Coexistence of sinus rhythm and segmental atrial fibrillation after maze procedure

We present the case of an 80-year-old man with chronic atrial fibrillation associated with mitral regurgitation. The atrial fibrillation was successfully treated with the maze procedure combined with mitral valve replacement. The electrophysiological data are also reported. Recordings of sinus rhythm and intraatrial activity demonstrated the coexistence of sinus rhythm and fibrillation of both atria. This finding indicates that the sinus node was protected from segmental atrial fibrillation by entrance block, and this, in turn, is evidence of the efficacy of the maze procedure.