Study objectives: Due to their inherent thrombogenicity, mechanical cardiac valves necessitate lifelong oral anticoagulation. Less intensive oral anticoagulation than recommended earlier might result in a lower incidence of bleeding complications without increasing the embolic hazard significantly.
Design: Comparison of three different intensities of oral anticoagulation in a prospective, randomized multicenter design. Three months after valve replacement, patients were randomly assigned to stratum A, international normalized ratio (INR) 3.0 to 4.5; stratum B, INR 2.5 to 4.0; or stratum C, INR 2.0 to 3.5.
Patients: Data from 2,735 patients following aortic valve replacement (AVR; n = 2,024), mitral valve replacement (MVR; n = 553), and combined AVR and MVR (n = 158) with the St. Jude Medical (SJM) valve (St. Jude Medical; St. Paul, MN) between July 1993 and May 1999 were analyzed, covering a total follow-up period of 6,801 patient-years. All complications were registered prospectively.
Measurements and results: Fifty-one thromboembolic events (TEs) were documented, resulting in a linearized incidence of 0.75 TEs per 100 patient-years, 22 of which were minor (0.32% per patient-year), 10 were moderate (0.15% per patient-year), and 19 were severe (0.28% per patient-year). Thromboembolism following AVR was significantly lower than after MVR (0.53% per patient-year vs 1.64% per patient-year). Patients reported 1,687 bleeding complications (24.8% per patient-year). The vast majority of bleeding complications (n = 1,509; 22.2% per patient-year) were classified as minor, 140 were classified as moderate (2.06% per patient-year), and 38 were classified as severe (0.56% per patient-year). The clinically relevant incidences of moderate and severe TEs and bleeding complications were not significantly different between the three prespecified INR strata.
Conclusions: The intention-to-treat analysis of the results of the German Experience With Low Intensity Anticoagulation study leads to the unexpected result that despite a sophisticated reporting system, the incidence of moderate and severe TE and bleeding complications was comparably low in all INR strata and more or less within the so-called background incidence reported for an age-related "normal" population. This study supports reexamination of the intensity of anticoagulation in patients with the SJM valve.