13th International Congress
THE "NEW FRONTIERS"
OF ARRHYTHMIAS 1998

January 24-31, 1998
Marilleva, Trento, Italy

RT-185

Internal low energy cardioversion of atrial fibrillation: patients' tolerance employing a step-up protocol

Giuseppe Boriani, Mauro Biffi, Gabriele Bronzetti, Francesco Pergolini, Romano Zannoli, °Gregory M. Ayers, Alessandro Capucci, Angelo Branzi, Bruno Magnani.
Institute of Cardiology, Bologna, Italy, °In Control Inc, Redmond, WA, USA

Introduction

External cardioversion is usually employed for restoring sinus rhythm in patients with persistent atrial fibrillation but general anesthesia is required for this procedure.

Transvenous internal atrial cardioversion has been initially studied in animal models¹ in order to find the optimal waveform and the optimal defibrillating leads location. Cooper et al¹ studied internal cardioversion in sheep, comparing different symmetrical monophasic and biphasic waveforms and varying defibrillating leads locations. In this study the 3/3 msec biphasic waveform had significantly lower energy requirements than longer biphasic or monophasic symmetrical waveforms. In the same paper, comparing different internal lead systems with catheters positioned in right atrial appendage, superior vena cava, coronary sinus or left pulmonary artery, in various combinations, the most effective lead system resulted to be that including a lead in the right atrial appendage and another lead in distal coronary sinus with a right to left orientation¹.

In animal models also the issue of ventricular proarrhythmia has been studied². Ayers et al² found that the risk of inducing a ventricular tachyarrhythmia was associated with a cycle length preceding shock delivery < 300 msec while when the cycle length preceding the shock was longer than 300 msec no ventricular arrhythmias were observed.

In addition to animal studies, more recently transvenous internal atrial cardioversion has been evaluated also in humans, specifically patients with paroxysmal or induced atrial fibrillation^3,4 or in patients with chronic atrial fibrillation^4-6. In transvenous internal atrial cardioversion, shock is applied directly to fibrillating regions, thus the procedure may be effective even in patients with long standing chronic atrial fibrillation and even despite previous ineffective transthoracic shocks^6-8.

In patients with paroxysmal or persistent atrial fibrillation internal atrial cardioversion can be effective at relatively low energies and thus can be performed without general anesthesia. In previous reports^5-8 intravenous sedation has been usually administered before shock delivery for reducing shock-induced discomfort.

The aim of the present study was to assess efficacy, safety and patients' tolerability of low energy internal atrial cardioversion in an unselected group of patients, mainly with chronic persistent atrial fibrillation.