Taggart P, Sutton P M, Treasure T, Lab M, O'Brien W, Runnalls M, Swanton R H, Emanuel R W
Department of Cardiology, Middlesex Hospital, London, England.
Circulation. 1988 Jun;77(6):1266-75. doi: 10.1161/01.cir.77.6.1266.
Mechanical dysfunction is the strongest predictor of sudden cardiac death due to arrhythmia. Contraction-excitation feedback whereby changes in myocardial length/tension influence the time course of repolarization and excitability would provide a possible mechanism. Such a relationship has been shown in animals but has yet to be demonstrated in man. A useful model for studying this relationship is provided by the process of weaning off cardiopulmonary bypass after routine coronary artery surgery. During this weaning period of approximately 1 min, the heart is converted from being partially empty and flaccid (i.e., a "nonworking" state) to being filled and stretched to support the circulation (i.e., a "working" state). Monophasic action potentials (MAPs) were recorded from the left ventricular epicardium as a measure of repolarization time in 16 patients at discontinuation of cardiopulmonary bypass. Systolic pressure was recorded from the radial artery line. Measurements were made at three stages that related to different dynamic states of the heart: (1) starting to come off bypass ("minimally working"), defined as the time of first appearance of an inflection on the arterial pressure trace indicating the start of left ventricular ejection and valve opening, when arterial pressures represent left ventricular pressure, (2) half off bypass ("partially working"), and (3) off bypass ("wholly working"). During the process of discontinuing bypass MAP duration shortened, while systolic pressure increased. MAP duration at 90% and 60% repolarization (MAP D90, MAP D60) decreased from 288.0 +/- 29.5 msec (mean +/- SEM) and 235.0 +/- 27.9 msec in the minimally working heart to 274.5 +/- 30.2 msec and 224.2 +/- 27.3 msec in the partially working heart (p less than .001), with a subsequent decrease to 261.0 +/- 28.8 and 214.0 +/- 28.7 when the heart was wholly working (p less than .001). Systolic pressure increased from 54.1 +/- 9.3 mm Hg in the minimally working heart to 65.9 +/- 13.8 mm Hg in the partially working heart (p less than .001) and subsequently increased to 75.5 +/- 13.3 mm Hg when the heart was wholly working (p less than .001). Mean heart rates did not change significantly. A strong correlation was obtained between absolute MAP duration and systolic pressure. Regression analysis revealed: MAP D90 vs systolic pressure (p less than .001) and MAP D60 vs systolic pressure (p less than .01).(ABSTRACT TRUNCATED AT 400 WORDS)
机械功能障碍是心律失常所致心源性猝死的最强预测因素。心肌长度/张力的变化会影响复极化时间进程和兴奋性的收缩-兴奋反馈，这可能是一种机制。这种关系已在动物实验中得到证实，但在人类中尚未得到证实。常规冠状动脉手术后脱离体外循环的过程为研究这种关系提供了一个有用的模型。在大约1分钟的脱离期内，心脏从部分空虚且松弛的状态（即“非工作”状态）转变为充盈并伸展以支持循环的状态（即“工作”状态）。在16例患者脱离体外循环时，从左心室心外膜记录单相动作电位（MAP）以测量复极化时间。从桡动脉导管记录收缩压。在与心脏不同动态状态相关的三个阶段进行测量：（1）开始脱离体外循环（“最小工作”），定义为动脉压波形上首次出现拐点的时间，此时表明左心室射血和瓣膜开放开始，动脉压代表左心室压力；（2）脱离体外循环一半（“部分工作”）；（3）完全脱离体外循环（“完全工作”）。在脱离体外循环的过程中，MAP持续时间缩短，而收缩压升高。在最小工作心脏中，90%复极化时的MAP持续时间（MAP D90）和60%复极化时的MAP持续时间（MAP D60）分别为288.0±29.5毫秒（均值±标准误）和235.0±27.9毫秒，在部分工作心脏中分别降至274.5±30.2毫秒和224.2±27.3毫秒（p<0.001），当心脏完全工作时，随后分别降至261.0±28.8毫秒和214.0±28.7毫秒（p<0.001）。收缩压从最小工作心脏中的54.1±9.3毫米汞柱升至部分工作心脏中的65.9±13.8毫米汞柱（p<0.001），当心脏完全工作时，随后升至75.5±13.3毫米汞柱（p<0.001）。平均心率无显著变化。绝对MAP持续时间与收缩压之间存在很强的相关性。回归分析显示：MAP D90与收缩压（p<0.001）以及MAP D60与收缩压（p<0.01）。（摘要截短于400字）
