Quality Of Anticoagulant Therapy Research Articles

Impact of Quality and Type of Anticoagulant Treatment, and Inflammatory Biomarkers on Quality of Life and Psychological Morbidity in Patients with Atrial Fibrillation: An Exploratory Study

Background: Owing to increasing worldwide life expectancy, the step rise in the prevalence of atrial fibrillation (AF) represents an urgent public health issue. Indeed, AF can severely affect a patient's quality of life (QoL) since it is associated with serious outcomes, such as stroke, cardiac failure, and cognitive impairment/dementia, resulting in increased morbidity and mortality and a burden for health-care systems. Anticoagulation therapy prevents stroke in individuals with AF, whether with vitamin K antagonists (VKA) or direct oral anticoagulants (DOACs). So far, effective AF management is missing since its etiology is unraveled. Within the research project [Cognitive Decline Risk Profiles and Quality of Life in Atrial Fibrillation: A Longitudinal Study- 2022.072(057-DEFI/058-CE)] a pilot study was conducted to assess a dynamic cohort of AF outpatients who attended the anticoagulation clinic at Santo António University Hospital Center, a Portuguese university public hospital. In this study, QoL, distress and cognitive impairment in patients with AF was assessed considering quality and type of anticoagulant treatment. Methods: With a cross-sectional design, quality of anticoagulation therapy was measured calculating Time in Therapeutic Range (TTR) using Rosendaal method for patients under VKA (TTR>70% as good control); for those patients under DOAC, the presence of plasma therapeutic levels of this drug, taking into account the time of blood sampling, meant an anticoagulant treatment of quality. QoL and distress were assessed by the Atrial Fibrillation Effect on Quality-of-life Questionnaire (AFEQT) and the Depression, Anxiety and Stress Scale (DASS-21), respectively. Cognitive impairment was assessed by the Montreal Cognitive Assessment (MoCA) scale. Data on sociodemographic, clinic [medical history including quality and type of anticoagulation therapy, stroke(CHA2DS2-VASc) and bleeding(HAS-BLED) risk scores, duration of illness) and inflammatory biomarkers were also collected. Results: A total of 62 AF patients were included (mean age 74.4±10.2 years, 59.7% women) with a mean CHA2DS2-VASc of 4.3±1.6 and HAS-BLED of 2.6±1.2. Fifty patients (80.6%) were on VKA and twelve (19.4%) on DOACs (all in apixaban). Those individuals under VKA showed a mean TTR score of 77.1 ± 14.7% (67.4% with a good control) and 11 patients in apixaban presented DOAC therapeutic plasma level. Participants had an illness duration average of 16.02 years±10.62. The mean scores of AFEQT was 2.65 ± .93 showing a good QoL and for MoCA was 21.66 ± 3.90 indicating mild cognitive impairment. Regarding anxiety, depression, and stress (DASS-21) the mean scores were 4.27 ± 4.08, 6.52 ± 4.92 and 7.37 ± 5.37, respectively showing non-clinical psychological morbidity. Patients with higher plasmatic levels of C Reactive Protein (CRP) reported more depression (r= .482; p= .005) and those with a longer illness duration presented a higher level of cognitive impairment, (r= -.398; p= .001). No other associations were found between inflammatory biomarkers and psychological variables. There were significant differences according to sex, age, and illness duration, with women reporting lower QoL (p = .002), higher depression (p = .004), higher stress (p = .005) and older patients (p = .017) as well as patients under VKA and longer disease duration reporting better TTR. (p = .007). No differences were found on patients' QoL (p = .342), anxiety (p = .370), depression (p = .167) and stress (p = .117), cognitive impairment, (p = .084) between good and non-good quality of anticoagulant treatment and between VKA versus DOAC therapy (p = .444). Conclusion: The majority of the patients showed good quality of anticoagulation and QoL, but they revealed mild cognitive impairment. Patients' QoL, distress and cognitive impairment were independent of quality and type of anticoagulation treatment. Older AF patients, particularly those with longer diagnosis, should be assessed for cognitive function on a regular basis, preventing dementia and economic burden. The association of depression with higher levels of CRP in AF patients underlines the nature of these two inflammatory conditions that coexisting associate to worse outcomes. Future studies should assess cognitive function over time to unravel the pathophysiology of cognitive decline and the effect of AF treatments on cognition to optimize and personalize AF therapy.

