BACKGROUND The mechanisms of persistent human atrial fibrillation (AF) are not well understood. OBJECTIVE The purpose of this study was to examine whether left atrial (LA) drivers are present in persistent AF by performing a comprehensive evaluation of atrial activation frequency and organization using multisite atrial recordings and correlating the findings with atrial waveform frequency and organization on surface ECG. METHODS Nine patients undergoing catheter ablation for persistent AF were studied. Electrograms were recorded from at least 10 sites in each atrium, tagged to an electroanatomic map, and subjected to spectral analysis. Dominant frequency (DF) and regularity index were calculated at each site. Surface ECG recordings were analyzed to obtain precordial lead DFs and AF vector stability index. RESULTS Mean, maximum, and minimum DF and mean regularity index were higher in LA than right atrium (RA). DF was correlated with regularity index (R = 0.59, P <.0001) and negatively correlated with distance from maximal DF site (R = -0.80, P <.0001). Precordial lead DFs were highly correlated with atrial DFs. Vector stability index was 0.39 +/- 0.12 (P <.01 vs predicted if AF vector direction was random). LA-RA DF gradient and vector stability index were negatively correlated (R = -0.83, P <.05). CONCLUSION The existence of LA-RA frequency gradients in most patients in this study along with the regularity of LA activation and centrifugal dissipation of activation frequency suggest that LA drivers are often present in persistent AF. Analysis of AF vectors from surface ECG demonstrates spatial stability and correlates with intracardiac recordings. These findings may have implications for catheter ablation of persistent AF.