Aspirin and Clopidogrel Reactivity in Patients With Critical Limb Ischemia (CLI)
Condition: Critical Limb Ischemia
MeSH terms: Chronic Limb-Threatening Ischemia; Ischemia
Study type: Observational

Summary: 
      Critical Limb Ischemia (CLI) is defined as limb pain that occurs at rest, or impending limb
      loss that is caused by severe compromise of blood flow to the affected extremity. CLI is a
      major cause of death and disability (secondary to myocardial infarction, stroke and
      amputation). The mortality in patients with CLI approaches 25% and 50% at one and five years
      respectively. High on-treatment platelet reactivity (HPR) in patients treated with aspirin
      and clopidogrel (previously referred to as "resistance") is associated with an increased risk
      of recurrent cardiovascular events after percutaneous coronary interventions and acute
      coronary syndromes. The prevalence and significance of High on-treatment Platelet Reactivity
      (HPR) in patients with critical limb ischemia treated with aspirin and/or clopidogrel is not
      known.

      The investigators project aims to investigate the prevalence of HPR (to aspirin and
      clopidogrel) in one hundred patients with diagnosis of critical limb ischemia encountered at
      University of Southern California (USC) affiliated hospitals (Los Angeles County Hospital and
      Keck Hospital of University of Southern California).
    

Detailed description: 
      This prospective clinical study will investigate the prevalence of high on- treatment
      platelet reactivity (HPR) in one hundred patients with critical limb ischemia (CLI), at the
      Keck Hospital of USC and Los Angeles County Medical Center (LAC+USC). Platelet inhibition to
      aspirin will be evaluated with the VerifyNow® aspirin (ASA) test. Clopidogrel platelet
      inhibition will be evaluated with two different tests: the vasodilator-stimulated
      phosphoprotein (VASP) and the VerifyNow® purigenic receptor P2Y12 (VN-P2Y12) assays. All
      platelet function analyses will be performed once after a minimum of one week of
      uninterrupted dual antiplatelet therapy with aspirin and clopidogrel. High on-treatment
      Platelet Reactivity on aspirin treatment (HPRA) group will be defined as aspirin reaction
      units (ARU) ≥550 by the VerifyNow® ASA assay. High on-treatment Platelet Reactivity on
      clopidogrel (HPRC) group will be defined as P2Y12 reaction units (PRU) ≥208 by the VerifyNow®
      assay and Vasodilator-stimulated phosphoprotein-platelet reactivity index (VASP-PRI) ≥50% by
      the vasodilator-stimulated phosphoprotein (VASP) assay. All other patients will be assigned
      to the adequate platelet reactivity on therapy (APR) group. Prevalence of high on-treatment
      platelet reactivity will then be calculated for aspirin and/or clopidogrel
    

Intervention name(s): Blood draw only
Intervention type(s): Other
Intervention description(s): Blood draw only
Observational model: Cohort
Time perspective: Prospective
Sampling method: Probability Sample
Study population: 
        The patient population will include one-hundred patients with a diagnosis of CLI. We will
        only include in the study CLI patients who as part of their standard of care medical
        treatment are receiving dual antiplatelet therapy with aspirin 81 mg and clopidogrel 75 mg
        daily for at least one week.
      
Biospecimen description: 
      Blood Draw
    
Keywords: ASA-PLAVIX Reactivity in CLI