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Figure 1 Activation Patterns and Associated Electrograms During Pacing the Septal Corner of the Plaque

Activation proceeds from red to blue. *Site of pacing. (A) In this patient from Group D (aortic stenosis), activation proceeds around the end of a line of block and then activates the posterior left atrium in a superior direction. Note the electrograms at sites a to c showing fractionated electrograms along this line. (B) In this patient from Group C (mitral regurgitation), activation breaks through a line of slow conduction and then activates the posterior left atrium in both superior and inferior directions. (C) In this patient from Group B (left ventricular failure/coronary artery bypass graft), on the left side of the plaque, there is activation away from the pacing site up until the line of block. On the right side of the plaque activation is in a superior direction. Note the presence of double potentials along the line of block.