Abstract
Background:
Many deaths during heat waves stem not just from body overheating, but also to heat stress, which can exacerbate pre-existing medical conditions, leading to fatal outcomes

Aim:
The aim of this study was 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, and to determine whether the histological structure of the myocardium and lungs varies accordingly.

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 HE-stained tissue. All lung samples from the 7 rats exposed to the highest temperatures displayed bronchiolitis and acute bronchitis, along with indications of early bronchopneumonia.

Conclusion:
While some organs exhibit greater tolerance to a 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 tissues intensified with higher temperatures and longer exposure durations to elevated wet-bulb temperatures (WT). However, the progression of morphological alterations in cardiomyocytes did not demonstrate marked significance, likely due to the brief exposure period. This short duration may limit the detection of subcellular changes when using hematoxylin-eosin staining.

Key words: Sudden death; Forensic; Microscopic; Organs; Post-mortem.