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peak anti-Xa levels, monitoring of the trough (pre-dose) anti-Xa level and dose-adjustment to maintain this trough level at >_0.6 IU/mL may be considered based on theoretical grounds, despite limited evidence.5,224,225 The starting dose for LMWH is 1 mg/kg body weight for enoxaparin and 100 IU/kg for dalteparin, twice daily subcutaneously. The dose should be adjusted daily according to peak (or peak and trough) anti-Xa levels and weekly when the target anti-Xa level is achieved.5,224,225 The routine addition of acetylsalicylic acid is not recommended.196,219,222 When UFH is used, after a stable aPTT has been achieved, UFH should be monitored weekly using aPTT, with a prolongation of >_2 times the control. During the second and third trimester, VKAs are the favoured therapy. For details on management see Figures 2–4.

6.5.3.2 Surveillance during pregnancy These high-risk pregnancies should be managed by a pregnancy heart team in an expert centre. The effectiveness of the anticoagulation regimen should be monitored weekly or every 2 weeks depending on the anticoagulation regimen (see Table 7), and clinical follow-up including echocardiography should be performed monthly.

Figure 3 Flowchart on anticoagulation in mechanical valves and low-dose VKA aweeks 6–12 bmonitoring LMWH: - starting dose for LMWH is 1 mg/ kg body weight for enoxaparin and 100 IU/kg for dalteparin, twice daily subcutaneously; -in-hospital daily anti-Xa levels until target, then weekly (I); -target anti-Xa levels: 1.0–1.2 U/ml (mitral and right sided valves) or 0.8–1.2 U/ml (aortic valves) 4–6 hours post-dose (I); -pre-dose anti-Xa levels >0.6 U/ml (IIb). aPTT = activated partial thromboplastic time; INR = international normalized ratio; i.v. = intravenous; LMWH = low molecular weight heparin; LVEF = left ventricular ejection fraction; UFH = unfractionated heparin; VKA = vitamin K antagonist.

Figure 4 Flowchart on anticoagulation in mechanical valves and target international normalized ratio for mechanical prostheses (modified from Baumgartner et al.204). INR = international normalized ratio; LVEF = left ventricular ejection fraction. aMitral or tricuspid valve replacement, previous thrombo-embolism, atrial fibrillation, mitral stenosis of any degree, or LVEF <35%. bCarbomedics, Medtronic Hall, ATS, or Medtronic Open-Pivot, St Jude Medical, On-X, or Sorin Bicarbon. cOther bileaflet valves with insufficient data. dLillehei-Kaster, Omniscience, Starr-Edwards (ball-cage), Bjo ̈rk- Shiley and other tilting-disc valves; any pulmonary valve prosthesis. Downloaded from academic.oup.com/eurheartj/article/39/34/3165/5078465 by guest on 07 October 2026