Atrial Morphology in Hearts with Congenitally Corrected Transposition of the Great Arteries: Implications for the Interventionist

INTRODUCTION: In view of the possible need for septal puncture to ablate left-sided lesions and the occasional difficulty in coronary sinus (CS) cannulation, we investigated relevant anatomic features in the right atrium of hearts with congenitally corrected transposition of the great arteries (ccTGA). METHODS AND RESULTS: Nine hearts with ccTGA and an intact atrial septum and eight weight-matched normal hearts were examined by studying the "septal" aspect of the right atrium with reference to the oval fossa (OF). The anterior margin was arbitrarily measured as the shortest distance from the OF to the superior mitral/tricuspid annulus. The posterior margin was measured from the OF to the posterior-most edge of the right atrial "septal" surface. The total "septal" surface width was measured at the middle of the OF. The stretched OF dimensions and CS isthmus length were noted. Mann-Whitney test was used to compare absolute and indexed dimensions, i.e.. normalized to total width. The posterior margin in hearts with ccTGA was shorter than in controls (6.3+/-2.4 mm vs 11+/-1.9 mm, P < 0.001; normalized margin P = 0.09). The CS isthmus also was significantly shorter (5.3+/-2.7 mm vs 11.4+/-2.2 mm, P < 0.001). In two hearts with ccTGA, the CS opening into the right atrium was on the same side of the eustachian valve as the inferior caval vein. CONCLUSION: The shorter posterior "septal" margin in hearts with ccTGA may increase the risk of exiting the heart while performing septal puncture when pointing the needle posteriorly. The shorter CS isthmus and the abnormal location of the CS opening in some of these hearts are important when contemplating radiofrequency ablation in this area.