Degeneration of atrioventricular nodal reentrant tachycardia into polymorphic ventricular tachycardia

Atrioventricular nodal reentrant tachycardia (AVNRT) is the most common form of paroxysmal supraventricular tachycardia and is usually treated successfully by radiofrequency catheter ablation. We report on a 38-year-old woman whose AVNRT attacks occasionally degenerated into polymorphic ventricular tachycardia (VT). The patient presented with a complaint of palpitations. The electrocardiogram was in sinus rhythm with a normal corrected QT interval. During Holter monitoring, narrow QRS complex tachycardia with a heart rate of 220 beats/min was noted at nighttime, that lasted for 90 minutes, during which two episodes of polymorphic VT were also seen. The diagnosis of AVNRT was confirmed on an electrophysiologic study and AVNRT was successfully treated by radiofrequency catheter ablation. The patient had no complaint during a follow-up of eight months, with no signs of arrhythmia on repeat Holter monitoring.