An exemplary method includes selecting a first pair of electrodes to define a first vector and selecting a second pair of electrodes to define a second vector; acquiring position information during one or more cardiac cycles for the first and second pairs of electrodes wherein the acquiring comprises using each of the electrodes for measuring one or more electrical potentials in an electrical localization field established in the patient; and determining a dyssynchrony index by applying a cross-covariance technique to the position information for the first and the second vectors. Another method includes determining a phase shift based on the acquired position information for the first and the second vectors; and determining an interventricular delay based at least in part on the phase shift.