Department of Radiology, University of Michigan, Ann Arbor, MI 48109-5667, USA.
Ultrasound Med Biol. 2011 Feb;37(2):312-20. doi: 10.1016/j.ultrasmedbio.2010.11.012.
The objective of this study was to explore the relationship between premature complexes (PCs) in the electrocardiogram (ECG) and lethal injury of cardiomyocytes induced by ultrasound exposure of the heart with contrast-agent gas bodies in the circulation. Anesthetized rats were exposed in a heated water bath to 1.55 MHz focused ultrasound with bursts triggered at end systole during contrast agent infusion. PCs were detected in ECG recordings and cardiomyocyte necrosis was scored by identifying Evans blue-stained cells in multiple frozen sections. With 0.1 μL/kg/min infusion of contrast agent for 5 min, both effects increased strongly for 2-ms bursts with increasing peak rarefactional pressure amplitude >1 MPa. At 8 MPa, statistically significant effects were found even for no agent infusion relative to sham tests. For 2-ms bursts at 2 MPa, the highly significant bioeffects seen for 10-, 1- and 0.1-μL/kg/min infusion became marginally significant for 0.01 μL/kg/min, which indicated a lower probability of cavitation nucleation. Burst duration variation from 0.2-20 ms produced no substantial trends in the results. Overall, the two effects were well correlated (r(2) = 0.88). The PCs occurring during contrast-enhanced ultrasound therefore appear to be electrophysiological responses to irreversible cardiomyocyte injury induced by ultrasonic cavitation.
本研究旨在探讨心电图（ECG）中过早复合波（PCs）与循环中含对比剂气体的心脏超声暴露引起的心肌细胞致死性损伤之间的关系。麻醉大鼠在加热水浴中接受 1.55MHz 聚焦超声照射，在对比剂输注期间在收缩末期触发突发。在 ECG 记录中检测到 PCs，并通过在多个冷冻切片中识别伊文思蓝染色的细胞来评分心肌细胞坏死。以 0.1μL/kg/min 的速度输注对比剂 5 分钟，对于 2ms 的突发，随着峰值稀疏压幅度>1MPa 的增加，两种效应都强烈增加。在 8MPa 下，即使相对于假测试不输注对比剂，也发现了统计学上显著的效应。对于 2MPa 的 2ms 突发，对于 10、1 和 0.1μL/kg/min 的输注，观察到高度显著的生物效应，对于 0.01μL/kg/min，其变得略微显著，这表明空化核化的可能性降低。从 0.2-20ms 变化的突发持续时间对结果没有产生实质性趋势。总的来说，这两种效应相关性良好（r²=0.88）。因此，增强超声期间发生的 PCs 似乎是超声空化引起的不可逆心肌细胞损伤的电生理反应。
