Tachycardia-Related Channel in the Scar Tissue in Patients With Sustained Monomorphic Ventricular Tachycardias

Abstract

Background-Endocardial mapping before sustained monomorphic ventricular tachycardia (SMVT) induction may reduce mapping time during tachycardia and facilitate the ablation of unmappable VT. Methods and Results-Left ventricular electroanatomic voltage maps obtained during right ventricular apex pacing in 26 patients with chronic myocardial infarction referred for VT ablation were analyzed to identify conducting channels (CCs) inside the scar tissue. A CC was defined by the presence of a corridor of consecutive electrograms differentiated by higher voltage amplitude than the surrounding area. The effect of different levels of voltage scar definition, from 0.5 to 0.1 mV, was analyzed. Twenty-three channels were identified in 20 patients. The majority of CCs were identified when the voltage scar definition was Յ0.2 mV. Electrograms with Ն2 components were recorded more frequently at the inner than at the entrance of CCs (100% versus 75%, PՅ0.01). The activation time of the latest component was longer at the inner than at the entrance of CCs (200Ϯ40 versus 164Ϯ53 ms, PՅ0.001). Pacing from these CCs gave rise to a long-stimulus QRS interval (110Ϯ49 ms). Radiofrequency lesion applied to CCs suppressed the inducibility in 88% of CC-related tachycardias. During a follow-up of 17Ϯ11 months, 23% of the patients experienced a VT recurrence. Conclusions-CCs represent areas of slow conduction that can be identified in 75% of patients with SMVT. A tiered decreasing-voltage definition of the scar is critical for CC identification.

Early Reperfusion During Acute Myocardial Infarction Affects Ventricular Tachycardia Characteristics and the Chronic Electroanatomic and Histological Substrate

“…The mean length of these channels was 23Ϯ11 mm, and the mean cycle length of the channel-related VT was 365Ϯ77 ms, similar to the VT cycle length found in nonreperfused patients in our study. 17 The larger and confluent dense scar areas found in patients without reperfusion are more likely to contain longer protected slow-conducting channels, which may explain the observed longer arrhythmia cycle length. 15 In contrast, in reperfused patients, small areas of dense scars are interspersed with areas of preserved voltages and likely preserved conduction velocity referred to as a patchy pattern.…”

Correlation of Scar in Cardiac MRI and High‐Resolution Contact Mapping of Left Ventricle in a Chronic Infarct Model

“…Substrate mapping to identify the abnormal low‐voltage areas and the critical components of possible VT circuits (surviving myocardial bundles) is an effective strategy and often the only method available. Although several approaches have been utilized for substrate mapping,3, 4, 5, 6 one of the simplest and most direct is to record the isolated late potentials (ILPs) generated by the late activation of the isolated myocardial bundles during sinus rhythm5, 7, 8, 9 or ventricular pacing. This approach has two limitations.…”

Role of catheter ablation of ventricular tachycardia associated with structural heart disease

“…In "unmappable" VTs, the approach most frequently used is substrate mapping during sinus rhythm or right ventricular pacing combined with pace-mapping techniques [23][24][25] . This method aims at localizing the substrate for possible reentry circuits based on identification of areas of low voltage and slow conduction, assuming that the clinical "unmappable" arrhythmia is sustained by reentry.…”

“…Ventricular pacing is finalized to: (1) reproduce a QRS complex morphology identical or similar to the target VT; and (2) identify an area of slow conduction as assessed by a long interval between the pacing stimulus and the paced QRS complex. In the majority of cases, a slow conducting channel related to a VT can be identified in a discrete area, so that limited ablation can be performed to transect this channel [24] . An example of a non inducible VT ablated using this strategy is shown in Figures 3 and 4.…”