Signal processing is essential in cardiology decision system, with the electrocardiogram (ECG) providing important information for various related diagnosis. Heart Rate Variability (HRV) is quantified from ECG signal by various methods and algorithms. MATLAB, meanwhile, is a tool to analyse these signals to reveal wide range of information about health conditions. This book is important to understand the various recent applications and different methods of analysis of HRV in time, frequency and time-frequency domains. This book contains six chapters where various methods for quantification of HRV from ECG and feature extraction of HRV from different techniques together with MATLAB source code are clearly discussed. The methodologies described in this book are beneficial to a broad range of readers, particularly students and academics in the fields of biomedical signal processing, biomedical instrumentation, cardiovascular engineering, rehabilitation, and clinical study. The book will also be helpful to professionals in hospital management, and hospital development/planning authorities for improving their understanding on ECG and HRV analyses and their recent applications.