Dobutamine on the Cardiac Conduction System

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.

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.

Dobutamine will then be administered at doses of 5mcg/kg/min, 10mcg/kg/min, 15mcg/kg/min and 20mcg/kg/min.

The change in sinus cycle length and anterograde atrioventricular node Wenckebach cycle length with Dobutamine

The difference between the change in the sinus cycle length from baseline to the highest dose of Dobutamine compared to the change in the anterograde AV node Wenckebach cycle length from baseline to the highest dose of Dobutamine.

The sinus cycle length and anterograde AV node Wenckebach cycle length will be measured from baseline and at the end of 5 minutes of each dobutamine dose of 5mcg/kg/min, 10mcg/kg/min, 15mcg/kg/min and 20mcg/kg/min for a total of 20 minutes.

The relative changes in baseline of escalating doses of Dobutamine on the sinus cycle length (msec), AH interval (msec), HV interval (msec), QRS duration (msec), QTc (msec), AV node Wenckebach cycle length (msec), AV node effective refractory period (msec) and VA block cycle length (msec).

The parameters noted above will be measured at baseline and at the end of 5 minutes of each dose of dobutamine at 5mcg/kg/min, 10mcg/kg/min, 15mcg/kg/min and 20mcg/kg/min for a total of 20 minutes.

The blood pressure will be measured at baseline and at the end of 5 minutes of each dose of dobutamine at 5mcg/kg/min, 10mcg/kg/min, 15mcg/kg/min and 20mcg/kg/min for a total of 20 minutes.

Inclusion Criteria: Provision of signed and dated informed consent form Stated willingness to comply with all study procedures and availability for the duration of the study Male or female, ages 18-80 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. 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