October 7, 2008
View Full PaperIncomplete Inhibition of Thromboxane Biosynthesis by Acetylsalicylic Acid
Key Result
Highest quartile urinary 11-dehydro thromboxane B(2) levels increased the risk of stroke, MI, or CV death versus the lowest quartile in aspirin-treated patients (HR 1.66; 95% CI 1.06-2.61; P=0.03).
Study Design
Type
RCT (n=3,261)
Structured PICO
Does incomplete inhibition of thromboxane biosynthesis (indicated by high urinary 11-dehydro thromboxane B2) increase the risk of cardiovascular events in aspirin-treated patients?
P
Population
3,261 aspirin-treated patients at high atherothrombotic risk enrolled in the CHARISMA trial.
I
Intervention
Highest quartile of baseline urinary 11-dehydro thromboxane B(2) concentrations
C
Comparator
Lowest quartile of baseline urinary 11-dehydro thromboxane B(2) concentrations
O
Outcome
Composite of stroke, myocardial infarction, or cardiovascular deathcomposite
In aspirin-treated patients, elevated urinary 11-dehydro thromboxane B2 levels are associated with an increased risk of cardiovascular events, and this risk is not mitigated by the addition of clopidogrel.
Main Result
Hazard Ratio: 1.66 (95% CI 1.06–2.61)
p-value: p=0.03
Abstract
BACKGROUND: Incomplete inhibition of platelet thromboxane generation, as measured by elevated urinary 11-dehydro thromboxane B(2) concentrations, has been associated with an increased risk of cardiovascular events. We aimed to determine the external validity of this association in aspirin-treated patients enrolled in the Clopidogrel for High Atherothrombotic Risk and Ischemic Stabilization, Management and Avoidance (CHARISMA) trial and to determine whether there are any modifiable factors or interventions that lower urinary 11-dehydro thromboxane B(2) concentrations that could thereby reduce cardiovascular risk. METHODS AND RESULTS: Urinary 11-dehydro thromboxane B(2) concentrations were measured in 3261 aspirin-treated patients at least 1 month after they had been randomly assigned to placebo or clopidogrel. Baseline urinary 11-dehydro thromboxane B(2) concentrations in the highest quartile were associated with an increased risk of stroke, myocardial infarction, or cardiovascular death compared with the lowest quartile (adjusted hazard ratio 1.66, 95% CI 1.06 to 2.61, P=0.03). Increasing age, female sex, history of peripheral artery disease, current smoking, and oral hypoglycemic or angiotensin-converting enzyme inhibitor therapy were independently associated with higher urinary concentrations of 11-dehydro thromboxane B(2), whereas aspirin dose > or =150 mg/d, history of treatment with nonsteroidal antiinflammatory drugs, history of hypercholesterolemia, and statin treatment were associated with lower concentrations. Randomization to clopidogrel (versus placebo) did not reduce the hazard of cardiovascular events in patients in the highest quartile of urinary 11-dehydro thromboxane B(2) levels. CONCLUSIONS: In aspirin-treated patients, urinary concentrations of 11-dehydro thromboxane B(2) are an externally valid and potentially modifiable determinant of stroke, myocardial infarction, or cardiovascular death in patients at risk for atherothrombotic events.