Assertion: stroke's cause | /r/HasProperty | atrial fibrillation
Facets:
Source sentences:
text: The most common cause of cerebral embolism is atrial fibrillation, a disorder of the heart beat.
text: The most common cause of these blood clots is a heart arrhythmia called atrial fibrillation, where the upper chambers of the heart, the atria, do not beat in an organized rhythm.