Akselrod S, Mor-Avi V, Oz O, David D
School of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Israel.
Clin Cardiol. 1988 Feb;11(2):112-8. doi: 10.1002/clc.4960110210.
Hypothermia is known to affect the electrophysiology of the myocardium in various ways. A marked increase in action potential duration, combined with a decrease in rate of depolarization and conduction velocity, has been observed. We studied the effect of localized hypothermia of the ventricular myocardium on the high-frequency (HF) components of the ECG waveform. Signals were obtained from 6 anesthetized dogs using simultaneous recording of three orthogonal body surface leads before, during, and following surface cooling of different areas of the epicardium. Computer analysis included digital averaging and filtering in a frequency range of 150-250 Hz. For each intervention in each animal, the variance of the average nonfiltered QRS complex was used for a quantitative estimate of the total power, whereas the variance of the derived filtered wave (HF QRS complex) expressed the power content in the HF range. The total power increased during localized cooling of the anterior as well as the inferior epicardial surface, while a clear reduction of power was observed in the HF range. This reduction was shown to be lead dependent and nonuniformly distributed during the course of the QRS. In all cases, hypothermia of either anterior or inferior ventricular epicardium produced a zone of reduced amplitude in the HF QRS complex of at least one lead. Thus, typical changes in the morphology of the HF QRS complex are reliable markers for cooling-induced localized electrophysiological (EP) variations. Therefore, the HF analysis of the body surface ECG may provide noninvasive insight into the EP properties of the myocardium.
已知体温过低会以多种方式影响心肌的电生理学。已观察到动作电位持续时间显著增加，同时去极化速率和传导速度降低。我们研究了心室心肌局部低温对心电图波形高频（HF）成分的影响。在麻醉的6只狗身上，通过同时记录三个正交体表导联，在不同区域的心外膜表面冷却前、冷却期间和冷却后获取信号。计算机分析包括在150 - 250 Hz频率范围内进行数字平均和滤波。对于每只动物的每次干预，未滤波的平均QRS复合波的方差用于定量估计总功率，而导出的滤波波（HF QRS复合波）的方差表示HF范围内的功率含量。在前壁和下壁心外膜表面局部冷却期间，总功率增加，而在HF范围内观察到功率明显降低。这种降低在QRS过程中显示出导联依赖性且分布不均匀。在所有情况下，心室前壁或下壁的心外膜低温都会在至少一个导联的HF QRS复合波中产生一个幅度降低的区域。因此，HF QRS复合波形态的典型变化是冷却诱导的局部电生理（EP）变化的可靠标志。因此，体表心电图的HF分析可以为心肌的EP特性提供非侵入性的见解。
