Young woman with repetitive syncopal episodes and strong family background

AK: 25 year old Caucasian woman

• Extensive work up for recurrent syncope and exertional chest pain
• 5 episodes over last 2 months
• No prodrome or seizure activity
• Somewhat related to exercise or sitting-to-standing
• Family History: one cousin died (cardiac arrest) at age of 27; uncle died at age of 30, unknown cause
• Transthoracic echo: normal RV and LV function; normal valves; LVEF: 65%
• Treadmill stress echo: 11 METS exercise capacity; no arrhythmia, no ST-T abnormalities; normal wall motion
• 30 day event monitor: one 11 beat irregular ventricular tachycardia;
• CT angiogram: normal coronary arteries; Ca2+ score: ‘0’
  Note: Exercise capacity is reported in terms of estimated metabolic equivalents of task (METs). The MET unit reflects the resting volume oxygen consumption per minute (VO2) for a 70-kg, 40-year-old man, with 1 MET equivalent to 3.5 mL/min/kg of body weight.

  Questions:

  1. Which is the most probable clinical diagnosis? Why?
  2. What are the appropriate steps for the diagnosis?