Streszczenie POWRÓT DO POPRZEDNIEJ STRONY Interatrial mechanical delay during different atrial pacing modes. Alicja D±browska-Kugacka, Ewa Lewicka-Nowak, Andrzej Kutarski*, Gra¿yna ¦wi±tecka Akademia Medyczna, II Klinika Chorób Serca, Gdañsk* Akademia Medyczna, Klinika Kardiologii, Lublin Background: Biatrial (BiA) pacing was reported to synchronize atrial activation time in pts with abnormally prolonged interatrial conduction (IACT). Data on the hemodynamic effects of BiA pacing, however, are limited. Aim: The aim of the study was to evaluate the influence of different atrial pacing modes on right (RA) and left atrial (LA) contraction sequence and cardiac output. Methods: The study population consisted of 13 patients with reccurent atrial fibrillation, prolonged P wave duration on the standard ECG (mean 129 ± 15 ms) and prolonged IACT (mean 108 ± 27ms). All pts had a BiA pacemaker implanted with one atrial lead in the RA appendage and the other in the coronary sinus pacing the LA. The study measured the delay between the contractions of RA and LA (Adif) and aortic velocity time integral (VTI) during sinus rhythm (SR) and RA, RA-LA synchronized (SST), BiA and LA pacing. The control group consisted of 10 healthy volunteers. Results: Adif during the different pacing modes were as follows: control group 10 ± 14 ms, SR 37 ± 28 ms, RA 15 ± 26 ms, SST -10 ± 49 ms, BiA -17 ± 24 ms, LA -50 ± 45 ms. During SR pts had a significantly longer Adif than the control group (37 ± 28 ms vs 10 ± 14 ms; p<0,05), RA pacing changed the Adif nonsignificantly to 15 ± 26 ms, while SST and BiA pacing reversed the right-to-left into left-to-right contraction sequence (Adif -10 ± 49 ms and -17 ± 24 ms respectively; p < 0,05 vs SR). Adif was further intensified by the LA pacing (Adif -50 ± 45 ms; p<0,0001 vs SR). There were no differences in the aortic VTI among different pacing modes. Conclusions: None of the investigated pacing modes synchronizes RA and LA contraction sequence in patients with prolonged IACT. The LA, BiA and SST pacing reverse the atrial mechanical timing from a right-to-left to a left-to-right contraction sequence, but it has no influence on the cardiac output. POWRÓT DO POPRZEDNIEJ STRONY © Copyright by Polskie Towarzystwo Kardiologiczne 2001