An example system and method of defining a rotational source associated with a heart rhythm disorder are disclosed. A plurality of center locations of wave fronts are calculated at a plurality of time points associated with the heart rhythm disorder. A rotational path that connects the plurality of center locations is then determined. The system and method can also determine a likely core associated with the rotational path. A plurality of relative diffusion shapes associated with the plurality of the center locations is calculated. A plurality of intersecting points of a smallest relative diffusion shape and other relative diffusion shapes is determined within the rotational path. A bounded polygon of the intersecting points is defined as the likely core.
