Heart Rate Response to Regadenoson and Sudden Cardiac Death

Prior to the implantation of a clinically indicated ICD, the heart rate response to regadenoson will be assessed. Regadenoson will be administered intravenously as a fixed intravenous bolus dose of 400 μg followed by a 5 mL saline flush. Medications (including beta-blockers) will be withheld on the morning of the test. The heart rate and blood pressure will be measured at baseline and every minute after regadenoson bolus for at least 5 minutes and until the heart rate and blood pressure are clearly returning towards baseline.