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.

Background—: Successful late potential (LP) abolition and postprocedural ventricular tachycardia (VT) noninducibility constitute significant end points after catheter ablation for VT. We investigated the prognostic impact of a combined procedural end point of VT noninducibility and LP abolition in a large series of post–myocardial infarction patients with VT. Methods and Results—: A total of 160 (154 men, 94% with implantable cardioverter defibrillators) consecutive post–myocardial infarction patients undergoing first-time ablation procedures from 2010 to 2012 were included. Of the 159 patients surviving the procedure, 137 (86%) were either inducible or in VT at baseline and 103 (65%) had baseline LP presence, of which 79 (77%) underwent successful LP abolition. The combined end point was assessable in 155 (97%) patients. There were 50 (32%) patients with VT recurrences and 17 (11%) cardiac deaths during follow-up. Patients who fulfilled the combined end point of VT noninducibility and LP abolition compared with inducible patients exhibited a significantly lower incidence of VT recurrence (16.4% versus 47.4%; log-rank P <0.001) and cardiac death (4.1% versus 42.1%; log-rank P <0.001). Among noninducible patients, those with additional LP abolition also had a lower incidence of VT recurrence (16.4% versus 46.0%; log-rank P <0.001). After multivariate analysis, the combined end point of VT noninducibility and LP abolition (hazard ratio, 0.205, P <0.001) was independently associated with VT recurrence and cardiac death (hazard ratio, 0.106; P =0.001). Conclusions—: Achieving a combined catheter ablation procedural end point of VT noninducibility and LP abolition reduces VT recurrence rates to low levels (16%). The overall strategy was associated with a significant impact on cardiac survival.

Background—: We report the experience in a cohort of consecutive patients receiving extracorporeal membrane oxygenation during catheter ablation of unstable ventricular tachycardia (VT) at our center. Methods and Results—: From 2010 to 2015, extracorporeal membrane oxygenation was initiated in 64 patients (average age: 63±15 years; left ventricular ejection fraction in 27±9%; cardiogenic shock in 23%, and electrical storm in 62% of patients) undergoing 74 unstable VT catheter ablation procedures. At least one VT was terminated in 81% of procedures with baseline inducible VT, and VT noninducibility was achieved in 69%. Acute heart failure occurred in 5 patients: 3 underwent emergency heart transplantation, 1 had left ventricular assist device (LVAD) implantation, and 1 patient eventually died because of subsequent mesenteric ischemia. All other patients were discharged alive. After a median follow-up of 21 months (13–28 months), VT recurrence was 33%; overall survival was 56 out of 64 patients (88%). Extracorporeal membrane oxygenation–supported ablation was the bridge to LVAD in 6.9% and to heart transplantation in 3.5% of patients. VT recurrence was related to ablation success (after 180 days of follow up: 19% when VT was noninducible, 42% if nonclinical VT was inducible, 75% when clinical VT was inducible, and 75% in untested patients, P <0.001). Incidence of all-cause death, heart transplantation, and LVAD was independently related to ablation outcome (at 180 days of follow-up: 9% when noninducibility was achieved, 50% in case of inducible VT, and 75% in untested patients, P <0.001). At multivariable analyses, noninducibility (hazard ratio 0.198; P =0.001) and left ventricular ejection fraction (hazard ratio 0.916; P =0.008) correlated with all-cause death, LVAD, and heart transplantation. Conclusions—: Ablation of unstable VTs can be safely supported by extracorporeal membrane oxygenation, which allows rhythm stabilization with low procedure mortality, bridging decompensated patients to permanent LVAD or heart transplantation. Successful ablation is associated with better outcomes than unsuccessful ablation.

