A basic EPS consists of a standard protocol that assesses baseline characteristics of the conduction system followed by attempted induction of arrhythmias. EPS begins with the measurement of baseline conduction intervals beginning with those on the surface electrocardiogram such as PR interval, and QRS width, and includes the intra-cardiac intervals measuring the time for conduction from the atrium to the His bundle deflection (AH interval), and from the His bundle deflection to the ventricular activation deflection (HV interval) (Fig. 21.2).

Pacing maneuvers are employed to assess sinoatrial (SA) node function and conduction properties from the atrium to ventricle (AV conduction), from the ventricle back to the atrium (VA conduction), and of the atrio-ventricular node (AVN)- including the rate at which the AVN displays both antegrade and retrograde Wenkebach and 2:1 conduction block. Introduction of premature atrial stimuli is performed in a standard fashion to further define the arrhythmogenic substrate (dual AVN pathways; accessory pathways), and to expose various forms of SVT’s (AV nodal reentry, AV reentry, atrial arrhythmias). These pacing maneuvers also help to define the refractoriness of the AV node, and to characterize the antegrade conduction properties of an existing accessory pathway. Similar maneuvers are performed from the ventricle (s) to characterize ventricular conduction and detect ventricular arrhythmias (VT, VF).

Various pacing maneuvers are performed in a variety of locations in an attempt to induce supraventricular or ventricular tachycardia. Extra-stimuli are delivered in increasing numbers [1–3] and prematurity after a drive train of eight beats from multiple sites (RA, RVA, RVOT, +/−CS/LA) in an attempt to induce an arrhythmia. The administration of drugs such as epinephrine, isoproterenol or atropine is often added to standard induction protocols to increase the chance of induction. Optimal therapy (drug, ablation, or device) can be planned if an arrhythmia is reproduced. Hemostasis is achieved with manual pressure at the end of the procedure after the catheters and sheaths are removed.