Epicardial catheter ablation of left ventricular tachycardias: the anatomic risk of inducing left phrenic nerve injury

Abstract

Epicardial catheter ablation is an increasingly important technique in the treatment of left ventricular tachycardia. The left phrenic nerve (LPN) is a structure especially at risk when procedures are carried out at the vicinity of the high left ventricular wall (HLVW). Detailed information of the anatomic relations between the LPN and the HLVW may be useful to perform the ablation procedures more safely. Twenty-two human cadavers (14 m, 8 f; 64±9 years old) without obvious signs of thoracic pathology or prior surgery were carefully dissected. We examined by gross inspection and histological sections the course of the LPN in relation with the epicardial aspect of the HLVW. The LPN, a branch of the left cervical plexus runs dorsal along the left brachiocephalic vein. It continues closely applied over the aortic arch, pulmonary trunk and descends in front of the root of the left lung embedded in between the fibrous pericardium to course between the mediastinal pleura and the lateral surface of the left ventricle. The course of the LPN along the border of the left ventricle was variable. In 4 specimens (18%), the nerve took an anterior course and was related to the anterior interventricular groove, high part of the right ventricular outflow tract and anterior part of the HLVW (distance LPN to HLVW was 3.5±0.5 mm; range 2.5-5.5 mm). In 13 specimens (59%) the nerve descended lateral to the HLVW (distance LPN to HLVW was 2.3±0.5 mm; range 1.5-5 mm). In 5 specimens (23%) with an inferior course the distance between the LPN and the HLVW was 2.0±0.5 mm (range 1.5-4.5 mm). In conclusion, the left phrenic nerve can be extremely close to the high left ventricular wall. This structure can be potentially damaged during epicardial ablation of left ventricular tachycardia.