Cardiac Vagal Effects of GES in Patients With Gastroparesis and Vagal Nerve Action Potentials in Vagus Nerve

All patients who are going to have a GES device implanted, or who already have the device are eligible to be part of the study. They will be followed according to the time point they enter the study and its schedule. The visit procedures will be conducted at the discretion of the investigator dependent on the clinical condition of the subject at that time. The study involves EKG and vagal nerve recordings. Three EKG electrodes will be placed (one on chest and 2 on either arms or legs). Separate electrodes will be placed on the neck overlying the vagus nerves

Baseline (Pre-GES Implantation) Visit:

Subjects who are being seen in clinic for possible gastroparesis and may be a possible candidate for GES later or will be undergoing the GES implantation may have a baseline visit. . The baseline visit can be held either at the time of the clinic visit or before the GES implantation. If the baseline visit occurs on the day of the GES implantation, 2 separate EKGs will be performed, one prior to GES pacemaker device implantation for up to a duration of 5 minutes and the second one after the implantation in the recovery room. This EKG will be performed for a total duration of up to 15 minutes with 5 minute "ON", 5 minutes :OFF" and another 5 minutes in the "ON" position. At the same visit with each EKG recording separate EKG electrode will be placed on the neck overlying the vagus nerve. Vagal nerve recordings will be documented for a total duration of upto 15 minutes with approximately 5 min at "ON", 5 min "OFF" and another 5 min "ON" settings of the stimulator in conjunction with the EKG recordings.

At the baseline visit separate EKG electrodes will also be placed on the neck overlying the vagus nerve and a 5 minute recording will be made in conjunction with the EKG recordings.\ before the implantation.

If the subjects already have the GES device implanted then a baseline visit will not be required. They will be included in the study at the time the consent form is signed and will be followed as needed according to the clinic visit schedule and at the discretion and clinical judgement of the investigator.

Post-GES Implantation Visits:

The subject may be asked at the clinic visits to repeat the EKG and vagal nerve study procedures at the discretion and clinical judgment of the investigator.

EKG electrodes will be placed on the chest and arms/legs, and vagal nerve electrodes will be placed on the neck overlying the vagus nerve. A butterfly catheter is inserted under aseptic conditions into a peripheral vein. Fifteen ml (1 tablespoon) of blood is withdrawn and placed on ice (labeled Baseline). With the subject at rest recordings may be made for upto a total duration of 15- 20 minutes. After 15- 20 minutes of recordings the GES device is then turned "OFF" and recordings will be made for up to 40 minutes. After 40 minutes additional 15 ml (1 tablespoon) of blood is withdrawn after the device has been in the OFF position for 40 minutes (labeled "OFF"). The device is then turned back in the "ON" position with the GES settings either at the original or changed settings from the previous settings based on the clinical judgement of the investigators, The EKG and vagal recordings may be made for up to 15-20 minutes. After 15- 20 minutes in the ON position 15 ml (1 tablespoon) is then withdrawn (labeled "ON". The butterfly catheter is then withdrawn, and a bandage is placed at the venipuncture site. The final setting on the GES will depend on the clinical decision of the investigator based on the subject's symptoms and presentation to the clinic.