LP abolition is an effective endpoint of VT ablation and its prognostic value compares favorably to that achieved by programmed electrical stimulation.

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Background-The aim was to relate distinct scar distributions found in nonischemic cardiomyopathy with ventricular tachycardia (VT) morphology, late potential distribution, ablation strategy, and outcome. Methods and Results-Eighty-seven patients underwent catheter ablation for drug-refractory VT. Based on endocardial unipolar voltage, 44 were classified as predominantly anteroseptal and 43 as inferolateral. Anteroseptal patients more frequently fulfilled diagnostic criteria for dilated cardiomyopathy (64% versus 36%), associated with more extensive endocardial unipolar scar (41 [22-83] versus 9 [1-29] cm 2 ; P<0.001). Left inferior VT axis was predictive of anteroseptal scar (positive predictive value, 100%) and right superior axis for inferolateral (positive predictive value, 89%). Late potentials were infrequent in the anteroseptal group (11% versus 74%; P<0.001). Epicardial late potentials were common in the inferolateral group (81% versus 4%; P<0.001) and correlated with VT termination sites (κ=0.667; P=0.014), whereas no anteroseptal patient had an epicardial VT termination (P<0.001). VT recurred in 44 patients (51%) during a median follow-up of 1.5 years. Anteroseptal scar was associated with higher VT recurrence (74% versus 25%; log-rank P<0.001) and redo procedure rates (59% versus 7%; log-rank P<0.001). After multivariable analysis, clinical predictors of VT recurrence were electrical storm (hazard ratio, 3.211; P=0.001) and New York Heart Association class (hazard ratio, 1.608; P=0.018); the only procedural predictor of VT recurrence was anteroseptal scar pattern (hazard ratio, 5.547; P<0.001). Conclusions-Unipolar low-voltage distribution in nonischemic cardiomyopathy allows categorization of scar pattern as inferolateral, often requiring epicardial ablation mainly based on late potentials, and anteroseptal, which frequently involves an intramural septal substrate, leading to a higher VT recurrence. (Circ Arrhythm Electrophysiol. 2014;7:414-423.)

Background-We investigated the impact of catheter ablation on ventricular tachycardia (VT) recurrence and survival in a large number of patients with structural heart disease treated in the setting of a dedicated multiskilled unit. Methods and Results-Since January 2007, we have implemented a multidisciplinary model, aiming for a comprehensive management of VT patients. Programmed ventricular stimulation was used to assess acute outcome. Primary end points were VT recurrence and the occurrence of cardiac and sudden cardiac death. Overall, 528 patients were treated by ablation (634 procedures; 1-4 procedures per patient). Among 482 tested with programmed ventricular stimulation after the last procedure, a class A result (noninducibility of any VT) was obtained in 371 patients (77%), class B (inducibility of nondocumented VT) in 12.4%, and class C (inducibility of index VT) in 10.6%. After a median follow-up time of 26 months, VT recurred in 164 (34.1%) of 472 patients. VT recurrence was documented in 28.6% of patients with a class A result versus 39.6% of patients with class B and 66.7% with class C result (log-rank P<0.001). The incidence of cardiac mortality was lower in class A patients than in those with class B and class C (8.4% versus 18.5% versus 22%, respectively; log-rank P=0.002). On the basis of multivariate analysis, postprocedural inducibility of index VT was independently associated both with VT recurrence (hazard ratio, 4.030; P<0.001) and with cardiac mortality (hazard ratio, 2.099; P=0.04). Conclusions-Within a dedicated VT unit, catheter ablation prevents long-term VT recurrences, which may favorably affect survival in a large number of patients who have VT.

Background Ventricular tachycardia with structural heart disease is dependent on re-entry within scar regions. We set out to assess the VT circuit in greater detail than has hitherto been possible, using ultra highdensity mapping. Methods All ultra high-density mapping guided ventricular tachycardia ablation cases from six high-volume European centres were assessed. Maps were analysed offline to generate activation maps of tachycardia circuits. Topography, conduction velocity and voltage of the VT circuit were analyzed in complete maps. Results Thirty-six tachycardias in 31 patients were identified, 29 male and 27 ischaemic. VT circuits and isthmuses were complex, eleven were single-loop and 25 double-loop; three had two entrances, five had two exits and 15 had dead ends of activation. Isthmuses were defined by barriers which included anatomical obstacles, lines of complete block and slow conduction (in 27/36 isthmuses). Median conduction velocity was 0.08m/s in entrance zones, 0.29m/s in isthmus regions (p<0.001), and 0.11m/s in exit regions (p=0.002). Median local voltage in the isthmus was 0.12mV during tachycardia and 0.06mV in paced/sinus rhythm. Two circuits were identifiable in five patients. The median timing of activation was 16% of diastole in entrances, 47% in the mid isthmus, and 77% in exits. Conclusions VT circuits identified were complex, some of them having multiple entrances, exits and dead ends. The barriers to conduction in the isthmus appear to be partly functional in 75% of circuits. 3 Conduction velocity in the VT isthmus slowed at isthmus entrances and exits, when compared with the mid isthmus. Isthmus voltage is often higher in VT than in sinus or paced rhythms.