14th International Congress
THE "NEW FRONTIERS"
OF ARRHYTHMIAS 2000

Jan. 29 - Feb. 5, 2000
Marilleva, Trento, Italy

RT-106

Single-chamber versus dual-chamber implantable cardioverter defibrillators for prevention of tachyarrhythmias: a proposed trial

Stefano Favale, Ursula Appl*, Frida Nacci, Luciano Sallusti**, Luigi de Luca Tuppati Schinosa.
Arrhythmia Service-Cardiosurgery, Unit-Department of Emergency and Transplantation, University of Bari, Italy, *Guidant Europe, **Guidant Italy

Introduction

Dual-chamber implantable cardioverter-defibrillator may allow advantages in managing patients at risk of tachyarrhythmic death favouring a reduction of inappropriate interventions due to atrial tachyarrhythmias, a greater hemodynamic stability and a more appropriate stimulation in cases with the evolution toward the bradycardia and/or the atrio-ventricular block.

An estimated 20-30% of implantable cardioverter-defibrillator recipients have atrial tachyarrhythmias: this group represents a majority who feels inappropriate interventions^1-3. Therefore the association of atrial sensing and pacing may be useful: the algorithm using atrial sensing can increase specificity in ventricular tachycardia recognition while atrial pacing can provide better atrial electrical stability which can be further increased by drugs⁴, such as sotalol and amiodarone.

The dual-chamber implantable cardioverter-defibrillator is certainly advantageous to hemodynamic performance. Prevention of sudden death does not significantly prolong the life of patients with very severe left ventricular dysfunction: in such cases, where life expectancy is very low, it has been considered that implantable cardioverter-defibrillator only determines the “conversion” of the type of death, from sudden to non-sudden⁵. In this kind of patient, therefore, an improvement in left ventricular function obtained by dual-chamber stimulation^6,7, eventually biventricular if indicated⁸, could determine a reduction in non-sudden deaths and considerably prolong life expectancy. The aim of DDD pacing in these cases is thought to provide: adequate chronotropism at rest and during exercise; optimal delay in the atrio-ventricular sequence; a more adequate left ventricular volume and higher atrial stability.

Without doubt, candidates for implantable cardioverter-defibrillator implantation with congestive heart failure who also require a pacemaker can gain the greatest advantage from dual-chamber rather than ventricular stimulation. However, the long term usefulness of sequential pacing in subjects with congestive heart failure and normal chronotropism and atrio-ventricular conduction has still to be demonstrated^6,9.

While the need for pacing may not seem necessary at the time of cardioverter-defibrillator implantation, the serious cardiac pathology present in the majority of patients with ventricular tachyarrhythmias can, however, be complicated after implantation by sinus node dysfunction or atrio-ventricular block.

Moreover, in patients with left ventricular dysfunction or congestive heart failure atrial pacing may favour a wider use of betablockers which demonstrated a significant reduction in non-sudden cardiac and all cause mortality^10-12.

The benefit of atrial pacing and a programmed short atrio-ventricular delay is still questionable^5,8 and seems to be confirmed only in patient subsets with mitral regurgitation and diastolic dysfunction^5,6,13,14.

Atrial pacing at fixed rate¹⁵ and with rate responsive rate¹⁶ significantly decreases the recurrence frequency of atrial fibrillation in patients with sick sinus syndrome and frequent episodes of paroxysmal atrial fibrillation. The DDDR pacemaker was programmed to ensure consistent atrial pacing at rest and during activity with regulation at a relatively high lower rate and with the use of betablockers for reducing sinus rate¹⁶. A significant reduction in thromboembolic events and mortality was also observed in atrial paced versus ventricular-paced patients¹⁵.