Diagnostic Electrophysiology (EP) Study

A baseline EP study may last anywhere from one to three hours. The patient is prepared for an invasive sterile procedure and the staff will monitor patient vital signs, patient symptoms, and termination of hemodynamically untolerated arrhythmias with cardioversion or defibrillation. Two to four catheters are placed into the right side of the heart, typically through the femoral vein. Other access sites may be used if necessary such as the subclavian or internal jugular vein. Occasionally, the femoral artery is used if access to the left side of the heart is mandated. Typical electrode placements are in the high right atrium, near the sinus node, the area of the His bundle, the coronary sinus that lies in the posterior atrioventricular groove and near the left atrium and ventricle, and in the right ventricle. The catheter electrodes are used to pace the heart and record intracardiac electrograms.

All aspects of the cardiac conduction system are evaluated, including the sinus node, the AV node, His-Purkinje system, and the input of the autonomic nervous system. Arrhythmia induction characteristics are noted and, in some cases, arrhythmia foci are identified. Sinus node function is evaluated by looking at the sinus node recovery time (SNRT). The AV node function is assessed during spontaneous rhythm via the atrium to His (A-H) interval. His-Purkinje function is seen in looking at the His to ventricle (H-V) interval during spontaneous rhythm. The autonomic nervous system controls the beat-by-beat function of the heart causing changes in heart rate, strength of contraction, and peripheral resistance to accommodate the ever changing needs for cardiac output. This is evaluated with carotid sinus massage and pharmacologic maneuvers that block the sympathetic and parasympathetic input to the heart. Infusion of medications such as atropine, isoproterenol, epinephrine, or beta blockers may be given and the cardiac response monitored.

Programmed electrical stimulation (PES) is used to determine the electrical properties of the heart and to initiate abnormal heart rhythms. These pacing protocols are designed to target specific components of the conduction system and will typically include the sinus node, AV node, His-Purkinje system and atrial and ventricular myocardium. The goal of initiating (and in some cases terminating) an arrhythmia is to provide the electrophysiologist with information to guide antiarrhythmic or ablation therapy. Induction protocols typically begin with the least aggressive techniques and progresses to more aggressive techniques.

Because the EP study involves catheter placement in multiple areas within the heart, catheter design and handling are critical to site access. Some catheters have fixed curve profiles that are optimized for targeted sites in the study. Steerable catheters provide ease of placement in a variety of anatomical locations. Also, due to varying anatomical conditions, some catheters may be best suited to a particular location. A decapolar catheter is useful in the coronary sinus because it maximizes sensing and recording capabilities.

Boston Scientific provides a wide array of diagnostic catheter options to meet the numerous challenges of a diagnostic EP study.