Synopsis: Aspirin-induced platelet inhibition was measured quantitatively on 468 patients with stable coronary artery disease who take 80-325 mg of aspirin per day. The study found 128 patients were aspirin resistant. Aspirin resistance was more prevalent with increased age, female gender, renal insufficiency, anemia, and with use of low-dose aspirin. At follow up, aspirin-resistant patients were more likely to develop a primary outcome event: cardiovascular deaths, myocardial infarction, stroke, transient ischemic attack, and unstable angina. Aspirin resistance was an independent risk factor for developing the aforementioned outcomes, as are diabetes, prior myocardial infarction, and low hemoglobin.

Bottom line: Aspirin resistance, as defined by an aggregation-based assay, is associated with adverse outcomes in patients with stable coronary artery disease.

Citation: Chen W, Cheng X, Lee PY, et al. Aspirin resistance and adverse clinical events in patients with coronary artery disease. Am J Med. 2007 Jul;120(7):631-635.

Which Agents Best Prevent Venous Thromboembolism?

Background: Pulmonary emboli have been linked to 10% of in-hospital deaths. There continues to be a strong emphasis on prevention. Unfractionated heparin (UFH), low-molecular-weight heparin (LMWH), and selective factor Xa inhibitors are used for prophylaxis.

Study design: A meta-analysis of randomized controlled trials

Synopsis: The meta-analysis included 36 studies of hospitalized medical patients that compared UFH with control, LMWH with control, LMWH with UFH, and a selective factor Xa inhibitor with a placebo.

When each was compared with a control, UFH and LMWH were associated with a decreased risk of deep venous thrombosis (DVT) (risk ratio=0.33; 0.56) and pulmonary embolism (PE) (risk ratio=0.64; 0.37). Compared with control, LMWH three times daily was more effective than twice-daily dosing (risk ratio=0.27, 0.52). Through direct comparison of UFH and LMWH, LMWH was shown to have decreased DVT risk (risk ratio=0.68) and fewer injection site hematomas (risk ratio=0.47).

Neither UFH nor LMWH reduced mortality. LMWH and UFH were associated with significantly more bleeding events than control, but this increased risk was significant only for minor bleeding.

Bottom line: LMWH appears to have greater efficacy than UFH as a prophylactic agent against DVT/PE. If UFH is used, three times daily dosing is preferred.

Citation: Wein L, Wein S, Haas SJ, et al. Pharmacological venous thromboembolism prophylaxis in hospitalized medical patients. Arch Intern Med. 2007;167(14):1476-1486.

What Is the Association Between Antipsychotic Drugs and Mortality?

Background: Atypical antipsychotics prescribed off-label for problematic behaviors in dementia have been associated with risks including diabetes, stroke, and increased mortality. This resulted in the FDA placing a “black box” warning on atypical antipsychotics used for dementia. Subsequent studies have suggested that conventional antipsychotics are perhaps even more problematic.

Study Design: Retrospective cohort study

Synopsis: This trial found a small but significant increase in the risk of death in patients taking an antipsychotic medication.

The adjusted hazard ratio for death with the use of atypical antipsychotics in community dwelling patients with dementia was 1.3 (confidence interval 1.02-1.70). Similar to prior research, the authors found that conventional antipsychotics carried a higher risk than atypical agents.

Patients in long-term care settings also suffered increased risk compared with community dwelling patients. Interestingly, the increased risk of death was apparent after as little as a month of treatment.

As with all retrospective observational cohort trials, there remains the risk that an unanticipated confounding factor could skew the data and create a false association. However, the findings of this research support prior concerns that antipsychotics carry risk of increased mortality. This research bolsters the argument that these agents should not be used lightly or without full discussion of risks and benefits with the patient and/or proxy.