Transmural Activation Mapping of Ventricular Arrhythmias With High–Frame Rate Echocardiography and Validation Against Contact Mapping

BACKGROUND: The restriction of activation mapping to the ventricular surface of contemporary mapping systems often leads to failure to correctly identify the true sites of origin (SoOs) of intramural and/or subepicardial ventricular arrhythmias (VAs), reducing procedural success. OBJECTIVES: The aim of this study was to evaluate if noninvasive electromechanical wave imaging (EWI) can locate the SoOs of VAs along the endo-epicardial axis in patients with and without structural heart disease. METHODS: Patients with VAs requiring ablation underwent preprocedural transthoracic EWI to identify the SoOs and validate using contact mapping. Local electromechanical activation was defined as time point of the downward zero crossing on the incremental axial strain curve. The site of earliest activation on contact mapping and/or successful ablation was employed as ground truth for VA SoO. RESULTS: Twenty-eight patients underwent EWI, and 25 proceeded to contact mapping (56% men, mean age 53 ± 16 years, mean left ventricular ejection fraction 47% ± 28%, 52% with late gadolinium enhancement (LGE) on magnetic resonance imaging). Five patients were excluded (insufficient or different ventricular tachycardia or ventricular ectopic activity at the time of EWI vs contact mapping). EWI mapping correctly localized the VA SoOs in 17 of 20 (85%) of the cases and mapped them to the adjacent segments in the remaining ones. In the presence of scar, EWI localized 81.8% of the VA SoOs (n = 9 of 11) correctly compared with 88.9% (n = 8 of 9) in patients without (P = NS). The transmural SoOs (endocardial, midmyocardial, or epicardial) were successfully identified in 18 of 20 cases (90%; P = NS for LGE-positive vs LGE-negative patients). CONCLUSIONS: EWI correctly identified the transmural SoOs of focal VAs, including in the presence of scar, in the majority of cases using contact mapping as the gold standard and thus could support preprocedural planning, including requirement for epicardial access and/or ablation techniques. The absence of a true gold standard for clinical transmural mapping remains an important challenge for the validation of novel mapping technologies.