CHANGES IN INTRACARDIAC ATRIAL CARDIOVERSION THRESHOLD AT REST AND DURING EXERCISE

Objectives. We sought to analyze in patients with chronic atrial fibri llation (AF) the change in the intracardiac atrial defibrillation thre shold (ADT) at rest and during exercise, to quantify the effective ris k of low energy endocavitary cardioversion during the effort and to co mpare the ADT of chronic and reinduced AF. Background. Low energy endo cavitary cardioversion is a new alternative to transthoracic shock in patients with chronic AF, Nevertheless, patient discomfort and possibl e induction of ventricular arrhythmias should be further evaluated.Met hods. Sixteen patients with chronic AF were included in the study, Two 6F custom-made catheters (Electro Catheter, Inc.) were used for shock delivery and one tetrapolar lead for ventricular synchronization. Wit hout sedation and in a random order, patients underwent two sequences of shocks to determine the ADT at rest and during exercise, Exercise w as performed isometrically by the superior limbs. Atrial fibrillation was reinduced by atrial pacing. After each shock, the patients were re quested to grade their discomfort with a score from 1 to 5. The power of the study was >90% in detecting a 25% difference in the ADT between groups. Results. Patients were classified into two groups: Nine patie nts (group A) underwent the first cardioversion during exercise; seven patients (group B) underwent the first cardioversion at rest, In tota l, the mean (+/-SD) ADT was 6.70 +/- 1.54 J during exercise and 7.01 /- 1.82 J at rest (p = 0.59). A significantly lower ADT was observed i n the second shock sequence than the first one (6.32 +/- 2.09 J vs, 7. 40 +/- 0.87 J, p < 0.05), The discomfort score was 3.25 +/- 0.86 at re st and 2.94 +/- 0.77 during exercise (p = 0.09), No complications occu rred. Conclusion. Low energy endocavitary cardioversion is a safe and effective procedure in patients with chronic AF. Discomfort is not gen erally severe enough to result in procedure termination, The ADT is no t influenced by exercise and is higher in chronic than in reinduced AF . (C) 1997 by the American College of Cardiology.