Detection of Phrenic Nerves and Their Relation to Cardiac Anatomy Using 64-Slice Multidetector Computed Tomography

The improved temporal and spatial resolution allowed by multidetector computed tomography (MDCT) has facilitated the noninvasive assessment of cardiac anatomy before transcatheter electrophysiologic procedures. Clarification of spatial relations of phrenic nerves and key cardiac structures is important to decrease potential complications. The purpose of this study was to reconstruct the course of the right and left phrenic pericardiophrenic bundles and their relations to cardiac structures using 64-slice MDCT. One hundred six consecutive subjects (age 61 ± 13 years; 39% women) who underwent self-referred coronary computed tomographic angiography using 64-slice MDCT underwent retrospective assessment of the phrenic nerves contained within the pericardiophrenic bundles. The course of the nerves was outlined in relation to the left atrial appendage, coronary sinus, and cardiac veins. The ability to individually detect the left and right phrenic nerves, as well as the frequency of direct contact between the left phrenic nerve and cardiac veins, was recorded. The left phrenic nerve was identified in 78 of 106 patients (74%). It crossed the left atrial appendage (n = 72, 91%), great cardiac vein (n = 63, 80%), posterior vein of the left ventricle (n = 39, 49%), posterior interventricular vein (n = 8, 10%), and anterior interventricular vein (n = 7, 9%). Mean Hounsfield units (HUs) of the left phrenic nerve was 81 ± 25. The right phrenic nerve was identified in 50 of 106 patients (47%). Mean HUs of the right phrenic nerve were 94 ± 26. In conclusion, cardiac imaging using 64-slice MDCT enabled adequate detection of the left and right phrenic nerves in relation to cardiac anatomy. In the setting of electrophysiologic interventions, MDCT before a procedure may elucidate anatomic relationships and help minimize inadvertent complications.