Hi Chris,
Thought you may find this information useful.
A ten year study results:
For aortic valve replacement, the target therapeutic range with the lowest complication prevalence is an INR range of 2.2 to 3.5; the optimum range is 2.7 to 2.8.
For mitral valve replacement, the lowest cumulative incidence for thromboembolic and bleeding complications is an INR range of 2.5 to 3.6; the optimum range is 2.9 to 3.1.
Also,
According to the American College of Cardiology/American Heart Association Guidelines for the Management of Patients With Prosthetic Heart Valves1, the following International Normalized Ratios (INR) are recommended for bileaflet valves:
Indication
First 3 months after valve replacement INR 2.5-3.5
3 months after valve replacement:
Aortic Valve Replacement (AVR) 2.0 - 3.0
AVR with risk factors* 2.5 - 3.5
Mitral Valve Replacement 2.5 - 3.5
*Risk factors: Atrial fibrillation, Left Ventricular dysfunction, previous thromboembolism, and hypercoagulable condition.
For complete INR Guidelines, please see the American Heart Association website.
Horstkotte, et al.: Lower intensity anticoagulation therapy results in lower complication rates with the St. Jude Medical prosthesis. J Thorac Cardiovasc Surg 1994;107(4):1136-1145. Summary of this article follows:
This study reviewed data collected from a cohort of 600 patients with a mean age of 50.7 years. Patient follow-up was 100%, averaging 10 years. When the prothrombin times, measured with different thromboplastins, were converted into INRs, four patient groups with different anticoagulation intensities were identified. Review of the incidence of thromboembolic and bleeding complications for each INR-patient group led to recommended target therapeutic ranges. For patients with aortic St. Jude Medical® mechanical valves, the target therapeutic range with the lowest complication rate was an INR of 2.2 to 3.5 (optimum range of 2.7 to 2.8). For patients with mitral St. Jude Medical® mechanical valves, the target INR range was 2.5 to 3.6 (optimum range of 2.9 to 3.1). The authors concluded that the generally recommended INR of 3.0 to 4.5 may be too high for patients with St. Jude Medical® mechanical heart valves.
Because of the unique and rigid follow-up method used in this study, the authors reported thromboembolic and bleeding rates much higher than typically reported, especially for St. Jude Medical® mechanical heart valve patients. The authors caution against comparing their results with those of other series. In spite of the strict follow-up protocol used in the study, more than one-third of all measurements showed that patients were outside their initial INR range. The risk of intracardiac thrombus can vary significantly given patients' underlying morphologic and physiologic conditions, in spite of using the same type of prosthesis. The study confirms the authors' hypothesis that generally recommended INRs between 3.0 and 4.5 or between 3.6 and 4.8 are based on older generation mechanical heart valves and are too high for the improved design and lower thrombogenicity associated with newer models of St. Jude Medical® mechanical heart valves.
