ObjectiveEndovascular repair of aortic dissections may be complicated by inadequate sealing zones, persistent false lumen (FL) perfusion, and limited space for catheter manipulation and target artery incorporation. The aim of this study was to describe the indications, technical success, and early outcomes of transcatheter electrosurgical septotomy (TES) during endovascular repair of aortic dissections. MethodsWe reviewed the clinical data of consecutive patients treated by endovascular repair of aortic dissections with adjunctive TES in two centers between 2021-2023. Endpoints were technical success, defined by successful septotomy without dislodgment of the lamella or target artery occlusion, and 30-day rates of major adverse events (MAEs). ResultsAmong 197 patients treated by endovascular repair for aortic dissections, 36 (18%) patients (median age, 61.5 years (IQR 55-72.5); 83% males) underwent adjunctive TES for acute (n = 3, 8%), subacute (n = 1, 3%), or chronic post-dissection aneurysms (n = 32, 89%). Indications for TES were severe true lumen (TL) compression (≤ 16mm) in 28 patients (78%), target vessel origin from FL in 19 (53%), creation of suitable landing zone in 12 (33%), and organ/limb malperfusion in four (11%). Endovascular repair included fenestrated-branched endovascular aortic repair (FB-EVAR) in 18 patients (50%), thoracic EVAR (TEVAR)/ EVAR/PETTICOAT in 11 (31%), and arch branch repair in 7 (19%). All patients had dissections extending through Zones 5 to 7, and 28 patients (78%) underwent TES across the renal-mesenteric segment. Technical success of TES was 92% (33/36) for all patients and 97% (32/33) among those with subacute or chronic post-dissection aneurysms. There were three technical failures, including two patients with acute dissections with inadvertent SMA dissection in one patient and distal dislodgement of the dissection lamella in two patients. There were no arterial disruptions. Mean post-septotomy aortic lumen increased from 13.2±4.8mm to 28.4±6.8mm (P<.001). All 18 patients treated by FB-EVAR had successful incorporation of 78 target arteries. There was one (3%) early death from stroke, and three (8%) patients had MAEs. After a median follow-up of 8 months (IQR, 4.5-13.5 months), 13 (36%) patients had secondary interventions, and two (6%) died from non-aortic-related events. There were no other complications associated with TES. ConclusionTES is an adjunctive technique that may optimize sealing zones and luminal aortic diameter during endovascular repair of subacute and chronic post-dissection. Although no arterial disruptions or target vessel loss occurred, but patients with acute dissections are prone to technical failures related to dislodgement of the lamella.