Assertion: atrial fibrillation | /r/HasProperty | heart's two upper chambers
Facets:
Source sentences:
text: During atrial fibrillation the heart's two upper chambers (atria) beat chaotically and irregularly — out of coordination with the two lower chambers (ventricles).
text: During atrial fibrillation the heart's two upper chambers (atria) beat chaotically and irregularly — out of coordination with the two lower chambers (ventricles).