Warfarin reversal: consensus guidelines, on behalf of the Australasian Society of Thrombosis and Haemostasis

To the Editor: The article by Baker et al was a timely review of managing anticoagulation therapy and balancing the risks of thrombosis and bleeding.1 However, in managing anticoagulation therapy before non-cardiac surgery in patients with mechanical cardiac valve prostheses, the suggested 5-day cessation of warfarin therapy, with only subcutaneous heparin cover, is not appropriate. I have had three patients with mechanical bileaflet mitral prostheses develop valve thrombosis while under this protocol, two with a fatal outcome. I have also had one patient with a mechanical bileaflet aortic valve develop a popliteal arterial embolus requiring thrombectomy, despite being treated according to the protocol.

The consequences of valve thrombosis and thromboembolism far outweigh the lesser complications of increased bruising or bleeding associated with non-cardiac surgery. To avoid the potentially devastating complications of valve thromboembolism associated with the routine cessation of warfarin therapy 5 days before surgery, warfarin ought to be continued to maintain an INR (international normalised ratio) of around 2.0, supplemented with subcutaneous heparin. Alternatively, full intravenous heparinisation can be used while ceasing warfarin treatment, and continued postoperatively until the INR is restored to the therapeutic level. Warfarin should never be reversed with vitamin K, except in cases of life-threatening haemorrhage.

Apropos of the therapeutic INR ranges generally recommended for mechanical cardiac valve replacements, the current generation of prostheses does not require the anticoagulation intensity of the older style prostheses.2,3 Lower intensity anticoagulation is sufficient to prevent thromboembolism at decreased risk of haemorrhagic complications.4 My personal practice for patients with bileaflet mechanical prostheses is to maintain an INR of 2.0–2.5 for aortic valves, and 2.5–3.0 for mitral valves. The higher intensity for mitral prostheses relates to potential increased thrombogenicity because of lower leaflet opening pressures, as well as the common association of left atrial dilatation and atrial fibrillation.