e0571 Effect of vagal nerve on the monophasic action potential of ventricular outflow tract

Objective Vagal nerve may be related with idiopathetic ventricular tachycardia (IVT). The present study was aimed to investigate the effect of vagal nerve on the monophasic action potential (MAP) of ventricular outflow tract. Methods Eight adult mongrel dogs were involved. Bilateral vagosympathetic tunks were decentralised for stimulation. Metoprolol was given to block sympathic effects. Three MAP recording electrode were placed at the left ventricular outflow tract (LVOT), right ventricular outflow tract (RVOT) and right ventricular apex (RVA) respectively through right femoral artery and vein. MAP was recorded at the LVOT, RVOT, RVA with or without vagal stimulation (VS) respectively. Results MAP duration (MAPD) under VS was significantly shorter than baseline (p>0.05). With or without VS, the MAPD at RVA were significantly shorter than that at RVOT and LVOT (p<0.05), while there was no difference of MAPD between RVOT and LVOT. With VS, the abbreviation of MAPD at outflow tract was greater significantly than that at RVA (APD90 12.1±3.9 at RVOT, 14.8±5.5 at LVOT vs 8.3±4.1 at RVA, p<0.05), while there was no difference of MAPD between LVOT and RVOT (p>0.05). Conclusions VS could reduce MAPD significantly. With VS, the abbreviation of MAPD at outflow tract was greater significantly than that at RVA. It suggested that outflow tract may be sensible to vagal modulation, which might be related to the occurrence of IVT.