A novel method of thrombelastograph analysis aids assessment of antiplatelet therapy in percutaneous coronary intervention.

Abstract

Background A near-patient test of responses to antiplatelet therapy would be of great value in percutaneous coronary intervention (PCI). However, at present, there are no widely accepted tests and varied definitions of “resistance”. Study aim To establish whether (i) a novel modification of thrombelastography (short TEG) can detect individual responses to Aspirin and Clopidogrel in 15 minutes and if so (ii) establish normal ranges of response (iii) test responses in patients with previous stent thrombosis (ST) and (iv) compare results with the VerifyNow system. Methods (A) Thirty volunteers and 85 patients undergoing PCI were recruited. Blood tests were taken before and after loading doses of Aspirin and Clopidogrel and from stable patients on maintenance therapy with either Aspirin or Aspirin & Clopidogrel. (B) Survivors of ST were identified from 3004 PCI patients and matched to patients without ST. Analysis was performed using conventional TEG parameters, the novel short TEG Area under curve at 15 minutes (AUC15) and % clotting inhibition (%CIn) and VerifyNow. Results (i) Short TEG reliably detects effects of both Aspirin and Clopidogrel in 15 minutes. The short TEG %CIn correlates closely with response to treatment calculated by comparison with baseline (R=0.93, p<0.001 for Aspirin and R=0.83, p<0.001 for Clopidogrel). (ii) Short TEG identifies important effects of gender on observed responses and evidence of cross-reactivity between Aspirin and Clopidogrel. (ii) In patients with previous ST there were no differences in responses to Aspirin but greater reactivity whilst on Clopidogrel when assessed with short TEG and VerifyNow. (iv) Short TEG correlated closely with results obtained with VerifyNow. Conclusions This modification has potential value in the rapid identification of patients responding poorly to Aspirin & Clopidogrel and as a bedside tool has potential to reduce risk of adverse clinical outcomes following PCI.