First‐Ever Atrial Fibrillation Documented After Hemorrhagic or Ischemic Stroke: The Role of the CHADS2 Score at the Time of Stroke

Background: The CHADS2 score (C, congestive heart failure [CHF]; H, hypertension [HT]; A, age ≥75 y; D, diabetes mellitus; S2, prior stroke or transient ischemic attack) is used to assess the risk of ischemic stroke in patients with atrial fibrillation (AF). However, its role in patients without documented AF is not well explored. Hypothesis: The goal of the current study was to explore if the incidence of hospitalization with first‐ever AF after stroke increased with increasing CHADS2 score. Methods: We identified 57636 patients with nonfatal stroke and no documented AF in the Swedish Stroke Register (Riks‐Stroke) during 2001–2004 and followed them for a mean of 2.2 years through record linkage to the Inpatient and Cause of Death registers. Cox regression hazard models were used to estimate the relative risk (RR) of new AF following stroke and its association with different CHADS2 scores. Results: Overall, 2769 patients were hospitalized with new AF (4.8%, 21.7 per 1000 person‐years). The incidence increased from 9.6 per 1000 person‐years in CHADS2 score 0 to 42.7 in CHADS2 score 6, conferring a RR of 4.2 (95% confidence interval [CI]: 2.5–6.8). For CHADS2 scores 3–5, the RRs were approximately 3 (vs CHADS2 score 0). Adjusted RRs were 1.9 (95% CI: 1.7–2.1) for CHF, 1.4 (95% CI: 1.3–1.5) for HT, 2.1 (95% CI: 2.0–2.3) for age ≥75 years, 0.9 (95% CI: 0.8–1.0) for diabetes, and 1.0 (95% CI: 0.91–1.07) for previous stroke. The risk of AF was higher in ischemic than in hemorrhagic stroke. Conclusions: In this retrospective register study, the incidence of AF following stroke was strongly influenced by higher CHADS2 scores where age ≥75 years, CHF, and HT were the contributing CHADS2 components. © 2011 Wiley Periodicals, Inc. Riks‐Stroke is funded by the National Board of Health and Welfare and the Swedish Association of Local Authorities and Regions. S. Åsberg has received a research scholarship from the National Association for Stroke Patients in Sweden. All authors have independent affiliations with universities in Sweden. B. Farahmand and K. Henriksson are employees of AstraZeneca R&D, Sweden. A. Terént has received funding from AstraZeneca. N. Edvardsson serves as medical advisor to AstraZeneca R&D, Sweden. The authors have no other funding, financial relationships, or conflicts of interest to disclose.