Cardiac and aortic lesions in chronic experimental poisoning with mercury vapors

The nature of the toxic influence of mercury and its effect on the cardio-vascular system are not well understood. In chronic poisoning with metallic mercury and its compounds, circulatory disorders have been observed in patients. The problem whether metallic mercury damages the endocardium and myocardium directly or indirectly through vascular changes or vegetative system stimulation remains unsolved. A study was undertaken in which a group of experimental rabbits was exposed to the chronic action of mercury vapors by inhalation and compared with a control group. Before the experiment and towards its end, ECG were taken and 24-hr urinary excretion of mercury was determined in both groups. After 3 months the animals were autopsied, and fragments of myocardium, papillary muscles, endocardium and ascending aorta were taken for histopathologic investigation. In the poisoned animals, the ECG tracings showed bradycardia. Morphologic lesions had the character of thrombosis in small and medium-caliber blood vessels, necrotic foci, thickening of the endocardium of the papillary muscles and perivalvular region and endothelial proliferation with inflammatory foci. The results indicate that, besides influencing the vegetative system, mercury vapor damages the endocardium directly and produces vascular lesions resulting in myocardial changes.