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  1. Justin Kinsella,
  2. Oliver Tobin,
  3. Sean Tierney,
  4. Timothy Feeley,
  5. Bridget Egan,
  6. Tara Coughlan,
  7. Ronan Collins,
  8. Desmond O'Neill,
  9. Joseph Harbison,
  10. Dominick McCabe
  1. AMNCH; St James Hospital, Trinity College Dublin


Introduction The relationship between ‘high on-treatment platelet reactivity (HTPR)’ and micro-embolic signals (MES) on transcranial Doppler ultrasound (TCD) has not been comprehensively assessed in carotid stenosis.

Methods This prospective, observational study assessed HTPR and MES in asymptomatic (N=31) versus ‘early symptomatic’ (≤4 weeks after TIA/ischaemic stroke; N=46) and ‘late symptomatic’ (≥3 months; N=35) ≥50% carotid stenosis patients. Longitudinal data from symptomatic patients were analysed. Platelet reactivity ex-vivo was assessed in whole blood with the PFA-100® (collagen-ADP and collagen-epinephrine [C-EPI] closure times). Bilateral, simultaneous MCA TCD classified patients as MES-positive or MES-negative.

Results There were no differences in HTPR prevalence between the overall asymptomatic and symptomatic groups. However, aspirin-HTPR prevalence was lower in ‘late symptomatic post-intervention (N=10)’ than asymptomatic patients (N=22) on aspirin (10% vs. 50% [C-EPI]; P=0.03). HTPR prevalence decreased in symptomatic patients between early and late phases (63% vs. 34%;P=0.017), including those on aspirin monotherapy (N=13; P=0.016). There were no differences in HTPR status in asymptomatic versus symptomatic MES-positive or MES-negative subgroups (p≥0.32).

Discussion Reduction in HTPR prevalence in symptomatic patients over time may reflect successful carotid intervention and/or acute phase response resolution. Larger studies should confirm whether therapeutic intervention(s) may reduce HTPR in symptomatic patients to enhance prevention.

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