Linear and Nonlinear Correlations Between Surface and Invasive Atrial Activation Features in Catheter Ablation of Paroxysmal Atrial Fibrillation

P-waves are vastly used to assess the outcome of catheter ablation (CA) of atrial fibrillation (AF). It remains unknown, however, if coronary sinus (CS), the key reference structure in CA procedures, follows similar patterns. This study's objective is to detect any correlations between the behavior of P-waves and CS local activation waves (LAWs) with regard to CA procedure. Duration, amplitude, area and slope rate were studied in P-waves and LAWs of five-minute recordings from 29 patients undergoing paroxysmal AF CA. Normalization (N) due to heart rate (HR) fluctuations was performed. Pearson's correlation (PC) between CA-induced variations $(\Delta)$ of P-waves and LAWs was calculated. Linear correlations between each P-wave/LAW were studied with PC and linear regression with 10-fold cross-validation. Cross-quadratic sample entropy (CQSE) assessed nonlinear correlations. $PC(\Delta: \rho < 52.27\%,p=0.015, P$-wave/LAW· $\rho <$ 40.37%, $p=0.001)$ and linear regression analysis $(R^{2}- adj < 16.02\%, p=0.015)$ showed low/mediocre linear correlations. CQSE ( 0.8 - 1.3) also suggested weak nonlinear relationships. P-waves and LAWs are poorly correlated and do not describe to the same degree the substrate modification after CA. It is possible that P-waves reflect the cumulative CA-induced modifications of various atrial sites, with CS being one of them but not the dominant.