The aim of the present study is to investigate whether in patients with chronic heart failure endothelial dysfunction and baroreceptor function is altered by ingestion of a flavonoid-rich dark chocolate in comparison to placebo chocolate (Nestlé Placebo Chocolate) on top of standard medication.

Moreover, we will evaluate the effect of chocolate on oxidative stress, platelet adhesion as well as systemic inflammatory response such as C-reactive protein and pro-inflammatory cytokines in patients with chronic heart failure.

Inclusion Criteria:

1. Heart failure ( NYHA ≥II, LVEF<50%, independent of aetiology)
2. Nonsmokers
3. Age: 30-80
4. Written obtained informed consent

Exclusion Criteria:

1. Decompensated Heart failure
2. Instable Angina pectoris
3. Smokers
4. Ventricular tachyarrhythmias or AV-Block >I°
5. Renal failure (>200 umol)
6. Liver disease (ALT or AST >150 IU)
7. Diabetes mellitus
8. Obesity (BMI >30 kg/m2)
9. Symptomatic hypotension, hypertension >160/100mmHg
10. Known allergy to compounds of Nestlé noir intense
11. History of gastric ulcer or bleeding, current diarrhea
12. Venous thrombosis or pulmonary embolism, at present or recurrent history of Infectious disease, acutely or chronic
13. Disease with systemic inflammation (e.g. rheumatoid arthritis, M. Crohn)
14. Neoplasia (unless healed or remission >5 years)
15. Participation in another study within the last month
16. Concomitant vitamin supplements