In the first wave of artificial intelligence (AI), rule-based expert systems were developed, with modest
success, to help generalists who lacked expertise in a specific domain. The second wave of AI, originally
called artificial neural networks but now described as machine learning, began to have an impact with multilayer
networks in the 1980s. Deep learning, which enables automated feature discovery, has enjoyed spectacular
success in several medical disciplines, including cardiology, from automated image analysis to the identification
of the electrocardiographic signature of atrial fibrillation during sinus rhythm. Machine learning is now embedded
within the NHS Long-Term Plan in England, but its widespread adoption may be limited by the “black-box”
nature of deep neural networks.