Core Isolation of Critical Arrhythmia Elements for Treatment of Multiple Scar-Based Ventricular Tachycardias

Abstract

Background-Radiofrequency ablation of multiple or unmappable ventricular tachycardias (VTs) remains a challenge with unclear end points. We present our experience with a new strategy isolating core elements of VT circuits. Methods and Results-Patients with structural heart disease presenting for VT radiofrequency ablation at 2 centers were included. Strategy involved entrainment/activation mapping if VT was hemodynamically stable, and voltage mapping with electrogram analysis and pacemapping. Core isolation (CI) was performed incorporating putative isthmus and early exit site(s) based on standard criteria. If VT was noninducible, the dense scar (<0.5 mV) region was isolated. Successful CI was defined by exit block (20 mA at 2 ms) within the isolated region. VT inducibility was also assessed. Forty-four patients were included (mean age, 63; 95% male; 73% ischemic cardiomyopathy; mean left ventricular ejection fraction, 31%; 68% with multiple unstable VTs [mean, 3+2]). CI area was 11+12 versus 55+40 cm 2 total scar area. Additional substrate modification was performed in 27 (61%), and epicardial radiofrequency ablation was performed in 4 (9%) patients. CI was achieved in 37 (84%) and led to better VT-free survival (log rank P=0.013). Conclusions-CI is a novel strategy with a discrete and measurable end point beyond VT inducibility to treat patients with multiple or unmappable VTs. The CI region can be selected based on standard characterization of suspected VT isthmus surrogates thus limiting ablation target size. Exit block within the isolated area is achievable in most and may further improve long-term success. (Circ Arrhythm Electrophysiol. 2015;8:353-361.

Efficacy of Intensive Radiofrequency Energy Delivery to the Localized Dense Scar Area in Post-Infarction Ventricular Tachycardia Ablation ― A Comparative Study With Standard Strategy Targeting the Infarcted Border Zone ―

“…Isthmus Channel Mapping-Guided Ablation successful core isolation group is also similar. 15 Additional substrate modification was also performed in 61% of cases of core isolation, and this fact suggests that prophylactic ablation in addition to clinical VT is probably necessary to obtain a good VT-free survival rate, even if we target mainly the DSA.…”

“…They also identified conducting channels by carefully adjusting the voltage threshold, and showed that the voltage threshold in the conducting channels ranged from 0.1 to 0.7 mV. Tzou et al 15 recently proposed a new strategy isolating core elements of VT circuits. Core isolation was performed by incorporating putative isthmus and early exit site based on standard criteria.…”

Feasibility of Rapid Linear-Endocardial and Epicardial Ventricular Ablation Using an Irrigated Multipolar Radiofrequency Ablation Catheter

“…5 Ablation by these methods requires delivery of many focal lesions, typically in a linear pattern, resulting in long radiofrequency and procedural times. In the first study of linear radiofrequency ablation for VT by Marchlinski et al, 1 a mean of 14.7 lesions was required to create lines of 3.9-cm mean length.…”

“…3 Radiofrequency ablation around scar borders to achieve core isolation has been demonstrated as a promising approach for the treatment of VT but is also associated with long procedure time (mean 5.4 hours) and a large number of individual radiofrequency applications (111 lesions). 5 Thus, tools to create contiguous linear radiofrequency lesions rapidly could significantly enhance these VT ablation strategies by significantly decreasing procedure and radiofrequency time.…”

Development of Time- and Voltage-Domain Mapping (V-T-Mapping) to Localize Ventricular Tachycardia Channels During Sinus Rhythm

“…Although VT morphology is widely emphasized to be relevant in planning ablation targets, 22,23,31 despite recent advances in substrate characterization, 32 identifying critical surviving myofiber channels by readily applicable and efficient methods has remained a challenge. The contemporary substrate-based ablation practices have evolved from linear anchoring ablation, 21 short lines, 33 spot ablation targeting areas of long S-QRS intervals, 31,34 to core element isolation, 35 however, finding isthmus regions in the expanse of large heterogeneous scar can be time-consuming. The requirements for a reentrant excitation include the 3 principle conditions-unidirectional conduction block, slow conduction, and re-excitation of the previously blocked myofiber bundle.…”