Our hypothesis is that Dobutamine will act in a similar fashion to Isoproterenol with respect to cardiac conduction. Our goal is to study the effects of Dobutamine on cardiac conduction and refractoriness during an Electrophysiology study (EPS). At the end of most EPS Isoproterenol is commonly administered in an effort to change the conduction properties of the heart. In our practice we have been using Dobutamine for this purpose for many years. Dobutamine has never been rigorously studied for this indication however. We designed this study to systematically study the effect of various doses of Dobutamine on the parameters of cardiac conduction and refractoriness that are commonly measured during an EPS. We are specifically looking to compare the effect that Dobutamine has on the sinus node with the effect it has on the atrioventricular node. Patients undergoing an EPS at Long Island Jewish Hospital will be recruited and consented. Measurements of various conduction parameters will be taken at baseline as is standard protocol for an EPS. Dobutamine will then be administered at doses of 5mcg/kg/min, 10mcg/kg/min, 15mcg/kg/min and 20mcg/kg/min. At each of these dosages the same conduction parameters will be measured. A comparison will then be made between the conduction parameters at baseline and when the Dobutamine is administered.

Inclusion Criteria:

1. Provision of signed and dated informed consent form
2. Stated willingness to comply with all study procedures and availability for the duration of the study
3. Male or female, ages 18-80
4. Patients must be diagnosed with a condition that necessitates an EPS. They must also be deemed to be in good enough medical health to be eligible to safely undergo an EPS. Medical eligibility will be determined by the Attending Electrophysiologist performing the EPS.
5. For females of reproductive potential a negative pregnancy tes

Exclusion Criteria:

Patients with a resting left ventricular outflow gradient > 30mmHg

Patients with severe aortic stenosis

Patients with prior sustained ventricular tachycardia or ventricular fibrillation

Patients who are not able to consent for themselves

Patients with a prior allergic reaction to Dobutamine or any of its compounds including sulfites

Pregnant patients

Patients receiving B-blockers