Preserved atrial response to dobutamine stress after the modified maze procedure for chronic atrial fibrillation: echocardiographic assessment of atrial function.

BACKGROUND: The maze operation is effective in varying degrees for the restoration of atrial function at rest. However, the atrial mechanical function under stressed conditions has not been investigated.

METHODS: Thirteen patients who regained normal sinus rhythm after the modified maze procedure for atrial fibrillation (Af) associated with valvular disease were enrolled in this study. A two-staged, low-dose protocol (at doses of 5 and 10 microg/kg/min) of dobutamine stress echocardiography (DSE) was performed to assess the probability of the appearance of atrial wave in 20 consecutive beats (Paw), the velocity of atrial filling wave (Av), and the early filling wave (Ev) with their ratio (A/E), as well as the left atrial area fraction (LAAF) which represents an ejection fraction of the left atrium.

RESULTS: Under resting conditions, Paw was 72% and 50% at tricuspid (T) and mitral (M) position, respectively. During dobutamine stress (5 microg/kg/min), Paw tended to increase both at T and M position (86% and 60%, respectively). Av was significantly accelerated by dobutamine stress (10 microg/kg/min) in both T (from 0.36 to 0.54 m/s) and M (from 0.46 to 0.69 m/s) valvular flow, which was accompanied by a significant increase in A/E (from 0.69 and 0.31 to 0.87 and 0.40, respectively). Although heart rate was significantly increased during dobutamine stress, LAAF remained at the same level (0.18, 0.22 and 0.19 at rest, 5 and 10 microg/kg/min) and atrial output was expected to be enhanced by dobutamine stress.

CONCLUSION: Restoration of atrial mechanical function after the maze operation is accompanied by preserved response to dobutamine stress.