A miracle which has been performed in London over two centuries ago – resuscitation of a girl by an electrical discharge – is known now as a standard medical therapeutic method – defibrillation. How could a phenomenon - always and everywhere known as a killer – be transformed into human life savior? In this particular case, the answer was obvious: the Leyden jars – being used as the very first defibrillator - accumulated and reimbursed much less energy than a lightning produces. But, to find a comprehensive answer to this question, decades of intensive medical and technological efforts worldwide have been spent. Now, for majority of heart failures types, the optimal energy and efficient waveforms of defibrillation have been found. The research goes on, e. g., on implantable defibrillation. Due to the very nature of this research field, the only optimization tool remains to be modeling. Both energy of defibrillation waveform and its modeling – based on signal analysis approach - are the main topics of this book. It can be useful for cardiologists, medical students as well as for researchers and electrical engineers who are specialized in development and design of medical equipment.