Background: At present, the adequacy of anticoagulation at the Out-Patient Department of the Philippine Heart Center for post valve replacement patients is not known. The general objective of this study is to determine a more effective method of anticoagulation titration in patients with prosthetic mechanical heart valve in the Philippine Heart Center. The specific objectives are to determine the outcomes of anticoagulation among patients receiving traditional INR management and nomogram-based INR management, to compare embolic and bleeding outcomes between the two methods of INR management and to determine anticoagulation control in the two methods of INR management.
Method: We randomly allocated post mechanical valve replacement patients who required warfarin either to the traditional or nomogram-based INR management arm. The quality of oral anticoagulant management was evaluated by comparing the proportion of time that the international normalized ratio (INR) of patients receiving warfarin was within the target therapeutic range in both arms. The rates of thromboembolic and major hemorrhagic events were measured.
Results: A total of 62 patients were enrolled with 31 patients randomized to each arm of the study. There were no bleeding or thrombotic complications observed in either study group. The INR of patients in the traditional INR management arm were within range 36.46 ± 27.91 % of the time, while the INR of patients in the nomogram INR management arm were within range 42.55 ± 27.64% of the time (p = 0.391). There was no significance difference in the percentage of time INR values were within range between the traditional INR management arm and nomogram-based INR management arm (p = 0.96) in patients with target ~INR of 2.0-3.0. Among patients with target INR of 2.5-3.5, the percentage of time INR values were within range was higher in the nomogram-based INR management arm (38.48 ± 27.82) than that in the traditional INR management arm (24.11 ± 20.10) as but this difference did not reach statistical significance (p = 0.059). Patients who underwent mitral valve replacement or mitral and aortic valve replacement in the traditional INR management arm had a higher percentage of time INR values were below range (70.67±21.55) than patients in the nomogram-based INR management arm (51.01 ± 29.52) which was statistically significant (p = 0.017.
Conclusion: There was no significant difference in the anticoagulation control as measured by percentage of time INR values were within range between the traditional and nomogram-based INR management arm. However, patients who underwent mitral valve replacement or mitral .and aortic valve replacement in the traditional INR management had a higher percentage of time INR values were below therapeutic range as compared to those who received titration of warfarin based on nomogram.