Figure 2
Intracardiac electrograms during RV extrastimulation. (A) The earliest atrial activation is seen in the distal CS with ventricular extrastimulus coupling intervals from 400 to 290 ms at a basic pacing CL of 600 ms, suggesting the presence of a left lateral accessory pathway. (B) The earliest activation shifts to the HB region with a ventricular extrastimulus coupling interval of 280 ms, suggesting the presence of retrograde fast pathway conduction.
Abbreviations are as in Figure 1.