Changes in the plasma kinin system in patients with myocardial infarction.

The levels of kininogen, prekallikrein and kininase activity in the plasma of 54 patients with myocardial infarction were studied. It was demonstrated that in acute myocardial infarction (during the first two days after its onset) the level of kininogen and that of prekallikrein decreased simultaneously. After two weeks of the disease both these parameters returned to the values obtained in healthy controls. No correlation was observed between the degree of fall of kininogen and prekallikrein levels on the one hand, and the extent of myocardial infarction, on the other. Complications of myocardial infarction in the form of shock and pulmonary oedema affected only the level of kininogen which decreased, while they were without effect on prekallikrein. Kininase activity was reduced in all cases of myocardial infarction and did not change for two weeks. It seems likely that the biological activity of kinins in myocardial infarction may rise owing to their inadaequate breakdown by kininase.