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A comparison between six- and four-week intervals in surveillance of oral anticoagulant treatment
Vittorio Pengo1, Fabio Barbero, Alessandra Biasiolo
1Clinical Cardiology, Thrombosis Center, University of Padova School of Medicine, Ex Busonera Hospital, via Gattamelata 64, I-35128 Padova, Italy.
Insights
Extending the interval for international normalized ratio (INR) monitoring to 6 weeks for patients with prosthetic heart valves does not increase biologic risk. This change in monitoring frequency for oral anticoagulation therapy may offer benefits without compromising safety.
Area of Science:
- Cardiology
- Pharmacology
- Clinical Medicine
Background:
- Oral anticoagulation therapy is crucial for patients with prosthetic mechanical heart valves.
- Regular monitoring of international normalized ratio (INR) is essential to prevent thromboembolic and hemorrhagic complications.
- Current guidelines often recommend INR monitoring every 4 weeks for stable patients.
Purpose of the Study:
- To evaluate if extending INR monitoring to 6 weeks is safe and effective for patients on stable oral anticoagulation with prosthetic heart valves.
- To determine if a 6-week monitoring interval impacts the biologic risk of over- or underanticoagulation.
- To assess potential cost reductions associated with less frequent INR monitoring.
Main Methods:
- A randomized controlled trial involving 124 patients with prosthetic mechanical heart valves on stable oral anticoagulation.
- Patients were randomized to either a 6-week (group 1, n=59) or 4-week (group 2, n=65) maximum interval for INR determinations.
- The primary endpoint was the rate of INR values at risk (<1.5 or >5) over a 2-year follow-up period.
Main Results:
- The rates of INR values at risk were similar between the 6-week (3.27%) and 4-week (3.09%) monitoring groups (P = .81).
- No significant difference was observed in the time spent within therapeutic INR ranges between the two groups.
- The mean time between INR measurements was significantly longer in the 6-week group (24.9 days) compared to the 4-week group (22.5 days).
Conclusions:
- A 6-week interval for INR monitoring is safe for stable patients with prosthetic heart valves, as it does not increase the biologic risk of thromboembolic or hemorrhagic events.
- This extended monitoring interval can be safely implemented in anticoagulation clinics.
- The findings suggest that less frequent INR monitoring may be feasible for select patient populations, potentially reducing healthcare costs.
Abstract:
We determined whether international normalized ratio (INR) monitoring at 6 weeks rather than 4 weeks would benefit patients and reduce costs. Patients receiving stable oral anticoagulation treatment (target INR, 3.0) with a prosthetic mechanical heart valve for more than 6 months were randomized for a maximum interval between INR determinations of 6 weeks (group 1, n = 59) or 4 weeks (group 2 [control], n = 65). Patients were followed up for 2 years. The primary end point of the study was the biologic risk of overanticoagulation or underanticoagulation, estimated as the rate of values at risk (INR, < 1.5 and > 5). The rates of INR values at risk for hemorrhagic (INR, > 5) or thromboembolic (INR, < 1.5) complications were 3.27% in group 1 and 3.09% in group 2 (P = .81). The INRs of patients in group 1 trended toward higher values, but no difference between groups was observed in time spent at various INR ranges by using the method of linear change. The mean time between INR determinations was 24.9 +/- 18.1 days (1.20 per month) in group 1 and 22.5 +/- 9.5 days (1.33 per month) in group 2 (P < .0003). For patients in stable condition with a prosthetic heart valve who are monitored at an anticoagulation clinic, a 6-week interval between INR determinations does not increase the biologic risk of thromboembolic or hemorrhagic events.
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