Assertion: atrial fibrillation | /r/AtLocation | pulmonary veins
Facets:
value: often
type: TEMPORAL
Source sentences:
text: We know that the erratic electrical impulses that cause atrial fibrillation often originate in the pulmonary veins, at least in most paroxysmal (intermittent) atrial fibrillation, and that the impulses that cause persistent and longstanding persistent atrial fibrillation are believed to come from other areas as well, but what actually causes afib?