Lactate dehydrogenase isozymes in human cardiac transplantation.

Lactate dehydrogenase (LDH) isozyme activities have been followed in 17 human cardiac allografts. A pattern of abnormality associated with cardiac rejection during the first month after operation has been determined: (i) LDH-1 activity is greater than LDH-2 activity; (ii) LDH-1 activity is greater than 35 percent of total LDH activity; and (iii) LDH-1 activity is greater than 100 international units. The LDH-1 abnormality helps to meet the need for an index of cardiac rejection during the early weeks after operation when the electro-cardiogram is least reliable.