Finding the origin of an arrhythmia

A probe generates location signals, and has an electrode at a distal end which acquires from heart chamber surface positions electrical signals due to a conduction wave traversing the surface. A processor derives LATs from the electrical signals, calculates a first time difference between LATs at a first pair of positions and a second time difference between LATs at a second pair of positions. The processor calculates first and second LAT-derived distances as products of the first and second time differences with a conduction wave velocity, identifies an arrhythmia origin at a surface location where a first difference in distances from the location to the first pair of the positions is equal to the first LAT-derived distance, and a second difference in distances from the location to the second pair of the positions is equal to the second LAT-derived distance, and marks the origin on a surface representation.