Wenckebach phenomena (Mobitz type 1 second degree AV) originates in the atrioventricular node at fast regular rhythms. It is characterized by progressive lengthening of conduction time until complete block followed by AV nodal recovery, then the cycle repeats. The Wenckebach phenomenon is a well-known clinical feature, but the underlining electrophysiology and, in particular, the role of the AV nodal dual pathways are not fully understood. Our recent compact mathematical model of the AV node is based on the Aliev-Panfilov model of cardiac myocyte and was developed taking into account available experimental data on rabbit hearts. Being computationally efficient, the model successfully reproduces many of the important AV nodal behavior and allows for visualization of the processes inside the node – the interplay of the slow and fast pathways in the form of ladder diagrams. In our modeling, we obtained a variety of Wenckebach patterns, including typical and atypical types of His-His interval evolution. The model demonstrates that even a small atrial rate variation can significantly change the Wenckebach pattern, which is in line with experimental and clinical findings. The phenomenon takes place at regular atrial pacing rhythms with shorter cycles than effective refractory periods of the fast pathway. We observed the formation of the Wenckebach periodicity around the penetrating bundle and inferior node extension, where the most pronounced increase of Atria-His and His-His interval delays occurs. The results demonstrate that the interaction between the fast and slow pathways is responsible for the formation of Wenckebach rhythms.