Effect of Atrial Fibrillation on Atrial Refractoriness in Humans

Abstract

Background The acute effect of atrial fibrillation (AF) on the atrial effective refractory period (ERP) in humans is unknown. Methods and Results In 20 patients without structural heart disease, the atrial ERP was measured before and after pacing-induced AF at drive cycle lengths of 350 and 500 ms. Immediately after spontaneous AF conversion, the post-AF ERP was measured. The pre-AF ERPs at 350 and 500 ms were 206±23 and 216±17 ms, respectively. The time to spontaneous conversion of AF was 7.3±1.9 minutes. The first post-AF ERPs at drive cycle lengths of 350 and 500 ms were 175±30 ms ( P <.0001 versus pre-AF) and 191±30 ms ( P <.0001 versus pre-AF), respectively. The post-AF ERP returned to the pre-AF ERP value after a mean of 8.4±0.3 minutes. In 15 patients, during the determination of the post-AF ERP, secondary episodes of AF lasting 1±1.5 minutes were reinduced 6±3 times per patient. There was a significant inverse logarithmic relationship between the time to reinduction of AF and the duration of secondary episodes of AF ( P <.0001, r =.5). Conclusions In humans, several minutes of induced AF is sufficient to shorten the ERP for up to ≈8 minutes. The temporal recovery of the ERP is reflected in progressively shorter episodes of reinduced AF. These data imply that AF transiently shortens the atrial wavelength and suggest a mechanism by which AF may perpetuate itself.