Study of Spatial Relationship of Phrenic Nerves with Cardiac Structures Relevant to Electrophysiologic Interventions

Tracing the Right Phrenic Nerve - A Systematic Review and Meta-Analysis

Background

The Right phrenic nerve (RPN) is vulnerable to injury during the isolation of the right pulmonary veins (RPV). The study aimed to provide a comprehensive meta-analysis of the overall prevalence of right phrenic nerve injury (RPNI), its course and its association with the superior and inferior pulmonary veins.

Methods

Through December 2017, a database search was performed on PubMed, Science Direct, EMBASE, SciELO, and Web of Science. The references were also extensively searched in the included articles.

Results

Detection of the RPN may vary according to the identification method. It ranges from 100% in postmortem studies, 93% in intraoperative, to 57.88% in computer tomography (CT) imaging. Based on the included studies (n-507), the distance from the right superior pulmonary vein (RSPV) ostium to the RPN was 12.48mm (±6.21). In postmortem studies, the distance was 6.92mm (±3.94); in pre or intraoperative techniques, 13.32mm (±5.96) if noninvasive, 13.97mm (±7.8) if invasive. Distances ranged from 0DC342.6 mm. For the right inferior pulmonary vein (RIPV) (n-125) the mean distance was 16.53mm (±8.92) with distances from 0.4 68mm. The risk of RPNI with distance-included studies was 12.46% (47 RPNI in 377 cases). In the meta-analysis, the distance from the RSPV to the RPN that was associated with an increased risk of RPNI was 7.36mm.

Conclusions

RPNI is a relatively rare complication. A firm understanding of its course, relation to the PV ostium, and detection are vital for preventing future injuries and complications.

Epicardial Ablation of Supraventricular Tachycardias

Supraventricular arrhythmias are the most common cardiac arrhythmias encountered; however, it is uncommon that supraventricular tachycardias require percutaneous epicardial access for successful mapping and ablation. There are particular scenarios where epicardial access and ablation should be considered. Certain accessory pathways particularly in the posteroseptal region may require epicardial access for successful ablation. These pathways may also be approached from within the coronary sinus system. In addition, tachycardias near the phrenic nerve in the right atrium or left atrium may require epicardial access for successful ablation or to allow displacement of the phrenic nerve facilitating safe catheter ablation.

Imaging of Pericardiophrenic Bundles Using Multislice Spiral Computed Tomography for Phrenic Nerve Anatomy

INTRODUCTION

Phrenic nerve injury and diaphragmatic stimulation are common complications following arrhythmia ablation and pacing therapies. Preoperative comprehension of phrenic nerve anatomy via non-invasive CT imaging may help to minimize the electrophysiological procedure-related complications.

METHODS

Coronary CT angiography data of 121 consecutive patients were collected. Imaging of left and right pericardiophrenic bundles was performed with volume rendering and multi-planar reformation techniques. The shortest spatial distances between phrenic nerves and key electrophysiology-related structures were determined. The frequencies of the shortest distances ≤5 mm, >5 mm and direct contact between phrenic nerves and adjacent structures were calculated.

RESULTS

Left and right pericardiophrenic bundles were identified in 86.8% and 51.2% of the patients, respectively. The right phrenic nerve was <5 mm from right superior and inferior pulmonary veins in 92.0% and 3.2% of the patients, respectively. The percentage of right phrenic nerve, <5 mm from right atrium, superior caval vein, and superior caval vein-right atrium junction was 87.1%, 100%, and 62.9%, respectively. Left phrenic nerve was <5 mm from left atrial appendage, great cardiac vein, anterior and posterior interventricular veins, and left ventricular posterior veins in 81.9%, 1.0%, 39.1%, 28.6%, and 91.4% of the patients, respectively. Merely 0.06% left phrenic nerve had a distance <5 mm with left superior pulmonary vein, and none left phrenic nerve showed a distance <5 mm with left inferior pulmonary vein.

CONCLUSION

One-stop enhanced CT scanning enabled detection of phrenic nerve anatomy, which might facilitate avoidance of the phrenic nerve-related complications in interventional electrophysiology.