Limitations
This study has several limitations. The observational design did not allow for control of several important variables, in particular the heparin dose received, which was at physician discretion. In the protocol guided arm, there was operator adherence to the proposed bolus in those on pre-procedure DOAC. However, in the protocol guided arm the average bolus dose administered in those who received pre-procedure warfarin and no anticoagulant were greater than the protocol recommended bolus dose. There was an absolute increase of 17% in the proportion of heparin given prior to transseptal puncture in the protocol guided cohort, and an absolute decrease of 17% in the proportion of heparin bolus which were split before and after transseptal puncture. The change in bolus modality and timing may have been an additional effect of the protocol on physician practice, and certainly affected the reduction in time from transseptal to therapeutic ACT. However, a reduction in time to therapeutic ACT persisted when measured from time of heparin administration Anticoagulant therapy and dosing was prescribed at the operator’s discretion, and not prospectively assigned, possibly introducing selection bias. Additionally, there is assumption that patients were adherent to preoperative instructions for managing their anticoagulant therapy. Finally, the ACT machine did not provide an absolute value for values over 400, rather a truncated value.