The objective of this study was to evaluate the safety and efficacy of low-intensity warfarin treatment plus aspirin during the first 6 months after surgery in patients undergoing heart valve substitution with mechanical prostheses. Vitamin K antagonists (VKA) are able to reduce but not eliminate thrombosis and systemic embolism in patients with mechanical heart valves. The intensity of treatment and additional use of aspirin in these patients is still controversial. Consecutive patients undergoing aortic or mitral valve replacement (or a combination of the two) with mechanical prostheses were invited to participate in the study. After stratifying for site of prosthesis, patients were randomized to receive low intensity VKA treatment (target INR 2.5) plus aspirin (100 mg/day) for the first six months (Group A) or standard-intensity (INR target 3.7) VKA treatment (Group B). Mean follow-up was 1.5 years. Principal outcome events were systemic embolism, major bleeding, and vascular death. A total of 94 patients in Group A and 104 in Group B were randomized and followed up for 144 and 163 patient years, respectively. There were 5 (5%) events in Group A (4 major bleeding events and 1 vascular death) and 4 (4%) in group B (2 major bleeding events and 2 ischemic stroke). All the events except 1 occurred within the first 6 months after surgery. Cumulative incidence of primary outcome events was 5.8% (95% CI 0.9 to 10.7) in Group A and 4.3% (95% CI 0.2 to 8.4) in Group B (p=0.6). Low-intensity treatment plus aspirin during the first six months after surgery appears to be as effective and safe as moderate-high-intensity anticoagulation.

In the perioperative management of patients on long-term oral anticoagulant (OAC) therapy the problem is balancing the thromboembolic (TER) and the haemorrhagic risk (HR) in the perioperative period. The Federazione Centri per la diagnosi della trombosi e la Sorveglianza delle terapie Antitrombotiche (FCSA) activated an online registry from November 2001 to August 2003 in order to collect information on the management of these patients in Italy. Four hundred and eleven patients, undergoing elective major (18%) and minor surgery (82%), from 7 centres, were registered. Three hundred and ninety-nine out of 411 patients received LMWH either once a day (310 patients) or twice a day (89 patients) during OAC therapy discontinuation. Two thromboembolic (0.48%) and 16 bleeding events (7 major; 1.7%) were reported. Notwithstanding the lower doses of heparin (54.3 U/kg o.d. and 64.4 U/kg b.i.d.), the thromboembolic complications are in line with those reported in the literature. The data of this study suggest that the intervention with LMWH may be relevant only in the high-risk patients as already proposed by others.

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