Cohort study shows risk of pulmonary embolism rises with inactivity

Key Points

Over the study period, there were 268 cases (0.4%) of incident idiopathic pulmonary embolism. An association was found between time of sitting and risk of idiopathic pulmonary embolism in the most inactive women compared to the least inactive women. The risk of pulmonary embolism was more than twice that in women who spent the most time sitting compared with those who spent the least time sitting. The investigators controlled for a number of possible influencing factors including age, body mass index, total energy intake, smoking status and smoking pack years, race, spouse's highest educational attainment, parity, menopausal status, non-aspirin nonsteroidal anti-inflammatory drug use, warfarin use, multivitamin supplement use, hypertension, coronary heart disease, rheumatologic disease, physical activity, and dietary patterns.

Source: Kabrhel C, Varraso R, Goldhaber S, et al. Physical inactivity and idiopathic pulmonary embolism in women: Prospective study. BMJ. 2011;342:d3867.

Thromboembolism is a leading cause of maternal morbidity and mortality in high-risk pregnancies. Low-molecular-weight heparin (LMWH) is commonly used to prevent thromboembolism in this population because of its safety and ease of use. With progression of pregnancy, increases occur in maternal weight, renal clearance of LMWH, and the volume of distribution of LMWH, possibly causing the need for adjustments in dosing.

For initial treatment of venous thromboembolism, dosing recommendations are fairly well defined; however, monitoring and recommendations on dose changes are less clear. A recent retrospective, observational, cohort study of 49 women sought to evaluate dosing requirements and monitoring patterns of LMWH when used in high-risk pregnancy at either prophylactic or therapeutic doses.

Investigators monitored patients with antifactor Xa activity, measuring antifactor Xa levels with a target range of 0.4–0.6 U/mL for the prophylactic group, 0.6–1.0 U/mL for the therapeutic group, and 1.0–1.5 U/mL for participants with a mitral valve replacement. Dose changes were required in 9 (69%) of 13 pregnancies in the prophylactic group and 21 (55%) of 38 pregnancies in the therapeutic group to achieve target antifactor Xa activity.

The authors concluded that dose changes for LMWH throughout pregnancy were common. The significant increase in LMWH dose requirements in the prophylactic group suggests that monitoring antifactor Xa activity more frequently may be appropriate in pregnant patients to maintain target anticoagulant levels.

Source: Shapiro NL, Kominiarek MA, Nutescu EA, et al. Dosing and monitoring of low-molecular-weight heparin in high-risk pregnancy: Single-center experience. Pharmacotherapy. 2011;31:678-685.