Porter T R, Xie F
Section of Cardiology, University of Nebraska Medical Center, Omaha 68198-2265.
J Am Coll Cardiol. 1995 Feb;25(2):509-15. doi: 10.1016/0735-1097(94)00376-2.
The central hypothesis of this study was that microbubble survival, and subsequent left ventricular and myocardial ultrasound contrast, could be improved by altering microbubble gas to consist of a higher molecular weight (less diffusible) and less soluble gas.
Microbubble survival after intravenous injection is shortened because of rapid diffusion of blood-soluble room air gases (nitrogen and oxygen) across the permeable bubble membrane into blood.
Thirteen open chest dogs received intravenous injections of a constant dose of sonicated dextrose albumin that was incubated with either room air or 100% nitrogen, 100% helium or 100% sulfur hexafluoride. Nitrogen (100%) is less blood soluble than room air, whereas helium and sulfur hexafluoride are the least soluble. Sulfur hexafluoride has the slowest diffusion rate. To further decrease the diffusion rate, each sample was administered during inhalation of room air and again during brief inhalation of the same gas with which it had been incubated.
The highest peak videointensity in the left ventricular cavity was produced by the sonicated dextrose albumin incubated with sulfur hexafluoride, the gas having lowest blood solubility and diffusion rate, while sulfur hexafluoride was briefly inhaled during the period of intravenous injection (peak videointensity 139 +/- 10 vs. 54 +/- 11 for room air-exposed sonicated dextrose albumin, p < 0.001). Myocardial contrast was visually evident in > 80% of the intravenous injections of sulfur hexafluoride-exposed sonicated dextrose albumin when the agent was given as an 8-fold concentrated sample during brief inhalation of sulfur hexafluoride.
Visual myocardial echocardiographic contrast is possible after intravenous injection of sonicated dextrose albumin if the microbubbles contain a gas with low blood solubility and diffusivity.
本研究的核心假设是，通过改变微泡气体组成，使其包含更高分子量（扩散性更低）且溶解性更低的气体，可提高微泡存活率以及后续左心室和心肌的超声造影效果。
静脉注射后微泡存活率缩短，原因是血液可溶的室内空气气体（氮气和氧气）通过可渗透的泡膜迅速扩散到血液中。
13只开胸犬接受静脉注射恒定剂量的经超声处理的葡萄糖白蛋白，该白蛋白分别与室内空气、100%氮气、100%氦气或100%六氟化硫孵育。氮气（100%）的血液溶解性低于室内空气，而氦气和六氟化硫的溶解性最低。六氟化硫的扩散速率最慢。为进一步降低扩散速率，每个样本在吸入室内空气期间给药，然后在短暂吸入与其孵育的相同气体期间再次给药。
与六氟化硫孵育的经超声处理的葡萄糖白蛋白产生了左心室腔内最高的峰值视频强度，六氟化硫是血液溶解性和扩散速率最低的气体，且在静脉注射期间短暂吸入六氟化硫（峰值视频强度为139±１０，而暴露于室内空气的经超声处理的葡萄糖白蛋白为54±11，p<0.001）。当以8倍浓缩样本在短暂吸入六氟化硫期间给予暴露于六氟化硫的经超声处理的葡萄糖白蛋白时，在超过80%的静脉注射中可肉眼明显观察到心肌造影。
如果微泡包含血液溶解性和扩散性低的气体，静脉注射经超声处理的葡萄糖白蛋白后可实现可视化心肌超声造影。
