The usefulness of the lactate dehydrogenase macroreaction in autopsy practice.

The detection of recent myocardial damage by means of the macroscopic lactate dehydrogenase reaction (LDHr) linked to nicotinamide adenine dinucleotide diaphorase (NADHd), conducted in a liquid medium is greatly insensitive to postmortal autolysis. In 10 heart cones (i.e., cardiac ventricles severed underneath the coronary sulcus) stored at 6 degrees C for up to 114 h after death, no autolytic artifacts appeared on freshly cut apical surfaces of transverse myocardial slices. In 10 cones kept at room temperature for up to 95 h after death, no artifacts appeared in eight cases; in two cases the LDHr was impaired by postmortal bacterial spread and decomposition of the myocardium. Intravital perfusion of injured myocardium increases the sensitivity of the LDHr. Postmortal stand-still of circulation is decisive in preserving dehydrogenase activities in undamaged myocardium. An artificial decrease in enzyme activity always appeared on the nonrecent, basally facing cut surfaces of slices exposed to air and fluid oozing out of the myocardium for long periods, even if the exposed surface of the cone was kept at 6 degrees C and wrapped in plastic. In normal practice, when bodies are stored in a refrigerating unit, the LDHr may still indicate myocardial damage more than 114 h after death.