Magnitudes of Risk Factors of Venous Thromboembolism and Quality of Anticoagulant Therapy in Ethiopia: A Systematic Review.

BackgroundVenous thromboembolism is one of the major public health problems in the world. Though several studies were conducted to estimate common risk factors of venous thromboembolism and quality of anticoagulant therapy in Ethiopia, it is difficult to estimate the overall burdens of risk factors and quality of anticoagulant use because of the lack of a nationwide study.ObjectiveTo assess magnitudes of risk factors of venous thromboembolism and quality of anticoagulant therapy in Ethiopia.Materials and MethodsElectronic searching using PubMed, EMBASE, Science Direct, Cochrane Database, Scopus, Hinari, Sci-Hub, African Journals Online Library, and Free-text Web Searches using Google Scholar was conducted from September, 15 to October 27, 2021. Each of the original studies was identified by Mesh terms and Boolean search technique using full title, various keywords and was assessed using the Joanna Briggs Institute Critical Appraisal Checklist. The data were extracted using a format prepared in Microsoft Excel and exported to STATA 14.0 for the outcome analyses.ResultsThe database search delivered a total of 2118 studies. After articles were removed by duplications, titles, reading the abstract, and assessed for eligibility criteria, 12 articles were found suitable for the systematic review. Prolonged immobilization (41.30%) was the most commonly observed risk factor of venous thrombosis followed by acute infection (40.25%). The proportion of therapeutic range (INR = 2–3), sub-therapeutic range (INR <2), and supra-therapeutic range (INR >3) were 32.15%, 47.58%, and 17.62%, respectively. One hundred and thirty-eight patients (11.4%) have developed minor or major bleeding complications.ConclusionProlonged immobilization and acute infection were the main risk factors for venous thromboembolism. The quality of anticoagulant therapy in Ethiopia was poor and bleeding complications were high. A strong effort is needed to improve the quality of anticoagulation and close monitoring of patients’ international normalized ratio is required to improve treatment outcomes.

International Normalized Ratio Test Frequency in Left Ventricular Assist Device Patients Affects Anticoagulation Quality and Adverse Events.

Anticoagulation therapy in patients using left ventricular assist device (LVAD) is essential to reduce hemocompatibility related adverse events (HRAEs). Vitamin K-antagonist dosage must be adapted and monitored by INR point-of-care testing (POCT) in outpatients. The study aims to determine if the frequency of INR POCT in LVAD outpatients has an influence on the quality of anticoagulation therapy (ACQ), HRAEs, and outcomes. This retrospective study included n = 48 patients who received LVAD implantation (HMII, HM3, and HVAD) between 2013 and 2017. ACQ (% of INR tests in range, PTR), outcomes and HRAEs using Kaplan-Meier curves were compared in a daily (n = 36) and 3×/week (n = 12) INR POCT group. Further, based on the achieved PTR ranging from 0-60% (poor), 61-70% (acceptable), and 71-100% (well controlled), HRAEs and outcomes were compared. Daily and 3×/week groups were similar in perioperative risk factors and INR target (p = 0.28). Freedom from any HRAE (38.9% vs. 25.0%, p = 0.44), any readmission (72.2% vs. 75.0%, p = 0.97), and 1 year survival (91.7% vs. 91.7%, p = 0.98) were comparable in both groups. The PTR was significantly higher with the daily self-assessments (73.5% vs. 68.4%, p = 0.006). Well vs. poorly controlled INR POCT patients more often had (p = 0.01) a daily POCT frequency (92%) vs. poorly controlled (54%) and significantly higher freedom from neurologic events (96.0 vs. 69.2%, p = 0.024) as well as hemorrhagic strokes (100% vs. 76.9%, p = 0.011). Well-controlled anticoagulation of LVAD outpatients is associated with less neurologic events. The frequency of INR POCT could be one of the key factors in the reduction of HRAEs, so future prospective, large-scale studies should help to clarify the effects.

Quality of Anticoagulation With Warfarin at a Tertiary Hospital in Botswana.

