Medical devices and methods for making and using medical devices are disclosed. An example system for mapping the electrical activity of the heart includes a catheter shaft. The catheter shaft includes a plurality of electrodes including a first electrode and a second electrode. The system also includes a processor. The processor is capable of collecting a first signal corresponding to the first electrode and a second signal corresponding to the second electrode. Collecting the first and second signals occurs over a time period. The processor is also capable of generating a first time-frequency distribution corresponding to the first signal, identifying a first dominant frequency value occurring at a first dominant frequency and a first time point, generating a second time-frequency distribution corresponding to the second signal, identifying a second dominant frequency value occurring at a second dominant frequency and a second time point and determining an attraction point.