A case of congenital junctional ectopic tachycardia: diagnosis and successful radiofrequency catheter ablation in infancy.

It is difficult to make a definitive diagnosis of congenital junctional ectopic tachycardia (JET) in utero. We report a case in which congenial JET was suspected by fetal M-mode echocardiography. Fetal M-mode tracing of the atria and ventricle clearly showed a gradual acceleration of ventricular activity at the beginning of tachycardia, the warming-up sign of ectopic tachycardia, which was followed by simultaneous contractions of atrium and ventricle. This report also describes successful emergent radiofrequency catheter ablation of congenital JET in infancy with preservation of normal AV nodal conduction for this patient.