Septal coronary artery fistula after left bundle branch area pacing assessed by multi-imaging modalities and shunt volume quantification.

Septal coronary artery fistula is a rare but concerning complication of left bundle branch area pacing (LBBAP). We report the case of an 82-year-old man who was indicated for cardiac resynchronization therapy and underwent LBBAP. The patient had no chest symptoms during or after implantation. Postoperative echocardiography demonstrated a new abnormal tunnel inside the interventricular septum (IVS) and shunt flow from the IVS toward the right ventricle. Coronary angiography confirmed a septal coronary artery fistula, which might have been formed by failed deep screw attempts. Since the shunt volume assessed by the Q_p /Q_s was small, the patient was treated conservatively.