Non-invasive monitoring of spontaneous and antiarrhythmic drug induced changes in fibrillatory frequency in human atrial fibrillation

Automatic analysis of the frequency content of the fibrillatory baseline on the standard surface ECG during atrial fibrillation (AF) accurately reflects the average frequency of atrial fibrillatory activity. Atrial fibrillatory frequency (f) was determined from surface ECG recordings. After filtering averaged QRST complexes were subtracted in one-minute ECG segments. The resulting signal was subjected to Fourier transformation and the dominant f was determined in the 3 to 12 Hz frequency range. Assessment of f in 30 patients with persistent AF (18 male, 12 female, mean age 60±11 years) showed a decrease at night (6.8±0.7 Hz at 10 AM; 6.7±0.7 Hz at 4 PM; 6.6±0.7 Hz at 10 PM and 6.4±0.7 Hz at 4 AM, p=.028). In 12 patients (12 male, mean age 55±9 years) oral amiodarone (n=5), sotalol (n=5) or flecainide (n=2) reduced mean f from 7.0±0.5 Hz to 6.3±0.6 Hz (p=.003) without AF termination. Atrial fibrillatory frequency determined from ECG recordings shows a circadian pattern with a lower frequency at night. This test may be used to monitor directly the atrial response to antiarrhythmic medication