Electrocardiographic characteristics in patients with nonrheumatic atrial fibrillation and their relation to echocardiographic parameters

The aim of this study was to determine the relation between (1) ECG fibrill atory wave amplitude and left atrial diameter and left atrial appendage (LA A) flow velocity using different ECG recording,techniques, and (2) ECG fibr illatory frequency and frequency of LAA contractions in patients with nonrh eumatic AF. In 36 patients (22 men, 14 women, mean age 61 +/- 11 years) wit h persistent AF, ECG recordings were performed using a standard 12-lead ECG and an orthogonal ECG lead system using a high gain, high resolution ECG. AF was classified as coarse (fibrillatory amplitude; 1 mm) or fine (fibrill atory amplitude < 1 mm) in leads I, a VF, V, and corresponding leads X, Y, and Z. Fibrillatory frequency from the ECG was determined by subtracting av eraged QRST complexes and applying a Fourier analysis to the resulting sign al. Doppler flow was obtained from LAA during transesophageal echocardiogra phy and LAA emptying velocity was determined. Fourier analysis was also app lied to the Doppler signal generating the frequency of LAA contractions. Co arse AF was observed in 0, 9, and 18 patients in leads I, aVF, and V, respe ctively. It was more often (P < 0.05) detected in corresponding leads X (n = 13), Y (n = 31), and Z (n = 23). Fine AF in lead X was associated with a reduced LAA velocity (33 +/- 16 cm/s in coarse AF vs 22 +/- 13 cm/s in fine AF, P = 0.05). There was neither a relation between AF coarseness in any o ther ECG lead and LAA flow velocity, left atrial diameter, or echo contrast . In 25 patients with an active LAA flow, the mean frequency of LAA contrac tions was 6.8 +/- 0.8 Hz. The corresponding mean frequency obtained from th e ECG was 6.7 +/- 0.7 Hz (r = 0.85, P < 0.001). The mean difference between these two measures was 0.04 Hz, and the 95% confidence limits were 0.90 an d-0.82 Hz using the Bland-Altman method. In conclusion, AF coarseness and i ts relation to LAA flow velocity depend on the ECG recording technique used . LAA contractions represent one mechanical correlate of the electrical fib rillatory activity in AF.