Schwartz P J, Vanoli E, Stramba-Badiale M, De Ferrari G M, Billman G E, Foreman R D
Department of Physiology and Biophysics, University of Oklahoma, Oklahoma City.
Circulation. 1988 Oct;78(4):969-79. doi: 10.1161/01.cir.78.4.969.
We have suggested that among conscious dogs with a healed anterior wall myocardial infarction (MI) a depressed baroreflex sensitivity (BRS) carries a higher risk of developing ventricular fibrillation during a brief ischemic episode associated with an exercise stress test. The clinical and pathophysiological implications of our previous findings prompted the present study, which addressed three major questions: 1) Is, indeed, analysis of BRS after MI a specific and sensitive marker for sudden death-risk stratification? 2) Does MI modify BRS? 3) Does analysis of BRS before MI provide information about outcome during ischemic episodes occurring after MI? An anterior MI was produced in 301 dogs, and 4 weeks later, a 2-minute circumflex coronary artery occlusion beginning during the last minute of an exercise stress test could be performed in 192 animals. Ventricular fibrillation occurred in 106 (55%) dogs (susceptible to sudden death), whereas 86 (45%) dogs (resistant to sudden death) survived. BRS was assessed by the phenylephrine method and was expressed by the regression line relating RR intervals to blood-pressure changes. BRS was significantly lower among susceptible than among resistant dogs (9.1 +/- 6.0 vs. 17.7 +/- 6.5 msec/mm Hg, p less than 0.0001). The risk for sudden death increased from 20% (15 of 73 dogs) for a BRS greater than 15 msec/mm Hg to 91% (62 of 68 dogs) for a BRS less than 9 msec/mm Hg (p less than 0.001). An internal control study in 55 animals showed that BRS was reduced 4 weeks after MI compared with control conditions (13.5 +/- 6.7 vs. 17.8 +/- 6.6 msec/mm Hg, p less than 0.001) and that a reduction occurred in 73% of animals. Susceptible dogs and those that spontaneously died after MI had a lower BRS even before the MI (16.2 +/- 5.9 vs. 22.2 +/- 6.2 msec/mm Hg, p less than 0.001). The risk for sudden death after MI increased from 35% (nine of 26 dogs) for a BRS before MI greater than 20 msec/mm Hg to 85% (17 of 20 dogs) for a BRS before MI less than 14 msec/mm Hg (p less than 0.001). This study demonstrates that the presence of a reduced BRS is associated with a greater susceptibility to ventricular fibrillation during subsequent ischemic episodes. In the majority of dogs, BRS is reduced after an MI. The results in 192 conscious dogs with a healed MI indicate that analysis of BRS is a powerful tool for risk stratification not only after, but even before, the occurrence of an MI.
我们曾提出，在患有已愈合前壁心肌梗死（MI）的清醒犬中，压力反射敏感性（BRS）降低会使其在与运动应激试验相关的短暂缺血发作期间发生心室颤动的风险更高。我们先前研究结果的临床和病理生理学意义促使了本研究，该研究解决了三个主要问题：1）MI后BRS分析是否确实是猝死风险分层的特异性和敏感标志物？2）MI是否会改变BRS？3）MI前BRS分析是否能提供有关MI后缺血发作期间预后的信息？对301只犬造成前壁MI，4周后，192只动物可在运动应激试验的最后一分钟开始进行2分钟的回旋支冠状动脉闭塞。106只（55%）犬发生心室颤动（易发生猝死），而86只（45%）犬（对猝死有抵抗力）存活。通过去氧肾上腺素法评估BRS，并通过将RR间期与血压变化相关的回归线来表示。易患犬的BRS显著低于有抵抗力的犬（9.1±6.0对17.7±6.5毫秒/毫米汞柱，p<0.0001）。当BRS大于15毫秒/毫米汞柱时，猝死风险为20%（73只犬中的15只），而当BRS小于9毫秒/毫米汞柱时，猝死风险增加到91%（68只犬中的62只）（p<0.001）。对55只动物进行的一项内部对照研究表明，与对照情况相比，MI后4周BRS降低（13.5±6.7对17.8±6.6毫秒/毫米汞柱，p<0.001），73%的动物出现降低。易患犬以及MI后自然死亡的犬在MI前BRS就较低（16.2±5.9对22.2±6.2毫秒/毫米汞柱，p<0.001）。MI前BRS大于20毫秒/毫米汞柱时，MI后猝死风险为35%（26只犬中的9只），而MI前BRS小于14毫秒/毫米汞柱时，猝死风险增加到85%（20只犬中的17只）（p<0.001）。本研究表明，BRS降低与随后缺血发作期间对心室颤动的易感性增加有关。在大多数犬中，MI后BRS降低。对192只患有已愈合MI的清醒犬的研究结果表明，BRS分析不仅是MI发生后，甚至在MI发生前，都是风险分层的有力工具。
