Cardiac electrophysiologists focus on electrical system of the heart and on diagnosing and treating irregular heartbeats or arrhythmias. Electrophysiologists are qualified to perform special tests of heart’s electrical system, such as an electrophysiology study or an ablation. An electrophysiology (EP) study is done to assess heart’s electrical activity by inserting catheters which measure electrical activity, through blood vessels that enter the heart.