Effect of Activation Wavefront on Electrogram Characteristics During Ventricular Tachycardia Ablation

Area of Science:

• Electrophysiology
• Cardiology
• Medical Devices

Background:

• Catheter ablation for ventricular tachycardia (VT) in structural heart disease presents challenges due to non-inducibility and hemodynamic compromise.
• Identifying local abnormal ventricular activities (LAVAs) is crucial for ablation, but these signals can be obscured by far-field potentials.
• Understanding isthmus anatomy is key for successful VT ablation.

Purpose of the Study:

• To investigate if altering the activation wavefront affects activation timing and LAVA characterization.
• To determine if this approach enhances the understanding of isthmus anatomy for VT ablation.
• To assess the impact of modified activation wavefronts on identifying critical isthmuses in unmappable VTs.

Main Methods:

• Utilized ultra-high density mapping with the Rhythmia system in patients with ischemic cardiomyopathy.
• Generated activation maps during stable VT and with pacing from the atrium, right ventricular apex, and left ventricular coronary sinus branch.
• Analyzed conduction properties, scar size, and LAVA characteristics under different pacing conditions.

Main Results:

• In 79% of activation maps, lines of block were observed in the paced wavefront, with 93% fixed and 32% functional partial block.
• Bipolar scar size and LAVA areas varied significantly based on pacing site, with atrial pacing showing larger scar but smaller LAVA areas.
• LAVA areas were significantly larger when wavefront propagation was perpendicular versus parallel to the line of block along isthmus boundaries (19.3±7.1 vs. 13.6±7.4 cm², P=0.01).

Conclusions:

• Altering the activation wavefront can reveal critical isthmuses in unmappable VTs by highlighting conduction slowing and block.
• Modifying the activation wavefront significantly impacts myocardial tissue conduction properties, scar, and LAVA characterization.
• Employing an alternate activation wavefront perpendicular to the VT isthmus increases sensitivity for detecting arrhythmogenic substrate and reentry sites, especially when few LAVAs are initially identified.