Clinical Coagulation Laboratory and Oral Anticoagulant Therapy Treatment. Instrumentation and Methodology

Low-Dose Warfarin in Patients with Carbomedics Heart Valve Prostheses

All patients who received a Carbomedics heart valve prosthesis were assessed retrospectively by interview regarding thromboembolic, hemorrhagic, or other valve-related events. In cases of such events, the patient's practitioner or cardiologist was interviewed. Hospital records were reviewed in cases of hospital admission. Included in the study were patients who had isolated replacement of the aortic or mitral valve in whom it was possible to collect all International Normalized Ratio values from discharge through follow-up. There were 148 patients with isolated aortic valve replacement and 56 with isolated mitral valve replacement. Bleeding events were 3 times more frequent than thromboembolic events. Based on our results we will apply an International Normalized Ratio between 2 and 2.5 for patients with a Carbomedics heart valve prosthesis in aortic position and ratios between 2.5 and 3 for those with a mitral valve prosthesis.

Comparison of INR stability between self-monitoring and standard laboratory method: preliminary results of a prospective study in 67 mechanical heart valve patients

INTRODUCTION

Thromboembolic accidents and haemorrhage are the main complications observed during long-term follow-up of mechanical heart valve patients. Several suggestions for improving anticoagulation quality have been made, including international normalised ratio (INR) self-monitoring.

OBJECTIVES

We report the preliminary results of a single-centre, open, randomised study (scheduled population of 200 patients), which compares monthly laboratory monitoring (group A) versus weekly self-monitoring of INR (group B). The primary aim is INR stability improvement within the target range, and the secondary aim is adverse events reduction.

PATIENTS AND METHODS

Between May 2004 and June 2005, 67 patients with an average age of 56.6 years (+/-9.6), were enrolled in the study (group A: 34 patients, group B: 33 patients). The mean follow-up was 47 weeks (+/-11.5). The two groups differed only in the sex ratio (44.1 and 21.2% of women in groups A and B respectively, p=0.0459). Mechanical heart valves were aortic in 73% of patients, mitral in 13.5%, and multiple in 13.5%. Sixty-five patients (97%) were treated with fluindione, the others with acenocoumarol. The intraclass correlation coefficient between the self- and laboratory-monitored INR was 0.75.

RESULTS

The time spent in the INR target range (group A: 53+/-19%, group B: 57+/--19%, p=0.45) and the time spent in the INR therapeutic range, between 2 and 4.5, (group A: 86+/-14%, group B: 91+/-7%, p=0.07) are longer in group B, but not significantly so. For patients outside the range, the absolute mean deviation of INR from the target or therapeutic range (range standardized between 0 and 100) is lower for the self-monitoring group (41.1+/-39.3 and 11.27+/-11.2) than for the control group (62.4+/-72.6 and 39.2+/-52.8). This difference is significant (p=0.0004 and p=0.0005). Eighteen adverse events were reported: 17 haemorrhages, 13 in group A (9 mild, 4 serious) and four in group B (all mild), and one sudden death in group B, two days after the patient's discharge. No thromboembolic events were reported. Six patients (8.8 %), 3 in each group, dropped out of the study.

CONCLUSION

This first study evaluating INR self-monitoring in France shows that this method leads to better stability of the INR within the target range. On the basis of these preliminary data, this appears to be related to a decrease in serious haemorrhages (11.8% serious haemorrhage cases in group A versus 0% in group B, p=0.06, NS).

Monitoring oral anticoagulant therapy by telephone communication

The number of patients who need supervision during oral anticoagulant treatment is growing constantly. We have presently enrolled 156 patients who were referred to our anticoagulant clinic and who were taking sodium warfarin with target International Normalized Ratios (INR) of low (2-3), intermediate (2.5-3.5) and high (3-4) range. Patients performed the tests in laboratories situated in locations at their convenience and received further instructions from a specialist via telephone communication. A total of 8758 prothrombin times (5214, 1947 and 1597 tests for individuals in the low, intermediate and high range, respectively) were performed over the period of 3.16 +/- 2.6 years (range, 6 months-9.5 years) and reported to the specialist. It was found that in the aforementioned three groups of intensity 63.3, 57.0 and 47.7% of the INRs were within the target range, the respective percentages for the expanded (+/- 0.5) target INR being 92.8, 87.8 and 78.5%. The INTERDAY software was used to calculate the number and proportion of days within the target INR range, the respective results being 71.0, 64.0 and 51.6% and 96.2, 93.2, 86.4% for the expanded range. The number and percentage of bleeding and embolic complications' referrals to the emergency room and hospitalizations were similar to those reported for anticoagulant clinics in which patients have to actually pay a personal visit in order to receive instructions. Our study is significant in that it documents that trans-telephonic communication is feasible safe and cost-effective and that the clinical results are at least as good as those obtained by traditional consultation.

Analysis of Warfarin Therapy in Pediatric Patients: A Prospective Cohort Study of 319 Patients

This study details warfarin use in a large pediatric population followed in a central anticoagulation clinic. A prospective, consecutive cohort of nonselected children were studied. Patients were divided into groups by age, target international normalized ratio (INR) range, disease, medications, and vitamin K supplemented enteral nutrition use. Groups were analyzed on multiple aspects of warfarin therapy using multivariate methods. A total of 319 patients received 352 warfarin courses representing 391 treatment years. Age independently influenced all aspects of therapy. When compared with all older children, the ≤1 year of age group required increased warfarin doses, longer overlap with heparin, longer time to achieve target INR ranges, more frequent INR testing and dose adjustments, and fewer INR values in the target range. Although significantly different than children ≤1 year, children 1 to 6 years of age showed the same findings when compared with 7- to 18-year-olds. Fontan patients required 25% decreased dosage as compared with other congenital heart disease patients. Children on corticosteroids had less INRs in the target range and children on phenobarbital/carbamazepine required increased maintenance dosages of warfarin. Also, patients receiving enteral nutrition required increased dosages of warfarin. Serious bleeding occurred in 2 children (0.5% per patient year). Recurrent thromboembolic events (TEs) occurred in 8 children. Two children had recurrences while receiving warfarin (1.3% per patient year). This study outlines the profound effect of age and relative complexity of clinical management of warfarin therapy in children.

Analysis of Warfarin Therapy in Pediatric Patients: A Prospective Cohort Study of 319 Patients

This study details warfarin use in a large pediatric population followed in a central anticoagulation clinic. A prospective, consecutive cohort of nonselected children were studied. Patients were divided into groups by age, target international normalized ratio (INR) range, disease, medications, and vitamin K supplemented enteral nutrition use. Groups were analyzed on multiple aspects of warfarin therapy using multivariate methods. A total of 319 patients received 352 warfarin courses representing 391 treatment years. Age independently influenced all aspects of therapy. When compared with all older children, the ≤1 year of age group required increased warfarin doses, longer overlap with heparin, longer time to achieve target INR ranges, more frequent INR testing and dose adjustments, and fewer INR values in the target range. Although significantly different than children ≤1 year, children 1 to 6 years of age showed the same findings when compared with 7- to 18-year-olds. Fontan patients required 25% decreased dosage as compared with other congenital heart disease patients. Children on corticosteroids had less INRs in the target range and children on phenobarbital/carbamazepine required increased maintenance dosages of warfarin. Also, patients receiving enteral nutrition required increased dosages of warfarin. Serious bleeding occurred in 2 children (0.5% per patient year). Recurrent thromboembolic events (TEs) occurred in 8 children. Two children had recurrences while receiving warfarin (1.3% per patient year). This study outlines the profound effect of age and relative complexity of clinical management of warfarin therapy in children.