Warfarin treatment requires regular and proper monitoring to avoid overanticoagulation and at the same time to prevent thromboembolic complications. This study assessed the quality of warfarin anticoagulation at Princess Marina Hospital in Botswana. This cross-sectional study consecutively enrolled patients who were on warfarin for at least 3 months in the outpatient medical clinic. The level of anticoagulation was determined by the time in therapeutic range (TTR) using the Rosendaal method that calculates the percentage of days when the international normalized ratio is in the therapeutic range (2.0-3.0). Poor anticoagulation control was defined as an estimated TTR <65%. We performed univariate and multivariate logistic regression to assess predictors of poor anticoagulation control. Of total, 410 (68.8% women) patients whose median age was 46 (interquartile range [IQR], 35-58) years were enrolled. Indications for warfarin included mechanical heart valves, 185 (45.1%); deep vein thrombosis, 114 (26.8%); and atrial fibrillation, 68 (17.8%). Of the 2004 tests (an average of 4.9 tests per patient) assessed, only 20% of the tests were within the therapeutic range. The median TTR was 30.8% (IQR, 15.2-52.7). Most (85.1%) patients had poor anticoagulation control. Cigarette smoking and pulmonary hypertension perfectly predicted poor anticoagulation. Hypertension was a predictor of poor anticoagulation control (adjusted odds ratio = 2.24; 95% confidence interval: 1.02-4.94). The quality of anticoagulant therapy with warfarin in Botswana patients is poor. The evidence calls for efforts to improve the level of anticoagulation control among patients on warfarin in Botswana.

Evaluation of Quality of Anticoagulation Therapy Among Neurological Patients: An Institutional Based Study

Background: Oral anticoagulation (OAC) is used in neurology practice for primary and secondary stroke prevention in atrial fibrillation (AF), prosthetic mechanical valve; dilated cardiomyopathy (DCMP) and cerebral venous sinus thrombosis (CVST). This study evaluates the quality of oral anticoagulation therapy in neurology patients. Methods: Patients attending neurology service in KPC Medical College and Hospital, Jadavpur, Kolkata, West Benga (India); who were prescribed oral anticoagulant (OAC) were included. The international normalized ratio (INR) values of the patients who were already on OAC were analyzed. The level of anticoagulation, factors interfering with OAC and complications were noted. Results: Total 90 patients were included in study with median age 35±10 years. Ten were excluded as follow up was not done properly. Final study involves 80 patients. Fifty-eight patients received OAC for stroke prevention, 17 for cerebral venous sinus thrombosis (CVST) and 5 for deep vein thrombosis (DVT). Follow up was done for 2 years. Of the total 947 INR reports, 362 were below and 231 were above the therapeutic level. Stable INR was obtained in 36 patients only. INR level was improved by dose adjustment in 25 patients, and dietary adjustment in eight patients. Five patients were sensitive and three were resistant to OAC. Complications were noted in 14 instances. Conclusions: Stable therapeutic INR is difficult to maintain in neurological patients. However, modification of diet, drug and dose of oral anticoagulant may help in stabilization of INR. The findings support the need for educational interventions to improve the knowledge regarding OAT and, thereby, prevention of stroke.

Evaluation of SAMe-TT2R2 score and other clinical factors influencing the quality of anticoagulation therapy in non-valvular atrial fibrillation: a nationwide study in Spain

Objective: To assess the major clinical factors affecting the quality of anticoagulation and evaluate the predictive value of the SAMe-TT2R2 score to identify patients who will achieve a high average time in therapeutic range (T.T.R.) with vitamin K antagonist (V.K.A.) treatment. Research design and methods: This observational, cross-sectional, retrospective and nationwide multicenter study included 1524 patients from the primary care setting with non-valvular atrial fibrillation receiving V.K.A. (≥12 months). We performed a bivariate analysis to identify factors individually associated with the T.T.R. and a multiple regression analysis to identify the independent predictive factors. For the validation of the SAMe-TT2R2 score, the receiver operating characteristic (R.O.C.) curve was calculated and the Hosmer–Lemeshow test was used to test calibration. Results: A total of 94.8% of patients received acenocumarol (4.8% warfarin). A progressive decrease in mean T.T.R. was found when the SAMe-TT2R2 score increased from 0 points (72.1 ± 17.1%) to 4 points (64.1 ± 23.2%), p < 0.001. Other risk scores (CHADS2 and CHA2DS2-VASc, HAS-BLED) were also associated with the mean T.T.R. We found a significant association between low T.T.R. and the following clinical factors: female sex, three or more comorbidities, amiodarone treatment, dietary habits, bleeding history and the intake of ≥7 tablets per day besides V.K.A. (p < 0.01). Regarding SAMe-TT2R2 score validation, the R.O.C. curve showed significant capability, although not high, of discriminating good anticoagulation control (T.T.R. ≥65%) with an area under the curve of 0.562 (95% C.I. 0.533–0.592, p < 0.001) which increased, remaining modest, to 0.594 (95% C.I. 0.564–0.624, p < 0.001) when the factors not included in SAMe-TT2R2 score were added. Conclusion: In this cohort, the SAMe-TT2R2 score had a significant, although modest, ability to assess the likelihood of good international normalized ration (I.N.R.) control, and its predictive value might slightly improve by adding other simple clinical factors. Further research is needed to refine the predictive scales.

