Management of patients with prosthetic heart valves during non-cardiac surgery.

Non-cardiac surgery in patients with prosthetic heart valves poses the particular hazards of infective endocarditis, increased bleeding risk and the possibility of acute/subacute valve thrombosis or systemic thromboembolism associated with interrupted anticoagulation. Management is complicated by the absence of randomised trials examining peri-operative anticoagulation management. Thromboembolic risk increases substantially when oral anticoagulation is discontinued and valve thrombosis may be inapparent for 1-2 months. This delayed diagnosis makes it difficult to identify the inciting event, either clinically or in experimental trials. Furthermore, the absence of early post-operative events may falsely suggest that peri-operative anticoagulation was safe and adequate. The approach to management therefore remains controversial. Seamless oral anticoagulation is preferred whenever possible and this is safe for a range of minor procedures, including cardiac catheterisation, dental and ophthalmic surgery. Major surgical procedures require withdrawal of oral anticoagulation before surgery to lower the international normalised ratio (INR) to <1.5 and maintained anticoagulation with unfractionated heparin which should be started when the INR is <2.5 in high risk patients and <2.0 in those at lower risk. The evidence to support the safety of low molecular weight heparins in this situation is scanty and despite its widespread promulgation this approach is NOT recommended. Oral anticoagulation is then resumed post-operatively, though therapeutic levels are not achieved for several days. The determination of which patients require prolonged overlap of heparin and oral anticoagulants is difficult. Clinical judgement is required but these regimes are strongly recommended for those at highest risk of thromboembolism. With strict adherence to these guidelines, the incidence of major complications is low.