“…The implementation of surface isochronal and CV mapping to guide critical VT isthmus localization as a substrate-based ventricular mapping technique is increasingly used. 21 Isochronal late activation mapping (ILAM) annotates the LAT to the latest activation and identifies regions of LAT isochronal crowding, also referred as ‘deceleration zones’. 1 , 22 It essentially is a surface LAT measurement of CV.…”
Aims
Electroanatomical maps using automated conduction velocity (CV) algorithms are now being calculated using two-dimensional (2D) mapping tools. We studied the accuracy of mapping surface 2D CV, compared to the three-dimensional (3D) vectors, and the influence of mapping resolution in non-scarred animal and human heart models.
Methods and results
Two models were used: a healthy porcine Langendorff model with transmural needle electrodes and a computer stimulation model of the ventricles built from an MRI-segmented, excised human heart. Local activation times (LATs) within the 3D volume of the mesh were used to calculate true 3D CVs (direction and velocity) for different pixel resolutions ranging between 500 μm and 4 mm (3D CVs). CV was also calculated for endocardial surface-only LATs (2D CV). In the experimental model, surface (2D) CV was faster on the epicardium (0.509 m/s) compared to the endocardium (0.262 m/s). In stimulation models, 2D CV significantly exceeded 3D CVs across all mapping resolutions and increased as resolution decreased. Three-dimensional and 2D left ventricle CV at 500 μm resolution increased from 429.2 ± 189.3 to 527.7 ± 253.8 mm/s (P < 0.01), respectively, with modest correlation (R = 0.64). Decreasing the resolution to 4 mm significantly increased 2D CV and weakened the correlation (R = 0.46). The majority of CV vectors were not parallel (<30°) to the mapping surface providing a potential mechanistic explanation for erroneous LAT-based CV over-estimation.
Conclusion
Ventricular CV is overestimated when using 2D LAT-based CV calculation of the mapping surface and significantly compounded by mapping resolution. Three-dimensional electric field-based approaches are needed in mapping true CV on mapping surfaces.
“…The implementation of surface isochronal and CV mapping to guide critical VT isthmus localization as a substrate-based ventricular mapping technique is increasingly used. 21 Isochronal late activation mapping (ILAM) annotates the LAT to the latest activation and identifies regions of LAT isochronal crowding, also referred as ‘deceleration zones’. 1 , 22 It essentially is a surface LAT measurement of CV.…”
Aims
Electroanatomical maps using automated conduction velocity (CV) algorithms are now being calculated using two-dimensional (2D) mapping tools. We studied the accuracy of mapping surface 2D CV, compared to the three-dimensional (3D) vectors, and the influence of mapping resolution in non-scarred animal and human heart models.
Methods and results
Two models were used: a healthy porcine Langendorff model with transmural needle electrodes and a computer stimulation model of the ventricles built from an MRI-segmented, excised human heart. Local activation times (LATs) within the 3D volume of the mesh were used to calculate true 3D CVs (direction and velocity) for different pixel resolutions ranging between 500 μm and 4 mm (3D CVs). CV was also calculated for endocardial surface-only LATs (2D CV). In the experimental model, surface (2D) CV was faster on the epicardium (0.509 m/s) compared to the endocardium (0.262 m/s). In stimulation models, 2D CV significantly exceeded 3D CVs across all mapping resolutions and increased as resolution decreased. Three-dimensional and 2D left ventricle CV at 500 μm resolution increased from 429.2 ± 189.3 to 527.7 ± 253.8 mm/s (P < 0.01), respectively, with modest correlation (R = 0.64). Decreasing the resolution to 4 mm significantly increased 2D CV and weakened the correlation (R = 0.46). The majority of CV vectors were not parallel (<30°) to the mapping surface providing a potential mechanistic explanation for erroneous LAT-based CV over-estimation.
Conclusion
Ventricular CV is overestimated when using 2D LAT-based CV calculation of the mapping surface and significantly compounded by mapping resolution. Three-dimensional electric field-based approaches are needed in mapping true CV on mapping surfaces.
“…Although sites with LPs during substrate mapping often participate in re-entrant circuits, many sites of re-entry do not demonstrate LPs [ 34 ]. Whilst LPs may provide a reasonable target for ablation, their overall sensitivity (16–30%) and positive predictive value (30–36%) is limited [ 21 , 35 ]. This may lead to suboptimal targeting of ablation and important physiological substrate being missed.…”
“…This may lead to suboptimal targeting of ablation and important physiological substrate being missed. Additionally, the specificity of LPs may only be moderate (68–90%), leading to unnecessary ablation of passive areas and prolonged procedural times [ 21 , 35 ]. Fig.…”
“…One proposed strength of the LAVA-guided method is that it also provides targets in areas of normal voltage that may otherwise be missed, although it has been shown that most LAVAs are observed within areas of low voltage [ 38 ]. Subsequent studies have confirmed a high specificity (86% & 89%) for LAVAs predicting critical sites for VT re-entry, although reported a low sensitivity (32 & 19%) and positive predictive value (PPV; 14% and 19%) [ 21 , 35 ]. Whilst LAVA offer an attractive ablation target, their lack of PPV means they should not be the sole focus of a substrate-based ablation approach ( Fig.…”
“…Several studies have also used signal frequency analysis to aid identification of critical VT substrate sites with reasonable success rates, although the feasibility of performing this in real-time has yet to be investigated [ 87 , 88 ]. Finally, conduction velocity mapping has shown that slow conduction is a highly sensitive predictor of critical sites, although current automated conduction velocity mapping algorithms are not optimised for substrate mapping [ 89 ].…”
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