ECG tracing of a 12-year old girl, taken throughout cardiac evaluation for chest pain. No complaints of palpitations, vertigo, or syncope.
Assessing the ECG strip you notice negative P-waves, where they usually appear positive. What´s that rhythm?
Lead I shows almost equiphasic P waves, while Leads II & III show clearlyy negative P waves - inferior origin (red and green circles).
V1 & V2 show slightly positive P waves (red circle). V3 shows eqiphasic and V4-6 show negative P waves (blue circles) - origin probably somewhere septal.
Therefore, the most probable origin of this rhythm is within the coronary sinus or CS os. Such rhythm is not uncommon, especially in adolescent girls and with high vagal tone. No therapy is required as long as the patient is asymptomatic.