Septal Substrate Ablation Guided by Delayed Transmural Conduction Times: A Novel Ablation Approach to Target Intramural Substrates.

BACKGROUND: Intraprocedural identification of intramural septal substrate for ventricular tachycardia (ISS-VT) in nonischemic cardiomyopathy (NICM) is challenging. Delayed (>40 ms) transmural conduction time (DCT) with right ventricular basal septal pacing has been previously shown to identify ISS-VT. OBJECTIVES: This study sought to determine whether substrate catheter ablation incorporating areas of DCT may improve acute and long-term outcomes. METHODS: We included patients with NICM and ISS-VT referred for catheter ablation between 2016 and 2020. ISS-VT was defined by the following: 1) confluent septal areas of low unipolar voltage (<8.3 mV) in the presence of normal or minimal bipolar abnormalities; and 2) presence of abnormal electrograms in the septum. Substrate ablation was guided by the following: 1) activation and/or entrainment mapping for tolerated VT and pace mapping with ablation of abnormal septal electrograms for unmappable VTs (n = 57, Group 1); and 2) empirically extended to target areas of DCT during right ventricular basal septal pacing regardless of their participation in inducible VT(s) but sparing the conduction system when possible (n = 24, Group 2). RESULTS: There were no significant baseline differences between Groups 1 and 2. Noninducibility of any VT programmed stimulation at the end of ablation was higher in Group 2 compared with Group 1 (80% vs 53%; P = 0.03). At 12-month follow-up, single-procedure VT-free survival was significantly higher (79% vs 46%; P = 0.006) and the time to VT recurrence was longer (mean 10 ± 3 months vs 7 ± 4 months; P = 0.02) in Group 2 compared with Group 1. CONCLUSIONS: In patients with NICM and ISS-VT, a substrate ablation strategy that incorporates areas of DCT appears to improve freedom from recurrent VT.

Adverse Prognosis of Patients With Septal Substrate After VT Ablation Due to Electrical Storm.

BACKGROUND: Data about ventricular tachycardia (VT) ablation in patients with electrical storm (ES) is limited. OBJECTIVES: This study sought to compare the prognostic outcome of patients undergoing VT ablation after ES with and without a septal substrate. METHODS: In this large single-center study, consecutive patients presenting with ES and undergoing VT ablation from June 2018 to April 2021 were included. Patients with septal substrate were compared with patients without septal substrate regarding endpoints of cardiovascular mortality, VT recurrences, recurrences of the clinical VT, and rehospitalization rates. RESULTS: A total of 107 patients undergoing a first VT ablation because of electrical storm (ES) were included (age 65 ± 13 years, 86% male, 45% ischemic cardiomyopathy). Major complications occurred in 11% of all patients with increased postinterventional third-degree atrioventricular blocks among patients with septal substrate (9% vs 0%; P = 0.063). Partial ablation successes were similar (95% with a septal substrate vs 100% without a septal substrate; P = 0.251). Complete ablation success was achieved in 63% with a septal substrate and in 87% without a septal substrate (P = 0.004). After a median 22 months of follow-up, patients with septal substrate died significantly more often from cardiovascular causes (26% vs 7%; log-rank P = 0.018). In univariate analysis cardiovascular mortality for ES patients with septal substrate was 4.1-fold higher (HR: 4.192; CI: 1.194-14.719; P = 0.025). Independent predictors of adverse outcome in multivariable regression analysis were presence of septal substrate (HR: 5.723; P = 0.025) and increased age (HR: 1.104; P = 0.003). Recurrences of any ventricular arrhythmia (67% vs 56%; log rank P = 0.554) and rehospitalization rates (80% vs 66%; log rank P = 0.515) were similar between groups. Recurrences of clinical VT were similar (7% vs 2%; P = 0.252). CONCLUSIONS: Presence of a septal substrate is associated with adverse long-term cardiovascular mortality in patients admitted for VT ablation after ES. Despite decreased acute ablation successes in these patients, VT recurrence rates were similar to those without a septal substrate during follow-up.

Acute and long-term outcomes of VT radiofrequency catheter ablation in patients with versus without an intramural septal substrate.

INTRODUCTION: Aim of this study was to evaluate efficacy and safety of ventricular tachycardia (VT) catheter ablation in patients with structural heart disease (SHD) in relation to the presence of an intramural septal substrate. METHODS: Consecutive patients undergoing VT ablation between January 2019 and October 2020 were included. All patients were stratified based on the presence of relevant septal substrate and freedom from VT recurrences were analyzed. RESULTS: In total, 199 consecutive patients (64.2 ± 13.0 years; 89% male; 55% ischemic cardiomyopathy (ICM)) undergoing VT ablation were included. 129/199 patients (65%) showed significant septal substrate (55/90 patients (61%) with non-ischemic cardiomyopathy (NICM) compared to 74/109 patients (68%) with ICM; p = 0.37). Acute procedural success with elimination of all inducible VTs was achieved in 66/70 patients (94%) without and in 103/129 patients (80%) with a septal substrate (p = 0.007). In the cohort including patients with a clinical FU, 15/60 patients (25%) without a septal substrate and 48/123 patients (39%) with a septal substrate experienced VT recurrence during a FU of 8.1 ± 5.9 months (p = 0.069). CONCLUSION: Presence of septal VT substrate in patients with a structural heart disease or coronary artery disease is common. Acute success of VT catheter ablation was significantly higher and mid-term success tended to be higher in patients without a septal substrate.

