Anticoagulation in Patients with the St. Jude Medical Prosthesis

Kim, Chong Whan; Kim, Young Tae

Abstract

Two hundred and nine (41.6%) out of a total consecutive 502 patients who had undergone cardiac valve replacement with the St. Jude Medical valve from August 1984 to December 1995 were studied on the postoperative anticoagulant therapy. They were isolated mitral (MVR n=122), aortic (AVR n=39) and double mitral and aortic valve replacement (DVR n=48), respectively. All patients were placed on life-long oral coumadin treatment to keep the intensities of prothrombin activity within the prospectively set therapeutic target range of the International Normalized Ratios (INRs) between 1.5 and 2.5, which was managed by a single surgeon according to the monthly prothrombin time measurements through the visit to and examination along with continuing education at the out-patient clinic. The anticoagulation follow-up period extended to 1,082.0 patient-years (mean 62.1 months) during a total postoperative follow-up of 1,185.6 patient-years (68.1 months), and the INRs of 10,205 (mean+/-SD 48.8+/-25.1) prothrombin time measurements were available for the analysis. The INR values in the replacement groups as a whole were 2.034+/-0.660 in MVR, 2.010+/-0.600 in AVR and 2.072+/-0.738 in DVR; and the levels of the mean INRs in individual patient were 2.030+/-0.219 in MVR, 1.993+/-0.261 in AVR and 2.054+/-0.264 in DVR, respectively. The INR values, however, varied widely in the replacement group as a whole in distribution, and only 65.6% (6,690 of the total prothrombin time measurements) of INRs were within the therapeutic target range: 65.2% in MVR, 65.9% in AVR and 66.2% in DVR. Variations of INRs in individual patient were similarly broad throughout the follow-up period with the proportions of INRs within the target range of 65.0%+/-11.5% in MVR, of 63.9%+/-18.1% in AVR and of 64.7%+/-15.7% in DVR. In conclusion, patients are likely to be exposed to the high risks of thromboembolism from the inadequate anticoagulant intensities or of bleeding from the excessive anticoagulation sometime during the one-third of the follow-up in spite of strict adherence to the protocol of anticoagulation management. It was suggested strongly that the optimal and safe anticoagulation management should be directed toward minimization of the risky period of these complications in individual patient, and it was also stressed that the clinical reports of valve replacement should be accompanied with the practically achieved results of anticoagulation in detail.