An otherwise healthy 20 year old presents with palpations on exercise. He was put on cardiac monitoring and this pattern was seen; it was short-lived and terminated spontaneously. On a further history, you find that a few of his family members have had sudden cardiac death. They follow an autosomal dominant inheritance. All other organ systems are negative. The patient is not taking any medications.
Challenge: What does the EKG show? What is the most likely cause?
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