Hyperthermia-induced sudden death: Morphological insights from the lung and heart in an experimental study of Wistar rats

Background: Many deaths during heat waves stem not only from body overheating but also from heat stress, which can intensify pre-existing medical conditions, leading to fatal outcomes. Aim: This study aimed to investigate whether the intensity of pathological changes in the heart muscle and lung tissue of albino rats exposed to hyperthermia correlates with different water temperatures (WT) and to determine whether the histological structure of the myocardium and lungs varies. Methods: A sample of 21 albino rats was exposed to water temperatures of 37°C, 41°C, and 44°C. Temperature readings were recorded before immersion, immediately after immersion, at the point of reaching hyperthermia, at 20 minutes, and at the time of death. Tissue samples were collected from the dissected rats, fixed in 10% buffered formalin at room temperature, embedded in paraffin, sectioned into 4–5 μm slices, and stained using the hematoxylin-eosin method. Results: The severity of myocardial histopathological alterations increased with both higher temperatures and longer exposure durations WT. However, the progression of morphological alterations in cardiomyocytes was not markedly significant, likely due to the brief exposure time, which limited the visualization of subcellular alterations in Hematoxylin and Eosin staining-stained tissue. All lung samples from the seven rats exposed to the highest temperatures displayed bronchiolitis and acute bronchitis, along with early bronchopneumonia. Conclusion: While some organs exhibit greater tolerance to heat stroke than other organs, most organs show similar alterations characterized by capillary dilation, vascular pathway disruption, and extravasation. The extent of pathological changes in myocardial and lung tissue intensified with higher temperatures and longer exposure durations to elevated WT. However, the progression of morphological alterations in cardiomyocytes did not demonstrate marked significance, likely because of the brief exposure period. This short duration may limit the detection of subcellular changes when using hematoxylin-eosin staining.