Identification and acute targeting of gaps in atrial ablation lesion sets using a real-time magnetic resonance imaging system

Abstract

Background: Radiofrequency ablation is routinely used to treat cardiac arrhythmias, but gaps remain in ablation lesion sets because there is no direct visualization of ablation-related changes. In this study, we acutely identify and target gaps using a real-time magnetic resonance imaging (RT-MRI) system, leading to a complete and transmural ablation in the atrium.

Methods and results: A swine model was used for these studies (n=12). Ablation lesions with a gap were created in the atrium using fluoroscopy and an electroanatomic system in the first group (n=5). The animal was then moved to a 3-tesla MRI system where high-resolution late gadolinium enhancement MRI was used to identify the gap. Using an RT-MRI catheter navigation and visualization system, the gap area was ablated in the MR scanner. In a second group (n=7), ablation lesions with varying gaps in between were created under RT-MRI guidance, and gap lengths determined using late gadolinium enhancement MR images were correlated with gap length measured from gross pathology. Gaps up to 1.0 mm were identified using gross pathology, and gaps up to 1.4 mm were identified using late gadolinium enhancement MRI. Using an RT-MRI system with active catheter navigation gaps can be targeted acutely, leading to lesion sets with no gaps. The correlation coefficient (R(2)) between the gap length was identified using MRI, and the gross pathology was 0.95.

Conclusions: RT-MRI system can be used to identify and acutely target gaps in atrial ablation lesion sets. Acute targeting of gaps in ablation lesion sets can potentially lead to significant improvement in clinical outcomes.

Figures

Figure 1

Panels A and B show axial LGE cardiac MR images showing the two ablation lesions in the posterior wall of the right atrium. Panel A is the more cranial of the two axial planes. Panel C is a coronal section showing both the lesions. Panel D is a sagittal section showing the two lesions. The cranial lesion is marked by blue arrow and the caudal lesion is marked by a green arrow.

Figure 2

Screen shot of the real time MRI navigation system. On the left are three MR images in three perpendicular planes. The location of these planes can be adjusted by the user for optimal performance. The right panel shows a sagittal viewing plane with the shell of the right atrium (in orange) and the ablated lesions (marked in purple with blue and green arrows) imported to the real time catheter navigation interface. In this image the catheter tip is in the gap area between the two ablation lesions.

Figure 3

LGE MR images acquired after ablating the gap between prior ablation lesions. Panels A and B are axial planes through the cranial (A) and caudal (B) ablation lesions. Panel C is a coronal section showing the gap area between the two lesions is also ablated (marked by the red arrow). Panel D is a sagittal section showing the continuous ablation line. The lesions made in the EP lab using fluoroscopy are marked by the blue and green arrows, and the gap area ablated in the MR scanner using the real time MR system is marked with red arrow.

Figure 4

LGE cardiac MR images showing ablation lesions with gap between them. Panels A and B are perpendicular planes showing the same ablation lesions in the right atrial wall. The ablation lesions are marked by black arrows. Panels C and D are magnified areas with the ablation lesions shown in panels A and B respectively. The gap length between the lesions measured using the measurement tool in Osirix was 1.8 mm and is shown in panels C and D.

Figure 5

Correlation between gap length determined by gross pathology versus MRI.