Long-term vagal stimulation for heart failure: Eighteen month results from the NEural Cardiac TherApy foR Heart Failure (NECTAR-HF) trial. - De Ferrari GM; Stolen C; Tuinenburg AE; Wright DJ; Brugada J; Butter C; Klein H; Neuzil P; Botman C; Castel MA; D'Onofrio A; de Borst GJ; et al. (International journal of cardiology, 2017)