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Risk for CV events lower with oral estradiol vs. equine estrogen
In postmenopausal women using oral hormone therapy, conjugated equine estrogens may increase the risk for CV events such as incident venous thrombosis and, possibly, MI.
A recent population-based, case-control study identified 384 postmenopausal women aged 30 to 79 years who were participants in the Heart and Vascular Health Study and members of the Group Health Cooperative (GHC) in Washington state. Cases identified for evaluation all reported oral hormone therapy use and were observed between 2003 and 2009.
The researchers evaluated 68 venous thrombosis cases, 67 MI cases and 48 ischemic stroke cases, along with 201 matched controls who did not develop incident venous thrombosis, MI or ischemic stroke. All patients had no history of CV events, were on a regimen of oral conjugated equine estrogens (CEEs) or estradiol during assessment, and were not using anticoagulants.
Incident venous thrombosis was the primary study outcome, with incident MI and ischemic stroke defined as secondary outcomes. The researchers evaluated thrombotic potential in controls using the endogenous thrombin potential-based normalized activated protein C (APC) sensitivity ratio (nAPCsr). In February 2005, the preferred formulary estrogen of the GHC was changed from CEEs to oral estradiol. The researchers accounted for this change in the logistic model.
Within the cohort, a current oral CEE regimen was associated with an increased venous thrombosis risk (adjusted OR=2.08; 95% CI, 1.02-4.27) and a nonsignificantly higher MI risk (OR=1.87; 95% CI, 0.91-3.84) compared with oral estradiol use. No association was observed between CEE use and increased ischemic stroke risk. In a subset of 140 controls who underwent phlebotomy, those on a CEE regimen had higher endogenous thrombin potential-based nAPCsr (P<.001), suggesting a greater likelihood of clotting.
The study researchers said these findings must be replicated in future study, but they may be useful for patients and health care professionals when selecting treatments for the management of menopause symptoms.
“The number of avoidable venous and possibly cardiac thrombotic events may be lowered by selecting lower-risk medications,” they wrote.
Disclosure: See the full study for a list of relevant financial disclosures.