Abstract Body (Do not enter title and authors here):
Background: The left ventricular epicardium is a common site of origin (SOO) among patients with idiopathic premature ventricular complexes (PVCs) undergoing catheter ablation procedures. Less is known about epicardial PVC ablation among patients with structural heart disease and cardiac scar.

Objective: To report on the presence and impact of cardiac scar among patients with epicardial PVCs undergoing ablation procedures.

Methods: In a retrospective analysis, patients with epicardial PVCs and delayed enhancement cardiac magnetic resonance imaging were included. Acute and long-term procedural outcomes were examined and stratified by the presence or absence of cardiac scar.

Results: Twenty-nine patients were included (male 17/29(59%), age 55±14years, ejection fraction 48±12%, PVC burden 25±12%, ischemic cardiomyopathy (CM) n=3, non-ischemic CM n=7, PVC induced CM n=5). The SOO was left ventricular summit (n=20), great cardiac vein (n=2), cardiac crux (n=4), or basal anterolateral epicardium (n=3). Ablation within the CVS was limited by proximity to the coronary arteries (n=16), inaccessibility of ablation catheter (n=5), or elevated baseline impedance (n=2). LGE-CMR scar was present at the arrhythmia SOO in 14/29(48%) patients. LGE-CMR was detected in 4/15 (27%) patients with normal ejection fraction and no previously known structural heart disease. There were no differences in procedural, radiofrequency, or fluoroscopy times between patients with and without scar (p>0.05). Ablation was successful in 20/29(69%) patients, the post-ablation PVC burden was 8±6% with no differences among those with or without cardiac scar (P>0.05).

Conclusion: Epicardial PVCs may be encountered in patients with and without structural heart disease, with LGE-CMR located at the PVC SOO in 48% of patients. Routine LGE-CMR detected cardiac scar in 27% of patients with epicardial PVCs and no previously known structural heart disease. Ablation is frequently limited by the proximity of the coronary arteries to the PVC SOO and challenges navigating within the CVS. Mapping and ablation in multiple cardiac chambers is often required to attain procedural success.