To examine the morphology and emptying score of the left atrial appendage (LAA) by real-time three-dimensional echocardiography (RT-3D TEE) in patients with atrial fibrillation (AF), and to identify the independent risk factors for left atrial thrombosis.

In total, 90 patients who underwent RT-3D TEE examination in Zhuhai People′s Hospital from January 2015 to January 2017 were enrolled, including 53 with AF (AF group) and 37 without AP (NAF group). Of the 53 cases of AF, 11 had LAA thrombus (thrombus group), 13 had spontaneous development (spontaneous development group), and 29 had no abnormal LAA (non-abnormal group). RT-3D TEE was used to measure and calculate the LAA lobe number, emptying fraction, width index (LAA-WI), length index (LAA-LI), open area index (LAA-OI), maximum volume index (LAA-VImax), minimum volume index (LAA-VImin), ejection fraction (LAA-EF), velocity (LAA-v), and maximum volume index (LA-VImax). Analysis of variance was used to compare LAA lobe number among the thrombus group, spontaneous development group, non-abnormal group, and NAF group, and LSD-t test was adopted for further comparisons between any two groups. The t-test was used to compare the emptying fractions measured by the two-dimensional area method, three-dimensional area method, and three-dimensional volume method between the AF group and NAF group, as well as age, LAA-WI, LAA-LI, LAA-OI, LAA-VImax, LAA-VImin, LAA-EF, LAA-v, LA-VImax, and lobe number between the thrombus group or spontaneous development group and non-abnormal group. Logistic regression analysis was used to analyze the independent risk factors for left atrial thrombosis.

The average number of LAA lobes in the thrombus group, spontaneous development group, non-abnormal group, and NAF group were (3.57±0.77), (3.28±0.99), (2.57±0.68), and (2.76±1.13), respectively. The average number of LAA lobes was higher in the thrombus group than in the spontaneous development group, non-abnormal group, and NAF group, and the difference between the thrombus group and NAF group was statistically significant (t=2.294, P<0.05). The emptying fractions measured by the two-dimensional area method, three-dimensional area method, and three-dimensional volume method were significantly lower in the AF group than in the NAF group (t=8.671, 7.082, 10.432, all P<0.05). LAA-WI, LAA-OI, LAA-VImax, LAA-VImin, LA-VImax, and lobe number in the thrombus group or the spontaneous development group were all significantly greater than those in the non-abnormal group [(18.27±2.14) mm/m² vs (12.76±1.93) mm/m², (3.45±0.46) cm²/m² vs (2.64±0.37) cm²/m², (6.63±0.73) ml/m² vs (4.72±0.48) ml/m², (4.22±0.53) ml/m² vs (2.51±0.22) ml/m², (4.57±0.32) ml/m² vs (4.21±0.28) ml/m², (3.62±0.11) vs (2.57±0.08)], while LAA-EF and LAA-v were significantly smaller than those in the non-abnormal group [(34.12±2.31)% vs (48.09±2.74)%, (29.11±1.08) cm/s vs (48.18±2.11) cm/s] (t=9.849, 7.107, 11.000, 14.787, 4.367, 40.471, 19.814, 42.417, all P<0.001), although there was no significant difference in age or LAA-LI. Logistic regression analysis showed that LAA emptying fraction was an independent risk factor for thrombosis or spontaneous development (OR=2.323, 95% CI: 1.471-2.821).

Using RT-3DTEE to evaluate the complex structure of LAA is feasible and accurate. Increased lobe number and decreased emptying fraction are associated with thrombosis. Decreased emptying fraction is an independent risk factor for thrombosis.