Are left atrial appendage flow velocities adequate surrogates of global left atrial function? A population-based transthoracic and transesophageal echocardiographic study

Background: Left atrial appendage (LAA) contraction velocities are used frequently as surrogates of global left atrial (LA) function, but the validity of this approach has not been confirmed. Objective: The objective of our study was to assess the relationship between LAA flow velocities and multiple global LA variables. Methods The correlations between LAA contraction velocities and global LA variables (difference between maximal and minimal LA volumes, mitral inflow A velocity, atrial ejection force, mitral annulus late diastolic [a'] velocity, pulmonary vein atrial reversal velocity) were assessed in 349 subjects participating in the Stroke Prevention: Assessment of Risk in a Community study (age, 67 +/- 11 years; 53% men; all subjects in sinus rhythm), who were examined with transthoracic and transesophageal echocardiography. Results The correlations between LAA contraction velocities and multiple global LA variables were poor or nonsignificant. The best correlations, albeit weak, were between LAA velocities and mitral annulus a' velocities (r = 0.32 and r = 0.35 for correlations with septal and lateral annulus a' velocities, respectively, P < .001). Low LAA contraction velocities (lowest 10%, velocities < 56 cm/s) were not sensitive in detecting low values (lowest 10%) of LA variables (sensitivity < 0.2 for most LA variables). In a subgroup of subjects with lower left ventricular ejection fraction (less than or equal to 50%), the correlations between LAA velocities and LA variables were not apparently better than those in the total population. LAA velocities correlated negatively with LAA orifice diameter (r = -0.29, P = .002). The correlations between LAA velocities and global LA variables remained poor after correcting for LAA orifice size. Conclusion: LAA contraction velocities correlate poorly with multiple LA variables. Therefore, LAA flow velocities should not be used as surrogates of global LA function.