Circadian variation of platelet aggregation and blood rheology

Abstract

Many vascular pathologies have been reported to follow a diurnal rhythm (AMI, angina, stroke, sudden cardiac death, pulmonary thromboembolism) with a peak in the early morning. Aim of the study was to evaluate the existence of a diurnal rhythm of platelet aggregability and blood rheology. The study was carried out in 12 subjects; blood withdrawings were performed every 3 hour for 24 hours and in each blood sample platelet aggregation (on PRP and on washed platelets) and haemorheological parameters (blood viscosity, blood filterability, haematocrit and fibrinogen) were measured. Moreover systolic and diastolic blood pressure was recorded by dynamic monitoring. The results show that a circadian rhythm of the above mentioned parameters does exists. Even if our data do not prove a strict correlation between these parameters and the incidence of the vascular pathology, it could be interesting to keep in mind the existence of a temporal parallelism when starting preventive therapy.