Study of atrial function using echocardiographic automatic boundary detection following external or internal cardioversion for idiopathic atrial fibrillation.

Introduction: The aim of this study was to evaluate the validity of an echocardiographic method of automatic boundary detection (ABD) in the assessment of the degree of atrial dysfunction in patients who had undergone external or internal cardioversion for idiopathic atrial fibrillation.

Methods: The study population included 31 patients (mean age 48 +/- 6.5 years) with idiopathic atrial fibrillation. The patients were randomised into two groups: Group 1 (14 patients, 8 +/- 3.13 joules), where internal cardioversion was applied, and Group 2 (17 patients, 200-360 joules), where external cardioversion was used for restoration of sinus rhythm. During the following 24 hours the ABD method was used in both groups to assess the following functional indices for both the left and the right atrium: a) total fractional change of atrial area (delta1), b) passive change of atrial area (delta2), c) change of atrial area due to atrial contraction (delta3) and d) index of % atrial expansion (delta4).

Results: All patients in both groups were successfully cardioverted (100%, p: NS). Post-cardioversion indices delta1-delta4 for both left and right atria did not differ between the 2 groups (p:NS). A negative correlation was found between left atrial function as assessed by ABD and the mean energy in joules delivered through the catheter in each patient for successful cardioversion (r = -0.55 to r = -0.67 and p = 0.04 to p = 0.01). However, no relevant correlations were found for the right atrium (p:NS).

Conclusions: 1) The atrial dysfunction which follows the cardioversion of idiopathic atrial fibrillation (atrial stunning) is not related to the type of cardioversion (internal or external). 2) The higher the amount of energy delivered during internal cardioversion, the greater the degree of left atrial dysfunction observed.