Monitoring Oral Anticoagulant Therapy In Patients With Mechanical Heart Valve Replacement

Objective: Purpose of this study was to discuss monitoring method after prosthetic valve replacement and the significance of low intensity of oral anticoagulant therapy, and to define the optimal local intensity of oral anticoagulant therapy.Methods: Patients underwent valve replacement in the first affiliated hospital of Shanxi medical university were involved in this study. Mid-low temperature extracorporeal circulation and myocardial protection were applied. SorinBicarbon valves, Medtronic Hall valves and Beijing GK valves were implanted by interval or continuous sewing. Warfarin therapy began after drainage tubes were removed 24 or 48 hours after operation, with initial dose of 3mg. The dosage was rectified with INR values acquired by interval blood test of thrombin. Anticipated range of INR value was from 1.3 to 2.3, i.e., 1.5 (from 1.3 to 1.8) for AVR patients and 2.0 (from 1.8 to 2.3) for MVR and DVR patients. Cases with abnormal hepatic functions were screened out. All the cases enrolled were followed up by telephone consultation and clinic callback. The curative effect of anticoagulation therapy and complications were analyzed,and then the optimal intensity of oral anticoagulant therapy was defined.Results: 141 patients were involved, in which there were 93 cases with MVR, 13 ones with AVR and 35 ones with DVR. 6 ones died in or after operation soon. 12 cases were screened out for their abnormal hepatic function. Totally 123 patients were followed up by telephone consultation (33cases) and clinic callback (90 cases). The final mean value of INR was 1.90±0.57 totally. It is 1.66±0.58 for AVR and 1.92±0.57 for MVR and DVR. INR values of 86 patients meet the anticipated values. Those of 10 patients were lower and those of 27 patients were higher. The mean dose of warfarin was 2.83±0.77mg/day. No thrombopoiesis, thrombosis or hemorrhage occurred.Conclusions: INR instead of PTR makes intensity of anticoagulation therapy comparable. It rectifies errors owing to reagents of different sensitivities. At low level intensity of anticoagulation therapy, incidences of thrombopoiesis, thrombosis events and hemorrhagic events could be greatly prevented. The optimal intensity of anticoagulation therapy is probably the range of INR 1.60 (from 1.20 to 2.10) for AVR patients and 1.90 (from 1.40 to 2.30) for MVR and DVR patients. Individual variations can be seen from the statistic charts. It is suggested that more study should be done to get more samples. It is also hypothesized that new better monitoring method be found to make anticoagulation therapy safer.