Quality of anticoagulation therapy in neurological patients in a tertiary care hospital in north India.

Background & objectives:There is paucity of studies on the quality of anticoagulation in neurological patients from India. This study evaluates the quality of oral anticoagulation therapy in neurology patients.Methods:Consecutive patients attending a tertiary care neurology service in north India who were prescribed oral anticoagulant (OAC), were included. Their international normalized ratio (INR) values were prospectively monitored and the earlier INR values of the patients who were already on OAC were retrospectively analyzed. The patients with multi-organ dysfunction, pregnancy and those below 18 yr of age were excluded. The therapeutic INR range was defined as per standard recommendations. The level of anticoagulation, factors interfering with OAC and complications were noted.Results:The results were based on 77 patients with median age 40 yr. Fifty one patients received OAC for secondary stroke prevention, 23 for cerebral venous sinus thrombosis (CVST) and three for deep vein thrombosis (DVT). A total 167.9 person-years of follow up was done with a median of 1.2 (0.3-9.3) years. Of the 1287 INR reports, 505 (39.3%) reports were in the therapeutic range, 496 (38.5%) were below and 282 (21.91%) were above the therapeutic level. Stable INR was obtained in 33 (42.86%) patients only. INR level was improved by dose adjustment in 20 (26%), drug modification in two (2.6%), and dietary adjustment in six (7.8%) patients. Three patients were sensitive and five were resistant to OAC. Complications were noted in 28 instances; thromboembolic in 16 and haemorrhagic stroke in 12. The overall complication rate was 16.7 per 100 person-years.Interpretation & conclusions:It may be concluded that stable therapeutic INR is difficult to maintain in neurological patients. Optimal modification of diet, drug and dose of oral anticoagulant may help in stabilization of INR.

Evaluation of Time in Therapeutic Range (TTR) in Patients with Non-Valvular Atrial Fibrillation Receiving Treatment with Warfarin in Tehran, Iran: A Cross-Sectional Study.

Anticoagulant control is assessed by Time in Therapeutic Range (TTR). For a given patient, TTR is defined as the duration of time in which the patient's International Normalized Ratio (INR) values were within a desired range. To assess TTR in patients receiving treatment with warfarin for non-valvular atrial fibrillation at a referral center for cardiovascular diseases in Tehran, Iran. Over 6 months, we enrolled eligible patients presenting to Shaheed Rajaie Hospital in Tehran for regular INR testing. Demographic data, medical history, and current medications were determined for all participants. TTR was assessed by the Rosendaal method. A total of 470 patients (mean age 58.0±14.2 years, 60.2% women) underwent 1450 INR measurements. The mean TTR was calculated as 54.9±11.9%. Of the sample patients, 37.3% were in the good control category (TTR > 70%), 24.6% were in the intermediate category (50% < TTR < 70%), and 38.1% were in the poor control category (TTR < 50%). The number of current medications above four was a significant predictor of poor control (OR = 2.06; 95% CI, 1.87, 2.23). The mean TTR of the studied patients (54.9%) was below the good control range. The quality of anticoagulant therapy with warfarin in Iranian patients was poorer than that reported in European countries. Based on these results, research considering the causes of poor TTR among Iranian patients is recommended.

