Magnetic resonance imaging for identification of myocardial injury during ablation for atrial fibrillation: first experiences with the Miyabi MRI system

Introduction

Pulmonary vein antrum isolation (PVAI) has become an effective therapy in patients with paroxysmal atrial fibrillation (AF). Extension and location of ablation lesions often remain unclear during the procedure.

Purpose

We evaluated a new approach on visualization of myocardial injury using cardiac magnet resonance imaging (CMR) during PVAI procedure.

Methods

Patients who underwent PVAI, received CMR before and at the terminal phase of PVAI using the Miyabi-MRI system (Siemens, Germany). Delayed enhancement (DE-CMR) free breathing sequences were applied, and maximum intensity projections (MIP) obtained. Myocardial injury size was then measured on manually segmented 3D images by a computer algorithm using dynamic thresholding.

Results

30 patients received PVAI from February to July 2008. In a subset of 14 patients, CMR was performed before and during the procedure. Using DE-CMR, the increase in average lesion to healthy myocardium ratio was 10.3 ± 4.1% during PVAI. Figure 1 shows an example of MIP of a DE-CMR scan in 2D (A, B) and 3D segmentation (C, D) in a anterior view pre (A, C), and during PVAI (B, D). Myocardial injury is identifiable as white tissue around PV single ostia (full arrows) and common trunk (dashed arrows).

Figure 1

Conclusion

Using CMR is feasible in the course of ablation procedures. In PVAI patients, DE-CMR allowed identification of location and extension of myocardial injury. Therefore, this new CMR approach might improve ablation techniques, and thus long-term success of PVAI.