CHICAGO – An elevated baseline D-dimer level is helpful to women and their physicians in clarifying decision making about oral hormone therapy for troublesome menopausal symptoms, Mary Cushman, MD, said at the American Heart Association scientific sessions.
She was lead investigator in a nested case-control study embedded in the landmark Women’s Health Initiative (WHI), which showed that participants who had a baseline D-dimer greater than 0.54 mg/L – putting them in the top 25% – and were randomized to oral menopausal hormone therapy had a 5-year incidence of venous thromboembolism (VTE) of 6%. That’s 500% higher than in women with a lower D-dimer randomized to placebo.
“The number needed to test for D-dimer in advance of prescribing in order to prevent one VTE over 5 years of hormone therapy was only 33. So this is potentially something in the toolbox you can use in counseling women about oral hormone therapy,” said Dr. Cushman, professor of medicine and pathology and medical director of the thrombosis and hemostasis program at the University of Vermont, Burlington.
The biomarker study included 1,082 WHI participants aged 50-79 years randomized to oral conjugated equine estrogen with or without medroxyprogesterone acetate or to placebo, 215 of whom experienced VTE during a mean 4.1 years of follow-up. Levels of a variety of biomarkers obtained at baseline were assessed in terms of their associated risk of future VTE. The biomarkers included C-reactive protein and procoagulant, anticoagulant, and fibrinolytic factors.
In a logistic regression analysis adjusted for age, race, body mass index, and hysterectomy, the strongest association with VTE was a high D-dimer. That 500% increased risk of VTE with hormone therapy in women with a D-dimer greater than 0.54 mg/L was comparable in magnitude with the risk Dr. Cushman and her coinvestigators previously reported for the combination of factor V Leiden and hormone therapy.
Dr. Cushman and her associates also took a first step towards developing a multibiomarker risk score. They found that WHI participants randomized to hormone therapy who had abnormal baseline values for any three or more of eight biomarkers had a 1,450% greater risk of future VTE than women with zero or one abnormal biomarker who were assigned to placebo. The eight-biomarker panel described in the recently published study comprised D-dimer, factor V Leiden, protein C, total protein S, free protein S, antithrombin, plasmin-antiplasmin complex, and fragment 1.2. However, the investigators indicated the risk score needs further study before it’s ready for adoption in clinical practice (Res Pract Thromb Haemost. 2018 Apr 17;2:310-9).
Dr. Cushman noted that, although the main findings of the WHI have largely resulted in abandonment of menopausal hormone therapy for disease prevention, many women still want to take oral hormone therapy for relief of bothersome menopausal symptoms. She tries to steer them instead to safer nonoral formulations. Transdermal estrogen replacement has no associated risk of VTE and doesn’t activate anticoagulation. Neither does vaginal estradiol.
In offering what she called “the 30,000-foot view of the impact of venous thrombosis on women’s health,” Dr. Cushman noted that VTE is the third-most common vascular disease in the United States, with up to 900,000 cases per year. The lifetime risk in women after age 45 is 8.4%. Half of VTEs are provoked and therefore potentially preventable, with common triggers being surgery, cancer, pregnancy, trauma, and immobilization, especially during travel.
In addition, a retrospective study conducted in the Worcester, Mass., area showed that 1-month mortality after VTE remained static in the 5%-10% range during 1999-2009.
“This is a fatal disease, even though we treat it as an outpatient quite a lot,” Dr. Cushman observed.
Common nonfatal complications of VTE include major bleeding in 5%-10% of cases, a recurrence rate of 5%-10% annually, a 20%-40% of the burdensome and not infrequently disabling condition known as postthrombotic syndrome, and a 3%-4% incidence of chronic thromboembolic pulmonary hypertension. Yet despite the seriousness of VTE, awareness about VTE is poor among both patients and physicians, and appropriate prophylaxis is underutilized, she said.
The key to improved primary prevention of VTE, Dr. Cushman continued, is greater attention to modifiable behavioral risk factors, along with more use of prophylactic medication when needed.
The traditional cardiovascular risk factors, like hypertension, smoking, and hyperlipidemia, aren’t relevant to VTE risk. But obesity and sedentary lifestyle have come to be recognized as important modifiable risk factors. In one study of more than 30,000 Americans, the risk of VTE was shown to be reduced by 40% in individuals who exercised at least four times per week, compared with the physically inactive.
And in an analysis led by Dr. Cushman of nearly 21,000 participants over age 45 years with 12.6 years of follow-up in the Longitudinal Investigation of Thromboembolism Etiology (LITE), the investigators found that greater levels of all body size measures – not just body mass index, but calf circumference, waist-hip ratio, hip circumference, and others – were associated with increased VTE risk. These associations weren’t affected by levels of circulating biomarkers for inflammation or hypercoagulability, suggesting that it’s obesity per se, with its associated adverse impact on blood flow caused by physical factors, that explains the mechanism underlying obesity as a risk factor for VTE (Thromb Res. 2016 Aug;144:127-32).
At the meeting’s opening ceremonies, AHA President Ivor Benjamin, MD, of the Medical College of Wisconsin, Milwaukee, presented Dr. Cushman with the AHA Population Research Prize. She was honored for her “critically acclaimed research utilizing biomarker assessments in population studies to elucidate pathways of disease etiology for the three most common vascular diseases – coronary heart disease, stroke, and venous thromboembolism – as well as their risk factors,” said Dr. Benjamin.
Dr. Cushman reported having no financial conflicts regarding her D-dimer study, which was funded by the National Institutes of Health.