Incident Co-Morbidities in Patients with Atrial Fibrillation Initially with a CHA ₂ DS ₂ -VASc Score of 0 (Males) or 1 (Females): Implications for Reassessment of Stroke Risk in Initially 'Low-Risk' Patients

Background Oral anticoagulants (OACs) are not recommended for 'low-risk' patients with atrial fibrillation (AF). We investigated the incidences of new risk factors developing, and the temporal trends in the CHA ₂ DS ₂ -VASc score in initially 'low-risk' AF patients. Second, we propose a reasonable timing interval at which stroke risk should be reassessed for such AF patients. Methods We studied 14,606 AF patients who did not receive anti-platelet agents or OACs with a baseline CHA ₂ DS ₂ -VASc score of 0 (males) or 1 (females). The CHA ₂ DS ₂ -VASc scores of patients were followed up and updated until the occurrence of ischaemic stroke or mortality or 31 December 2011. The associations between the prescription of warfarin and risk of adverse events once patients' scores changed were analysed. Decile values of durations to incident co-morbidities and from the acquirement of new co-morbidities to ischaemic stroke were studied. Results During a mean follow-up of 4 years, 7,079 (48.5%) patients acquired at least one new stroke risk factor component(s) with annual risks of 6.35% for hypertension, 3.68% for age ≥ 65 years, 2.77% for heart failure, 1.99% for diabetes mellitus and 0.33% for vascular diseases. The incidence for CHA ₂ DS ₂ -VASc score increments was 12.1%/year. Initiation of warfarin was associated with a lower risk of adverse events (adjusted hazard ratio, 0.530; 95% confidence interval, 0.371-0.755). Among 6,188 patients who acquired new risk factors, 80% would acquire these co-morbidities after 4.2 months of AF diagnosis. The duration from the acquirement of incident co-morbidities to the occurrence of ischaemic stroke was longer than 4.4 months for 90% of the patients. Conclusion The CHA ₂ DS ₂ -VASc score increases in approximately 12% of initially 'low-risk' AF patients each year, and the initiation of warfarin once the score changed was associated with a better prognosis. Three to four months may be a reasonable timing interval at which stroke risk should be reassessed so that OACs could be prescribed in a timely manner for stroke prevention.