Propagation Vectors Facilitate Differentiation Between Conduction Block, Slow Conduction, and Wavefront Collision

Background: Differentiation between conduction block, slow conduction, and wavefront collision can be difficult using activation mapping alone, often requiring differential pacing. Therefore, a real-time method for determination of complex patterns of conduction may be desired. We hereby report a novel algorithm for displaying propagation vectors, allowing differentiation between complex patterns of conduction and facilitating real-time detection of block during ablation. Methods: In 10 swine, a chronic transcaval ablation line with an intentional gap or complete block was created, simulating conduction block, slow conduction, and wavefront collision. The line was mapped during atrial pacing using Carto 3 and a novel high-resolution array that includes 48 minielectrodes (surface area, 0.9 mm2, spacing 2.4 mm) distributed over 6 splines (Optrell, Biosense Webster). Propagation vectors were created from unipolar waveforms of adjacent electrodes along and across splines that were acquired at single beats. To examine the utility of propagation vectors for detection conduction block during ablation, a cavotricuspid isthmus line was created during coronary sinus pacing with the array positioned lateral to the line. Results: Propagation vectors detected the gap in all 6 interrupted ablation lines, while activation maps only identified gap in 3/6 lines; in the remainder, activation maps alone could not differentiate between conduction block, slow conduction, or wavefront collision. Propagation vectors accurately determined block in all 4 contiguous ablation line, while activation maps suggested conduction block or were indeterminant due to wavefront collision in 2/4 lines. Cavotricuspid isthmus line block was detected during ablation by abrupt reversal of propagation vectors from a lateral-to-septal direction, and acute reconnection was detected by reversal of the propagating vectors back to a lateral direction. Conclusions: Real-time propagation vectors enhance the ability of standard activation maps to differentiate between complex patterns of conduction, including determination of conduction block during ablation.