CardioMark: An open-source MATLAB toolbox for ECG annotation for machine learning and academic research

With the growing use of machine learning, especially deep learning, in ECG analysis, access to well-annotated databases has become increasingly important. However, most public ECG databases lack detailed QRS morphology labels or complete 12-lead ECG recordings. Manual annotation remains essential but is time-consuming, subjective, and often requires multiple reviewers. CardioMark is an open-access MATLAB toolbox that simplifies and improves ECG annotation through an intuitive graphical interface. It supports multi-observer input, session-based work, and easy export for machine learning applications. Its modular design allows customization for various ECG tasks, making it a useful tool for both research and education in clinical cardiology.