The electrophysiological effects of calcium channel blockade during standard hyperkalemic hypothermic cardioplegic arrest

A perspective on postoperative atrial fibrillation

Some patients develop atrial fibrillation after any type of surgery, some patients develop atrial fibrillation only after cardiac surgery, and still other patients never develop postoperative atrial fibrillation. Despite the inherent difficulty in identifying the causes of postoperative atrial fibrillation, several important observations have been made during the recent past that may play a role in treating or even preventing this common and serious postoperative problem. This communication provides a framework within which the problem of postoperative atrial fibrillation can be evaluated and treated.

Electrical activity in the heart during hyperkalemic hypothermic cardioplegic arrest: site of origin and relationship to specialized conduction tissue

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