Repeat Left Atrial Catheter Ablation: Cardiac Magnetic Resonance Prediction of Endocardial Voltage and Gaps in Ablation Lesion Sets

BACKGROUND: -Studies have reported an inverse relationship between LGE CMR signal intensity and LA endocardial voltage following LA ablation. However, there is controversy regarding the reproducibility of atrial LGE CMR and its ability to identify gaps in ablation lesions. Using systematic and objective techniques, this study examines the correlation between atrial CMR and endocardial voltage.

METHODS AND RESULTS: -20 patients who had previous ablation for AF and represented with PAF or AT underwent pre-ablation LGE CMR. During the ablation procedure, high-density point-by-point Carto voltage maps were acquired. 3D CMR reconstructions were registered with the Carto anatomies to allow comparison of voltage and LGE signal intensity. Signal intensities around the left and right PV antra, and along the LA roof and mitral lines on the CMR-segmented LA shells were extracted to examine differences between electrically isolated and reconnected lesions. There were a total of 6767 data points across the 20 patients. Only 119 (1.8%) of the points were ≤0.05 mV. There was only a very weak inverse correlation between either unipolar (r=-0.18) or bipolar (r=-0.17) voltage and LGE CMR signal intensities with low voltage occurring across a large range of signal intensities. Signal intensities were not statistically different for electrically isolated and reconnected lesions.

CONCLUSIONS: -This study demonstrates that there is only a very weak point-by-point relationship between LGE CMR and endocardial voltage in patients undergoing repeat LA ablation. Using an objective method of assessing gaps in ablation lesions, LGE CMR is unable to reliably predict sites of electrical conduction.