Risk factors for stroke and primary prevention of stroke in atrial fibrillation

The management of anticoagulants in the periendoscopic period for patients with atrial fibrillation: a decision analysis

PURPOSE

The management of patients who undergo endoscopy while being treated with warfarin is challenging. We used decision analysis to determine the preferred strategy to manage anticoagulants in the periendoscopic period.

METHODS

We designed a Markov model to estimate costs and quality-adjusted survival during a 10-year period in patients with nonvalvular atrial fibrillation undergoing screening colonoscopy. We compared six alternatives to the continue-warfarin strategy, which was to perform colonoscopy while the patient was taking full-dose warfarin. The hold-warfarin strategy was to stop warfarin 5 days before the colonoscopy. The repeat endoscopy strategy was to continue warfarin for a diagnostic colonoscopy, followed by a repeat procedure after cessation of warfarin if polypectomy was required. The dose-reduction strategy was to reduce the warfarin dose before colonoscopy. The low molecular weight heparin strategy was to administer subcutaneous low molecular weight heparin for 2 days before and 2 days after colonoscopy. The unfractionated heparin strategy was to administer intravenous unfractionated heparin for 2 days before and 2 days after the procedure. The vitamin K strategy was to hold warfarin for 4 days and to administer vitamin K if the international normalized ratio (INR) exceeded 2.0 the day before the procedure, or low molecular weight heparin if the INR was less than 1.5.

RESULTS

For screening colonoscopy, assuming that polyps would be removed in 35% of examinations, the hold-warfarin and dose-reduction arms were both cost-effective strategies. The hold-warfarin arm was most cost-effective if the likelihood of polypectomy exceeded 60%, or if there was a low risk of stroke despite atrial fibrillation. The continue-warfarin strategy was preferred if the probability of polypectomy was 1% or less.

CONCLUSION

Temporary warfarin cessation or halving the warfarin dose for several days before endoscopy was the preferred strategy for most patients. Periendoscopic heparin therapy was not cost-effective for patients with nonvalvular atrial fibrillation.

Factors influencing physicians' reported use of anticoagulation therapy in nonvalvular atrial fibrillation: a cross-sectional survey

BACKGROUND

Some elderly patients with nonvalvular atrial fibrillation (NVAF) who might benefit from warfarin therapy do not receive it.

OBJECTIVE

The goal of this cross-sectional study was to identify physicians' attitudes and beliefs that are associated with their reported use of warfarin in case scenarios.

METHODS

A self-administered survey was mailed to a cross-section of general internists randomly selected from a national pool of physicians in the American Medical Association Masterfile. Fourteen clinical vignettes were used, incorporating various comorbid conditions and risk factors for either major bleeding episode or embolic cerebrovascular accident (CVA). The outcome measure was the number of case vignettes for which warfarin was recommended.

RESULTS

A total of 142 completed surveys (33% of 426 eligible respondents; 109 men, and 32 women [1 respondent did not provide gender]; mean [SD] age, 45 [10] years) were received. The median number of case vignettes for which warfarin was recommended was 10 (interquartile range, 8-12). We found no relationship between the perceived benefits of warfarin and its use in the case vignettes. However, the perceived risk for warfarin associated hemorrhage was strongly associated with reported warfarin use (P < 0.001). The physicians in our sample provided estimates of the annual rate of warfarin-associated intracerebral hemorrhage that were >10-fold higher than literature-based estimates, and physicians providing higher risk estimates tended to use warfarin less often. On multivariate logistic regression, physicians who recommended warfarin use in more vignettes were less likely to report anticipated regret of committing an error of omission (ischemic CVA in an untreated NVAF patient) (P < 0.001) or a loss-aversive risk preference (P = 0.027), and had a lower perceived annual risk for hemorrhage with warfarin (P < 0.001). Physician age, sex, primary mechanism of reimbursement, academic appointment, and the NVAF patient volume all were unrelated to warfarin use.

CONCLUSIONS

Although the decision to use warfarin in NVAF was not driven by the perceived benefit, the perceived risks strongly affected warfarin use. Response bias is a potential limitation, but our data strongly suggest that physicians' attitudes toward anticipated regret and risk aversion can impact on their treatment recommendations.