Methods: A total of 46 subjects with PIHD who are stable in the 3 months prior to the Study, who continue in treatment with statins and have elevated concentrations of HDL-C (HDL-C ≥2.0mmol/L in females and ≥1.8mmol/L in males) and an LDL-C <100mg/dL. This is a double-blind, randomised Study; after 6 weeks of lifestyle stabilisation, the subjects will be treated with NA or placebo for 16 weeks. At the start and end of treatment, HDL composition will be studied through density gradient preparative ultracentrifuge separation and FBLC (fast protein liquid chromatography) and through the changes in vasodilation induced by the endothelium through ultrasound. Primary endpoint: change in the apoA1 content associated to treatment. Secondary endpoints: variations in the change of the brachial artery diameter with reactive hyperaemia and changes in the content of other lipid and protein components of HDL including apoA2, paraoxonase, amyloid A and LCAT. The changes in HDL composition and endothelial function will be assessed with an analysis of variance with repeated measurements and a 2x2 design.