• Changes in transthoracic impedence [ Time Frame: 8 hours ] [ Designated as safety issue: No ]
• Changes in BNP [ Time Frame: 8 hours ] [ Designated as safety issue: No ]
• Changes in norepinephrine [ Time Frame: 8 hours ] [ Designated as safety issue: No ]
• Changes in renin [ Time Frame: 8 hours ] [ Designated as safety issue: No ]

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 enroll participants from a pool of patients who already have biventricular pacemakers implanted. We will screen them using a blood test that is a rough estimate of volume overload and then confirm the results of this test with echocardiography, an ultrasound of their heart. Patients who meet the inclusion criteria will be randomly assigned to have their pacemakers adjusted or to have no intervention. 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 observation period in both groups. Following the second set of tests, patients who had their pacemakers adjusted will be reset to their original settings.

Many patients with heart failure suffer from chronotropic incompetence, an inability to raise their heart rate in response to metabolic demand. Previous studies have shown that brief increases in pacing rates in patients with biventricular pacemakers can improve cardiac contractility. We hypothesize that the benefits of an increased biventricular pacing rate could be sustained and would improve cardiovascular and neurohormonal parameters in patients suffering from volume overload. We intend to prospectively evaluate this hypothesis in a singleblind randomized trial. We will screen 40 patients who have previously implanted biventricular pacemakers and an elevated BNP level and confirm that their wedge pressure is increased by echocardiography. Following enrollment, patients with elevated wedge pressure will be randomly assigned to have their atrial pacing rate increased to 85 beats per minute or to be unchanged. Patients will be unaware of their treatment assignment. They will be observed for six hours in a monitored setting. The primary outcome will be cardiac output, as measured noninvasively by the Innocor and by the NICOM system before and after the observation period. Secondary outcomes will include changes in neurohormonal measures, six-minute walk time and transthoracic impedance as measured by the OptiVol system. If this proof-of-concept study demonstrates a positive effect, future research would evaluate the ability of increased pacing rates to prevent or abort decompensation of CHF.

• Device: Medtronic CRT (InSync or Concerto)
• Device: Medtronic CRT (Insync or Concerto)

• Experimental: Ambulatory out-patients will be identified at Columbia-Presbyterian and New York University Medical Centers.
• Sham Comparator: Ambulatory out-patients will be identified at Columbia-Presbyterian and New York University Medical Centers.

Inclusion Criteria:

1. Age>18 2. CHF (>6 months duration) 3. LVEF <40% 4. Functional Class III 5. Stable oral treatment (>1 month), 6. Implanted Medtronic CRT system (ideally 50% of them with the OptiVol system) with an atrial pacing lead 7. Low HR (SR or atrial pacing <70 bpm) 8. Symptomatically stable (with no clinical requirement for adjustments in medical therapy, i.e. diuretics) 9. Increase in intrathoracic fluid as evidenced by: i. BNP>200; and ii. TTE wedge (E/E') >15.

Exclusion Criteria:

1. Atrial fibrillation
2. Stable or unstable angina
3. Myocardial infarction within 6 months before the study
4. Intravenous inotropic support
5. Noncardiac condition limiting exercise ability (i.e. severe rheumatoid arthritis or osteoarthritis, chronic pulmonary disease requiring daily beta-agonists)
6. Pregnant or breast feeding women. Women of child bearing potential must have a negative serum pregnancy test prior to enrollment.
7. Severe renal failure (creatinine> 2.5 mg/dl, hemodialysis or peritoneal dialysis)
8. Known hepatic impairment (total bilirubin >3 mg/dL, albumin <2.8 mg/dL, or increased ammonia levels if performed)
9. Hgb <8 mg %, or active bleeding requiring transfusion-