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

Studies of patients with cardiovascular implantable electronic devices show a relationship between atrial fibrillation (AF) duration and stroke risk, although 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 patients with cardiovascular implantable electronic devices as a function of both CHA₂DS₂-VASc score and AF duration.

Data from the Optum electronic health record deidentified database (2007-2017) were linked to the Medtronic CareLink database of cardiovascular implantable electronic devices capable of continuous AF monitoring. An index date was assigned as the later of either 6 months after device implantation or 1 year after electronic health record data availability. CHA₂DS₂-VASc score was assessed using electronic health record data before the index date. Maximum daily AF burden (no AF, 6 minutes-23.5 hours, and >23.5 hours) was assessed over the 6 months before the index date. SSE rates were computed after the index date.

Among 21 768 nonanticoagulated patients with cardiovascular implantable electronic devices (age, 68.6±12.7 years; 63% male), both increasing AF duration (P<0.001) and increasing CHA₂DS₂-VASc score (P<0.001) were significantly associated with annualized risk of SSE. SSE rates were low in patients with a CHA₂DS₂-VASc score of 0 to 1 regardless of device-detected AF duration. However, stroke risk crossed an actionable threshold defined as >1%/y in patients with a CHA₂DS₂-VASc score of 2 with >23.5 hours of AF, those with a CHA₂DS₂-VASc score of 3 to 4 with >6 minutes of AF, and patients with a CHA₂DS₂-VASc score ≥5 even with no AF.

There is an interaction between AF duration and CHA₂DS₂-VASc score that can further risk-stratify patients with AF for SSE and may be useful in guiding anticoagulation therapy.