Buxton A E, Marchlinski F E, Miller J M, Morrison D F, Frame L H, Josephson M E
Clinical Electrophysiology Laboratory, Hospital of the University of Pennsylvania, Philadelphia 19104.
Circulation. 1989 Feb;79(2):271-80. doi: 10.1161/01.cir.79.2.271.
We defined the atrial strength-interval relation in 23 patients at cycle lengths of 600, 450, and 300 msec before and after procainamide. The atrial diastolic threshold was similar at cycle lengths of 600 and 450 msec, but the threshold at 300 msec was significantly higher than that determined at 600 and 450 msec both before and after procainamide. Procainamide significantly increased the diastolic threshold only at a cycle length of 300 msec. The strength-interval relation was nonlinear, showing progressively decreasing decrements in the measured refractory period as the stimulating current was increased. Progressive decreases in the drive cycle length from 600 to 450 to 300 msec caused similar decreases in refractory periods. The shape of the curves was similar at cycle lengths of 600 and 450 msex. However, at low current strengths, the slope of the curve determined at 300 msex was significantly more vertical than the slopes of the curves at the longer drive cycle lengths. Procainamide caused similar increases in apparent refractory periods at each paced cycle length. Procainamide did not alter the shape of the curves at any paced cycle length. These observations confirm the importance of stimulation frequency on atrial excitability. They suggest that the effects of procainamide on the effective refractory period of the atrium are not cycle length dependent, although the drug effects on threshold are dependent on the drive cycle length.
我们在23例患者中，于使用普鲁卡因胺前后，分别在600、450和300毫秒的心动周期长度下测定了心房强度-间期关系。在600和450毫秒心动周期长度时，心房舒张阈值相似，但在300毫秒时，无论在使用普鲁卡因胺之前还是之后，其阈值均显著高于在600和450毫秒时测定的阈值。普鲁卡因胺仅在300毫秒的心动周期长度时显著提高了舒张阈值。强度-间期关系呈非线性，随着刺激电流增加，测得的不应期递减幅度逐渐减小。驱动心动周期长度从600毫秒逐渐降至450毫秒再降至300毫秒，导致不应期出现类似程度的缩短。在600和450毫秒心动周期长度时，曲线形状相似。然而，在低电流强度下，300毫秒时测定的曲线斜率比在较长驱动心动周期长度时测定的曲线斜率明显更陡。在每个起搏心动周期长度下，普鲁卡因胺均使表观不应期出现类似程度的延长。在任何起搏心动周期长度下，普鲁卡因胺均未改变曲线形状。这些观察结果证实了刺激频率对心房兴奋性的重要性。它们表明，普鲁卡因胺对心房有效不应期的影响不依赖于心动周期长度，尽管该药物对阈值的影响依赖于驱动心动周期长度。
