Implantable devices for treating tachyarrhythmias

doi:10.1136/bmj.327.7410.333

BMJ 2003;327:333-336 (9 August), doi:10.1136/bmj.327.7410.333

Clinical review

ABC of interventional cardiology

Implantable devices for treating tachyarrhythmias

Timothy Houghton, specialist registrar in cardiology, Gerry C Kaye, consultant cardiologist at Hull and East Yorkshire Trust

Castle Hill Hospital, Hull

The first 150 words of the full text of this article appear below.

Introduction

Pacing treatment for tachycardia control has achieved success,notably in supraventricular tachycardia. Pacing terminationfor ventricular tachycardia has been more challenging, butan understanding of arrhythmia mechanisms, combined with increasinglysophisticated pacemakers and the ability to deliver intracardiacpacing and shocks, have led to success with implantable cardioverterdefibrillators.

Mechanisms of pacing termination

There are two methods of pace termination.

Underdrive pacing was used by early pacemakers to treat supraventricularand ventricular tachycardias. Extrastimuli are introduced at a constant interval, but at a slower rate than the tachycardia,until one arrives during a critical period, terminating thetachycardia. Because of the lack of sensing of the underlyingtachycardia, there is a risk of a paced beat falling on theT wave, producing ventricular fibrillation or ventricular tachycardia,or degenerating supraventricular tachycardias to atrial fibrillation.It is also not particularly successful at terminating supraventriculartachycardia or ventricular tachycardia and is no longer used routinely.