Dae Michael W, Gao Dong Wei, Sessler Daniel I, Chair Kamel, Stillson Carol A
Cardiovascular Research Institute, University of California, San Francisco, California 94143, USA.
Am J Physiol Heart Circ Physiol. 2002 May;282(5):H1584-91. doi: 10.1152/ajpheart.00980.2001.
Mild hypothermia reduces myocardial infarct size in small animals; however, the extent of myocardial protection in large animals with greater thermal mass remains unknown. We evaluated the effects of mild endovascular cooling on myocardial temperature, infarct size, and cardiac output in 60- to 80-kg isoflurane-anesthetized pigs. We occluded the left anterior descending coronary artery for 60 min, followed by reperfusion for 3 h. An endovascular heat-exchange catheter was used to either lower core body temperature to 34 degrees C (n = 11) or maintain temperature at 38 degrees C (n = 11). Additional studies assessed myocardial viability and microvascular perfusion with (99m)Tc-sestamibi autoradiography. Endovascular cooling reduced infarct size compared with normothermia (9 +/- 6% vs. 45 +/- 8% of the area at risk; P < 0.001), whereas the area at risk was comparable (19 +/- 3% vs. 20 +/- 7%; P = 0.65). Salvaged myocardium showed normal sestamibi uptake, confirming intact microvascular flow and myocyte viability. Cardiac output was maintained in hypothermic hearts because of an increase in stroke volume, despite a decrease in heart rate. Mild endovascular cooling to 34 degrees C lowers myocardial temperature sufficiently in human-sized hearts to cause a substantial cardioprotective effect, preserve microvascular flow, and maintain cardiac output.
轻度低温可减小小动物的心肌梗死面积；然而，对于热容量更大的大型动物，心肌保护的程度仍不清楚。我们评估了轻度血管内降温对体重60至80千克、异氟烷麻醉的猪的心肌温度、梗死面积和心输出量的影响。我们阻断左前降支冠状动脉60分钟，然后再灌注3小时。使用血管内热交换导管将核心体温降至34℃（n = 11）或维持体温在38℃（n = 11）。另外的研究用（99m）锝- sestamibi放射自显影评估心肌活力和微血管灌注。与正常体温相比，血管内降温减小了梗死面积（危险区域面积的9±6%对45±8%；P < 0.001），而危险区域面积相当（19±3%对20±7%；P = 0.65）。挽救的心肌显示sestamibi摄取正常，证实微血管血流完整且心肌细胞存活。尽管心率降低，但由于每搏输出量增加，低温心脏的心输出量得以维持。将人体大小心脏的温度轻度血管内降温至34℃可充分降低心肌温度，从而产生显著的心脏保护作用，保留微血管血流并维持心输出量。
