BACKGROUND: The mean, median, and minimum local atrial activation (A-A) intervals have been used to determine the local atrial effective refractory period (AERP) during atrial fibrillation (AF), the underlying assumption being that AF is due to multiple reentrant wavelets. OBJECTIVE: We tested the hypothesis that when AF is due to a single, rapid, stable reentrant circuit (driver), the minimum and mean local A-A intervals will be similar at sites in the reentrant circuit, but will vary widely at sites with fibrillatory conduction, making these latter intervals unreliable indicators of AERP. METHODS: During sustained AF due to a left atrial (LA) driver in 6 sterile pericarditis dogs, electrograms were recorded from 186 bipolar electrodes from both atria. A-A intervals were measured from each recording site during 1.2 seconds of AF. Minimum A-A intervals as well as temporal (within site) and spatial (between sites) variability were determined from all sites. RESULTS: A-A intervals from each site during AF demonstrated that (1) 90-100% of right atrial (RA) sites and 18-39% of LA sites showed considerable (SD > 6 ms) temporal variability; (2) RA and LA sites with fibrillatory conduction (SD > 6 ms) showed considerable (a) spatial variability (RA: 9-36 ms; LA: 5-27 ms) and (b) variability of the minimum A-A intervals (RA: 14-35 ms; LA 11-28 ms). CONCLUSION: During AF due to a driver, areas with fibrillatory conduction manifested considerable variability in the mean and the minimum A-A intervals. Therefore, it is unlikely that any of the A-A intervals reflect AERP.
BACKGROUND: The mean, median, and minimum local atrial activation (A-A) intervals have been used to determine the local atrial effective refractory period (AERP) during atrial fibrillation (AF), the underlying assumption being that AF is due to multiple reentrant wavelets. OBJECTIVE: We tested the hypothesis that when AF is due to a single, rapid, stable reentrant circuit (driver), the minimum and mean local A-A intervals will be similar at sites in the reentrant circuit, but will vary widely at sites with fibrillatory conduction, making these latter intervals unreliable indicators of AERP. METHODS: During sustained AF due to a left atrial (LA) driver in 6 sterile pericarditisdogs, electrograms were recorded from 186 bipolar electrodes from both atria. A-A intervals were measured from each recording site during 1.2 seconds of AF. Minimum A-A intervals as well as temporal (within site) and spatial (between sites) variability were determined from all sites. RESULTS: A-A intervals from each site during AF demonstrated that (1) 90-100% of right atrial (RA) sites and 18-39% of LA sites showed considerable (SD > 6 ms) temporal variability; (2) RA and LA sites with fibrillatory conduction (SD > 6 ms) showed considerable (a) spatial variability (RA: 9-36 ms; LA: 5-27 ms) and (b) variability of the minimum A-A intervals (RA: 14-35 ms; LA 11-28 ms). CONCLUSION: During AF due to a driver, areas with fibrillatory conduction manifested considerable variability in the mean and the minimum A-A intervals. Therefore, it is unlikely that any of the A-A intervals reflect AERP.