Principal component analysis of atrial fibrillation: Inclusion of posterior ECG leads does not improve correlation with left atrial activity

BACKGROUND: Lead V(1) is routinely analysed due to its large amplitude AF waveform. V(1) correlates strongly with right atrial activity but only moderately with left atrial activity. Posterior lead V(9) correlates strongest with left atrial activity. AIMS: (1) To establish whether surface dominant AF frequency (DAF) calculated using principal component analysis (PCA) of a modified 12-lead ECG (including posterior leads) has a stronger correlation with left atrial activity compared to the standard ECG. (2) To assess the contribution of individual ECG leads to the AF principal component in both ECG configurations. METHODS: Patients were assigned to modified or standard ECG groups. In the modified ECG, posterior leads V(8) and V(9) replaced V(4) and V(6). AF waveform was extracted from one-minute surface ECG recordings using PCA. Surface DAF was correlated with intracardiac DAF from the high right atrium (HRA), coronary sinus (CS) and pulmonary veins (PVs). RESULTS: 96 patients were studied. Surface DAF from the modified ECG did not have a stronger correlation with left atrial activity compared to the standard ECG. Both ECG configurations correlated strongly with HRA, CS and right PVs but only moderately with left PVs. V(1) contributed most to the AF principal component in both ECG configurations.