An example system and method of locating a source of a heart rhythm disorder are disclosed. In accordance with the method, a first pair of cardiac signals is processed to define a first coefficient associated with variability of the first pair of signals at a first region of the heart. Further, a second pair of cardiac signals is processed to define a second coefficient associated with variability of the second pair of signals at a second region of the heart. Thereafter, the first coefficient of variability is compared to the second coefficient of variability to determine a direction towards the source of the rhythm disorder.