This book offers a historical account of the development of the On-X carbon mechanical heart valve, discussing the steps involved in developing the materials, and describes how the design of the valve has evolved over the years. It explores both the scientific and corporate problems researchers have encountered over the years in the journey of making a mechanical heart valve. The chapters provide a detailed description of the design of the mechanical leaflet-based prosthetic valve, with a particular focus on blood flow characteristics. This book includes an overview of the state-of-the-art in the chemistry and physics of carbon, and compiles the advances in carbon-based technology and its applications in cardiac and thoracic surgery.