RATE-DEPENDENCE OF ATRIAL ELECTROGRAM AMPLITUDE

Purpose: The magnitude of fibrotic replacement of atrial myocardium can be estimated by electroanatomic voltage mapping. The amplitude of atrial electrograms (EGMs), however, depends on atrial rhythm or dominant cycle length in case of atrial fibrillation (AF). The relationship between EGM characteristics in AF and in sinus rhythm is generally unknown. We investigated left atrial (LA) EGMs while pacing at different rates from the right atrium. Methods: The study was completed in 13 pts (63±7yrs, 9 males) with paroxysmal AF undergoing pulmonary vein isolation. Atrial EGMs were recorded in inferoposterior (IP) region close to the right inferior pulmonary vein and in anteroseptal (AS) region close to the right superior pulmonary vein. The stimulation protocol consisted of series of pacing trains delivered from right atrial appendage with basic cycle length of 600ms followed by single extrastimulus with coupling interval gradually shortened in 20-ms steps until the atrial effective refractory period (ERP). Results: The atrial ERP was 214±28ms. In comparison to reference (in-train voltage), significant (P<0.05) reduction of EGM amplitude proportional to coupling interval of extrastimulus was observed in both IP and AS regions (detailed results in Table). Conclusions: Left atrial EGM voltage is rate-dependent. Relative reduction of voltage (up to 50% of reference value) was observed for short-coupled extrastimuli. Further reduction could be expected at shorter atrial cycle length in the setting of AF.