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Stroke Risk as a Function of Atrial Fibrillation Duration and CHA2DS2-VASc Score.

Background: Studies of patients with cardiovascular implantable electronic devices (CIED) show a relationship between atrial fibrillation (AF) duration and stroke risk, though the interaction with CHA2DS2-VASc score is poorly defined. The objective of this study is to evaluate rates of stroke and systemic embolism (SSE) in CIED patients as a function of both CHA2DS2-VASc score and AF duration. Methods: Data from the Optum© electronic health record (EHR) de-identified database (2007-2017) were linked to the Medtronic CareLinkTM database of CIEDs capable of continuous AF monitoring. An index date was assigned as the later of 6 months after device implant or 1 year after EHR data availability. CHA2DS2-VASc score was assessed via EHR data prior to the index date. Maximum daily AF burden (No AF, 6 minutes-23.5 hours, and >23.5 hours) was assessed over the 6 months prior to index date. SSE rates were computed post-index date. Results: Among 21,768 non-anticoagulated CIED patients (68.6±12.7 years, 63% male), increasing AF duration (p<0.001) and increasing CHA2DS2-VASc score (p<0.001) were both significantly associated with annualized risk of SSE. SSE rates were low in CHA2DS2-VASc 0-1 patients regardless of device-detected AF duration. However, stroke risk crossed an actionable threshold defined as >1%/year in CHA2DS2-VASc 2 patients with >23.5 hours of AF, CHA2DS2-VASc 3-4 patients with >6 minutes of AF, and in CHA2DS2-VASc ≥5 patients even with no AF. Conclusions: There is an interaction between AF duration and CHA2DS2-VASc score which can further risk stratify AF patients for SSE and may be useful in guiding anticoagulation therapy.