Septal Coronary Venous Mapping to Guide Substrate Characterization and Ablation of Intramural Septal Ventricular Arrhythmia.

OBJECTIVES: This study describes the use of septal coronary venous mapping to facilitate substrate characterization and ablation of intramural septal ventricular arrhythmia (VA). BACKGROUND: Intramural septal VA represents a challenge for substrate definition and catheter ablation. METHODS: Between 2015 and 2018, 12 patients with structural heart disease, recurrent VA, and suspected intramural septal substrate underwent a septal coronary venous procedure in which mapping was performed by advancement of a wire into the septal perforator branches of the anterior interventricular vein. A total of 5 patients with idiopathic VA were also included as control subjects to compare substrate characteristics. RESULTS: Patients were 63 ± 14 years of age, and 11 (92%) were men. Most patients with structural heart disease had nonischemic cardiomyopathy (83%). Six patients underwent ablation for premature ventricular contractions (PVC) and 6 for ventricular tachycardia. All patients had larger septal unipolar voltage abnormalities than bipolar voltage abnormalities (mean area 35.3 ± 16.8 cm2 vs. 10.7 ± 8.4 cm2, respectively; p = 0.01), Patients with idiopathic VA had normal voltage. Septal coronary venous mapping revealed low-voltage, fractionated, and multicomponent electrograms in sinus rhythm in all patients with substrate compared to that in patients with idiopathic VA (amplitude 0.9 ± 0.9 mV vs. 4.4 ± 3.7 mV, respectively; p = 0.007; and duration 147 ± 48 ms vs. 92 ± 10 ms, respectively; p = 0.03). Ablation targeted early activation, pace map match, and/or good entrainment sites from intraseptal recording. Over a mean follow-up of 339 ± 240 days, the PVC and insertable cardioverter-defibrillator therapies burden were significantly reduced (from a mean of 22 ± 11% to 4 ± 8%; p = 0.005; and a mean 5 ± 2 to 1 ± 1; p = 0.001, respectively). Most patients (80%) with idiopathic VA remained arrhythmia free. CONCLUSIONS: In patients with suspected intramural septal VA, mapping of the septal coronary veins may be helpful to characterize the arrhythmia substrate, identify ablation targets, and guide endocardial ablation.

Outcomes of simultaneous unipolar radiofrequency catheter ablation for intramural septal ventricular tachycardia in nonischemic cardiomyopathy.

BACKGROUND: Radiofrequency (RF) ablation of intramural septal ventricular tachycardia (VT) in patients with nonischemic cardiomyopathy (NICM) is challenging. OBJECTIVE: The purpose of this study was to investigate the outcomes of simultaneous unipolar RF ablation for intramural septal VT in NICM. METHODS: We included patients with NICM and mid-myocardial septal substrate referred for VT ablation. After failed prolonged sequential unipolar RF lesions, simultaneous unipolar RF was delivered using 2 open-irrigated catheters at the site of earliest activation and/or best entrainment or pace mapping and at an anatomically adjacent/opposite site (up to 40 W for up to 3 minutes; RF energy independently titrated for each catheter to achieve an impedance drop of at least 15% from the baseline values). RESULTS: A total of 6 patients (mean age 62±13 years; mean left ventricular ejection fraction 38%±17%) were included. The clinical VTs were mapped at the anterior interventricular septum in 2 (33%) patients and at the inferior septum in 4 (67%). In all patients, prolonged sequential unipolar RF at the best activation/entrainment/pace-mapping site and at an anatomically opposite/adjacent site failed to eliminate VT. In 3 cases (50%), late VT termination with VT reinducibility was observed after sequential unipolar RF. Simultaneous unipolar ablation was then delivered, resulting in VT elimination and noninducibility in all patients. No procedural complications and no steam pops were observed. After a median follow-up of 20 months (range 13-20 months), 4 patients (67%) remained free of VT recurrence. CONCLUSION: In patients with NICM and intramural septal VT refractory to conventional RF ablation, simultaneous unipolar RF ablation is a safe and effective alternative ablation approach to improve long-term VT control.

Unique preferential conduction within the isolated septal substrate in a patient with ventricular tachycardia complicated with non-ischemic dilated cardiomyopathy.

We describe the case of a 67-year-old woman with non-ischemic dilated cardiomyopathy who underwent successful radiofrequency catheter ablation for ventricular tachycardia (VT) originated from the isolated ventricular septal substrate. Pacemapping exhibited either left, identical to clinical VT, or right bundle branch block like wide QRS morphology. Time interval from the stimulus to QRS onset (St-QRS) was prolonged at the center of the substrate, while St-QRS at the border was shortened. Difference in the morphology of pacemapping was dependent on whether or not the pacing stimulus could propagate directly into the right ventricle due to the possible intramural conduction disturbance.