Purpose: The study takes a qualitative and explorative approach to capture the concepts that German medical students have of the physiological electrocardiogram (ECG) which they acquired during their preclinical training. These concepts are then considered for possible misconceptions. Afterwards a theory-based intervention which allows subjects to see the connection of the curve progression with the spatial spreading of excitation (animated vector loop) is put to the test. Methods: In the course of a diagnosis of learning potentials, individual students participated in problem-centred, guided interviews. The developed intervention was tested in separately conducted teaching experiments using thinking aloud protocols. The data evaluation was done through qualitative content analysis. Based on the conceptual metaphor theory, conceptions and their underlying embodied cognition were analysed. Results: One of the subjects’ typical misinterpretations is taking the progression of the ECG tracing for a mere increase and decrease of the myocardium’s electrical activity, rather than connecting it with its spatial and temporal aspects. The data evaluation has shown that the newly developed theory-based intervention can lead to re-learning. Reconstructed metaphorical concepts illustrate this process of understanding. It is exemplarily shown how, through the course of the interviews, students are enabled to appropriately explain ECGs as the two-dimensional representation of the spatial excitation propagation in the heart. Conclusion: By capturing typical misconceptions of the physiological electrocardiogram and demonstrating interventions that support learning, the study provides a contribution to comprehensive learning which can be used in the basic education of medical students. © 2019 Trauschke.