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Adjusting anticoagulation to prosthesis thrombogenicity and patient risk factors. Recommendations for the Medtronic
E G Butchart1, P A Lewis, J A Bethel
1Department of Cardiac Surgery, University Hospital, Cardiff, Wales, UK.
Insights
For Medtronic Hall valve patients, an International Normalized Ratio (INR) of 3.0 is optimal after mitral valve replacement (MVR), while 2.5 is best after aortic valve replacement (AVR). Stroke risk factors influence these recommendations.
Area of Science:
- Cardiology
- Biomedical Engineering
- Clinical Trials
Background:
- The Medtronic Hall mechanical valve is widely used for heart valve replacement.
- Determining optimal anticoagulation levels is crucial for patient safety and valve function.
- Previous studies have suggested varying anticoagulation targets for mechanical valves.
Purpose of the Study:
- To determine the optimal anticoagulation level (International Normalized Ratio [INR]) for the Medtronic Hall valve.
- To compare event-free survival rates at different INR levels following mitral valve replacement (MVR) and aortic valve replacement (AVR).
Main Methods:
- A retrospective study analyzing 345 MVR and 241 AVR patients with Medtronic Hall valves.
- Patients were stratified into low (mean INR 2.5) and moderate (mean INR 3.0) anticoagulation groups.
- Event-free survival (thrombosis, embolism, bleeding) was calculated over 3 years.
Main Results:
- No valve thrombosis occurred in any group.
- Mitral valve replacement (MVR): Moderate anticoagulation (INR 3.0) showed higher event-free survival (89%) than low (80%) at 3 years.
- Aortic valve replacement (AVR): Low anticoagulation (INR 2.5) demonstrated superior event-free survival (99%) compared to moderate (87%), with fewer embolic and bleeding events.
Conclusions:
- Optimal INR for Medtronic Hall valve is 3.0 after MVR and 2.5 after AVR.
- Stroke risk factors necessitate individualized anticoagulation adjustments.
- Patients without stroke risk factors experienced no embolic events regardless of anticoagulation intensity.
Abstract:
In order to determine optimum anticoagulation levels for the Medtronic Hall valve, the effect of low anticoagulation (mean International Normalized Ratio [INR] 2.5, 1979-1984) and moderate anticoagulation (mean INR 3.0, 1985-1989) was determined in 345 patients (183 low, 162 moderate) undergoing isolated mitral valve replacement (MVR) and 241 patients (91 low, 150 moderate) undergoing isolated aortic valve replacement (AVR). There were no cases of valve thrombosis. Embolic events and bleeding events were graded in severity and multiple decrement event-free survival calculated according to valve site and anticoagulation level: MVR low, MVR moderate, AVR low, and AVR moderate. In the MVR low group, 80% were free of all events and 93% free of serious events at 3 years compared with 89% and 98%, respectively, in the MVR moderate group. The AVR low group experienced a very small incidence of embolic events (one only) and no bleeding events. The AVR moderate group suffered more bleeding and more embolic events and at 3 years only 87% were event-free compared with 99% in the AVR low group. In both AVR groups, all embolic events were associated with one or more known stroke risk factors. Patients under 70, in sinus rhythm who were normotensive and were nonsmokers suffered no embolic events irrespective of their anticoagulation level. We conclude that the optimum INR for the average Medtronic Hall patient is 3.0 after MVR and 2.5 after AVR but some adjustments may be required in relation to stroke risk factor analysis.