Background The majority of life-threatening ventricular tachycardias (VTs) are sustained by heterogeneous scar substrates with narrow strands of surviving tissue. An effective treatment for scar-related VT is to modify the underlying scar substrate by catheter ablation. If activation sequence and entrainment mapping can be performed during sustained VT, the exit and isthmus of the circuit can often be identified. However, with invasive catheter mapping, only monomorphic VT that is hemodynamically stable can be mapped in this manner. For the majority of patients with poorly tolerated VTs or multiple VTs, a close inspection of the reentry circuit is not possible. A noninvasive approach to fast mapping of unstable VTs can potentially allow an improved identification of critical ablation sites. Methods For patients who underwent catheter ablation of scar-related VT, CT scan was obtained prior to the ablation procedure and 120-lead body-surface electrocardiograms (ECGs) were acquired during induced VTs. These data were used for noninvasive ECG imaging to computationally reconstruct electrical potentials on the epicardium and on the endocardium of both ventricles. Activation time and phase maps of the VT circuit were extracted from the reconstructed electrograms. They were analyzed with respect to scar substrate obtained from catheter mapping, as well as VT exits confirmed through ablation sites that successfully terminated the VT. Results The reconstructed reentry circuits correctly revealed both epicardial and endocardial origins of activation, consistent with locations of exit sites confirmed from the ablation procedure. The temporal dynamics of the reentry circuits, particularly the slowing of conduction as indicated by the crowding and zig-zag conducting of the activation isochrones, collocated well with scar substrate obtained by catheter voltage maps. Furthermore, the results indicated that some reentry circuits involve both the epicardial and endocardial layers, and can only be properly interpreted by mapping both layers simultaneously. Conclusions This study investigated the potential of ECG-imaging for beat-to-beat mapping of unstable reentrant circuits. It shows that simultaneous epicardial and endocardial mapping may improve the delineation of the 3D spatial construct of a reentry circuit and its exit. It also shows that the use of phase mapping can reveal regions of slow conduction that collocate well with suspected heterogeneous regions within and around the scar.

Background-The majority of life-threatening ventricular tachycardias (VTs) are sustained by heterogeneous scar substrates with narrow strands of surviving tissue. An effective treatment for scar-related VT is to modify the underlying scar substrate by catheter ablation. If activation sequence and entrainment mapping can be performed during sustained VT, the exit and isthmus of the circuit can often be identified. However, with invasive catheter mapping, only monomorphic VT that is hemodynamically stable can be mapped in this manner. For the majority of patients with poorly tolerated VTs or multiple VTs, a close inspection of the reentry circuit is not possible. A noninvasive approach to fast mapping of unstable VTs can potentially allow an improved identification of critical ablation sites.

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Sustained ventricular tachycardia (VT) often involves a reentry circuit formed by narrow channels of surviving tissue within the scar. Catheter ablation is an effective technique to intercept the circuit by targeting these critical channels. The success of VT ablation relies on our ability to assess the mechanism of the VT circuit and identify the location of the ablation targets. This study aims to analyze the VT substrate using high-resolution anatomical and electrical imaging techniques including contact EGM mapping, contrast-enhanced cardiac magnetic resonance (CMR) imaging, and noninvasive electrocardiographic (ECG) imaging. The results indicate that joint electro-anatomical analysis could reveal critical isthmus of the VT circuit. In addition, ECG-imaging was able to identify sites of a scar and signal fractionation visually consistent with the other two modalities, and the reconstructed VT circuit revealed an exit around the critical site identified by combined CMR-EGM data.

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Background-The majority of life-threatening ventricular tachycardias (VTs) are sustained by heterogeneous scar substrates with narrow strands of surviving tissue. An effective treatment for scar-related VT is to modify the underlying scar substrate by catheter ablation. If activation sequence and entrainment mapping can be performed during sustained VT, the exit and isthmus of the circuit can often be identified. However, with invasive catheter mapping, only monomorphic VT that is hemodynamically stable can be mapped in this manner. For the majority of patients with poorly tolerated VTs or multiple VTs, a close inspection of the reentry circuit is not possible. A noninvasive approach to fast mapping of unstable VTs can potentially allow an improved identification of critical ablation sites.

A common setting for scar-related ventricular tachycardia is a reentry circuit formed by narrow channels of surviving tissue inside the myocardial scar. It is challenging to identify the critical components of these circuits using invasive catheter mapping due to its inability to map the vast majority of unstable VTs. While electrocardiographic imaging (ECGi) provides a promising noninvasive solution for rapid mapping of unstable VTs, its validation in the setting of scar-related VT remains challeging. In this paper, we report our initial results in the effort to integrate ECGi results with late gadolinium enhanced cardiac magnetic resonance imaging (LGE-cMR) of scar. We report quantitative association between ECGi features and CMR scar data, as well as qualitative relation between ECGireconstructed VT circuits and myocardial scar and critical channels identified from LGE-CMR data.

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