The myocardium of 37 rabbits with a fulminant (Group 1) and acute (Group 2) course of experimental acute pulmonary heart of vascular genesis produced by intravenous administration of thrombin in subcutaneous administration of histamine was studied. The control consisted of 9 hearts of rabbits sacrificed by intravenous novocain injection. Combined methods were used to examine the myocardium, including special staining methods suitable for detection of early cardiomyocyte damage, polarization and electron microscopy, histoenzymological methods, and histostereometry. The volumetric density of focal alterations in comparison of the results between groups both for the heart as a whole and for both its parts was found to be statistically significantly higher than that in the controls. Similar results were obtained in the right to left ventricle ratio. No significant differences in the values compared were found in the controls. The volumetric density of focal lesions reached the maximum values in Group 2 by 24 hours in the right parts. The results indicate that the alterative form of cardiac insufficiency underlies sudden death in acute pulmonary heart of the vascular genesis.