Phrenic nerve displacement by intrapericardial balloon inflation during epicardial ablation of ventricular tachycardia: Four case reports

Abstract

BACKGROUND

Phrenic nerve (PN) injury is one of the recognized possible complications following epicardial ablation of ventricular tachycardia (VT). High-output pacing is a widely used maneuver to establish a relationship between the PN and the ablation catheter tip. An absence of PN capture is usually considered an indication that it is safe to ablate, and that successful ablation may be performed at adjacent sites. However, PN capture may impact the procedural outcome. Only a few cases have been reported in the literature that avoid PN injury by using different techniques.

CASE SUMMARY

Three patients with a previous history of myocarditis and one patient with ischemic cardiomyopathy underwent epicardial ablation for drug-refractory VT. Before the procedure, transthoracic echocardiogram, coronary angiogram, and cardiac magnetic resonance imaging were performed on all patients. Under general anesthesia, endo/epicardial three-dimensional anatomical and substrate maps of the left ventricle were accomplished. Before radiofrequency delivery, the course of the PN was identified by provoking diaphragmatic stimulation with high-output pacing from the distal electrode of the ablation catheter. In every case, a scar region with late potentials was mapped along the PN course. After obtaining another epicardial access, a second introducer sheath was placed, and a vascular balloon catheter was inserted into the epicardial space and inflated with saline solution to separate the PN from the epicardium. Once the absence of PN capture had been proven, radiofrequency was applied to aim for complete late potential elimination and avoid VT induction.

CONCLUSION

PN injury can occur as one of the complications following epicardial VT ablation procedures, and may prevent successful ablation of these arrhythmias. PN displacement by using large balloon catheters into the epicardial space seems to be feasible and reproducible, avoid procedure-related morbidity, and improve ablation success when performed in selected centers and by experienced operators.

Keywords: Catheter ablation, Epicardial access, Myocarditis, Nonischemic cardiomyopathy, Ventricular tachycardia, Phrenic nerve, Case series

Core tip: Epicardial ventricular tachycardia ablation procedures are constantly increasing in number. Among the complications potentially carried by this approach, Phrenic nerve (PN) injury can be prevented using certain precautions. However, when ablation is at risk of being unsuccessful due to PN proximity, there are some helpful tips and tricks available. We herein present a case series of epicardial ablation of ventricular tachycardia, in which PN displacement was necessary to successfully eliminate the arrhythmia. This case series highlights the importance of an accurate definition of PN course, and reports upon the feasibility of PN displacement through use of a vascular balloon placed into the epicardial space.