The invention relates to an apparatus for locating an arrhythmogenic focus or pathway in a location of a living subject, comprising a mapping catheter operative for stimulating multiple locations endocardially or epicardially detecting respective sets of pace-mapped electrocardiographic signals at respective locations of said catheter, said catheter having a position sensor a position processor receiving position signals from said position sensor and operative for determining said respective locations of said catheter and an analysis processor, receiving a reference set of electrocardiographic signals and receiving said sets of pace-mapped electrocardiographic signals from said catheter, said reference and pace-mapped sets of electrocardiographic signals each comprising 12-lead electrocardiograms, said analysis processor operative for correlating the leads of said electrocardiograms comprising said sets of pace- mapped electrocardiographic signals with the corresponding leads of said electrocardiograms comprising said reference set of electrocardiographic signals, making a determination that a correlation between a predefined number of leads of said sets of pace-mapped electrocardiographic signals and the corresponding number of leads of said reference set of electrocardiographic signals meets a predefined criterion.
