Clinical Trial of Systolic Heart Failure Treatment of IvabRadine Hemisulfate Sustained-release Tablets （FIRST）

Inclusion Criteria: * aged from 18 to 75 years, males or females * Willing to provide written informed consent * NYHA Class II, III, or IV for≥4 weeks, in stable clinical condition for ≥4 weeks * Optimized and unchanged chronic heart failure medications and dosages for≥4 weeks * Sinus rhythm with resting heart rate≥70 b.p.m. * Left-ventricular systolic dysfunction, with ejection fraction≥40% documented within previous 1 month Exclusion Criteria: * Unstable cardiovascular condition(for example, hospital admission for worsening heart failure) * Recent (\<2 months) myocardial infarction or recent or scheduled coronary revascularization * Stroke or transient cerebral ischaemia within previous 4 weeks * Severe primary valvular disease * Scheduled surgery of valvular heart disease * Active myocarditis * Congenital heart diseases * peripartum cardiomyopathy * hyperthyroid heart disease * On list for cardiac transplantation * Cardiac resynchronization therapy started within previous 6 months * Pacemaker with atrial or ventricular pacing (except biventricular pacing)˃40% of the time, or with stimulation threshold at the atrial or ventricular level˃60 b.p.m. * Permanent atrial fibrillation or flutter * Sick sinus syndrome, sinoatrial block, second and third degree atrio-ventricular block * History of symptomatic or sustained (≥30 s) ventricular arrhythmia unless a cardioverter/defibrillator implanted * Cardioverter/defibrillator shock within previous 6 months * Family history or congenital long QT syndrome or treated with selected QT-prolonging products(except amiodarone) * Contraindication or intolerance to ivabradine or lactulose * Severe or uncontrolled hypertension (SBP≥180 mmHg or DBP≥110 mmHg) * known anaemia(Hb\<100 g/L) * Known moderate or severe liver disease(ALT/AST˃3ULN), known severe renal disease(Cr˃2ULN) * Pregnant or lactating women and women planning to become pregnant * Use of an investigational drug within 30 days of enrollment * Has a history of psychological illness/condition that interferes with ability to understand or complete requirements of the study