Repeat accessory pathway ablation: Challenges, surprises, and lessons learned

Figure 1. A: Electrocardiogram at baseline showing intermittent preexcitation. B: Clinical supraventricular tachycardia with a cycle length of 340 ms (177 beats/min).

Figure 2. A: Left anterior oblique (LAO) view of the duodecapolar catheter placed along the mitral annulus and the earliest atrial activation during ventricular pacing at the posterolateral, 4 o’clock mitral annular position. Coronary sinus catheter tip is hooked at the os, unable to be advanced. B: LAO view of the earliest ventricular activation during preexcited sinus conduction at the posteroseptal, 6 o’clock mitral annular position.

Figure 3. All images are at a sweep speed of 100 ms. A: Preexcited supraventricular tachycardia (SVT) cycle length: 468 ms. A His-refractory premature ventricular contraction does not alter SVT cycle length, and causes a narrow QRS owing to concealment in the pathway while the SVT continues without a change in cycle length. B: Clinical SVT with mitral annular catheter showing VAHV response suggestive of orthodromic reciprocating tachycardia. C: The earliest local ventricular electrogram preceding the onset of surface QRS by 0 to -5 ms, and pathway potential seen during anterograde conduction. D: Complete heart block after ablation of pathway atrial insertion site at the 4 o’clock mitral annulus. E: Electrograms seen with pathway potential (arrow) at the 4 o’clock mitral annulus prior to ablation. First vertical line coincides with onset of surface preexcited QRS. Second vertical line coincides with pathway potential on distal ablation catheter.