EFFICACY OF VENTRICULAR RATE STABILIZATION BY RIGHT-VENTRICULAR PACING DURING ATRIAL-FIBRILLATION

To assess the effect of right ventricular pacing on rate regularity du ring exercise and daily life activities, 16 patients with sinoatrial d isease and chronic atrial fibrillation (AF) were studied. Incremental ventricular pacing was commenced at 40 beats/min until > 95% of ventri cular pacing were achieved during supine, sifting, and standing. Thirt een patients also underwent randomized paired submaximal exercise test s in either a fixed rate mode (VVI) or a ventricular rate stabilizatio n (VRS) mode in which the pacing rate was set manually at 10 beats/min above the average AF rate during the last minute of each exercise sta ge. The pacing interval for rate regularization was shortest during st anding (692 +/- 26 ms) compared with either supine or sitting (757 +/- 30 and 705 +/- 26 ms, respectively, P < 0.05). During exercise, VRS p acing significantly increased the maximum rate (119 +/- 5.2 vs 106 +/- 4.2 ms, P < 0.05), percent of ventricular pacing (85% +/- 5% vs 23% /- 7%, P < 0.05), rate regularity index (5.8% +/- 1.6%, vs 13.4% +/- 1 .9%, P < 0.05), and maximum level of oxygen consumption (12.4 +/- 0.5 vs 11.3 +/- 0.5 mL/kg, P < 0.05) compared with VVI pacing. There was n o change in oxygen pulse or difference in symptom scores in this acute study between the two pacing modes. If is concluded that right ventri cular pacing may significantly improve rate regularity and cardiopulmo nary performance in patients with chronic AF. This may be incorporated in a pacing device for rate regularization of AF using an algorithm t hat is rate adaptive to postural and exercise stresses.