A 22-year-old female presented with a history of palpitations. During follow-up the electrocardiogram (ECG) shown below (Fig. 1) was recorded. Her baseline ECG during sinus rhythm showed no pre-excitation. Physical examination and echocardiogram were both unremarkable.

Fig. 1
figure 1

ECG at presentation

What is the most likely diagnosis for the arrhythmia?

Answer

You will find the answer elsewhere in this issue.