Impact of genetic and clinical factors on dose requirements and quality of anticoagulation therapy in Polish patients receiving acenocoumarol

Despite the recent emergence of new oral anticoagulants, vitamin K antagonists remain the primary therapy in patients with atrial fibrillation and the only therapy licensed for use in patients with artificial heart valves. The aim of this study was (a) to assess the impact of clinical and genetic factors on acenocoumarol (AC) dose requirements and the percentage of time in therapeutic range (%TTR) and (b) to develop pharmacogenetic-guided AC dose calculation algorithm. We included 235 outpatients of the Institute of Cardiology (Warsaw), mean age 69.3, 46.9% women, receiving AC for artificial heart valves and/or atrial fibrillation. A multiple linear-regression analysis was performed using log-transformed effective AC dose as the dependent variable, and combining CYP2C9 and VKORC1 genotyping with other clinical factors as independent predictors. We identified factors that influenced the AC dose: CYP2C9 polymorphisms (P=0.004), VKORC1 polymorphisms (P<0.0001), age (P<0.0001), creatinine clearance lower than 40 ml/min (P=0.035), body mass (P=0.02), and dietary vitamin K intake (P=0.026). Clinical and genetic factors explained 49.0% of AC dose variability. We developed a dosing calculation algorithm that is, to the best of our knowledge, the first one to assess the effect of such clinical factors as creatinine clearance and dietary vitamin K intake on the AC dose. The clinical usefulness of the algorithm was assessed on separate validation group (n=50) with 70% accuracy. Dietary vitamin K intake higher than 200 mcg/day improved international normalized ratio control (%TTR 73.3±17 vs. 67.7±18, respectively, P=0.04). Inclusion of a variety of genetic and clinical factors in the dosing calculation algorithm allows for precise AC dose estimation in most patients and thus improves the efficacy and safety of the therapy.

Implementation and Impact of a Hybrid Pharmacist-Assisted Anticoagulation Clinic Model on the Quality of Anticoagulation Therapy

Implementation and Impact of a Hybrid Pharmacist-Assisted Anticoagulation Clinic Model on the Quality of Anticoagulation Therapy

Evaluation of anticoagulation in patients with antiphospholipid syndrome

The quality of anticoagulation therapy in patients with antiphospholipid syndrome (APS) was evaluated. The high risk of unnecessary anticoagulation and recent changes in the recommended International Normalized Ratio (INR) target range prompted a performance-improvement initiative to improve the care of patients with APS within the University of Iowa Hospitals and Clinics internal medicine and family medicine anticoagulation clinics. Twenty-three patients with an initial diagnosis of APS were evaluated through chart review to determine the anticoagulation indication, occurrence of thromboembolic events, and INR target range. Confirmation of APS diagnosis was made using Sapporo criteria. Recommendations were made to the patients' physicians for confirmatory APS testing and changes in the anticoagulation regimen. INR target ranges were 2.0-3.0, 2.5-3.5, and 2.5-3.0 for 57%, 39%, and 4% of patients, respectively. Only 6 (26%) of the 23 patients met Sapporo criteria for a definite diagnosis of APS. Of the 17 patients (74%) who did not meet these criteria, 8 (47%) had another indication for indefinite anticoagulation. Repeat APS testing was indicated for 7 patients, 5 of whom met Sapporo criteria for APS. A lower target INR range of 2.0-3.0 was determined appropriate for 6 (26%) of the 23 patients evaluated. A majority of patients with an initial diagnosis of APS did not meet criteria for a definite diagnosis of APS. Of those patients, approximately half had another indication for long-term anticoagulation, and one third were receiving warfarin dosages based on an INR target range that was higher than clinically indicated.

Existing Warfarin Therapy in Long-Term Care Facilities Maybe Inadequate.

Despite evidence-based guidelines derived from large clinical trials supporting the use of warfarin for stroke prophylaxis, studies in elderly patients have shown that oral anticoagulants are not used optimally. The risk associated with inappropriate use is compounded by the observation that the elderly are at enhanced risk of thromboembolic complications compared with younger atrial fibrillation patients. All patients with atrial fibrillation who do not have a contraindication to warfarin, and who meet inclusion criteria, should be treated with warfarin to achieve a target International Normalized Range (INR) of 2.5 (range 2.0–3.0). INR levels of 2.0–3.0 have been shown to be relatively safe and more efficacious than lower target INR values in all age groups including the elderly. Patients with INR values below this range remain at increased risk of thrombosis, while those with INR values above the given range are at increased risk of bleeding. The primary objective of this study was to determine the achieved intensity of warfarin therapy in a cohort of patients living at long-term care facility. In such facilities optimal anticoagulation should be achievable, since laboratory monitoring, dose adjustment, and compliance can be achieved. In this study, data were collected on physicians' warfarin prescribing practices as well as INR levels of 108 residents in five long-term care facilities in the Hamilton-Wentworth area over a period of 12 months. In total, 3146 INR values, extending over 28,256 patient-days of monitoring, were analyzed. Indications for warfarin were atrial fibrillation, transient ischemic attack, pulmonary embolus, cardiac valve replacement, myocardial infarction, and deep vein thrombosis. In general, the warfarin dosage was not determined using an established dosing algorithm. Our findings revealed that LTC residents spent approximately 40 percent of the time with INR values below 2.0. We therefore conclude, that the overall quality of anticoagulant therapy in long-term care patients may be inadequate. Our observations suggest that organized dosing algorithms may be of benefit in such settings, however this hypothesis needs to be confirmed in prospective studies. For this purpose we plan to implement a warfarin dosing algorithm in order to determine whether the percentage of time spent within the therapeutic INR range can be improved.

