Dynamic component of internal carotid artery stenosis in patients with cerebrovascular disease: effects of nifedipine.

By means of Doppler spectral analysis, it was shown that internal carotid artery stenosis has a dynamic component that determines the possibility of changes in the area of stenosis under various influences. It was demonstrated that cold pressor test may increase the area of stenosis in some patients for up to 3-5 hours. In such cases, reduction of volume blood flow in the commun carotid artery and decrease of cerebral blood flow in the ipsilateral hemisphere of the stenosis are observed. Such a response was effectively prevented by nifedipine. At the same time, nifedipine can itself change the area of stenosis in some patients examined. In 31 cases it decreased the area by 22.9 +/- 5.9% and in 11 cases it increased it by 26.4 + 7.7%. When the decrease in the area of stenosis was observed, nifedipine enhanced cerebral blood flow. However, it provoked a depression of cerebral blood flow in the patients in whom the area of stenosis was increased. The data obtained disclose one of the reasons of the variability of therapeutic effects of vasodilators in patients with cerebrovascular disorders.

Dose-dependent aspirin hydrolysis and platelet aggregation in patients with atherosclerosis.

In a double blind, randomized trial, the effects of aspirin (1, 5, and 15 mg/kg) were compared with the changes in platelet aggregation at 6 and 24 hours after dosage. It is found that there is a negative correlation between aspirin hydrolysis velocity in blood and capability of aspirin to decrease platelet aggregation with ADP and collagen in patients with atherosclerosis. Relationship between these parameters depends on aspirin dosage. The correlation was more marked for low doses of aspirin. It is suggested that the effect of aspirin in low dosage on platelet aggregation might be ineffective in many patients without control of aspirin hydrolysis velocity in blood.