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There is evidence that rotors could be drivers that maintain atrial fibrillation. Complex fractionated atrial electrograms have been located in rotor tip areas. However, the concept of electrogram fractionation, defined using time intervals, is still controversial as a tool for locating target sites for ablation. We hypothesize that the fractionation phenomenon is better described using non-linear dynamic measures, such as approximate entropy, and that this tool could be used for locating the rotor tip. The aim of this work has been to determine the relationship between approximate entropy and fractionated electrograms, and to develop a new tool for rotor mapping based on fractionation levels. Two episodes of chronic atrial fibrillation were simulated in a 3D human atrial model, in which rotors were observed. Dynamic approximate entropy maps were calculated using unipolar electrogram signals generated over the whole surface of the 3D atrial model. In addition, we optimized the approximate entropy calculation using two real multicenter databases of fractionated electrogram signals, labeled in 4 levels of fractionation. We found that the values of approximate entropy and the levels of fractionation are positively correlated. This allows the dynamic approximate entropy maps to localize the tips from stable and meandering rotors. Furthermore, we assessed the optimized approximate entropy using bipolar electrograms generated over a vicinity enclosing a rotor, achieving rotor detection. Our results suggest that high approximate entropy values are able to detect a high level of fractionation and to locate rotor tips in simulated atrial fibrillation episodes. We suggest that dynamic approximate entropy maps could become a tool for atrial fibrillation rotor mapping., JPU, CT, and JB were partially supported by Departamento Administrativo de Ciencia, Tecnologia e Innovacion de la Republica de Colombia (www.colciencias.gov.co), project # 121056933647; AO was supported by the Programa de Formacion de Investigadores Francisco Jose de Caldas (www.colciencias.gov.co); VK and DN were partially supported by research project # MSM6840770012 Interdisciplinary Biomedical Engineering Research II from the Ministry of Education (www.msmt.cz), Youth and Sports of the Czech Republic, and VK was partially supported by post-doctoral research project GACR # P103/11/P106 of the Czech Science Foundation (www.gacr.cz). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.