Mehra R, Furman S, Crump J F
Circ Res. 1977 Aug;41(2):159-66. doi: 10.1161/01.res.41.2.159.
We studied the difference between myocardial vulnerability to arrhythmias caused by cathodal, anodal, and bipolar stimulation in 29 dogs with partial right coronary artery occlusion. We used 2-msec duration stimuli of up to 8 mA to determine the ventricular vulnerable periods, their relationship to the refractory periods, and the fibrillation or multiple response thresholds for unipolar anodal and cathodal stimulation after two premature ventricular contractions. The vulnerable period for arrhythmias began at the end of the respective refractory periods and terminated at a specific time within the cardiac cycle. Within this period the arrhythmia and excitation thresholds were equal. Because shorter refractory periods were obtained with anodal stimulation than cathodal, the vulnerable periods for anodal stimulation were longer. This indicated that the vulnerable periods for bipolar stimulation also would be longer than for unipolar cathodal stimulation since bipolar and anodal refractory periods are equal when the cathode and anode are of similar surface area. Results from seven of the experiments showed that a dual focus of excitation, which can only occur with bipolar stimulation, did not make the ventricle more vulnerable to arrhythmias than did unifocal stimulation. These results indicate that the difference between the arrhythmia vulnerability to unipolar cathodal, anodal, and bipolar stimulation is dependent on the relationship between their excitability characteristics, i.e., their strength-interval curves.
我们研究了29只部分右冠状动脉闭塞犬的心肌对阴极、阳极和双极刺激所致心律失常易感性的差异。我们使用持续时间为2毫秒、强度高达8毫安的刺激来确定心室易损期、其与不应期的关系，以及在两次室性早搏后单极阳极和阴极刺激的颤动或多次反应阈值。心律失常的易损期始于各自不应期结束时，并在心动周期内的特定时间终止。在此期间，心律失常和兴奋阈值相等。由于阳极刺激获得的不应期比阴极刺激短，阳极刺激的易损期更长。这表明双极刺激的易损期也会比单极阴极刺激的易损期更长，因为当阴极和阳极表面积相似时，双极和阳极不应期相等。七个实验的结果表明，仅在双极刺激时才会出现的双兴奋灶，并不会使心室比单灶刺激更容易发生心律失常。这些结果表明，单极阴极、阳极和双极刺激导致心律失常易感性的差异取决于它们兴奋性特征之间的关系，即它们的强度-间期曲线。
