Effort-induced syncopal episodes in a child with family history of sudden death

IGS, male, 11-year-old patient, student, born and living in Ubajara, Ceará, Brazil. Reason for the visit: fainting.
History of current disease:

• Report of 2 episodes of sudden loss of consciousness while doing physical exercise, with no prodromes. He recovers conscious after some minutes, with no complaints after the event.
• He was referred by the neurologist after the second episode of syncope.
• Referred to cardiological evaluation after normal neurological tests.
• The first episode was 2 years ago when he was playing soccer and the second 8 months ago, riding a bicycle.

  Personal history:

• Previously healthy.
• He mentioned 2 previous episodes of passing out during physical activity.
• He denies using medication regularly
• He was born through C-section, in term, without problems during pregnancy.

  Family history:

• His brother died at the age of 8, while doing physical exercise. Lab tests: normal.

Two-dimensional transthoracic echocardiography color Doppler: normal Electrophysiological study (EPS)

• It was not able to induce ventricular tachyarrhythmia after stimulation of the right ventricle.
• Triggered episode of polymorphic ventricular tachycardia with isoproterenol infusion.
  

  Questions

1. Which is the clinical diagnosis? And why?
2. Which are the electrocardiographic diagnose during treadmill stress testing and isoproterenol infusion?