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Figure 2 Example of a Gap-Related Septal AT
(A) Electroanatomical map of the left atrium from a patient with paroxysmal atrial fibrillation, in an anteroposterior (AP) projection. The red circles represent sites of radiofrequency energy delivery. The open circles indicate areas at which radiofrequency energy with an 8-mm-tip catheter could not be applied for more than a few seconds because of an abrupt decrease in the delivered power. (B) An activation map performed several months later during a septal atrial tachycardia (AT) in the same patient, in an AP view with cranial angulation. There is a figure-of-8 activation pattern that is stabilized superiorly by a corridor of widely split (90 ms) double potentials (red arrows) related to prior ablation at the roof, by the mitral annulus, and by the right-sided pulmonary veins (PV). The tachycardia is likely utilizing gaps in the incomplete ablation line shown in (A). Gold circles represent sites at which the post-pacing interval matched the tachycardia cycle length. Linear ablation (dashed circles) from the mitral annulus to the right-sided pulmonary veins resulted in prolongation of the tachycardia cycle length but was unsuccessful in terminating the tachycardia. Entrainment mapping showed that the right atrial septum also was part of the circuit; however, ablation at this site also failed to terminate the tachycardia. L = left; R = right.
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