Pranav Bhagirath

101 Left atrial sphericity: a promising parameter to predict response to ablation To the best of our knowledge, this is the first study to report the time-course of LA geometrical remodeling following pulmonary vein isolation and its predictive value with respect to the outcome of a repeat ablation. Post-ablation remodeling of the left atrium The impact of arrhythmias on the LA remodeling process and vice versa is well described (14-16) . Sotomi et al (3) demonstrated a reduction of LA volume and improvement of LA ejection fraction irrespective of AF recurrence whereas Marsan et al (5) reported an increase of LA volume and deterioration of LA ejection fraction in patients with recurrence of AF. Besides these controversies, estimating the extent of remodeling by analyzing size and function still remains a challenging task despite all (advanced) imaging modalities available. The results from this study demonstrated that a conventional remodeling parameter such as LA volume failed to predict the outcome of the repeat procedure. Furthermore, the observed discordance between volumetric and geometric remodeling in nine cases (36%) suggests that volumetric changes are not necessarily correlated with geometrical changes. In line with recent observations, it may be concluded that changes in LA geometry are of clinical relevance and could provide a more direct measure of the remodeling process (11) . More importantly, the current results indicated a strong correlation between AF recurrence and changes in LASP following the index ablation. Patients with a reduction in the LASP following index PVI had a 100% success rate of the repeat procedure. Furthermore, all cases with an increase in the LASP had recurrence of AF during follow- up. These findings, although in a relatively small patient group, suggest that therapy stratification for repeat ablation may benefit by incorporating LASP. Recurrence of atrial fibrillation after catheter ablation Patients with a lower LASP demonstrated a higher number of isolated PV’s during the repeat procedure as indicated by the inverse relation between pre-procedural LASP and total number of isolated PV’s (Pearson’s r=-0.528, p=0.007). A potential cause for this effect could be that higher LA sphericity leads to continuous volume overload and results in an increased level of wall stress and myocardial stretch. As described in a recent animal study, excessive elevation of left atrial wall stress leads to a loss of cardiomyocyte structure, calcium homeostasis and contractile function (17) , and could eventually result in a persisting, non-reversible structural dilatation of the LA cavity, susceptible for arrhythmia recurrence. This theory is further supported