Frequent sampling by clear venipuncture in unstable angina is a reliable method to assess haemostatic system activity

Sudden limitations in coronary flow account for the majority of cases of UA. Measurement of TAT in peripheral blood represent a reliable marker of an ongoing thrombotic process. The aim of the study was to assess the reliability of frequent blood sampling (Phase A) and to correlate TAT fluctuation to clinical symptoms of ischemia in patients with UA (Phase B). We included into the study 6 normal volunteers (Phase A) and 31 patients with unstable angina admitted to our Coronary Care Unit within 24 hours from the last ischemic episode (Phase B). In both groups the blood was collected every 6 hours for 24 hours and then every day for 2 days. After venipuncture the blood was immediately collected in CTAD tubes placed in melting ice and centrifuged at 2000 g and 4°C for 20 minutes, plasma aliquots of 500 μl were snap-frozen and stored at −80°C. The aliquots were assayed for TAT complexes using a commercially available ELISA assay. TAT levels in normas remained stable and below pathologic levels during the study and no significant increase was observed with repeated venipuncture. In 11 out of 31 patients (35%) no episode of TAT increase was observed, in 20 (65%) at least 1 episode was observed. Five patients without episodes of TAT increase did not have any ischemic event during the hospitalization, but all patients with episodic elevation had recurrent ischemia during the study (p < 0.005). Our data demonstrate that sampling by clear venipuncture do not cause itself an activation of the haemostatic system and suggest that frequent sampling might be important for better understanding the pathophysiology of UA.