Researchers at the Complejo Hospitalario Universitario de Albacete have uncovered new evidence explaining why patients infected with SARS-CoV-2 faced an elevated risk of dangerous blood clots during the pandemic’s early waves. According to a study published in Acta Neuropathologica, scientists identified higher levels of free hemoglobin and iron inside the brain thrombi of COVID-19 patients compared to uninfected individuals.
The peer-reviewed investigation, titled “Niveles elevados de hemoglobina libre y hierro en los trombos cerebrales de pacientes con ictus y COVID-19 en la etapa pre-Ómicron,” focuses on ischemic stroke cases from the first wave of the pandemic. By examining microstructural differences in these clots, the medical team aims to clarify the exact biological triggers behind the hypercoagulable state induced by the virus.
Microscopic Analysis of Brain Thrombi in Early COVID-19 Patients
The research team examined 12 brain thrombi retrieved via mechanical thrombectomy procedures from patients who suffered acute ischemic strokes. According to study details provided by the Gerencia de Atención Integrada de Albacete, half of the samples came from individuals testing positive for COVID-19, while the remaining six control samples originated from patients without the viral infection.
Through a multi-disciplinary approach combining molecular, cellular, and structural techniques, the team found that clots from COVID-19 patients harbored elevated quantities of iron and hemoglobin subunits. Authors of the study suggest that red blood cell destruction, combined with local iron accumulation and resulting oxidative stress, creates an environment that could contribute to favor clot formation.
Structural Differences and the Role of Immunothrombosis
Beyond chemical composition, microscopic examination revealed distinct architectural differences in clots formed during SARS-CoV-2 infection. COVID-related thrombi displayed irregular structures, lower overall platelet counts, and a heavy infiltration of macrophages—immune cells tied directly to inflammation.
This distinct cellular makeup points directly toward immunothrombosis, a pathological process where the body’s immune response and its blood-clotting pathways interact. The heightened inflammatory response observed in the tissue samples helps explain the severe cerebrovascular complications frequently documented during the early stages of the pandemic.
Collaborative Research Network and Institutional Support
The project was conceived and designed in Albacete, drawing on experts from Neurology, Pathology, Radiology, and the Research Unit at the Complejo Hospitalario Universitario de Albacete. All participating clinicians belong to the Castilla-La Mancha Health Service (SESCAM) and the Castilla-La Mancha Health Research Institute (IDISCAM).
Financial backing for the project was provided by the RICORS-ICTUS network and research project PI24/00742, supported by the Carlos III Health Institute alongside the European Regional Development Fund.
While publishing in a high-impact journal ranked in the first decile of its category, the authors emphasize that the work remains exploratory due to its small sample size. Future multicenter studies involving larger patient cohorts will be necessary to validate these mechanisms and translate the findings into targeted preventative therapies.
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