Electrical activity in the heart during @entity6564 hypothermic XXXX : site of origin and relationship to specialized conduction tissue.

@entity235 @entity33650 @entity460 @entity1167 @entity6564
Previous studies from this laboratory have shown that low-amplitude electrical activity ( @entity33650 ) may occur during standard @entity6564 hypothermic @entity1167 and be undetected by routine monitoring techniques. The present study was designed to elucidate the electrophysiological nature of @entity33650 . Ten @entity235 were monitored continuously during standard @entity1167 using a 32-channel data acquisition system. In 7 animals (Part I), electrophysiological mapping of the lower right atrial septum during arrest was performed. The initial site of activation of @entity33650 was consistently recorded from the region of the lower atrial septum prior to atrial or ventricular electrical activation. The site of origin of @entity33650 was thus localized to the anatomical region of the atrial septum containing the atrioventricular nodal conduction tissue. In Part II, the electrophysiological mechanism of @entity33650 was investigated in the remaining 3 animals utilizing an intrinsic property of specialized conduction tissue. Inclusion of a @entity460 channel-blocking agent in standard cardioplegic solution completely prevented the development of @entity33650 in all 3 animals, which is in contrast to findings in previous studies using standard cardioplegic solution alone. These data suggest that @entity33650 may be related to @entity460 -mediated activation of specialized conduction tissue. This mechanism of activation may explain why @entity33650 cannot be detected by the intraoperative monitoring techniques routinely employed.
