Cardiovascular and Neurohormonal Effects of Faster Atrial Pacing Rate

Many patients with heart failure are unable to increase their heart rate appropriately when their body needs increased blood flow. As a result, they may be unable to mobilize excess fluid that their body retains. We hypothesize that we can provide assistance to their body in mobilizing this fluid by artificially increasing their heart rate using a pacemaker. We plan to conduct a prospective clinical trial to evaluate this hypothesis. We will use a cross over design to study patients who already have biventricular pacemakers implanted or a narrow QRS and volume overload. We will screen them using a blood test that is a rough estimate of volume overload. Patients who meet the inclusion criteria will be randomly assigned to have their pacemakers adjusted or to have no intervention during the first of 2 visits. They will be unaware of which group they are in. Following adjustment, they will be monitored for six hours. Prior to the pacemaker adjustment, several tests will be performed to evaluate heart function and the levels of hormones related that are affected by heart failure. These tests will be repeated at the end of the six hour intervention period in each visit. At the end of the visit patients who had their pacemakers adjusted will have it reset to their original settings.