Hospitalized Patients With Atrial Fibrillation and a High Risk of Stroke Are Not Being Provided With Adequate Anticoagulation

Vitamin K supplementation can improve stability of anticoagulation for patients with unexplained variability in response to warfarin

Patients receiving warfarin who have unstable control of anticoagulation have a significantly lower intake of dietary vitamin K compared with their stable counterparts. We hypothesized that supplementation with oral vitamin K would improve stability in patients with previously unstable control of anticoagulation. Seventy warfarin-treated patients with unstable anticoagulation control were randomly assigned in a double-blinded fashion to receive a daily amount of 150 mug oral vitamin K or placebo orally for 6 months. Measures of stability of anticoagulation control in the 6-month study period were compared with those in the 6 months immediately prior to it. Vitamin K supplementation resulted in a significantly greater decrease in standard deviation of international normalized ratio (INR) compared with placebo (-0.24 +/- 0.14 vs -0.11 +/- 0.18; P < .001) and a significantly greater increase in percentage time within target INR range (28% +/- 20% vs 15% +/- 20%; P < .01). Anticoagulation control improved in 33 of 35 patients receiving vitamin K supplementation; of these, 19 fulfilled our criteria for having stable control of anticoagulation. However, only 24 of 33 patients receiving placebo demonstrated some degree of improvement, with only 7 patients fulfilling the criteria for having stable control. Concomitant supplementation of vitamin K, perhaps through reducing the relative day-to-day variability in dietary vitamin K intake, can significantly improve anticoagulation control in patients with unexplained instability of response to warfarin.

Optimising stroke prevention in non-valvular atrial fibrillation

Atrial fibrillation is associated with substantial morbidity and mortality. Pooled data from trials comparing antithrombotic treatment with placebo have shown that warfarin reduces the risk of stroke by 62%, and that aspirin alone reduces the risk by 22%. Overall, in high-risk patients, warfarin is superior to aspirin in preventing strokes, with a relative risk reduction of 36%. Ximelagatran, an oral direct thrombin inhibitor, was found to be as efficient as vitamin K antagonist drugs in the prevention of embolic events, but has been recently withdrawn because of abnormal liver function tests. The ACTIVE-W (Atrial Fibrillation Clopidogrel Trial with Irbesartan for Prevention of Vascular Events) study has demonstrated that warfarin is superior to platelet therapy (clopidogrel plus aspirin) in the prevention af embolic events. Idraparinux, a Factor Xa inhibitor, is being evaluated in patients with atrial fibrillation. Angiotensin-converting enzyme inhibitors and angiotensin II receptor-blocking drugs hold promise in atrial fibrillation through cardiac remodelling. Preliminary studies suggest that statins could interfere with the risk of recurrence after electrical cardioversion. Finally, percutaneous methods for the exclusion of left atrial appendage are under investigation in high-risk patients.

Atrial Fibrillation

Over 2 million people in the Untied States are known to have AF, and this number is expected to rise to 5 to 6 million in the next 50 years. In spite of advances in detection and treatment of AF, it is still associated with significant morbidity and mortality. Treatment currently consists of rhythm management and prevention of embolic events (anticoagulation). Although two strategies of rhythm management exist (heart rate control and heart rhythm control), a distinct advantage of one over the other has not yet been determined. Because of the increasing numbers of patients who have AF in the general population and newer surgical approaches to dealing with AF, the anesthesiologist encounters patients who have AF on an almost daily basis. Fortunately, national and international guidelines exist for the treatment of pre-existing AF and dealing with anticoagulated patients in the perioperative period, clearly indicating whether a patient is adequately managed or not by current standards of practice. With respect to the new development of AF in the perioperative period, cardiac and thoracic surgeries are particularly associated with this phenomenon. Guidelines have been published for the perioperative management of AF after cardiac surgery, and are in accordance with the findings from studies in thoracic surgery. Beta-blockers and amiodarone are strongly recommended for the pre-emptive treatment of AF in high-risk patients, whereas amiodarone and sotalol are the agents of choice in those patients developing AF after surgery not requiring urgent cardioversion. The recent discoveries of properties of statins other than their lipid-lowering abilities has sparked wide interest in the possibility of this family of drugs having a protective role against AF in many scenarios. It remains to be seen whether statins will prove to be adjunct in patients at high risk for AF in the perioperative period.

Stroke prophylaxis in atrial fibrillation: who gets it and who does not?

AIMS

Underuse of warfarin for stroke prophylaxis in atrial fibrillation (AF) is extensive and represents a major problem in clinical practice. To identify factors associated with warfarin treatment in eligible AF patients.

METHODS AND RESULTS

The study population consisted of all Swedish resident AF patients at the Stockholm South General Hospital during 2002 (n=2796). Medical records were examined and complemented by data from the Swedish National Hospital Discharge Register. Sixty-eight percent of the patients (1898/2796) had indications, and no apparent contraindications for warfarin treatment. Of these 54% (1029/1898) got warfarin. Factors favouring warfarin treatment after adjustment for other factors were history of ischaemic stroke, an implanted pacemaker, treatment in a cardiology rather than internal medicine ward and valvular defect. Factors associated with a reduced likelihood of warfarin treatment were paroxysmal type of AF and age >80 years. Important risk factors for stroke in AF like heart failure, hypertension, and diabetes did not increase the chances of warfarin treatment.

CONCLUSION

Risk stratification using known risk factors of stroke seems to affect warfarin treatment only to a minor degree in clinical practice. Undertreatment was particularly common in patients with paroxysmal AF and in patients aged >80 years and calls for improved clinical routines in accordance with international guidelines.

Translating the Results of Randomized Trials into Clinical Practice

BACKGROUND AND PURPOSE

Numerous studies have documented under use of warfarin particularly among elderly patients. A better understanding of the discrepancy between trials and clinical practice will help inform stroke prevention strategies in this vulnerable age group. The study objective was to prospectively assess the use of antithrombotic therapy among a contemporary cohort of patients with atrial fibrillation at the time of hospital discharge. In addition to baseline characteristics, we sought to define the physician-cited reason for not prescribing warfarin for each patient.

METHODS

Patients with atrial fibrillation were prospectively identified and followed to hospital discharge. Enrolled patients were > or =65 years of age, not taking warfarin on admission, and had their longitudinal care provided at our institution. Predictors of warfarin use were determined and physician-cited contraindications were compared across age groups.

RESULTS

Fifty-one percent (n=206) of patients were discharged on warfarin: 75% of those 65 to 69 years of age, 59% 70 to 79, 45% 80 to 89, and 24% age > or =90 years. Of the remaining 199 patients, 83% had > or =2 major risk factors for stroke, and 98% were felt to have contraindications including nearly 25% who were unable to tolerate warfarin in the past. Among patients age > or =80, falling was the most often physician-cited reason for not prescribing warfarin (41%) followed by hemorrhage (28%).

CONCLUSIONS

Our findings suggest that many elderly patients at high risk for stroke may not be optimal candidates for anticoagulant therapy. There is a pressing need for alternative stroke prevention strategies for this expanding patient population.