Methods and systems for mapping cardiac fibrillation in a patient include deploying a catheter in the patient's heart, wherein the catheter includes an array of at least one stacked electrode pair having a first electrode and a second electrode. Each electrode pair is configured to be orthogonal to the surface of a cardiac tissue substrate. A plurality of measurements are obtained from the electrode array in response to electrical activity in the cardiac tissue substrate for a duration indicative of a number of electrical circuit cores and distribution of the electrical circuit cores across the cardiac tissue substrate in the patient's heart. These are processed to obtain the density and distribution of electrical circuit cores which are mapped onto a representation of the patient's heart.
