Intramyocardial mapping of ventricular premature depolarizations via septal venous perforators: Differentiating the superior intraseptal region from left ventricular summit origins

Background: The intramyocardial aspect of the left ventricular summit (LVS) can be mapped by advancing a unipolar guidewire into septal perforator branches of the anterior interventricular vein. Objective: The purpose of this study was to differentiate between ventricular premature depolarizations (VPDs) with a basal superior intraseptal (SIS) site of origin and those originating from the epicardial LVS using septal intramyocardial mapping. Methods: A retrospective cohort of patients with suspected LVS VPDs who underwent SIS unipolar mapping were reviewed for their clinical characteristics, mapping findings, and procedural outcomes. Results: SIS mapping was successful in 44 of 47 cases (93.6%). VPD origin was SIS (defined as earliest activation from the intraseptal wire) in 20 patients (45.5%; median 23 ms pre-QRS). Procedure success was similar in patients with (group 1) and without (group 2) SIS origin (84% vs 87.5%, respectively; P = .842). Of the 10 patients in group 1 without presystolic endocardial activation, 5 (11.3% of all 44 cases) were successfully ablated from the left ventricular endocardium by using an anatomical approach targeting the endocardium closest to the earliest intraseptal activation site. Conclusion: A significant proportion (45.5%) of VPDs that appear to arise from the left ventricular summit can be demonstrated to have a SIS origin using septal perforator venous mapping. A significant minority (11.3%) of these can be ablated from the endocardium by targeting from an anatomic vantage point closest to the earliest intraseptal activation site. The described strategy may help differentiate true LVS VPDs from those with SIS sites of origin.