This study will involve asking fifty children coming to the hospital for their standard of care procedure to treat a separate cardiac condition to participate. Patients approached will already have an intravenous line in place for their procedure. After consent and assent as necessary are obtained, the patient be brought to a separate room for the low-dose epinephrine infusion trial. The patient will lie down on a table, be hooked up to an EKG machine and the infusion will start. The amount of epinephrine actually infused is based on the weight of the patient but is substantially less than the dose received from an epinephrine auto-injection for anaphylaxis. After about 40 minutes, the trial will be completed and the patient may return to the waiting room for their original procedure. We have performed this test on a number of pediatric patients suspected of having LQTS with promising results and with little to no side effects. The patient will be awake for the procedure and will be able to verbalize concerns or complaints. A pediatric electrophysiologist and nurse will be present throughout the entire procedure.