Low target-INR anticoagulation is safe in selected aortic valve patients with the Medtronic Open Pivot mechanical prosthesis: long-term results of a propensity-matched comparison with standard anticoagulation

OBJECTIVES: To investigate the long-term results of a low international normalized ratio ( INR)-anticoagulation program in selected patients after aortic valve replacement (AVR) with the Medtronic Open Pivot mechanical heart valve (OPMHV). METHODS: From January 1993 to December 2012, 909 OPMHV valves were used for single AVR. Patients with preserved sinus rhythm and left ventricular function (Low-INR, n = 552), were managed to an INR of 1.5-2.5 and compared to patients (Standard-INR, n = 357) treated with standard anticoagulation (INR 2.5-3.5). Long-term outcome was analysed for survival and valve-related events, on propensity score matched pairs of 169 patients/group. RESULTS: Within a follow-up cumulating 3096 patient-years, 10- and 15-year survival was significantly better for Low-INR patients: 79% and 63% vs 63% and 34% (P < 0.001). Multivariate analysis of late mortality identified older age [odds ratio (OR) = 1.05], chronic pulmonary disease (OR = 1.90) and coronary artery disease (OR = 1.57) as patient-related risk factors, and erratic INR (OR= 2.57) as anticoagulation-related factor. The linearized thromboembolic rate was 0.72%/patient-year in Low-INR patients, vs 0.87%/patient-year in Standard-INR patients (P = 0.59), revealing INR variability as sole predictor (OR 3.54, 95% confidence interval (CI) 1.20-10.51, P = 0.022). The linearized bleeding incidence was respectively 0.61%/patient-year and 1.21%/patient-year for Low-INR and Standard-INR patients (P = 0.04), retaining older age (OR 1.06, 95% CI 1.02-1.12, P = 0.009), hypertension (OR 2.06, 95% CI 1.00-4.25, P = 0.05) and erratic INR (OR 9.83, 95% CI 5.21-18.56, P < 0.001) as independent risk factors. CONCLUSIONS: This study demonstrated that application of an anticoagulation regimen, aiming a low INR, individualized to selected aortic OPMHV patients, is safe and effective over more than 20 years, without increasing the thromboembolic complication rate while lowering the haemorrhagic events. However, INR variability remains worrisome because of its deleterious effect on outcome.