Warfarin is used as anticoagulation for children for a wide range of cardiac indications but carries the disadvantage of requiring international normalised ratio monitoring and dose adjustment. Management of warfarin therapy is challenging due to its narrow therapeutic window and is further complicated in children by dietary changes, frequent illnesses, and developing systems of metabolism and haemostasis.

A retrospective review was performed of patients’ medical records to assess the indication for warfarin use, percentage of international normalised ratio values in target range (%ITR), and frequency of phlebotomy.

Twenty-six patients were identified. The most common indication for warfarin use was in patients post-total cavo-pulmonary connection (n = 19, 73%). We demonstrated a variability in duration of warfarin therapy following total cavo-pulmonary connection (median of 11.1 months). Nineteen (73%) patients had used the CoaguChek machine for home measurement of international normalised ratio. The median frequency of phlebotomy for all indications was once every 10 days, and the median %ITR was 55.4 % (29.7–86.4%). Of note, the percentage under target range in the patients with mechanical mitral (n = 2) and aortic valves (n = 1) was found to be 23% and 33%, respectively.

These data demonstrate a high frequency of international normalised ratio values outside of the target range as seen in previous studies of warfarin in children. This necessitates frequent phlebotomy and dose changes, which can have a significant effect on the quality of life of these patients and their families highlighting the need to focus on quality improvement in the area of anticoagulation in paediatric cardiac patients.