Spontaneous initiation of atrial fibrillation by ectopic beats originating from the pulmonary veins. - Haissaguerre,M.; Jais,P.; Shah,D.C.; Takahashi,A.; Hocini,M.; Quiniou,G.; Garrigue,S.; Le Mouroux,A.; Le Metayer,P.; Clementy,J. (N Engl J Med, 1998)