Effect of phenylephrine on focal atrial fibrillation originating in the pulmonary veins and superior vena cava

OBJECTIVES This study was aimed at evaluating the effects of phenylephrine infusion on the occurrence of focal atrial fibrillation (AF). BACKGROUND Paroxysmal AF can be initiated by ectopic atrial beats originati ng in the pulmonary vein (PV) or superior vena cava (SVC). The effect of ch ange in autonomic tone on this focal AF is unknown. METHODS This study included 12 patients with frequent bursts of AF document ed by 24-h Holter monitoring. The number and coupling interval of spontaneo us ectopic activity and bursts of AF were evaluated for 1 min before and af ter phenylephrine (2 to 3 mu g/kg) injection. RESULTS After detailed mapping, four patients had a focus located in the le ft superior PV, six in the right superior PV and two in the SVC. In 10 pati ents with AF foci originating in the PVs, the frequency of ectopic activity (19.5 +/- 27.4 vs. 11.4 +/- 22.9 beats/min, p = 0.059) was reduced as well as AF bursts (14 +/- 3 vs. 1.8 +/- 2.7 bursts/min, p = 0.005) before versu s after phenylephrine injection; the minimal coupling interval of ectopic a ctivity and AF bursts became longer compared with baseline. The maximal per cent increase in sinus cycle length after phenylephrine injection was signi ficantly greater in patients with complete suppression of AF compared with those with partial suppression (43 +/- 19 vs. 14 +/- 5%, p = 0.01). However , no significant effect of phenylephrine on AF originating in the SVC was f ound. CONCLUSIONS Change in autonomic tone induced by phenylephrine injection was effective in suppressing focal AF originating in the PVs but not in the SV C. (C) 2000 by;he American College of Cardiology.