Conditions: Congestive Heart Failure
Allocation: RANDOMIZED | Intervention model: CROSSOVER
Enrollment: 43
Healthy volunteers: no

Brief summary:
This study is being done to determine the effects of subcutaneous (under the skin) injection of human B-type natriuretic factor (BNP), Natrecor (nesiritide), a hormone produced by the heart, in combination with Tadalafil on:

* The pumping function of the heart
* Kidney function
* Hormonal function (levels of different hormones in your blood) in persons with lower pumping function of their heart.

Detailed description:
In the American Heart Association/American College of Cardiology classification of heart failure (HF), stage B is defined as patients with abnormal heart structure/function (systolic or diastolic dysfunction) without symptoms. This concept of preclinical HF is based on the fact that abnormal heart structure/function can be detected by complementary methods before the development of symptoms. Patients with those abnormalities may progress to heart failure and are at increased risk of adverse cardiac events. Preclinical systolic dysfunction (PSD) is the initial compensated phase of left ventricular systolic dysfunction without symptoms of HF. We have established that diastolic dysfunction is common in the general population being present in approximately 25% of the population over age 45, the majority of whom are asymptomatic i.e., preclinical diastolic dysfunction (PDD). Cyclic guanosine monophosphate (cGMP) is the second messenger of the natriuretic peptide system (NPS) and the nitric oxide system (NO) and plays an important role in the preservation of myocardial, vascular, and renal function. Hence, disruption of this signal transduction process may contribute to the development of cardiorenal dysfunction. Type V phosphodiesterase (PDEV) metabolizes cGMP and is abundant in the kidney, vasculature, and has been recently reported in the heart. We and others have demonstrated that renal PDEV is up-regulated in experimental HF and may lead to the attenuation of renal cGMP generation in response to both endogenous and exogenous BNP, thus serving as a mechanism for renal resistance to BNP. Furthermore, in experimental overt HF, 10 days of PDEV inhibition treatment resulted in reduction of left ventricular (LV) mass, increased LV fractional shortening and cardiac output but did not improve renal function. However, chronic PDEV inhibition did enhance the renal actions of exogenous BNP, specifically improving glomerular filtration rate (GFR) and renal cGMP generation. PDEV inhibitors are FDA approved for erectile dysfunction and pulmonary hypertension.

Arms:
arm 1: First intervention period: oral Tadalafil; after 1 hour, subcutaneous (sc) placebo given in the abdomen. After a lead in period of 15 min, a 30-min clearance was repeated, then acute saline load was given. During the 1 hour saline load, one 30-min clearance repeated with subject in supine position, then second 30-min clearance repeated with subject sitting. There was a one week washout period. Second intervention period: oral Tadalafil; after 1 hour, sc Nesiritide given in the abdomen. After a lead in period of 15 min, a 30-min clearance was repeated, then acute saline load was given. During the 1 hour saline load, one 30-min clearance repeated with subject in supine position, then second 30-min clearance repeated with subject sitting. arm 2: First intervention period: oral Tadalafil; after 1 hour, sc Nesiritide given in the abdomen. After a lead in period of 15 min, a 30-min clearance was repeated, then acute saline load was given. During the 1 hour saline load, one 30-min clearance repeated with subject in supine position, then second 30-min clearance repeated with subject sitting. There was a one week washout period. Second intervention period: oral Tadalafil; after 1 hour, sc placebo given in the abdomen. After a lead in period of 15 min, a 30-min clearance was repeated, then acute saline load was given. During the 1 hour saline load, one 30-min clearance repeated with subject in supine position, then second 30-min clearance repeated with subject sitting.

Interventions: intervention 1: Nesiritide intervention 2: Tadalafil intervention 3: Placebo intervention 4: Saline load
Intervention descriptions: intervention 1: 10 ug/kg intervention 2: 5 mg intervention 3: The pharmacy will create a placebo subcutaneous injection volume to match the volume of Nesiritide dose. intervention 4: Normal saline 0.9% 0.25 ml/kg/min for 60 minutes

Protocol document: