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J Cardiovasc Pharmacol Ther. 2014 Sep;19(5):451-6. doi: 10.1177/1074248414524302. Epub 2014 Mar 6.

Monitoring of anti-Xa in pregnant patients with mechanical prosthetic valves receiving low-molecular-weight heparin: peak or trough levels?

Author information

1
Heart Institute, Kaplan Medical Center, Affiliated to the Hebrew University and Hadassah Medical School, Jerusalem, Israel.
2
Department of Medicine, Division of Cardiovascular Disease, University of Southern California, Los Angeles, CA, USA Department of Obstetrics and Gynecology, University of Southern California, Los Angeles, CA, USA.
3
Department of Medicine, Division of Cardiovascular Disease, University of Southern California, Los Angeles, CA, USA Department of Obstetrics and Gynecology, University of Southern California, Los Angeles, CA, USA elkayam@usc.edu.

Abstract

OBJECTIVES:

We hypothesized that the guideline-recommended peak anti-Xa levels for pregnant women with mechanical prosthetic heart valves (MPHVs) receiving adjusted dose low-molecular-weight heparin (LMWH) are associated with subtherapeutic trough levels and consequently with an inadequate level of anticoagulation.

BACKGROUND:

Low-molecular-weight heparin is often used for anticoagulation in pregnant women including those with MPHV. American College of Cardiology/American Heart Association guidelines recommend monitoring of plasma anti-Xa factor peak levels and adjustment of the dose to achieve peak levels of 0.7 to 1.2 U/mL. In spite of these recommendations, cases of valve thrombosis during pregnancy continue to occur.

METHODS AND RESULTS:

We studied 30 pregnant patients receiving anticoagulation for various indications with adjusted dose LMWH given subcutaneously twice a day which had both trough and peak anti-Xa levels throughout pregnancy for a total of 187 paired determinations. The recommended peak anti-Xa levels (0.7-1.2 U/mL) were obtained in 123 (66%) of the measurements but in 80% of them, the trough levels were found to be subtherapeutic (<0.6 U/mL). Subtherapeutic trough levels were found in 8 (73%) of the 11 measurements with peak levels of 0.7 to 0.79 U/mL, 17 (74%) of the 23 of 0.8 to 0.89 U/mL, 21 (72%) of the 29 of 0.9 to 0.99 U/mL, and 28 (44%) of the 63 of 1.0 to 1.2 U/mL. There were 42 measurements with peak anti-Xa levels >1.2 U/mL and even in these cases, 13 (31%) of the trough levels were found to be subtherapeutic.

CONCLUSIONS:

Anticoagulation with adjusted dose LMWH aimed to achieve guideline-recommended peak levels of anti-Xa for patients with MPHVs is commonly associated with subtherapeutic trough levels. Routine measurement of trough anti-Xa levels is therefore advisable in women with MPHV treated with LMWH during pregnancy to assure adequate level of anticoagulation.

KEYWORDS:

anticoagulation; low-molecular-weight heparin; mechanical prosthetic heart valves; pregnancy

PMID:
24607762
DOI:
10.1177/1074248414524302
[Indexed for MEDLINE]

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