Windle J R, Miles W M, Zipes D P, Prystowsky E N
Am J Cardiol. 1986 Feb 15;57(6):381-6. doi: 10.1016/0002-9149(86)90757-5.
This study tested whether a subthreshold stimulus (Sc) inserted before a premature stimulus prolonged the right ventricular effective refractory period in humans, and whether the degree of effective refractory period lengthening was influenced by heart rate, Sc current intensity or Sc pulse duration. Sc at current intensity 10 mA and pulse width 2 ms prolonged mean effective refractory period from 255 ms to 277 ms (p less than 0.001, n = 20). The increase in effective refractory period was similar in 6 patients studied at pacing cycle lengths 600 (259 to 289 ms) and 400 ms (236 to 258 ms). When Sc current intensities were varied at 2, 5 or 10 mA at a constant pulse duration of 100 ms the effective refractory period progressively prolonged by 6, 40 and 81 ms respectively (p less than 0.02, n = 6). The pulse duration of Sc at a constant current of 10 mA significantly influenced effective refractory period prolongation. With Sc pulse durations of 2, 10, and 100 ms the effective refractory period prolonged by 16, 33 and 66 ms respectively (p less than 0.01, n = 7). Thus, subthreshold impulses prolong the effective refractory period in human right ventricular myocardium. The prolongation of effective refractory period depended on Sc current intensity and pulse duration but was independent of heart rate at the cycle lengths tested. The use of subthreshold stimuli as antiarrhythmic therapy may be feasible in some patients.
本研究旨在测试在过早刺激之前插入阈下刺激（Sc）是否会延长人类右心室有效不应期，以及有效不应期延长的程度是否受心率、Sc电流强度或Sc脉冲持续时间的影响。电流强度为10 mA、脉冲宽度为2 ms的Sc将平均有效不应期从255 ms延长至277 ms（p<0.001，n = 20）。在起搏周期长度为600（259至289 ms）和400 ms（236至258 ms）的6例患者中，有效不应期的增加相似。当在100 ms的恒定脉冲持续时间下将Sc电流强度分别设置为2、5或10 mA时，有效不应期分别逐渐延长6、40和81 ms（p<0.02，n = 6）。在10 mA的恒定电流下，Sc的脉冲持续时间显著影响有效不应期的延长。Sc脉冲持续时间为2、10和100 ms时，有效不应期分别延长16、33和66 ms（p<0.01，n = 7）。因此，阈下冲动可延长人类右心室心肌的有效不应期。有效不应期的延长取决于Sc电流强度和脉冲持续时间，但在所测试的周期长度下与心率无关。在某些患者中，使用阈下刺激作为抗心律失常治疗可能是可行的。
