A system and associated method is disclosed for determining whether a signal is ambiguous. The system comprises a plurality of electrodes configured to be located proximate tissue of a patient. A display apparatus comprises a graphical user interface configured to present information to a user. A computing apparatus is coupled to the electrode apparatus. The computing apparatus is configured to calculate a first derivative of a signal acquired from the electrodes, determine a first minimum from the first derivative, determine a second minimum from the second derivative and a second index within a window, calculate a ratio of the first and second derivatives, calculate a difference between a first and second index. In response to determining the ratio and the difference between the first and second index, the display apparatus displays whether the signal is ambiguous.