USMLE® Step 1 style questions USMLE
An 11-year-old girl comes to the emergency department by her parents after collapsing outside while running. Prior to the collapse, she had difficulty breathing and moving, and complained of transient heart palpitations. She is disoriented but responsive, with focal deficits indicative of a minor stroke. A syncope workup is performed and an electrocardiogram is obtained, showing a supraventricular tachycardia. Which of the following best describes the finding pointed out by the arrow?