Greenspan A M, Camardo J S, Horowitz L N, Spielman S R, Josephson M E
Am J Cardiol. 1981 Feb;47(2):244-50. doi: 10.1016/0002-9149(81)90393-3.
The ventricular effective refractory period is commonly employed as a measurement of ventricular excitability. Because the current strength used to make this determination varies among laboratories, the relation of refractoriness and current was examined over a range of current strengths from 0.1 to 10 mA. Sixty determinations of refractoriness at variable current strengths were made in 40 patients using the extrastimulus technique with a rectangular pulse of 1 ms duration. These data were obtained by measuring the effective refractory period at threshold current and at 0.25 to 0.50 mA increments from threshold up to 10 mA. In these studies the drive stimulus (S1) and extrastimulus (S2) were kept at the same amplitude. In all patients the ventricular effective refractory period decreased as the current increased. The total decrease ranged from 8 to 100 ms (mean +/- standard deviation 36.9 +/- 17.1). The current strength at which the ventricular effective refractory period became fixed (that is, less than 2 ms change in ventricular effective refractory period with further increase in current strength) varied among the patients, but in all instances equaled or exceeded 1.8 mA, which in all but three patients was greater than three times threshold. The curves relating current strength and refractoriness were shifted to the left at shorter cycle lengths with no change in threshold. These data suggest that (1) current strength-effective refractory period curves more completely characterize ventricular excitability than does a ventricular effective refractory period at single current strength; and (2) studies of drug effects, alterations of autonomic tone, or reentrant arrhythmias, which may affect or are affected by ventricular refractoriness, may be enhanced by more complete measurements of refractoriness afforded by the current strength-effective refractoriness curves.
心室有效不应期通常被用作心室兴奋性的一项测量指标。由于各实验室用于测定心室有效不应期的电流强度不同，因此我们在0.1至10 mA的电流强度范围内研究了不应期与电流之间的关系。采用1 ms持续时间的矩形脉冲额外刺激技术，对40例患者在不同电流强度下进行了60次不应期测定。这些数据是通过测量阈值电流以及从阈值至10 mA以0.25至0.50 mA递增时的有效不应期而获得的。在这些研究中，驱动刺激（S1）和额外刺激（S2）的幅度保持相同。在所有患者中，随着电流增加，心室有效不应期缩短。缩短的幅度范围为8至100 ms（平均值±标准差为36.9±17.1）。心室有效不应期固定时（即随着电流强度进一步增加，心室有效不应期变化小于2 ms）的电流强度在不同患者中有所不同，但在所有情况下均等于或超过1.8 mA，除3例患者外，所有患者的该电流强度均大于阈值的三倍。在较短的心动周期长度下，电流强度与不应期的曲线向左移动，阈值无变化。这些数据表明：（1）电流强度-有效不应期曲线比单一电流强度下的心室有效不应期能更全面地描述心室兴奋性；（2）对于可能影响心室不应期或受心室不应期影响的药物作用、自主神经张力改变或折返性心律失常的研究，通过电流强度-有效不应期曲线进行更全面的不应期测量可能会得到加强。
