Phrenic Nerve Injury
Phrenic Nerve Injury
Introduction: Phrenic nerve injury (PNI) is a well-known, although uncommon, complication of pulmonary vein isolation (PVI) using radiofrequency energy. Currently, there is no consensus about how to avoid or minimize this injury. The purpose of this study was to determine how often the phrenic nerve, as identified using a high-output pacing, lies along the ablation trajectory of a wide-area circumferential lesion set. We also sought to determine if PVI can be achieved without phrenic nerve injury by modifying the ablation lesion set so as to avoid those areas where phrenic nerve capture (PNC) is observed.
Methods and Results We prospectively enrolled 100 consecutive patients (age 61.7 ± 9.2 years old, 75 men) who underwent RF PVI using a wide-area circumferential ablation approach. A high-output (20 mA at 2 milliseconds) endocardial pacing protocol was performed around the right pulmonary veins and the carina where a usual ablation lesion set would be made. A total of 30% of patients had PNC and required modification of ablation lines. In the group of patients with PNC, the carina was the most common site of capture (85%) followed by anterior right superior pulmonary vein (RSPV) (70%) and anterior right inferior pulmonary vein (RIPV) (30%). A total of 25% of PNC group had capture in all 3 (RSPV, RIPV, and carina) regions. There was no difference in the clinical characteristics between the groups with and without PNC. RF PVI caused no PNI in either group.
Conclusion High output pacing around the right pulmonary veins and the carina reveals that the phrenic nerve lies along a wide-area circumferential ablation trajectory in 30% of patients. Modification of ablation lines to avoid these sites may prevent phrenic nerve injury during RF PVI.
Phrenic nerve injury (PNI) is a well-recognized complication of atrial fibrillation (AF) ablation using the cryoballoon system with a published incidence ranging from 8% to 11%. Because of the potential for PNI, it is now standard practice to pace the right phrenic nerve from the superior vena cava during cryoballoon ablation of the right-sided pulmonary veins and to terminate cryoablation if any change in diaphragmatic capture is observed. In contrast to cryoballoon ablation, radiofrequency (RF) ablation, especially delivered with wide-area circumferential ablation (WACA) strategy, very rarely causes phrenic nerve injury. When PNI is observed, it is often associated with concomitant isolation of the SVC or RF ablation with a segmental osital ablation in the right-sided pulmonary veins. The reported incidence of PNI ranges from 0.17% to 0.48% in RF pulmonary vein isolation (PVI) using different approaches. Consistent with the extremely low incidence of PNI, the 2012 HRS Consensus Document on AF ablation does not recommend specific measures to prevent this complication.
Our study was motivated by the experience of 3 patients who developed phrenic nerve injury after RF PVI using the WACA approach at our institution between December 2006 and August 2012 (Fig. 1). Although each of these patients recovered fully, PNI resulted in diminished quality of life until recovery occurred. As a result of these clinical experiences, we designed this study to develop a new approach to WACA that might prevent this complication in the future. The goal of this study was to evaluate the incidence of phrenic nerve capture (PNC) using high-output pacing along the trajectory that we typically ablate using the WACA approach. If PNC was seen, we modified our ablation line to prevent the application of RF energy in the proximity of the phrenic nerve.
(Enlarge Image)
Figure 1.
Electroanatomical map image of a typical WACA lesion set around right pulmonary veins. (A) CXR during inspiration of 1 of the patients who suffered phrenic nerve injury in our institution after a RF PVI with WACA approach. The CXR shows elevated right hemidiaphragm. (B) Normalization of right lung expansion in the same patient after recovery in 8 months (C). 131×41 mm (300 × 300 DPI).
Abstract and Introduction
Abstract
Introduction: Phrenic nerve injury (PNI) is a well-known, although uncommon, complication of pulmonary vein isolation (PVI) using radiofrequency energy. Currently, there is no consensus about how to avoid or minimize this injury. The purpose of this study was to determine how often the phrenic nerve, as identified using a high-output pacing, lies along the ablation trajectory of a wide-area circumferential lesion set. We also sought to determine if PVI can be achieved without phrenic nerve injury by modifying the ablation lesion set so as to avoid those areas where phrenic nerve capture (PNC) is observed.
Methods and Results We prospectively enrolled 100 consecutive patients (age 61.7 ± 9.2 years old, 75 men) who underwent RF PVI using a wide-area circumferential ablation approach. A high-output (20 mA at 2 milliseconds) endocardial pacing protocol was performed around the right pulmonary veins and the carina where a usual ablation lesion set would be made. A total of 30% of patients had PNC and required modification of ablation lines. In the group of patients with PNC, the carina was the most common site of capture (85%) followed by anterior right superior pulmonary vein (RSPV) (70%) and anterior right inferior pulmonary vein (RIPV) (30%). A total of 25% of PNC group had capture in all 3 (RSPV, RIPV, and carina) regions. There was no difference in the clinical characteristics between the groups with and without PNC. RF PVI caused no PNI in either group.
Conclusion High output pacing around the right pulmonary veins and the carina reveals that the phrenic nerve lies along a wide-area circumferential ablation trajectory in 30% of patients. Modification of ablation lines to avoid these sites may prevent phrenic nerve injury during RF PVI.
Introduction
Phrenic nerve injury (PNI) is a well-recognized complication of atrial fibrillation (AF) ablation using the cryoballoon system with a published incidence ranging from 8% to 11%. Because of the potential for PNI, it is now standard practice to pace the right phrenic nerve from the superior vena cava during cryoballoon ablation of the right-sided pulmonary veins and to terminate cryoablation if any change in diaphragmatic capture is observed. In contrast to cryoballoon ablation, radiofrequency (RF) ablation, especially delivered with wide-area circumferential ablation (WACA) strategy, very rarely causes phrenic nerve injury. When PNI is observed, it is often associated with concomitant isolation of the SVC or RF ablation with a segmental osital ablation in the right-sided pulmonary veins. The reported incidence of PNI ranges from 0.17% to 0.48% in RF pulmonary vein isolation (PVI) using different approaches. Consistent with the extremely low incidence of PNI, the 2012 HRS Consensus Document on AF ablation does not recommend specific measures to prevent this complication.
Our study was motivated by the experience of 3 patients who developed phrenic nerve injury after RF PVI using the WACA approach at our institution between December 2006 and August 2012 (Fig. 1). Although each of these patients recovered fully, PNI resulted in diminished quality of life until recovery occurred. As a result of these clinical experiences, we designed this study to develop a new approach to WACA that might prevent this complication in the future. The goal of this study was to evaluate the incidence of phrenic nerve capture (PNC) using high-output pacing along the trajectory that we typically ablate using the WACA approach. If PNC was seen, we modified our ablation line to prevent the application of RF energy in the proximity of the phrenic nerve.
(Enlarge Image)
Figure 1.
Electroanatomical map image of a typical WACA lesion set around right pulmonary veins. (A) CXR during inspiration of 1 of the patients who suffered phrenic nerve injury in our institution after a RF PVI with WACA approach. The CXR shows elevated right hemidiaphragm. (B) Normalization of right lung expansion in the same patient after recovery in 8 months (C). 131×41 mm (300 × 300 DPI).
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