We present clinical, electroanatomical mapping (EAM), imaging, and catheter ablation (CA) strategies in patients with myocarditis-related ventricular tachycardia (VT). Between January 2010 and July 2012, 26 consecutive patients underwent imaging-guided CA of myocarditis-related ventricular arrhythmias, 23 of 26 using a combined endo–epicardial approach. Segment per segment correspondence of late enhanced (LE) scar localization with EAM scar was assessed in all patients with available uni/bipolar maps (n = 19). Induced VTs were targeted prior to substrate modification. Late potentials (LPs) abolition constituted a procedural endpoint independently from VT inducibility. Clinical monomorphic VT was induced in 15 of 26 patients (57.7%) and was associated with epicardial LPs in 10 of 15, completely abolished in 7 of 10 patients. Of the 10 patients rendered non-inducible VTs were ablated epicardially in 7. Late potentials were also detected in 7 of 11 initially non-inducible patients and completely abolished in 4. After a median follow-up of 23 (15–31) months, 20 of 26 patients (76.9%) remained free from VT recurrence. Bipolar mapping revealed low-voltage scar (<1.5 mV) in 1 patient endocardially and in 14 of 19 epicardially. Unipolar mapping revealed low-voltage scar (<8 mV) in 12 of 19 patients endocardially and in 18 of 19 epicardially. Correspondence of LE scar localization with endocardial bipolar scar was 1%, with endocardial unipolar scar 23.7%, with epicardial bipolar scar 39.8%, and with epicardial unipolar scar 66.2%. Pre-procedural scar imaging and EAM findings support the necessity of an epicardial approach in patients with prior myocarditis. Epicardial unipolar mapping (<8 mV) is superior in scar identification and CA based on substrate modification is safe and effective in this setting.

Aims In persistent atrial fibrillation (PsAF), success rates for pulmonary vein isolation (PVI) alone are limited and additional substrate modification is often performed. The two most widely used substrate-based strategies are the ablation of complex fractionated atrial electrograms (CFAE) and left atrial linear ablation (LALA) at the roof and mitral isthmus. However, it is unclear whether adjunctive CFAE ablation or LALA add significant benefit to PVI alone. We performed a meta-analysis to better gauge the benefit of adjunctive CFAE ablation and LALA in PsAF. Methods and results Electronic databases were systematically searched. We included studies that examined the impact of CFAE ablation or LALA in addition to a PVI-based strategy on clinical outcomes in PsAF. We included both randomized and non-randomized studies. Totally 10 studies (n = 1821) were included: 6 evaluating CFAE ablation, 3 LALA, and 1 both approaches. In comparison with PVI alone, the addition of CFAE ablation [RR 0.86; 95% confidence intervals (CI) 0.64, 1.16; P = 0.32] or LALA (RR 0.64; 95% CI 0.37, 1.09; P = 0.10) offered no significant improvement in arrhythmia-free survival. However, adjunctive CFAE ablation was associated with significant increases (P < 0.05) and LALA non-significant increases in procedure and fluoroscopy times. Conclusion In PsAF, the addition of CFAE ablation or LALA, in comparison with PVI alone, offers no significant improvement in arrhythmia-free survival. Furthermore, they are associated with increases in both procedural and fluoroscopy times. The optimal ablation strategy for PsAF is currently unclear and needs further refinement.

Background—: The mechanism of cardiac resynchronization therapy (CRT)–induced proarrhythmia remains unknown. We postulated that pacing from a left ventricular (LV) lead positioned on epicardial scar can facilitate re-entrant ventricular tachycardia. The aim of this study was to investigate the relationship between CRT-induced proarrhythmia and LV lead location within scar. Methods and Results—: Twenty-eight epicardial and 63 endocardial maps, obtained from 64 CRT patients undergoing ventricular tachycardia ablation, were analyzed. A positive LV lead/scar relationship, defined as a lead tip positioned on scar/border zone, was determined by overlaying fluoroscopic projections with LV electroanatomical maps. CRT-induced proarrhythmia occurred in 8 patients (12.5%). They all presented early with electrical storm (100% versus 39% of patients with no proarrhythmia; P <0.01), requiring temporary biventricular pacing discontinuation in half of cases. They more frequently presented with heart failure/cardiogenic shock (50% versus 7%; P <0.01), requiring intensive care management. Ventricular tachycardia was re-entrant in all. The LV lead location within epicardial scar was significantly more frequent in the proarrhythmia group (60% versus 9% P =0.03 on epicardial bipolar scar, 80% versus 17% P =0.02 on epicardial unipolar scar, and 80% versus 17% P =0.02 on any-epicardial scar). Ablation was performed within epicardial scar, close to the LV lead, and allowed CRT reactivation in all patients. Conclusions—: CRT-induced proarrhythmia presented early with electrical storm and was associated with an LV lead positioning within epicardial scar. Catheter ablation allowed for resumption of biventricular stimulation in all patients.