Low Frequency / High Frequency / Heart Failure / Humans / Female / Male / Oscillations / Body Mass Index / Respiration / Clinical Sciences / Middle Aged / Public health systems and services research / Chronic Heart Failure / Circulation / Nervous System / Sympathetic Nervous System / Heart Transplantation / Cardiac Transplantation / Muscle sympathetic nerve activity / Male / Oscillations / Body Mass Index / Respiration / Clinical Sciences / Middle Aged / Public health systems and services research / Chronic Heart Failure / Circulation / Nervous System / Sympathetic Nervous System / Heart Transplantation / Cardiac Transplantation / Muscle sympathetic nerve activity