Pranav Bhagirath

25 Multimodality imaging for patient evaluation and guidance of catheter ablation for atrial fibrillation PRE-PROCEDURAL IMAGING LA structural remodeling - LA dimensions LA dimensions are strongly related to adverse cardiovascular events and clinical outcome in patients ablated for AF (15;16) . Maintenance of sinus rhythm after ablation for AF is associated with a reduction of LA size (17) , and in return the LA volume is correlated to procedural success (18;19) . Therefore, accurate knowledge of these parameters is mandatory in order to correctly ascertain patient eligibility for ablation. Assessment of these parameters can be performed with various techniques including echocardiography, CMR and CT. Despite its higher temporal resolution, TTE regularly underestimates the LA dimensions by 15-30 ml as a consequence of reduced image quality (20;21) . This modality also has a twice as high inter-observer variability (8.7 ± 24%) when compared to CMR (3 ± 10%) or CT (1±11%) (20;21) .WhenmeasuredwithTEE, further underestimationof these parameters occurs by up to 10% (22;23) . This is caused due to incomplete visualization of the LA in the scan sector owing to its close proximity to the structure. Therefore, echocardiographic stratification may exert unjustified expectations on the ablation result. CMR and CT show a good correlation for LA dimensions, with a correlation coefficient between 0.85 and 0.97 (20;21;24) . CT makes a small yet significant overestimation of LA maximal volume when compared to CMR (20;24) . This difference is augmented in examinations performed during AF (21) . Despite a lower spatial resolution than CT and a lower temporal resolution compared to echocardiography, CMR seems to be the most ideal modality for the assessment of LA dimensions. LA structural remodeling - LA geometry Changes in dimensions cause alteration of the geometry. These geometrical changes have been marked as an independent predictor of AF recurrence post-ablation and can also be used for patient selection (25;26) . Results indicate that LA roof shapes can be considered a marker of atrial remodeling with flat and coved roof shape related to higher incidence of non-PV foci AF and AF inducibility after the ablative procedure (25) . LA sphericity, a new method for LA geometrical analysis, has recently been identified as a strong predictor of AF recurrence (26) .