Yes, mapping is what is done during an EP study. You can have an EP study and nothing that is ablatable may be found. Not every palpitation or arrhythmia is ablatable although many are. In addition, a source of an arrhythmia may be found to be too close to the heart's natural pacemaker to ablate safely and, especially if the arrhythmia benign if annoying, may not be something worth medical risk. In addition, although it rarely happens, they electrophysiologist may not be able to provoke an arrhythmia during an EP study in order to map it for an ablation. Having said all of this, EP studies are extraordinarily safe and so are most ablations. The technology has progressed by proverbial leaps and bounds.