Disparities in emptying velocity within the left atrial appendage

Pulsed Doppler measurement of left atrial appendage (LAA) emptying velocity, a marker of left atrium contractile function, has been shown to predict success of cardioversion, thrombo-embolic risk, and maintenance of sinus rhythm after cardioversion and pulmonary vein isolation. However, in the published literature, emptying velocity measurement location is not uniform, and no standard currently exists. We assessed the hypothesis that emptying velocity when acquired near the LAA orifice differs from that at the LAA apex. The study group comprised 44 patients (32 in sinus rhythm and 12 in atrial fibrillation) who were able to complete a non-emergent transoesophageal echocardiography. Pulsed Doppler recordings were obtained with the sample volume first positioned 1 cm from the LAA orifice, and then positioned within 1 cm of the LAA apex. At each location, we calculated the average of the peak end-diastolic LAA emptying velocity from five consecutive cardiac cycles. LAA orifice emptying velocity was higher than the apex emptying velocity in all patients. The median velocity at the orifice was 72 cm/s, which was 45% higher than the median velocity at the apex (43 cm/s, P < 0.001). Lower LAA emptying velocity at the orifice was associated with a larger discrepancy between orifice and apex velocities. The ratio of orifice to apex velocity did not vary with orifice velocity. Multivariate analysis demonstrated that clinical patient characteristics were not significant predictors of the discrepancy between orifice and apex velocities. LAA emptying velocity is greater at the LAA orifice compared with the LAA apex. Higher, more easily measured velocity and greater variability observed with orifice measurements make it the location of choice for research and clinical applications.