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Treatment thresholds for stroke prevention in atrial fibrillation: observations on the CHA2DS2-VASc score

Atrial fibrillation (AF) is an expanding epidemic,1 and ischaemic stroke due to cardioembolism remains a trademark serious complication of AF.2 The now historical stroke prevention in AF trials demonstrated that compared with placebo/control, anticoagulation with a vitamin K antagonist (VKA, e.g. warfarin) reduced stroke by 64% while also reducing all-cause mortality in patients with non-valvular AF, whereas platelet inhibition with aspirin had a non-significant 19% reduction in stroke and no benefit on mortality.3 Thus, effective stroke prevention means oral anticoagulation.

Although highly effective, antithrombotic drugs increase the risk of bleeding events, and the expected benefits and harms for the individual patient must be carefully weighed when deciding on whether or not to initiate treatment. More specifically, a certain absolute level of thromboembolic risk is required before the protective antithrombotic effect outweighs the associated serious bleeding risk. To alleviate this clinical conundrum and aid decision making, the use of validated stroke and bleeding risk scores is recommended.4

Most contemporary guidelines recommend using the CHA2DS2-VASc score to determine whether an atrial fibrillation (AF) patient has an indication for antithrombotic treatment.5–8 Nonetheless, guideline recommendations are conflicting (see Table 1 ). 

View this table:

Table 1 
Conflicting guideline recommendations for antithrombotic management of women and men with atrial fibrillation



Some guidelines have used the CHA2DS2-VASc score in a categorical manner, artificially dividing patients into low-, moderate- and, high-risk strata—and making treatment recommendations based on these strata. Also, all guidelines actually provide treatment recommendations that extend beyond what has been specifically investigated in randomized trials.

Randomized trials are the gold standard to testing the effectiveness and safety of an intervention but clinical trials focus on highly selected populations with specific inclusion/exclusion criteria. The historical stroke prevention trials testing the effect of antithrombotic therapy against no treatment or …