All patients enrolled in the study will have their device tested to determine if the device can automatically measure how much energy is needed to pace the patient's heart. If the test is successful, the patient's device will be programmed to turn that feature on. 3 months after enrollment, the patient will return to the clinic to have their device re-tested using an automatic test method to measure the amount of energy needed to make the patient's heart beat. A manual test method will also be used to measure the amount of energy needed to make the patient's heart beat. The intent of the study is to show the automatic method works just as well as the manual method.
