SildenafilSildenafil in US Heart Failure Patients (SilHF-US)

Inclusion Criteria:

1. Men and women
2. 18 - 80 years of age.
3. Outpatients with chronic HF. NYHA class II-III on optimal treatment in sinus rhythm or atrial fibrillation
4. LVEF ≤ 40% measured during the past 12 months
5. SPAP ≥ 40mmHg using echocardiography
6. 6MWTD < 475 meters
7. NT-pro BNP ≥ 400 pg/ml or BNP ≥100 pg/ml, measured during the past 12 months
8. Receiving optimal therapy, including diuretic, ACE-inhibitor, ARB, beta-blocker and aldosterone antagonist. Doses of all medication should be unchanged during the last 30 days before inclusion.
9. ICDs and CRTs (CRT-P, CRT-D) are permitted. Implantation should have been performed at > 3 months before inclusion to the trial.

Exclusion Criteria: -

1. Acute Coronary Syndrome, including myocardial infarction, or coronary angiography, with or without intervention, within the last 3 months
2. Stroke within the last 3 months
3. Planned coronary angiography or planned device-implantation
4. Moderate to severe obstructive valve disease
5. Documented episodes of sustained ventricular tachycardia
6. Prior (past 30 days before the baseline visit) or ongoing use of oral nitrate therapy.
7. Concomitant disease which interfere with assessment of dyspnea , severe COPD, asthma, restrictive lung disease, severe obesity
8. Anemia (hemoglobin < 10g/dL)
9. Uncontrolled hypertension ( SBP >160 mmHg and / or DBP > 90 mmHg)
10. Symptomatic or orthostatic hypotension or systolic blood pressure < 90 mmHg
11. Clinically important renal dysfunction (GFR < 40m ml/min)
12. Women with child-bearing potential
13. Prior (past 30 days before the baseline visit) or ongoing use of i) alpha-1 antagonist: doxazosin ii) CYP3A4 inhibitors: erytromycin, ritonavir, sakinovir, itrakonazole, ketokonazole iii) CYP3A4-inducers: rifampicin iv) Any calcium channel blockers
14. V) Pulmonary vasodilators at the treatment dose level for Pulmonary hypertensionRetinitis pigmentosa, previous diagnosis of NAION (non-arteritic ischemic opticus-neuropathy), unexplained visual disturbance.
15. Sickle cell anemia, multiple myeloma, leukemia or penile anatomic deformities (angulation, cavernosal fibrosis, Peyronie's disease) that increases the risk of priapism.
16. Hepatic failure.
17. Drug and alcohol abuse which precludes compliance with the protocol.
18. Inability to understand or sign the written informed consent form of the study,