{"id":128976,"date":"2023-01-09T17:11:19","date_gmt":"2023-01-09T17:11:19","guid":{"rendered":"https:\/\/ccs.ca\/?post_type=guideline&p=128976"},"modified":"2023-04-19T07:52:00","modified_gmt":"2023-04-19T07:52:00","slug":"chapter-8-stroke-prevention","status":"publish","type":"guideline","link":"https:\/\/ccs.ca\/guideline\/2020-atrial-fibrillation\/chapter-8-stroke-prevention\/","title":{"rendered":"8. Stroke Prevention"},"content":{"rendered":"\n
Observations from the Framingham cohort and subsequent clinical trials revealed that NVAF is an independent risk factor for stroke (annual incidence of approximately 4.1%-4.5%) and combined stroke\/systemic embolism (annual incidence of 50%).[70]<\/a>,[169]<\/a><\/sup> The risk was further refined by the delineation of various baseline characteristics that might affect the risk of the stroke.[169]<\/a>–[173]<\/a><\/sup> The first widely adopted tool for stroke risk assessment was the C<\/strong>ongestive Heart Failure, H<\/strong>ypertension, A<\/strong>ge, D<\/strong>iabetes, S<\/strong>troke\/Transient Ischemic Attack (CHADS2) score, which assigns a single point for HF, hypertension, age 75 years or older, and diabetes, and 2 points for previous stroke\/systemic embolism.[26]<\/a>,[172]<\/a><\/sup> Unfortunately, CHADS2 was unable to adequately differentiate very low risk individuals (ie, in whom OAC is associated with a greater risk than benefit) from those at low but still clinically important stroke risk. This led to the development of the expanded C<\/strong>ongestive Heart Failure, H<\/strong>ypertension, A<\/strong>ge (75 years), D<\/strong>iabetes, S<\/strong>troke\/Transient Ischemic Attack, V<\/strong>ascular Disease, A<\/strong>ge (65-74 years), S<\/strong>ex (Female) (CHA2DS2-VASc) score. This score includes the additional risk factors of vascular disease (1 point), female sex (1 point), and age between 65 and 74 years (1 point), and also increases the risk weight to 2 points for age 75 years or older.[26]<\/a>,<\/sup>[171]<\/sup><\/a> The 2010 CCS guidelines recommended stroke prevention therapies[4]<\/a><\/sup> on the basis of the CHADS2 whereas the 2012 update[5]<\/a><\/sup> differentiated among patients at low CHADS2 risk on the basis of risk factors derived from the CHA2DS2-VASc.[174]<\/a><\/sup> The algorithm for antithrombotic prescription was further revised in 2014,[175]<\/a><\/sup> on the basis of data from a Danish national cohort study, which showed that the annual risk of \u201cstroke\u201d (defined as a thromboembolic event precipitating hospitalization or death) was 2.1% for patients aged 65-74 years and 4.4% for those 75 years of age or older.[174]<\/a><\/sup> Because age could be reliably determined in all patients, it was agreed that age 65 years or older should be the starting point for a revised algorithm.[175]<\/a><\/sup> Likewise, OAC was justified for younger patients with any CHADS2 risk factors (annual risk of stroke: 2.4% with HF, 1.6% with hypertension, 2.3% with diabetes, and 7.9% with previous stroke\/systemic embolism). The CCS Guidelines Committee judged that antiplatelet therapy has no role in AF-related stroke prevention and, therefore, no antithrombotic therapy was recommended for patients younger than 65 years with none of the CHADS2 risk factors. However, in the presence of vascular disease daily antiplatelet therapy is indicated to prevent ischemic vascular events independent of the presence of AF.[176]<\/a><\/sup> As such, antiplatelet therapy is only indicated in the presence of established vascular disease in NVAF patients aged younger than 65 years with no CHADS2 risk factors (see section 8.3.2.1). The CCS algorithm (CHADS-65) is presented in (Fig. 8). Among several organizations that publish guidelines for antithrombotic therapies for patients with AF, there are variations in the definitions of the component risk factors, and in the selection and interpretation of data on the stroke risk associated with the individual risk factors according to their preferred risk schemes.[10]<\/a>,[26]<\/a>,[177]<\/a><\/sup> These differences in definitions are unlikely to affect the categorization of patient stroke risk, however, they might provide different point estimates of the annual risk of stroke. It has also become evident that the risk of stroke varies among cohorts reported from different countries.[178]<\/a><\/sup> For similar baseline characteristics, the Taiwanese[179]<\/a><\/sup> and Danish cohorts[174]<\/a><\/sup> appear to have particularly high stroke risk, whereas cohorts from Sweden[180]<\/a><\/sup> and the United States[181]<\/a><\/sup> appear to be lower risk. The variation might be attributable to the dissimilarities in the definitions of stroke, treatment of comorbidities, and the protocols for data collection.<\/p>\n\n\n\n