Assessment of left ventricular systolic function in patients with persistent atrial fibrillation using the single beat method based on the ratio of preceding R-R intervals approaching to 1

Objective 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 Twenty-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. The 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); which were also affected by heart rate variability, when the heart rate variability was high (heart rate standard deviation≥30 beats/min), the measured SV was better correlated with RR1/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 RR1/RR2 to assess LV systolic function in patients with AF is as accurate as the time-consuming method of averaging multiple cardiac cycles.