Coagulation Counseling

JULY 01, 2008
Anna D. Garrett, PharmD, BCPS, CPP

Dr. Garrett is manager of the Health Education Center, Mission Hospitals, Asheville, North Carolina.


A recent review of all studies using the combination of aspirin and clopidogrel since 1950 is the source of new evidence-based recommendations regarding appropriate indications and length of therapy. The review included all studies that used the drug combination for any indication. Indications that have been studied include coronary artery disease (CAD), atherosclerotic ischemic stroke, and atrial fibrillation. This combination has been beneficial in patients with acute coronary syndrome (ACS) with or without percutaneous coronary intervention (PCI), and in PCI patients without an acute event. A small but significant risk exists for increased bleeding with dual antiplatelet therapy for these indications. When used in patients with a history of atherosclerotic ischemic stroke or for the prevention of cardioembolic stroke in patients with atrial fibrillation, this combination has been shown to increase bleeding, provide no clinical benefit, and increase adverse outcomes.

Evidence exists to support use of aspirin in combination with clopidogrel for patients presenting with all ACS types, as well as for patients presenting with PCI for any indication. The treatment duration varies, but patients who have received stenting should receive at least 1 year of combination therapy. No evidence exists to support this combination for primary prevention of CAD or atherosclerotic ischemic events, secondary prevention of stable CAD, or prevention of cardioembolic stroke in patients with atrial fibrillation.


A review of the medical records of 782 patients taking antidepressants found an increased risk of venous thromboembolism (VTE) in patients who were taking amitriptyline. Case patients were aged 70 or younger with a first-time diagnosis of VTE. Upon finding the association with amitriptyline, the researchers further analyzed the amitriptyline users by indication for the drug, postulating that use of amitriptyline for pain-related indications might signal some type of patient immobility that could contribute to an increased rate of VTE. The highest VTE risk was found in patients who received the drug for depression or other psychiatric illnesses, however. No increase was found in VTE risk associated with any other type of antidepressants.


A review of the medical records of 1691 patients with deep vein thrombosis (DVT) or pulmonary embolus (PE) showed that the 3-year rate of recurrent venous thromboembolism (VTE) did not differ between the 2 groups of patients. The PE patients had a higher risk of death, however, than those with a DVT (35.3% vs 29.6%), and major bleeding increased the risk of recurrence and death in both groups.

Among the 549 patients with a pulmonary embolism, 31 (5.7%) had a recurrence, 75 (13.7%) had recurrent VTE, 82 (14.9%) experienced a major bleeding episode requiring transfusion, and 226 (41.7%) died during the follow-up period. Among 1142 patients who presented with a DVT, 64 (5.6%) had a subsequent PE, 217 (19%) had a recurrent VTE, 146 (12.8%) experienced a major bleeding episode, and 411 (36%) died during the follow-up period.

Compared with the DVT patients, the PE patients were more likely to have been hospitalized within 3 months, to have had surgery, to have been admitted to an intensive care unit, to have had an infection, or to have had congestive heart failure.


The results of a recent study suggest that long-term exposure to particulate air pollution is associated with altered coagulation function and increased risk of deep vein thrombosis (DVT). Particulate air pollution is known to enhance coagulation and arterial thrombosis. The Italian and US authors examined the association between exposure to particulate matter of less than 10 µm in aerodynamic diameter (PM10) with DVT risk in 870 patients and 1210 controls, from the Lombardy region in Italy, who were examined between 1995 and 2005. They estimated exposure to PM10 in the year before DVT diagnosis (cases) or examination (controls) through area-specific mean levels obtained from ambient monitors.

A higher mean PM10 level in the year before the examination was associated with shortened prothrombin time (PT) in DVT cases and controls. Each increase of 10 µg/m3 in PM10 was associated with a 70% increase in DVT risk (odds ratio [OR] 1.70) in models adjusting for clinical and environmental covariates. The association between PM10 level and DVT risk was weaker in women (OR, 1.40), particularly in those using oral contraceptives or hormone therapy (OR, 0.97).