Levine H J, Avitall B, Pauker S G, Naimi S
Circ Res. 1978 Jul;43(1):63-72. doi: 10.1161/01.res.43.1.63.
Computerized techniques were employed to generate alternating anodal and cathodal or sequential anodal strength-interval curves during and following 15-minute coronary artery ligations in 14 anesthetized dogs. The right atrium was paced at 2.5 Hz, and unipolar ventricular strength-interval curves with simultaneous conduction times were recorded every 45-120 seconds during ischemia and reperfusion. Within 1--2 minutes of ligation, anodal midcurve and late diastolic thresholds fell sharply, and cathodal thresholds fell slightly or changed little. After 5 minutes of ischemia, anodal thresholds remained low, cathodal thresholds rose, and conduction times increased. At 10--15 minutes of ligation, if the ischemic zone was small, anodal thresholds were low, often approaching cathodal values, and conduction returned toward control values. When the ischemic zone was large, unipolar thresholds and conduction times increased late during the ligation period. Throughout the course of ischemia, the falling limb of the strength-interval curve shifted progressively to the left indicating shorter refractory periods. Following abrupt reperfusion, anodal phase 3 dips promptly reappeared; refractory periods returned toward control, and supernormal conduction was noted. By 3--5 minutes of reperfusion, the falling limb of the strength-interval curve had shifted to the right of control and conduction times increased. Thus, vulnerability to arrhythmias during early ischemia (i.e., 5 minutes) is characterized by low anodal midcurves and late diastolic thresholds, short refractory periods, and slow conduction. During the first minute of reperfusion, anodal excitability is increased during the early dip and conduction times are supernormal. Increases in anodal excitability correlate better with the peak incidence of early ligation and reperfusion arrhythmias than do changes in cathodal excitability.
采用计算机技术，在14只麻醉犬冠状动脉结扎15分钟期间及之后，生成交替的阳极和阴极或连续的阳极强度 - 间期曲线。右心房以2.5Hz的频率起搏，在缺血和再灌注期间，每45 - 120秒记录一次单极心室强度 - 间期曲线及同步传导时间。结扎后1 - 2分钟内，阳极曲线中部和舒张末期阈值急剧下降，阴极阈值略有下降或变化不大。缺血5分钟后，阳极阈值仍较低，阴极阈值升高，传导时间增加。结扎10 - 15分钟时，如果缺血区域较小，阳极阈值较低，常接近阴极值，传导恢复至对照值。当缺血区域较大时，单极阈值和传导时间在结扎后期增加。在整个缺血过程中，强度 - 间期曲线的下降支逐渐向左移位，表明不应期缩短。突然再灌注后，阳极第3期下降迅速再次出现；不应期恢复至对照水平，并出现超常传导。再灌注3 - 5分钟时，强度 - 间期曲线的下降支已移至对照值右侧，传导时间增加。因此，早期缺血（即5分钟）期间心律失常的易感性表现为阳极曲线中部和舒张末期阈值低、不应期短和传导缓慢。在再灌注的第一分钟内，早期下降期间阳极兴奋性增加，传导时间超常。阳极兴奋性的增加与早期结扎和再灌注心律失常的峰值发生率的相关性比阴极兴奋性的变化更好。
