Aims: To evaluate efficacy and safety of ventricular tachycardia (VT) catheter ablation in patients with a structural heart disease (SHD) with and without an intramural septal substrate.

Methods: Consecutive patients with a SHD and a VT catheter ablation procedure performed in our clinic between January 2019 and October 2020 were included in this retrospective study. The type of structural heart disease, concomitant morbidity and other patient characteristics as well as presence of an endocardial or epicardial substrate detected by an electroanatomic mapping system and / or other imaging modalities (i.e. cardiac MRI and CT) and peri- and post-procedural complications and clinical outcome were recorded. A possible association of the presence of a relevant septal substrate in patients with ischemic and non-ischemic cardiomyopathy and freedom from VT recurrences were analyzed.

Results: In total 199 consecutive patients (64.2 ± 13.0 years; 89% male; 55% ICM) undergoing a VT catheter ablation using standard open-irrigated radiofrequency ablation catheters in conjunction with an electroanatomic mapping system were included in the study. In total, 129/199 patients (65%) showed a relevant septal substrate. 55/90 patients (61%) with NICM compared to 74/109 patients (68%) with ICM (p=0.37) demonstrated a relevant septal substrate detected by voltage mapping using a 3DEAM system or/and by cardiac MRI or CT. Epicardial access was obtained in 10/109 (9%) patients with ICM and in 34/90 (38%) patients with NICM (p<0.001). 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%) demonstrating a relevant septal substrate experienced recurrence of sustained VT or VF with or without ICD therapy during a mean FU of 8.1 ± 5.9 months (p=0.069).

Conclusion: Presence of an intramural septal substrate in patients with a structural heart disease is common. In our cohort the rate of patients with a septal substrate was numerically but not significantly higher in the group of patients with an ICM. Acute success of VT catheter ablation was significantly higher and mid-term success tended to be higher in patients without a septal substrate.