Relation between quality of anticoagulant treatment and the development of the postthrombotic syndrome

About 30% of patients with an episode of adequately treated deep venous thrombosis (DVT) develop the postthrombotic syndrome (PTS) within 2 years. During treatment with vitamin K antagonists (VKA) patients spend only 60% of time between an International Normalized Ratio (INR) of 2.0 and 3.0. We hypothesized that patients who spend a large amount of their time beneath this range will have an increased risk of the PTS. To investigate the relation between the quality of anticoagulant therapy with VKA and the risk of the development of the PTS. The time spent beneath the therapeutic range was calculated for patients with a first episode of DVT, who were treated with VKA for at least 3 months. At follow-up assessments for a maximum of 5 years, presence and severity of signs and symptoms of PTS were recorded. A total of 244 patients, with a median duration of follow-up of 4.9 years were included for analysis. Of these, 81 patients (33%) developed the PTS. The multivariate model showed that patients who spend more than 50% of their time beneath an INR level of 2.0 are at higher risk for PTS [odds ratio (OR): 2.71, 95% CI: 1.44-5.10]. Low quality treatment with VKA, which is a common condition, is related to the occurrence of the PTS in patients with DVT. Strategies aimed at improving the quality of long-term anticoagulation might have the potential to reduce the incidence of this complication.

Self-management of Oral Anticoagulant Therapy for Mechanical Heart Valve Patients

Objective - Self-management of oral anticoagulant therapy (OAT) has shown good results on a short-term basis. We hypothesize that self-management of OAT provides a better quality of treatment than conventional management also on a long-term basis. The aim of this study was to assess the quality of self-management of OAT in patients with mechanical heart valve prostheses on a 4-year perspective in a prospective, non-randomized study. Design - Twenty-four patients with mechanical heart valves and on self-managed OAT were followed for up to 4 years. A matched, retrospectively selected group of conventionally managed heart valve patients (control group) was used as reference. Results -The median observation time was 1175 days (range: 174-1428 days). The self-managed patients were within therapeutic INR target range for a mean of 78.0% (range: 36.1%-93.9%) of the time compared with 61.0% (range 37.4%-2.9%) for the control group. Conclusion - Self-management of OAT is a feasible and safe concept for selected patients with mechanical heart valve prostheses also on a long-term basis. It provides at least as good and most likely better quality of anticoagulant therapy than conventional management assessed by time within the therapeutic International Normalized Ratio (INR) target range.

Thromboembolic and haemorrhagic risk in mechanical and biological aortic prostheses.

Thromboembolism, valve thrombosis and haemorrhagic events have been compared in 356 Starr-Edwards (SE) 1260, 113 Björk-Shiley (BS), and 178 aortic bioprostheses operated upon between 1968 and 1982, and reviewed by the same group with less than 2% of patients lost of follow-up. Expressed in actuarial rate at 7 years the percentage of patients free of thromboembolism event is 87% for SE, 86% for BS, 94% for bioprostheses; the linearized rate is 2.9%/patient/year for SE, 2.2 for BS, 1.9 for bioprostheses (NS). Valve thrombosis was not observed in bioprostheses; 97.9% of patients with mechanical valves were free of valve thrombosis at 6.5 years. Haemorrhagic risk was lower with bioprostheses than with mechanical valves 0.2% patient/year vs 2.33 (P less than 0.005). The most important factor influencing thromboembolic and haemorrhagic risks is the quality of anticoagulant therapy. Other contributing factors are the date of the operation and associated mitral disease.