Dual-energy CT (DECT) reveals persistent, wedge-shaped perfusion defects even in morphologically normal lung parenchyma. Quantitative CT (QCT) allows for the measurement of “vascular pruning,” showing a significant reduction in small vessel volume (PBV5). Hyperpolarized xenon-129 MRI (Hp-XeMRI) has identified a hallmark Red blood cell (RBC):barrier defect, indicating impaired gas transfer from the alveoli to red blood cells—a finding that persists even when standard CT and pulmonary function tests are normal. Functional techniques like V/Q SPECT and phase-resolved functional lung (PREFUL) MRI further confirm a “mottled” perfusion pattern indicative of diffuse small vessel vasculopathy. Short conclusion This review emphasizes that Long COVID involves a distinct vascular phenotype that requires functional and quantitative imaging for accurate diagnosis. Adherence to the 2025 international consensus guidelines—recommending imaging 3 months post-infection and the use of paired inspiratory/expiratory protocols—is essential for standardizing care and differentiating vascular from airway-related symptoms.