Abstract Body (Do not enter title and authors here): Background:
Epicardial radiofrequency ablation via percutaneous access is a common technique for ventricular tachycardia (VT) ablation. Rapid identification of and response to complications can reduce morbidity and mortality.

Objective:
We present a case of epicardial VT ablation complicated by a distal left internal mammary artery (LIMA) transection secondary to subxiphoid sheath insertion.

Report:
A 66-year-old man with hypertrophic cardiomyopathy was referred for endo-epicardial ablation of recurrent VT. Pericardial access was obtained using coronary vein exit and carbon dioxide insufflation technique. An 8.5F sheath was advanced over an indwelling pericardial wire, and ablation was performed. Following ablation, 400cc of blood was aspirated from the pericardial space after replacing the 8.5F sheath with a standard pericardial drain. Urgent angiography revealed intact coronary arteries, coronary sinus (CS) and LIMA. The 8.5F sheath was re-introduced and bleeding ceased. CT scan revealed no myocardial or great vessel damage. Mild pericardial drainage continued overnight. The next day, IR angiography demonstrated transection of the distal LIMA from the indwelling sheath. The patient underwent placement of a back-up pericardial drain, followed by coil embolization of the injured artery without complication (Fig).

Conclusion:
This case highlights the importance of maintaining a broad differential during apparent complications of epicardial access and the importance of staying close to midline for epicardial puncture given anatomic variability. The differential for acute blood loss and pericardial effusion following epicardial ablation includes 1) coronary artery damage, 2) CS damage, 3) extracardiac vascular injury, and 4) right ventricular injury. When extracardiac vascular injury is suspected, multidisciplinary collaboration is essential.