Atrial fibrillatory frequency predicts atrial defibrillation threshold and early arrhythmia recurrence in patients undergoing internal cardioversion of persistent atrial fibrillation.

This study was conducted to analyze the meaning of AF frequency obtained from the surface ECG for prediction of energy requirements and early arrhythmia relapse in patients undergoing internal cardioversion of persistent AF. Nineteen consecutive patients (mean age 58 +/- 11 years; 11 men, 8 women) with persistent AF (> 7 days) underwent internal cardioversion. A biphasic shock synchronized to the R wave was delivered between two catheters positioned in the high right atrium (HRA) and the coronary sinus (CS). AFfrequency was estimated prior to cardioversion from surface ECG lead V1. After filtering, QRST complexes were subtracted using a template matching and averaging algorithm. The resulting fibrillatory baseline signal was subjected to Fourier transformation, displayed as a frequency power spectrum and the peak frequency was determined in the 3-12 Hzfrequencyband. Atrial defibrillation threshold (ADFT) was determined using a step-up protocol. All patients were cardioverted successfully with a mean ADFT of 7.6 +/- 6.5 J(range 0.5-25). There was a strong positive correlation between fibrillatory frequency and ADFT (R = 0.71, P = 0.001). AF recurrence within 30 days after successful cardioversion occurred in 11 (58%) patients. Receiver operating characteristic (ROC) analysis revealed a fibrillatory frequency > or = 7 Hz to be 64% sensitive and 88% specific to predict AF recurrence. It was observed in 4 (36%) of 11 cases with a fibrillatory frequency < 7 Hz, as opposed to 7 (88%) of 8 cases with a fibrillatory frequency > or = 7 Hz (P = 0.02). Fibrillatory frequency obtained from the surface ECG predicts ADFT and early AF recurrence in patients with persistent AF undergoing internal cardioversion.