In pregnant women treated with dose-adjusted LMWH, the dose of LMWH required to maintain an adequate anti-Xa level 4 to 6 hours after admin- istration increases throughout pregnancy.9,15,39,41 16. A randomized clinical trial of dabigatran in non- pregnant patients with mechanical heart valves showed an increased rate of thromboembolic and bleeding complications with dabigatran com- pared with warfarin.45 The safety and effective- ness of anti-Xa direct oral anticoagulants has not been established in patients with mechanical heart valves. Additionally, the safety of anti-Xa direct oral anticoagulants in pregnancy is unknown.30 32 17. Anti-Xa direct oral anticoagulants have not been shown to be safe in patients with mechani- cal heart valves, so they should not be used in pregnancy. 14. SURGICAL CONSIDERATIONS Concomitant surgical procedures may be appropriate at the time of intervention for VHD in the interest of re- ducing periprocedural risk (eg, treatment of significant CAD) or for optimizing long-term outcomes (eg, adding a maze procedure for AF treatment). Consideration may also be given to treating moderate disease in the inter- est of obviating the need for subsequent reoperation for example, treating aortic dilation in the presence of a BAV. This is particularly true when one can anticipate particular difficulty in the conduct of a subsequent re- operation, as may be the case for mitral valve interven- tion after AVR or in a patient with prior mediastinal ir- radiation for whom postoperative adhesions are often severe. The benefits of such concomitant procedures must be balanced against the potential impact on peri- procedural risk due to added complexity. In particular, interventions that add significantly to aortic cross-clamp time may be discouraged in patients with poor LV func- tion or significant pulmonary hypertension. Prolonga- tion of cardiopulmonary bypass time may increase renal injury, particularly among those with preexisting renal dysfunction. 