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Figure 2 Activation Patterns in an Individual Patient

Activation proceeds from red to blue. (A) Activation pattern during sinus rhythm. Note uniform conduction occurs from septal to lateral aspect of the posterior left atrium. (B) Pacing from the septal inferior corner of the posterior left atrium. *Site of pacing. Note that activation occurs around a line of block and then superiorly up the posterior left atrium. (C) Pacing from the high posterior left atrium. (D) Pacing from the lateral inferior corner of the posterior left atrium. Note uniform conduction superiorly, however, as the wave front passes horizontally it traverses a line of slow conduction. These figures show the consistent location of the line on the posterior left atrium.