Patients After Atrial Switch Operation for Transposition of the Great Arteries Can Not Increase Stroke Volume Under Dobutamine Stress as Opposed to Patients With Congenitally Corrected Transposition

BACKGROUND: Patients after atrial switch operation for transposition of the great arteries have limited exercise performance. Rigid atrial baffles may cause a relative preload reduction. Previous studies have had suboptimal control groups, which ideally should consist of patients with congenitally corrected transposition of the great arteries (ccTGA) without previous heart surgery, having a systemic right ventricle, but lacking rigid atrial baffles. Therefore the aim of this study was to test the impact of atrial baffles by comparing 12 atrial switch patients with 11 ccTGA patients. METHODS AND RESULTS: Systemic right ventricular stroke volume (SV), heart rate, cardiac index, and other parameters were assessed during rest and dobutamine stress magnetic resonance imaging. The most important difference between the groups was that the atrial switch patients could not increase SV during stress, whereas ccTGA patients increased it significantly. There was no difference between groups in the rise of the cardiac index. Heart rate increased significantly more in atrial switch patients than in ccTGA patients. CONCLUSIONS: The results support the hypothesis that atrial baffles restrict a rise in SV under dobutamine stress in patients after atrial switch operation for transposition of the great arteries.