Liem L B, Mason D M, Swerdlow C D
Cardiac Arrhythmia Unit, Stanford University Medical Center, California 94305.
Am J Cardiol. 1988 Jan 1;61(1):88-92. doi: 10.1016/0002-9149(88)91310-0.
Successful initiation and termination of presumed reentrant ventricular tachycardia frequently depends on the ability to deliver closely coupled impulses to the region of the tachycardia origin. To evaluate systematically the relative influence of local latency and large-scale conduction delay in limiting the delivery of closely coupled impulses, the strength-interval relation of the effective refractory period (RP), and the local and remote functional RP in 35 patients at paced cycle length of 500 ms were measured. The pacing threshold was less than or equal to 0.25 mA in all patients. The drive-train (S1) and the extrastimulus (S2) were applied from the same site, the right ventricular (RV) apex, in 25 patients, and from separate sites (RV apex and RV outflow tract) in 10 patients. The effect of procainamide (plasma concentration 10.1 +/- 2.3 micrograms/ml) on the strength-interval relations in 10 patients was also assessed. Although effective RP decreased significantly with each successive increase in current strength (p less than 0.001), local functional RP decreased only up to current strength of 4 mA, and remote functional RP decreased only up to 2 mA. Procainamide shifted the effective RP and local and remote functional RP strength-interval curves uniformly to the right without altering their relation. These data indicate that large-scale conduction delay provides the principal limitation for using increasing current strengths of a single extrastimulus to initiate or terminate ventricular tachycardia.
推测折返性室性心动过速的成功起始和终止常常取决于向心动过速起源部位发放紧密耦合冲动的能力。为了系统评估局部潜伏期和大规模传导延迟在限制紧密耦合冲动发放方面的相对影响，在35例患者中，于起搏周期长度为500毫秒时测量了有效不应期（ERP）的强度 - 间期关系以及局部和远隔部位的功能性ERP。所有患者的起搏阈值均小于或等于0.25毫安。在25例患者中，驱动刺激（S1）和额外刺激（S2）从同一部位即右心室（RV）心尖发放，在10例患者中从不同部位（RV心尖和RV流出道）发放。还评估了普鲁卡因酰胺（血浆浓度10.1±2.3微克/毫升）对10例患者强度 - 间期关系的影响。尽管随着电流强度的每次连续增加，有效ERP显著降低（p＜0.001），但局部功能性ERP仅在电流强度达到4毫安时降低，远隔功能性ERP仅在电流强度达到2毫安时降低。普鲁卡因酰胺将有效ERP以及局部和远隔功能性ERP强度 - 间期曲线一致地向右移动，而不改变它们之间的关系。这些数据表明，大规模传导延迟是使用单个额外刺激增加电流强度来起始或终止室性心动过速的主要限制因素。
