Background: Venous ethanol ablation (VEA) can be effective for ventricular arrhythmias (VA) from the LV summit (LVS). However, there are concerns about excessive ablation by VEA.Objective: To delineate and quantify the location, extent, and evolution of ablated tissue after VEA as an intramural ablation technique in the LVS.Methods: VEA was performed in 59 patients with LVS VA. Targeted intramural veins were selected by electrograms from a 2F octapolar catheter or by guide-wire unipolar signals. Median ethanol delivered was 4 [IQR 4-7] mL. Ablated areas were estimated intraprocedurally as increased echogenicity on intracardiac echocardiography (ICE) and incorporated into 3D maps. In 44 patients, late-gadolinium enhancement cardiac magnetic resonance (CMR) imaged VEA scar and its evolution.Results: ICE-demonstrated increased intramural echogenicity (median volume of 2 cc; IQR 1.7-4.3) at the targeted region of the 3D maps. Post ethanol CMR showed intramural scar of 2.6 [IQR 2.1-3.5] cc. Early (within 48 hours after VEA) CMR showed microvascular obstruction (MVO) in 30/31 patients. Follow up CMR after a median of 51 [IQR 41-170] days showed evolution of MVO to scar. ICE-echogenicity and CMR scar volumes correlated with each other and with ethanol volume. Ventricular function and interventricular septum remained intact. Conclusion: VEA leads to intramural ablation that can be tracked intraprocedurally by ICE and creates regions of MVO that are chronically replaced by myocardial scar. VEA scar volume does not compromise septal integrity or ventricular function.