Percutaneous interventional electrophysiology

doi:10.1136/bmj.327.7409.280

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Gerry C Kaye, consultant cardiologist

Hull and East Yorkshire Trust, Castle Hill Hospital, Hull.

Introduction

Before the 1980s, cardiac electrophysiology was primarily used to confirm mechanisms of arrhythmia, with management mainly by pharmacological means. However, recognised shortcomings in antiarrhythmic drugs spurred the development of non-pharmacological treatments, particularly radiofrequency ablation and implantable defibrillators.

Mechanism of a re-entry circuit. An excitation wave is propagated at a normal rate down path A, but slowly down path B. An excitation wave from an extrasystole now encounters the slow pathway (B), which is still refractory, creating unidirectional block. There is now retrograde conduction from path A, which coincides with the end of the refractory period in path B. This gives rise to a persistent circus movement

The two major mechanisms by which arrhythmias occur are automaticity and re-entrant excitation. Most arrhythmias are of the re-entrant type and require two or more pathways that are anatomically or functionally distinct but in electrical contact. The conduction in one pathway must also be slowed to a sufficient degree to allow recovery of the other so that an electrical impulse may then re-enter the area of slowed conduction.

Classification of arrhythmias

Intracardiac electrophysiological studies

Intracardiac electrophysiological studies give valuable information about normal and abnormal electrophysiology of intracardiac structures. They are used to confirm the mechanism of an arrhythmia, to delineate its anatomical substrate, and to ablate it. The electrical stability of the ventricles can also be assessed, as can the effects of an antiarrhythmic regimen.

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Indications for electrophysiological studies

Atrioventricular conduction

Electrodes positioned at various sites in the heart can give only limited data about intracardiac conduction during sinus rhythm at rest. “Stressing” the system allows more information to be generated, particularly concerning atrioventricular nodal conduction and the presence of accessory pathways.

Diagrams showing position of pacing or recording electrodes in the heart in the right anterior oblique and left anterior oblique views (views from the right and left …