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Quantitative comparison of spontaneous and paced 12-lead electrocardiogram during right ventricular outflow tract ventricular tachycardia

^a Division of Cardiology, Department of Internal Medicine, University of Pennsylvania Health System, Philadelphia, Pennsylvania, USA

View larger version (42K): [in a new window]   Figure 1 Electroanatomic map of the right ventricular outflow tract as viewed in the coronal projection. Superior septal (1 = posterior, 2 = mid, 3 = anterior) and opposing free wall pace-map sites are shown by the light green tags, and the successful ablation site is shown by the red tag. Also noted is the His bundle area (His) and tricuspid valve (TV). The right ventricular apical pacing site was located fluoroscopically and not tagged in this map.

View larger version (11K): [in a new window]   Figure 2 The normalized mean absolute deviation (MAD) takes the sum of the difference between two mean subtracted waveforms and divides by the sum of the area under the curve of the two waveforms. The correlation coefficient () is calculated in the standard fashion (see text for formulas). For two completely opposite waveforms (top right panel), the MAD score therefore = 1 and the = –1. For two identical waveforms (middle right panel) the MAD score = 0 and = 1. The MAD score tends to be more sensitive to this amplitude difference between waveforms of similar morphology than the (bottom right panel). Two waveforms of similar morphology with one containing one-third the area of the other have a of 1 but a MAD of only 0.5.

View larger version (40K): [in a new window]   Figure 3 The left panel shows an example of right ventricular outflow tract (RVOT) ventricular tachycardia (VT) in a patient with sustained VT. The second VT complex has been identified as the target waveform by the annotation markers placed on either side of this complex. The middle panel shows a pace-map from free wall site 1 (FW1) next to the superimposed VT and pace-map waveforms after automatic computer alignment. There are substantial differences between these two waveforms (highlighted in gray), resulting in a mean absolute deviation (MAD) score of 31.5%. The right panel shows a pace-map from the successful ablation site (Abl S) near the posterior septum and the superimposed pace-map and VT waveform. Note in the Abl S panel that when these two waveforms are aligned they are nearly superimposable, and result in a very low MAD score of 5.3%. Correlation coefficients for these comparisons are also shown.

View larger version (28K): [in a new window]   Figure 4 (A) The mean absolute deviation (MAD) scores for the 14 patients with septal ventricular tachycardia (VT) origin comparing the clinical VT to pacing from posterior septal site 1 (S1), mid septal site 2 (S2), anterior septal site 3 (S3), free wall site 1 (F1), free wall site 2 (F2), free wall site 3 (F3), the right ventricular apex (RVA), unsuccessful ablation sites (Abl F), successful ablation sites (Abl S), and comparing the chosen VT beat to other similar morphology VT beats (VT). Note that the average MAD scores are significantly lower for septal compared with free wall sites. The average MAD score was also significantly lower for successful compared with unsuccessful ablation sites, and all successful ablation sites had a MAD score <15%. *p = 0.01. (B) The mean ± SD correlation coefficient () scores for the same comparison as in the previous graph. The overall pattern is similar to the previous graph, although there is less spread among the sites. The average correlation for successful ablation sites was not significantly lower than that of unsuccessful ablation sites.

View larger version (39K): [in a new window]   Figure 5 Examples of ventricular tachycardia (VT) morphology (first panel, blue tracing) and pace-maps (red tracing) from the three septal and free wall sites, an unsuccessful ablation site, and a successful ablation site after computer alignment with corresponding mean absolute deviation (MAD) scores below. Note the smaller amplitude in the inferior leads and later precordial transition for free wall compared with septal sites. The unsuccessful ablation site has a reasonable 12-lead "match" and a low MAD score, but not as low as the successful ablation site.

View larger version (14K): [in a new window]   Figure 6 The graph shows the relationship between the mean absolute deviation (MAD) score and the distance of the pace-map from the successful ablation site measured using electroanatomic mapping. The further away the pacing site from the ventricular tachycardia site of origin, the higher (worse) the MAD score, as one would expect (r = 0.63; p < 0.001).