A 39-year-old patient without any medical history except episodes of rapid palpitations was referred to our centre for electrophysiology study. Structural heart disease was excluded and the family history was negative for arrhythmias and sudden death. The electrocardiogram (ECG) of one of the episodes can be seen in Fig. 1. A narrow QRS complex tachycardia with a heart rate of 110 beats/min can be observed. In the patient’s medical history tachycardias with faster heart rates were also mentioned. What is the mechanism of this supraventricular tachycardia?

Fig. 1
figure 1

Twelve-lead surface ECG of the tachycardia

Answer

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