Induction of a Narrow QRS Tachycardia – What is the Mechanism?Sakthivel Ramasamy, Ashish Jain, Raja J SelvarajDepartment of Cardiology, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry, IndiaWord count: 905Short title: Induction of a narrow QRS tachycardiaDisclosures: None for any of the authorsFunding: (None)Address for Correspondence:Raja J. SelvarajProfessor, Department of CardiologyJIPMERDhanvantri Nagar, PuducherryIndia – 605006email: [email protected] :A young female with recurrent palpitations underwent an electrophysiology study. Delivery of a single ventricular extrastimulus from the right ventricular base repeatedly produced a wide QRS beat (*) and subsequently induced a narrow complex tachycardia (figure 1). What is the mechanism of the wide QRS beat? What is the mechanism of the tachycardia?