Successful ablation of atrioventricular node reentry tachycardia in a patient with crisscross heart and situs inversus levocardia.

Crisscross heart is a complex congenital anomaly that is rarely seen in the absence of important associated structural defects. We describe a 41-year-old woman with recurrent dizziness and tachycardia but no previous cardiovascular symptoms. Narrow-QRS tachycardia was detected, and magnetic resonance imaging showed situs inversus levocardia with a circulatory pattern typical of crisscross heart. Electrophysiologic study revealed atypical atrioventricular (AV) node reentry tachycardia of the "fast-slow" type. Despite the unusual anatomy, we successfully modified the AV node physiology by ablating the "slow AV node inputs" with the guidance of a multielectrode basket catheter in the anatomic right atrium.