Purpose: The analysis of difficulties in understanding the information content of an electrocardiogram revealed indications that these are also caused by misconceptions about cardiac excitation phenomena. Therefore, a re-analysis of these research data is intended to deepen the understanding that medical students have of cardiac excitation. Furthermore, the concept of excitation represented in academic textbooks will be examined from an educational perspective. Methods: In order to diagnose learning potentials, a previous study on ECG comprehension collected statements from students using problem-centred, guideline-based interviews. These data were subjected to a re-analysis. The evaluation was based on a qualitative content analysis. Ideas of heart excitation and the underlying basal cognitions were analysed in the light of the Conceptual Metaphor theory using systematic metaphor analysis. Conceptual metaphors, which structure the understanding of this abstract fact, were identified. In a similar proced-ure, scientific ideas from textbooks were examined, too. The model of educational reconstruction served as the research framework. Results: On the basis of the data from exemplary cases, it will be shown which subject-related inappropriate ideas students of human medicine can construct when dealing with the phenomenon of excitation in a cardiological context. For example, excitation can be misinterpreted synonymously with the extracellular potential differences responsible for the development of an ECG. Sometimes, excitation is even under-stood as the tone of the myocardium. Analyzing the educational potential of academic textbooks reveals possible barriers to understanding in that excitation is not clearly defined in terms of the de-and repolarization of heart muscle cells. Moreover, both students and textbooks show an inappropriate idea of repolarization. Conclusion: The presented analysis of learning and teaching potentials offers the opportunity to identify difficulties in understanding with regard to an appropriate concept of cardiac excitation. It also helps to develop conclusions for educational interventions.