Magnetocardiographic Mapping of the P-Wave in Patients with Paroxysmal Atrial Tachyarrhytmias

The role of magnetocardiographic mapping (MCG) in predicting recurrences of paroxysmal (Par) Atrial fibrillation (AF) and/or Atrial Flutter (AFL) has not been defined yet. Aim of this study was to evaluate if high-resolution (HR) P-wave (Pw) MCG could predict AF and/or AFL recurrences in comparison to age, sex, and 15 other clinical and echocardiographic (ECHO) parameters. Methods: 21 patients (M/F 17/4, mean age 55.4 ± 14.3), with at least one recurrence of ParAF and/or ParAFL preceding the MCG session, were retrospectivelly enrolled. Their clinical, ECHO and MCG parameters and arrhythmic events had been prospectively noted during e mean clinical follow-up of 63.8 ± 61.5 months. A 36-channels MCG system (sensitivity 20 fT/Hz½) was used to map, under SR, the cardiac magnetic field perpendicular to the anterior chest wall. 17 variables, among clinical non-cardiac, cardiac and ECHO parameters predictors of AF were considered, according to the Framingham Heart Study and the Cardiovascular Health Study. From signal averaged (SA) HR MCG, magnetic P wave duration (PwD) and atrial magnetic field due P wave depolarisation (Pwd) and repolarization (Pwr) components were measured in ms. Then Pwd/PwD, Pwr/PwD and (Pwd/Pwr)/PWD ratios were calculated. HR SA ECG PwD was also measured. Following univariate analysis ANOVA (UVA), the factors with an associated p value < 0.1 were tested in a multivariate model. Cox regression analysis was performed to predict independent factors of ParAF and/or ParAFL relapse. A p value < 0.05 was considered significant. Results: Among 11 factors with an associated p value < 0.1 at UVA, the multivariate Cox regression analysis found that the only independent predictors of ParAF and/or ParAFl were the MCG Pwr/PwD (p<0.045) and (Pwd/Pwr)/PWD (p<0.044) indexes. Conclusion: SA HR MCG is a novel method, which provides differentiation between atrial depolarisation and repolarization phenomena during the P wave. Interestingly our preliminary results show that the MCG Pwr/PwD and (Pwd/Pwr)/PWD indexes are independent predictors of ParAF and/or ParAFL recurrences. A larger population is needed to define the clinical value of this diagnostic approach.