Initial experience with magnetic resonance imaging of atrial scar and co-registration with electroanatomic voltage mapping during atrial fibrillation: Success and limitations

BACKGROUND: Ablation for atrial fibrillation (AF) frequently requires multiple procedures to achieve durable restoration of sinus rhythm. Early studies have suggested that delayed enhancement magnetic resonance imaging (DE-MRI) of the left atrium (LA) can assist in performing repeat ablation procedures. OBJECTIVE: The purpose of this study was to investigate the utility of DE-MRI in delineating regions of LA low voltage and PV reconnection sites in patients undergoing repeat PV isolation for recurrent AF. METHODS: We enrolled 10 patients undergoing repeat ablation for AF recurrence to undergo preprocedural DE-MRI of the LA in conjunction with high-density voltage mapping (>100 sites) of the LA during the ablation procedure. LA wall regions with hyperenhancement were segmented from DE-MRI images and retrospectively co-registered with the electroanatomic LA map. The association between scar on DE-MRI images and low-voltage regions of the LA was assessed, as was the association between scar gaps and electrogram-determined PV reconnection sites. RESULTS: Ten patients underwent successful DE-MRI imaging and repeat AF ablation without complication. In all 10 patients, the majority of PVs were found to have regained electrical continuity with the LA (30/37 PVs electrically active); all patients underwent successful reisolation of all PVs using standard ablation techniques. There was a significant association between scar identified by DE-MRI and low-voltage regions of the LA (-0.7±0.1 mV in scar regions; generalized estimating equations model clustered by patient, P<.001). However, there was no association between scar gaps and PV reconnection sites. CONCLUSION: We demonstrate the co-registration of DE-MRI scar imaging and electroanatomic LA mapping, with agreement between regions of scar on DE-MRI and low voltage by mapping. However, at our center, this technique did not provide accurate information on the location of PV reconnection sites in patients undergoing repeat ablation for AF.