Strategies for low-molecular-weight heparin management in pregnant women with mechanical prosthetic heart valves: A nationwide survey of Dutch practice.

Background: In this study we investigated current Dutch practice of low molecular weight heparin (LMWH) treatment in pregnant women with mechanical prosthetic heart valves (MPHV) in order to evaluate how management can be optimized. Methods: Between December 2020 and February 2021, we conducted a survey among Dutch congenital cardiologists of tertiary centers in the Netherlands. We collected and analyzed written, unstructured, open questionnaires that were send to all 8 specialized pregnancy heart teams. Results: Response was obtained from all centers (response rate 100%). The preferred LMWHs were nadroparin (62.5%), dalteparin (25%), and enoxaparin (12.5%). After replacing vitamin K antagonist (VKA) with LMWH, 7 centers measured the first anti-Xa level within a week, and 1 center measured anti-Xa levels daily until targeted levels were reached. All centers monitored weekly peak anti-Xa levels (4-6 h post-dose) throughout pregnancy. Four out of 8 centers monitored additional trough (i.e. pre-dose) anti-Xa levels, and 3 of these 4 centers switched to LMWH 3 times daily to achieve target levels when necessary. Conclusions: In Dutch clinical practice, a considerable variation exists in LMWH management for pregnant women with MPHV. In some centers, LMWH was dosed 3 times daily to maintain target anti-Xa levels. Standardizing treatment strategies would allow systematic assessment in prospective studies.