Recently the important role of clot inhibiting factors has been emphasized in the blood coagulation study. Antithrombin III is the best-known of all clot inhibiting factors and its close relation to arteriosclerotic disorders was clearly demonstrated in our previous paper on serum and plasma antithrombin III levels in patients with sequelae of cerebrovascular diseases. Because of the frequent appearance of biochemical changes in the blood of stroke patients, observation of antithrombin III, one of proteinase inhibitors, is also important in a study on the pathophysiologic status of cerebrovascular attacks complicating hemostatic unbalance. The purpose of this study is to evaluate the significance of serum antithrombin III in acute cerebrovascular stroke by comparing the levels of this factor with the patients' clinical features.
Serum antithrombin III levels were determined by means of the single radial immunodiffusion method in 73 serum specimens of 19 patients with cerebral hemorrhage and 129 specimens of 24 patients with cerebral infarction. The M±SD, 23.5±3.3mg/dl, which was the mean value and standard deviation of serum antithrombin III levels in 82 healthy adults aged 20 to 59 in our previous observation, was adopted as control. Mean values and standard deviations of 5 serum specimens of patients with cerebral hemorrhage and 9 of patients with cerebral infarction on the 1st day of the attacks were 27.5±7.8mg/dl and 26.5±8.5mg/dl, significantly higher than the value of the control. Significantly higher serum antithrombin III levels compared with the control maintained from the 1st day to the 25th day after the attacks, excluding values of hemorrhagic patients on the 7th and 8th day. In patients with cerebral infarction, the levels from the 6th to the 25 day after the attacks were significantly higher than that from the 1st to the 5th day. No difference was found in the types of the diseases. In 150 serum specimens obtained from the 1st to the 7th day, antithrombin III levels were significantly lower in patients with high fever, disturbance of consciousness, and abnormal electrocardiographic findings, than those in patients without these clinical findings. In serum specimens obtained from the 5th to the 7th day after attacks, antithrombin III level of survivals were significantly higher than that of the dead. Serum antithrombin III levels in patients with high FDP levels were higher than those in patients with normal FDP levels. In cerebral infarction serum antithrombin III levels were directly proportional to prothrombin and plasminogen, and were inversely proportional to α1-antitrypsin. From these results, it is supposed that high antithrombin III levels in acute stroke patients are caused by the protective effects on excess thrombus formation occurring primarily in cerebral infarction and secondarily in cerebral hemorrhage. The high levels without difference in the types of the strokes and with the close relation to the outcome of patients indicate its usefulness in the clinical evaluation of a patient's prognosis.
