title: Aspirin resistance in Indian patients with coronary artery disease and cardiovascular events.
abstract: BACKGROUND
  Aspirin resistance is a major problem and its incidence and clinical significance in Indian patients with documented coronary artery disease are not known.
  
  
  OBJECTIVE
  We sought to study the incidence of aspirin resistance and its clinical significance in a cohort of Indian patients with coronary heart disease on therapy with aspirin using urinary 11-Dehydrothromboxane B2 levels as a surrogate marker for antiplatelet efficacy.
  
  
  METHODS
  Non randomized single center prospective study in cohort of patients with stable cardiovascular disease on chronic aspirin therapy attending the cardiology outpatient clinic of a tertiary care hospital.
  
  
  METHODS
  Urinary dehydrothromboxane levels were analyzed in a cohort of 63 patients with stable documented coronary artery disease and in 21 healthy volunteers. The cases were followed up prospectively for a median period of 36 (1-53) months. The clinical endpoint was a composite of acute coronary syndrome, stroke, revascularization and death.
  
  
  METHODS
  Comparison of urinary dehydrothromboxane concentration values between various risk factors was done using Mann Whitney U test, a non parametric alternative of independent t test. All statistical analyses were done using SPSS 11.0 (Chicago, USA) software.
  
  
  RESULTS
  The median (range) absolute values of urinary11- dehydrothromboxane B2 levels for the healthy volunteers and cases were 440 (286-2050) pg/ml and 320 (72-2600) pg/ml (P=0.007). The corresponding normalized values were 87.3 (43-143) and 60.8 (16.7-943) ng/mmol of creatinine (P=0.131). Among the various vascular risk factors, patients who were overweight had higher absolute levels of 11- urinary dehydrothomboxane B2 levels (P=0.016). There were significantly more clinical events in patients with absolute urinary 11-dehydrothromboxane B2 levels in the upper two quartiles compared to the lower two quartiles (P=0.04).
  
  
  CONCLUSIONS
  The incidence of aspirin resistance in the cohort of patients with documented heart disease was 38.1%. Patients with elevated absolute urinary dehydrothomboxane levels (>320 pg/ml) on chronic aspirin therapy constitute a high risk subset for recurrent vascular events.
authors.affiliation: Department of Cardiology, Christian Medical College and Hospital, Vellore, India.
authors.forename: V S
authors.initials: VS
authors.lastname: Thomson
authors.forename: B
authors.initials: B
authors.lastname: John
authors.forename: P
authors.initials: P
authors.lastname: George
authors.forename: G
authors.initials: G
authors.lastname: Joseph
authors.forename: J
authors.initials: J
authors.lastname: Jose
mesh_terms: D000328:Adult; D044466:Asian People / Q000706:statistics & numerical data; D001241:Aspirin / Q000494:pharmacology*; D015415:Biomarkers / Q000652:urine; D002318:Cardiovascular Diseases / Q000188:drug therapy* / Q000453:epidemiology; D016022:Case-Control Studies; D015331:Cohort Studies; D003324:Coronary Artery Disease / Q000188:drug therapy* / Q000453:epidemiology; D004351:Drug Resistance; D005260:Female; D006801:Humans; D015994:Incidence; D007194:India / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology*; D011446:Prospective Studies; D012307:Risk Factors; D020521:Stroke / Q000453:epidemiology / Q000517:prevention & control; D013929:Thromboxane B2 / Q000031:analogs & derivatives* / Q000652:urine; D016896:Treatment Outcome
chemical_list: D015415:Biomarkers; D010975:Platelet Aggregation Inhibitors; D013929:Thromboxane B2; C049235:11-dehydro-thromboxane B2; D001241:Aspirin