Visualization and mapping of the right phrenic nerve by intracardiac echocardiography during atrial fibrillation ablation

Figures

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  Figure 1. Location of the RPN in the SVC. In 5.2%,15.8%,71.1%, and 7.9% of patients, the RPN is located on the anterior, anterolateral, lateral, and posterolateral walls of the SVC, respectively. RPN, right phrenic nerve; SVC, superior vena cava.

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  Figure 2. The intracardiac echocardiography (ICE) image of the right phrenic nerve (RPN). The RPN is a round, thin structure with a ‘straw’-like appearance, that is centrally hypoechoic and peripherally hyperechoic between the superior vena cava (SVC) and the mediastinal pleura. The arrow indicates the RPN (Figure 2A–B). Bottom row of arrows indicate the mediastinal pleura and up row of arrows indicate the intima of SVC, the RPN could not be identified due to a narrowed space between the SVC and the mediastinal pleura (<1 mm) (Figure 2C). Arrows on left indicate reflexed pericardium and arrows on right indicate the RPN; the fluid separates the visceral pericardium from the parietal pericardium in the inferior part of the SVC (Figure 2D).

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  Figure 3. The lowest pacing threshold for right phrenic nerve (RPN) capture. The lowest pacing threshold for RPN capture is achieved when the ablation catheter is placed close to the ‘straw’ pattern in the superior vena cava (SVC). Left image: the RPN imaging under intracardiac echocardiography (ICE). The up row of arrow indicates the RPN, and the bottom row of arrows indicates the mediastinal pleura. Middle and right images: the same patient’s 3D activation maps of the right atrium (RA) and SVC in right anterior oblique (RAO) 45° and RAO 145° views. The dots indicate the pacing site and the arrows indicate the RPN integrated into the electroanatomical shell.

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  Figure 4. The anatomical relationship of the right phrenic nerve (RPN) and the superior vena cava (SVC). The distance between the RPN and the SVC is increased from the craniocaudal direction in the 3D activation map of the right atrium (RA) and SVC in right anterior oblique (RAO) 30° and left anterior oblique (LAO) 165° views. Left image: the RPN imaging under intracardiac echocardiography (ICE). The middle arrow indicates the RPN, the bottom row of arrows indicate the mediastinal pleura, and the up row of arrow indicates the pericardial fluid. Middle and right images: the same patient’s 3D activation maps of the RA and SVC in RAO 30° and LAO 165° view. The arrows indicate the RPN integrated into the electroanatomical shell.

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  Figure 5. The anatomical relationship of the right phrenic nerve (RPN) and right superior pulmonary vein (RSPV) and sinus node. (A and D) illustrate RPN imaging under intracardiac echocardiography (ICE), where the up row of arrow indicates the RPN, and the bottom row of arrows indicate the mediastinal pleura. The anatomical distance from the RPN to the sinus node is quite close in the 3D activation map of the right atrium (RA) and superior vena cava (SVC) in the right anterior oblique (RAO) view (B) and left anterior oblique (LAO) view (C). The anatomical distance from the RPN to the RSPV is quite close in the 3D activation map of the RA and SVC in the RAO (E) and right lateral (RL) (F) views.

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  Figure 6. Scatter plot between the right phrenic nerve (RPN) pacing threshold and distance from the pacing site. The distance from the pacing site to the RPN is significantly correlated with the RPN pacing threshold (Spearman’s correlation coefficient = 0.728, P < 0.001).

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  Figure 7. Circumferential superior vena cava (SVC) ablation using intracardiac echocardiography (ICE). Left image: the right phrenic nerve (RPN) imaging under ICE. The up row of arrow indicates the RPN, and the bottom row of arrows indicate the mediastinal pleura. Middle and right images: the same patient’s circumferential SVC ablation in the 3D activation map of the right atrium (RA) and SVC in right anterior oblique (RAO) 45° and RAO 168° views. The dotted line indicates the regular circumferential superior vena cava isolation ablation line. The arrow indicates the last ablation point which is the closest ablation point of our actual circumferential superior vena cava ablation.