Chronotropic Incompetence (CI) Diagnostic Algorithm in Heart Failure Patients

Inclusion criteria for the case group: * Patient is greater than 18 years of age and less than 70 years of old. * Patient is willing and able to give informed consent. * Patient has been diagnosed with stable chronic HF according to European Society of Cardiology 2012 HF guidance. * New York Heart Association class I- III, including with HF with preserved ejection fraction and HF with reduced ejection fraction patients. * Patients can perform moderate exercise. * Left ventricular ejection fraction less than 55% but greater than 35%. Inclusion criteria for the control group: * Subject is greater than 18 years of age and less than 70 years of old. * Subject is willing and able to give informed consent. Exclusion criteria for the case group: * Patient is unable or unwilling to sign the patient informed consent. * Patient has implantable pacemaker, Implantable cardiovert defibrillator (ICD) or cardiac resynchronize therapy (CRT) device. * Patient has at least one pacemaker, ICD or CRT indications. * Patients has persistent atrial fibrillation (AF). * Patient whose hear rate baseline at the rest is greater than 95 beats per minutes (BPM). * Patient has contraindications for cardio-pulmonary exercise testing, including but not limited to, unstable angina, decompensated heart failure, active pericarditis or myocarditis and ECG ST-segment shift \> 2mm at the resting. * New York Heart Association Class IV. * Less than 45 days after myocardial infarction. * Less than 3 months after acute heart failure. * Patient has uncontrolled hypertension. * Patient is pregnant. * Patient has a medical condition that would limit study participation. * Patient is enrolled in a concurrent study that may affect the outcome of this study.