Twenty-four patients with known heart failure will be recruited. They will undergo a cardiac magnetic resonance for ventricular analyses and after this first exam they will be randomized to placebo or sildenafil. After one hour drug intake they will undergo another cardiac magnetic resonance to evaluate the drug impact on right and left ventricular function.~The first and second exams will be performed by the same staff. All patients will be evaluated by two, three and four chambers view. Left and right ventricle quantification analyses will be performed by Argus software.
Twenty-four patients with known heart failure will be recruited. They will undergo a cardiac magnetic resonance for ventricular analyses and after this first exam they will be randomized to placebo or Sildenafil. After one hour drug intake they will undergo another cardiac magnetic resonance to evaluate the drug impact on right and left ventricular function.