Refining Stroke Risk in Patients with Atrial Fibrillation

Bradley P. Knight, MD, FACC, FHRS, Editor-in-Chief
Bradley P. Knight, MD, FACC, FHRS, Editor-in-Chief
Dear Readers,

The European Society of Cardiology (ESC) recently updated their Guidelines for the management of atrial fibrillation (AF).1 One of the recommendations is to consider a new point-based scoring system that is more sophisticated than the current CHADS2 system, when determining the risk of stroke in patients with AF. The CHADS2 scoring system has been used for several years and can quantify a patient’s risk of stroke. The CHADS2 [congestive heart failure, hypertension, age, diabetes, stroke (doubled)] risk index evolved from the AF Investigators and Stroke Prevention in Atrial Fibrillation (SPAF) Investigators criteria, and is based on a point system in which 2 points are assigned for a history of stroke and 1 point each is assigned for age > 75 years, a history of hypertension, diabetes, or recent cardiac failure. Patients with a CHADS2 score of 2 have an annual risk of stroke of at least 4% without anticoagulation, and should be treated with warfarin, targeting an INR of 2.0–3.0, in the absence of a significant contraindication. The rationale is that the risk of intracranial bleeding with warfarin in these patients is less than the risk of stroke. Patients with a score of 1 should be treated with either warfarin or aspirin. Of course, patients with hypertrophic cardiomyopathy and mechanical valves should also receive warfarin regardless of their CHADS2 score. There remains controversy, however, surrounding the group of patients with a CHADS2 score of 1, who have a stroke risk of approximately 2.8% per year, as to whether or not these patients should all receive warfarin. The availability of the new direct thrombin inhibitor, dabigatran, adds to this controversy, because dabigatran appears to be more effective than warfarin and is more convenient to take.

The new ESC AF Guidelines emphasize that there are “clinically relevant non-major risk factors” that should be used to further refine the current CHADS2 system. They define prior stroke and age over 75 years as major risk factors, but suggest that factors previously not considered in the scoring system, such as age between 65 and 75 years, vascular disease, and being female, are relevant and associated with an increased risk of stroke. The acronym for the new scoring system is CHA2DS2VASc, which stands for congestive heart failure, hypertension, age ≥ 75 (doubled), diabetes, stroke (doubled), vascular disease, age 65–74, and sex category (female). The annual risk of stroke is approximately 1% for each point up to 4, after which the risk increases more than linearly. The ESC Guidelines state that a score of 2 or more would indicate a stroke risk that is high enough to warrant oral anticoagulation. They recommend oral anticoagulation or aspirin for patients with a score of 1, but state that oral anticoagulation is preferred. The biggest impact of the new ESC Guidelines on clinical care is that all patients (without contraindications) over age 75 years and women over 65 years now have a strong indication for oral anticoagulation and should not be treated with aspirin alone.

The new ESC Guidelines also introduce a bleeding risk score with the acronym HAS-BLED [hypertension, abnormal renal/liver function (1 point for each), stroke, bleeding history or predisposition, labile INR, elderly (> 65), drugs/alcohol concomitantly (1 point for each)]. Patients with a score of ≥ 3 are at high risk of bleeding. Caution is necessary in these patients before starting oral anticoagulation as the risks might outweigh the potential benefit. Much of our day taking care of patients with heart rhythm disorders involves weighing risks and benefits. The new CHA2DS2VASc and HAS-BLED scoring systems in the 2010 ESC AF Guidelines appear to improve our ability to better identify which patients with AF should receive oral anticoagulation.

Reference

1. Guidelines for the management of atrial fibrillation: The Task Force for the Management of Atrial Fibrillation of the European Society of Cardiology (ESC). Eur Heart J 2010;31:2369–2429. Epub 2010 Aug 29. DOI:10.1093/eurheartj/ehq278. Available at: http://eurheartj.oxfordjournals.org