Ferguson T B, Smith P K, Lofland G K, Holman W L, Helms M A, Cox J L
J Thorac Cardiovasc Surg. 1986 Oct;92(4):755-65.
A major objective of cardioplegic arrest for protection of the heart during cardiac operations is total electromechanical quiescence. Recent studies from our laboratory in which we used multiple bipolar intracardiac and unipolar intramural electrodes have detected the presence of electrical activity in the lower atrial septum, the atrioventricular node-His bundle complex, and in ventricular myocardium during elective cardioplegic arrest that cannot be detected on the limb-lead electrocardiogram. Moreover, this low-amplitude electrical activity is not associated with visible mechanical activity of the heart and occurs at ventricular septal temperatures previously thought to be adequate for myocardial protection. The present study was designed to determine the effect of cardioplegic solution potassium concentration and myocardial temperature on the occurrence and duration of low-amplitude electrical activity during elective cardioplegic arrest. Fifty adult mongrel dogs were subjected to two consecutive 20 minute periods of cardioplegic arrest. The animals were divided into six groups, depending upon the cardioplegic solution potassium concentration they received and on whether or not topical cooling techniques were employed. The probability of occurrence of low-amplitude electrical activity during the arrest interval was significantly decreased by application of topical hypothermic techniques and reinfusion of hyperkalemic, as compared to normokalemic, cardioplegic solution. These effects of hyperkalemic cardioplegic solution and myocardial hypothermia acted synergistically, but independently, to decrease the likelihood of low-amplitude electrical activity occurring during the period of cardioplegic arrest. Nevertheless, low-amplitude electrical activity did occur in all groups after each cardioplegic solution administration and was not detected by routine monitoring techniques. This suggests that low-amplitude electrical activity may represent a fundamental type of metabolic activity that can be recorded from the heart during arrest and may be responsible for the temporary depression in ventricular function that frequently follows a period of elective cardioplegic arrest.
心脏手术期间心脏停搏以保护心脏的一个主要目标是实现完全的电机械静止。我们实验室最近的研究使用了多个双极心内电极和单极心肌内电极，发现在择期心脏停搏期间，下房间隔、房室结 - 希氏束复合体以及心室心肌中存在电活动，而这些电活动在肢体导联心电图上无法检测到。此外，这种低振幅电活动与心脏的可见机械活动无关，且发生在先前认为足以保护心肌的室间隔温度下。本研究旨在确定心脏停搏液钾浓度和心肌温度对择期心脏停搏期间低振幅电活动的发生和持续时间的影响。五十只成年杂种犬接受了连续两个20分钟的心脏停搏期。根据它们接受的心脏停搏液钾浓度以及是否采用局部降温技术，将动物分为六组。与正常钾浓度的心脏停搏液相比，应用局部低温技术和再输注高钾心脏停搏液可显著降低停搏间隔期间低振幅电活动的发生概率。高钾心脏停搏液和心肌低温的这些作用协同但独立地降低了心脏停搏期间低振幅电活动发生的可能性。然而，在每次给予心脏停搏液后，所有组中均出现了低振幅电活动，且常规监测技术无法检测到。这表明低振幅电活动可能代表了一种在心脏停搏期间可从心脏记录到的基本代谢活动类型，并且可能是导致择期心脏停搏后心室功能经常出现暂时抑制的原因。
