VIENNA — Patients who experienced moderate Covid-19 during the first wave of the pandemic and continued to have post-infectious symptoms for at least 12 months after infection have lung perfusion abnormalities despite normal scans.
During the 2024 international congress of the European Respiratory Society (ERS), the researchers called for continued research in this area in order to understand the underlying mechanism of the observed abnormalities and to find possible therapeutic options for this cohort of patients.
This cohort of patients presented with symptoms that appeared consistent with a pulmonary microangiopathy phenotype Dr. Laura Price
The Dre Laura Priceconsultant pulmonologist at the Royal Brompton Hospital and honorary clinical lecturer at Imperial College London, told Medscape Medical News that this cohort of patients presented with symptoms that appeared to correspond to a pulmonary microangiopathy phenotype.
“Our clinics in the UK and around the world are full of people suffering from long Covid, persistent shortness of breath and fatigue. But it has been difficult to pinpoint why patients still experience these symptoms,” Medscape Medical News Timothy Hinksassociate professor and Wellcome Trust Career Development fellow (Nuffield Department of Medicine, NIHR Oxford Biomedical Research Center senior research fellow), and honorary consultant (Oxford Special Airway Service at Oxford University Hospitals, England), who was not involved in the ‘study.
Exercise intolerance is the predominant symptom
Researchers from Imperial College London recruited 41 patients who had persistent symptoms after Covid-19 infection, such as shortness of breath and fatigue, but normal scans after mild Covid-19 infection that did not. did not require hospitalization. Individuals with pulmonary embolism or interstitial lung disease were excluded. The cohort was mainly composed of women (87.8%) and non-smokers (85%), with an average age of 44.7 years. Patients were evaluated more than 1 year after initial infection.
Exercise intolerance was the predominant symptom, affecting 95.1% of the group. A significant proportion (46.3%) presented with myopericarditis, while a smaller subset (n = 5) presented with dysautonomia. Echocardiography did not reveal pulmonary hypertension. Laboratory tests revealed elevated angiotensin-converting enzyme and antiphospholipid antibodies. “These patients are young, female, non-smokers and in good health. This is not what you would expect to see,” said Dr. Price.
Baseline pulmonary function tests showed preserved spirometry with forced expiratory volume in one second and forced vital capacity greater than 100% of the predicted value. However, diffusing capacity was impaired, with a mean diffusing capacity of the lungs for carbon monoxide (DLCO) of 74.7%. Carbon monoxide transfer coefficient (KCO) and alveolar volume were also slightly reduced. Oxygen saturation was within normal limits.
A ventilation-perfusion mismatch
These abnormalities have been demonstrated by advanced imaging techniques such as dual-energy computed tomography and ventilation-perfusion scintigraphy. These tests revealed a non-segmental, “piecemeal” perfusion abnormality in the upper lungs, suggesting the problem is vascular in origin, Dr. Price said.
Cardiopulmonary exercise testing revealed other abnormalities in 41% of patients. Peak oxygen uptake was slightly reduced, and a significant proportion of patients had a high alveolar-arterial gradient and dead space ventilation during peak exercise, suggesting ventilation-perfusion mismatch.
Over time, a statistically significant improvement in DLCO was observed, from 70.4% to 74.4%, suggesting some degree of recovery of lung function. However, the DLCO values did not return to normal. KCO also improved, from 71.9% to 74.4%, although this change was not statistically significant. Most patients (n=26) were treated with apixaban, which may contribute to the observed improvement in gas transfer parameters, Dr. Price said.
Researchers identified a distinct phenotype of patients with persistent symptoms of post-Covid-19 infection, characterized by abnormal lung perfusion and reduced gas diffusion capacity, even when scans appear normal. The pulmonologist explains that this pulmonary microangiopathy can explain the persistent symptoms. However, questions remain regarding the underlying mechanisms, potential treatments, and long-term outcomes for this patient population.
Causes and treatments remain to be found
Previous studies have suggested that Covid-19 causes endothelial dysfunction, which could affect the small blood vessels in the lungs. Other viral infections, such as HIV, have also been shown to cause endothelial dysfunction. However, researchers do not fully understand how this process takes place in Covid-19 patients.
“It is possible that these patients have experienced inflammation that has damaged the pulmonary vascular endothelium, which predisposes them to either clot formation at a microscopic level or continued inflammation,” Dr. Hinks said.
Some patients (10 out of 41) in the cohort studied by researchers at Imperial College London had Raynaud’s syndrome, which could suggest a physiological link, explains Timothy Hinks. “Raynaud’s disease is a pathology of vascular control or dysregulation, and potentially, there could be a common factor contributing to both shortness of breath and Raynaud’s disease.
He said there is an encouraging signal that these patients are improving over time, but their recovery may be more complex and longer than for other patients. “This cohort will gradually improve. But it raises questions and shows that there is a real physiological deficit in certain people suffering from long Covid.”
Dr. Price encouraged doctors to look beyond conventional diagnostic tools when they encounter a patient whose scan appears normal but is experiencing fatigue and shortness of breath. Not knowing what causes the abnormalities seen in this group of patients makes treatment extremely difficult. “We need more research to understand the treatment implications and long-term impact of these pulmonary vascular abnormalities in patients with long Covid,” concluded Dr. Price.
Drs. Price and Hinks have disclosed no relevant financial relationships.
This article was translated from Medscape.com using several editorial tools, including AI, in the process. The content was reviewed by the editorial staff before publication.
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