D-dimer blood concentrations to exclude left atrial thrombus in patients with atrial fibrillation

Abstract

Objective: Left atrial (LA) thrombus is routinely excluded by transoesophageal echocardiography (TOE) before cardioversion for non-valvular atrial fibrillation (AF). In the D-dimer blood concentrations to exclude LA thrombus in patients with AF study, two D-dimer cut-offs were compared to exclude LA thrombus prior to cardioversion. One was fixed to 500 ng/mL (DD500), based on clinical practice where such values are commonly accepted to exclude a thrombus. The other cut-off was adjusted to 10 times the patient's age (DDAge), based on the cut-off used to exclude pulmonary embolism.

Methods: 142 consecutive patients with non-valvular AF aged 69.7±11.4 years (52% with paroxysmal AF) referred for precardioversion TOE to exclude LA thrombus were prospectively enrolled. D-dimers were measured at the time of TOE by an ELISA test.

Results: LA thrombus was excluded with TOE in 129 (91%) and confirmed in 13 (9%) patients. D-dimers were significantly lower in patients without LA thrombus (729±611 vs 2376±1081 ng/L; p<0.05). DDAge indicated absence of LA thrombus with higher specificity than DD500 (66.4% vs 50.4%; p<0.05). Both cut-offs were able to identify all 13 patients with LA thrombus (false negative 0%). Patients with D-dimers <DDAge and without LA thrombus (true negative) represented 60.6% of the population and could have safely avoided TOE (flow chart).

Conclusions: This study demonstrates the efficacy of D-dimer cut-offs to exclude LA thrombus in patients with AF. Age adjustment greatly increases the proportion of patients in whom LA thrombus can be safely excluded and consequently avoid precardioversion TOE.

Keywords: atrial fibrillation; echocardiography; stroke.