Anticoagulants for preventing stroke in patients with nonrheumatic atrial fibrillation and a history of stroke or transient ischemic attacks

Oral anticoagulants for preventing stroke in patients with non-valvular atrial fibrillation and no previous history of stroke or transient ischemic attacks

BACKGROUND

Non-valvular atrial fibrillation (AF) is associated with an increased risk of stroke mediated by embolism of stasis-precipitated thrombi from the left atrial appendage.

OBJECTIVES

The objective is to characterize the efficacy and safety of oral anticoagulants (OACs) for the primary prevention of stroke in patients with chronic AF.

SEARCH STRATEGY

We searched the Cochrane Stroke Group Trials Register (last searched in June 2004). In addition, we searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 4, 2004), MEDLINE (1966 to June 2004), and the reference lists of recent review articles. We also contacted the Atrial Fibrillation Collaboration and experts working in the field to identify unpublished and ongoing trials.

SELECTION CRITERIA

All randomized controlled trials comparing OACs with control in patients with chronic non-valvular atrial fibrillation and no history of transient ischemic attack (TIA) or stroke.

DATA COLLECTION AND ANALYSIS

Trials for inclusion were independently selected by two authors who also extracted each outcome and double-checked the data. The Peto method was used for combining odds ratios. All analysis were, as far as possible, intention-to-treat. Since the published results of four trials included 3% to 8% of participants with prior stroke or TIA, unpublished results excluding these participants were obtained from the Atrial Fibrillation Investigators.

MAIN RESULTS

Of 2313 participants without prior cerebral ischemia from five randomized trials, the mean age was 69 years. Participant features and study quality were similar between trials: the OAC in all five trials was warfarin. About half of participants (n = 1154) were randomized to adjusted-dose warfarin with mean achieved INRs ranging between 2.0 to 2.6. During 1.5 years mean follow up, warfarin was associated with large, highly statistically significant reductions in all strokes (odds ratio (OR) 0.39, 95% confidence interval (CI) 0.26 to 0.59), ischemic stroke (OR 0.34, 95% CI 0.23 to 0.52), all disabling or fatal stroke (OR 0.47, 95% CI 0.28 to 0.80), death (OR 0.69, 95% CI 0.50 to 0.94) and the combined endpoint of all stroke, myocardial infarction or vascular death (OR 0.56, 95% CI 0.42 to 0.76). The observed rates of intracranial and extracranial hemorrhage were not significantly increased by OAC therapy, but the confidence intervals were wide.

AUTHORS' CONCLUSIONS

Treatment with adjusted-dose warfarin to achieved INRs of 2 to 3 reduces stroke, disabling or fatal stroke, and death for patients with non-valvular AF. The benefits were not substantially offset by increased bleeding among these participants in randomized clinical trials. Limitations include relatively short follow up and imprecise estimates of bleeding risks from the selected participants enrolled in the trials. For primary prevention of stroke in AF patients, about 25 strokes and about 12 disabling or fatal strokes would be prevented yearly for every 1000 atrial fibrillation patients given OACs.

[Level of understanding of patients on anticoagulants at a health centre: relationship of this and monitoring of therapy]

OBJECTIVES

To ascertain the level of understanding that patients taking oral anti-coagulants (OAC) and monitored at a primary care centre have of their treatment and to relate this to the monitoring of the therapy.

DESIGN

Descriptive study lasting one year.

SETTING

Pintores Health Centre, Parla. Area 10.

PARTICIPANTS

Adult patients in treatment for at least 6 months with OAC treatment and monitored in PC. Method. Patients took a 9-question test. The replies were evaluated, with points from 0 to 3 awarded for the understanding the patient possessed. The highest score possible was 15. To assess the degree of therapy monitoring, the crossover analysis of the determinations of the international normalized ratio (INR) over the previous year was used, taking at random 6 determinations per patient. An association between patients' level of understanding (<10 points and >10 points) and the degree of therapy monitoring (<66% or >66% of determinations of INR in rank) was looked for, using the Chi-squared as a statistical test.

RESULTS

50 patients were assessed with a mean score of 7.14 points. In addition, 294 INR determinations were analysed, with 56.12% at satisfactory levels. No significant relationship was found between patients' level of understanding and the degree of therapy monitoring.

CONCLUSIONS

The level of understanding of patients on OAC about their illness and treatment is very low, and basically depends on age. Even so, monitoring by health professionals and patients' high degree of compliance with their therapy despite their scant understanding lead to excellent levels at monitoring, with a very low index of appearance of greater complications.

Atrial fibrillation in a primary care practice: prevalence and management

BACKGROUND

Atrial fibrillation is a common serious cardiac arrhythmia. Knowing the prevalence of atrial fibrillation and documentation of medical management are important in the provision of primary care. This study sought to determine the prevalence of atrial fibrillation in a primary care population and to identify and quantify the treatments being used for stroke prevention in this group of patients.

METHODS

A prevalence study through chart audit was conducted in the family medicine practice at the Sunnybrook campus of the Sunnybrook and Women's College Health Sciences Centre. The main outcome measures were the prevalence of atrial fibrillation in our primary care practice and the use of warfarin for stroke prevention in this population.

RESULTS

261 patients in our practice have atrial fibrillation. The overall prevalence in our family practice unit is 3.9%. When considering patients aged 60 and over, the prevalence rises to 12.2%. 204 of our patients with atrial fibrillation (78.2%) are currently being treated with warfarin. Another 21 patients were previously treated and discontinued for a number of reasons. Of the 57 patients not currently treated with warfarin, 44 are treated with ASA, 2 with ticlopidine, and 11 are receiving no preventative treatment.

CONCLUSIONS

The prevalence of atrial fibrillation in our practice is higher than the range of prevalence reported in the general literature. However, our coverage with warfarin treatment exceeds previous reports in the literature.