In electrophysiologic studies (EPS), recording and stimulating electrodes are inserted into all 4 cardiac chambers via right- or left-sided cardiac catheterization Cardiac Catheterization Cardiac catheterization is the passage of a catheter through peripheral arteries or veins into cardiac chambers, the pulmonary artery, and coronary arteries and veins. Cardiac catheterization... read more 
. Atria are paced from the right or left atrium, ventricles are paced from the right ventricular apex or right ventricular outflow tract, and cardiac conduction is recorded. Various mapping techniques are available. Programmed stimulation techniques may be used to trigger and terminate a reentrant arrhythmia.
Electrophysiologic studies are indicated primarily for evaluation and treatment of arrhythmias that are
Serious
Sustained
Difficult to capture
These studies may be used to make a primary diagnosis, to evaluate the efficacy of antiarrhythmic drugs, or to map arrhythmia foci before catheter ablation Ablation for Cardiac Arrhythmia The need for treatment of arrhythmias depends on the symptoms and the seriousness of the arrhythmia. Treatment is directed at causes. If necessary, direct antiarrhythmic therapy, including antiarrhythmic... read more .
