Haemostatic and haemodynamic abnormalities associated with left atrial thrombosis in non-rheumatic atrial fibrillation.

OBJECTIVE: To evaluate the role of haemostatic and haemodynamic variables in left atrial thrombosis in non-rheumatic atrial fibrillation. DESIGN: Case-control study. SUBJECTS: One hundred and nine patients with non-rheumatic atrial fibrillation. INTERVENTIONS: Peak blood velocity measured at three sites in the left atrium. Venous blood sampled for coagulant proteins and markers of haemostatic activation. MAIN OUTCOME MEASURES: Presence of left atrial thrombus and spontaneous echo contrast at transoesophageal echocardiography. RESULTS: Left atrial thrombus was identified in 19 patients (18%), 16 of whom had spontaneous echo contrast. Patients with thrombus had reduced peak left atrial appendage velocity compared with those without (0.17 v 0.26 m/s; P < 0.001), but no significant reductions in peak mid-left atrial or mitral valve outflow velocity. Patients with thrombus had increased plasma markers of platelet activation-beta thromboglobulin (56.8 v 30.4 IU/ml; P < 0.001) and platelet factor 4 (6.1 v 3.5 IU/ml; P < 0.01)-and of thrombogenesis: thrombin-antithrombin complexes (5.59 v 3.06 micrograms/ml; P < 0.001) and D-dimers (479 v 298 ng/ml; P < 0.01). von Willebrand factor was also increased (1.81 v 1.52 IU/ml; P < 0.05). A multiple logistic regression model identified left atrial appendage velocity (P = 0.001), beta thromboglobulin (P = 0.002), and von Willebrand factor (P = 0.04) as the independent associates of left atrial thrombosis, ahead of the presence of spontaneous echo contrast. CONCLUSIONS: Haemostatic and haemodynamic abnormalities are associated with left atrial thrombus in non-rheumatic atrial fibrillation, and may help stratify thromboembolic risk.