RESUMO
To observe the effect of different R‐R interval on left ventricular systolic function measured by echocardiography in patients with persistent atrial fibrillation ( AF ) ,and assess the clinical feasibility of the use of an index that is based on the RR1/RR2 ratio to accurately estimate left ventricular systolic function during AF . Methods T wenty‐one patients with persistent AF received echocardiographic examination ,left ventricular ejection fraction ( LVEF ) and stroke volume ( SV ) were recorded at least 10－20 consecutive cardiac cycles for each patient . T he effects of different R‐R intervals on LVEF and SV determined by echocardiography were analyzed . Bland‐Altman analysis was used to assess the correlation and agreement between the systolic parameters of a single beat method based on the ratio of preceding R‐R intervals approaching to 1 and the average value of multiple cardiac cycles as the golden standard . Results In the same patient with AF ,LVEF and SV measured in different cardiac cycles were unstable with great variation . LVEF and SV were not only correlated with heart rate ,showing significantly positive correlations with RR interval ( all r ＞ 0 .4 , P ＜ 0 .05 ) ; w hich were also affected by heart rate variability ,w hen the heart rate variability was high ( heart rate standard deviation ≥ 30 beats/min ) ,the measured SV was better correlated with RR 1/RR2 ( r :0 .581 vs 0 .835 , P ＝ 0 .009 ) . Bland‐Altman analysis showed excellent correlation and agreement between the LVEF and SV of a single beat with identical RR1and RR2 intervals and measured average values over all cardiac cycles ( r ＝0 .897 ,0 .918 ; all P ＜ 0 .001 ) . Conclusions LV systolic function is significantly correlated with RR interval and is also affected by heat rate variability . Single beat based on ratio of RR 1/RR2 to assess LV systolic function in patients with AF is as accurate as the time‐consuming method of averaging multiple cardiac cycles .