Mapping Strategy Associated with QRS Morphology for Catheter Ablation in Patients with Idiopathic Ventricular Outflow Tract Tachyarrhythmia

BACKGROUND: In catheter ablation of idiopathic ventricular arrhythmia (VA), it is still unclear whether pace mapping or activation mapping is more useful for successful catheter ablation. The depth of origin in the ventricular wall especially affects the success rate of endocardial-approached catheter ablation. Thus, we examined the relationship between these tactics and QRS morphology. METHODS: We evaluated the relationship among pace mapping score, activation time, and peak deflection index (PDI) in 28 patients, with a total of 30 origins, who underwent successful catheter ablation of idiopathic VA. RESULTS: All origins were located in the ventricular outflow tract area, including three in the left coronary cusp (LCC). PDI, activation time, and pace mapping score at successful ablation sites were 0.60 ± 0.08, 26.3 ± 9.9 ms, and 19.1 ± 4.6, respectively. The pace mapping score inversely correlated with the PDI (R = -0.540, P = 0.0017), but the activation time did not correlate with the PDI. When excluding the three VAs originating from the LCC, in which perfect pace mapping was obtained from epicardial sites despite high PDI, this correlation coefficient became more intensive (R = -0.734, P < 0.0001). CONCLUSIONS: Our study suggests that pace mapping with an endocardial approach could not reproduce the precise QRS morphology for VA originating from the intramural site of the ventricular wall. With such origins, we should rely on activation mapping to detect the optimal ablation site.