Comparison of Extrastimulus Pacing Strategies for the Detection of Arrhythmogenic Substrate for Ventricular Tachycardia: Insights From a Porcine Ischemia-Reperfusion Injury Model.

Background: Multiple extrastimulus (ES) pacing protocols exist for ventricular substrate mapping. Despite being increasingly adopted in clinical practice, direct protocol comparisons have been limited. This study aims to compare the substrate delineation and mapping efficiency of right ventricular pacing+ES (RVp+ES) and sensed ES pacing strategies in a large animal ischemia-reperfusion injury model.

Methods: Four swine underwent 90-minute balloon occlusion of the mid-left anterior descending artery, followed by late gadolinium-enhanced cardiac magnetic resonance between days 30 and 58 and invasive electroanatomic mapping. Late gadolinium-enhanced cardiac magnetic resonances were segmented for scar topography and border zone channel geometry.

Results: Sensed ES substrate maps had greater point density (12.90±4.20 pts/cm² versus 5.75±0.52 pts/cm²; P=0.032) and faster acquisition (113.71±22.38 s/pt per cm² versus 228.57±77.30 s/pt per cm²; P=0.027) than RVp+ES. Despite this, RVp+ES substrate maps had greater uncovering of split potentials within border zone channels (76.5% [15.4%-95.5%] versus 16.7% [0%-52.9%]; P=0.028), higher sensitivity (53% versus 30%), and similarly high specificity (91% versus 93%) than sensed ES, as well as better visual correlation on decrement-evoked potential maps. Bipolar voltage in sinus rhythm and RVp did not reliably predict tissue response to ES, with 46% to 57% of split potentials within border zone channels arising from seemingly normal voltage (≥1.5 mV).

Conclusions: RVp+ES is more sensitive than sensed ES and highly specific for the detection of late gadolinium-enhanced cardiac magnetic resonance border zone channels postmyocardial infarct.