Factors associated with resistance to resolution of left atrial appendage thrombus in patients with atrial fibrillation: 12-month follow-up results

Aim . To study the dynamics of left atrial appendage (LAA) thrombosis and to determine the factors associated with resistant LAA thrombus in patients with non-valvular atrial fibrillation (AF) during 12 months of follow-up. Methods . A prospective study included 83 patients with LAA thrombosis detected by transesophageal echocardiography (TEE). The end point was resolution or stability of the thrombus. All patients underwent clinical examination, complete blood count and biochemical blood test, coagulation testing, transthoracic echocardiography (TTE) and TEE. Results . According to the results of TEE, the patients were divided into two groups: group 1 (n=45) with resolution LAA thrombus and group 2 (n=38) with resistant LAA thrombus. Group 2 patients were more likely to take beta-adrenoblockers (57.9% and 31.1%, p=0.014), diuretics (60.5% and 35.6%, p=0.023) and rivaroxaban (39,5% и 13,3%, р=0,010). According to TTE data, group 2 had a higher right atrial volume index (30.7 [24.7; 34.7] vs 24.5 [21.0; 32.2] ml/m 2 , respectively, p=0.034). Laboratory data analysis showed that group 2 had higher mean platelet volume (MPV) levels (9.1 [8.3; 9.8] vs 8.4 [7.9; 9.4] fl, p=0.035), platelet distribution width (PDW) (15.9 [15.7; 16.2] vs 15.7[15.5; 15.9] %, p=0.007) and platelet large cell ratio (P-LCR) (30.0±9.2 vs 25.3±7.4%, p=0.014). There were significant direct correlations of MPV and P-LCR with the following parameters: right atrial volume, left atrial volumes, pulmonary artery systolic pressure, red blood cell level, hemoglobin level and hematocrit. The inverse association of MPV and P-LCR was with platelet count. Conclusions . Resistance of LAA thrombus to resolution in patients with non-valvular AF is associated with morphofunctional parameters of platelets, which correlate with atrial structural remodeling. The results obtained indicate the need to continue research aimed at studying the contribution of the platelet activity to resistance to LAA thrombus, despite taking oral antocoagulants.