Echocardiographic [correction of Ehocardiographic] evaluation of regional left atrial function after rapid atrial pacing.

Rapid regular atrial pacing (RAP) produces changes in atrial function similar to those caused by atrial fibrillation in animal models. Left atrial appendage (LAA) function represents regional atrial function. The aim of our study was to investigate the influence of RAP on left atrial regional function and to evaluate the reversibility of changes after termination of pacing in a canine model. Eight dogs were subjected to RAP (400 bpm) for 16 days. Transesophageal echocardiography was performed at baseline, immediately after RAP and 4 weeks after the termination of RAP. The LAA peak late emptying velocity (LAA-E) and filling wave (LAA-f) were measured. LAA-E velocities were significantly reduced and filling wave velocities (LAA-f) were significantly less negative after RAP compared with the baseline values. Four weeks after termination of pacing, the LAA-E and LAA-f velocities were normal. RAP results in impaired regional atrial systolic and diastolic function. The changes were completely reversible 4 weeks after termination of pacing. These results suggest that the LAA is mechanically stunned after RAP.