Department of Radiology, University of Michigan Health System, 1301 Catherine St, Ann Arbor, MI 48109-5667, USA.
J Ultrasound Med. 2009 Nov;28(11):1519-26. doi: 10.7863/jum.2009.28.11.1519.
Premature complexes (PCs) in the electrocardiogram (ECG) signal have been reported for myocardial contrast echocardiography and also for burst mode (physical therapy) ultrasound with gas body contrast agents at lower peak rarefactional pressure amplitudes (PRPAs). For contrast echocardiography, irreversibly injured cardiomyocytes have been associated with the arrhythmia. The objective was to determine whether cardiomyocyte injury is associated with the PCs induced by the burst mode at lower PRPAs.
Anesthetized rats were exposed to focused 1.5-MHz ultrasound in a water bath. Evans blue dye was injected intraperitoneally to stain injured cardiomyocytes, and a perflutren lipid microsphere ultrasound contrast agent was infused intravenously. The continuous burst mode simulated physical therapy ultrasound. Intermittent 2-millisecond bursts, or envelopes of pulses simulating diagnostic ultrasound, were triggered 1:4 at end systole. Premature complexes were observed on ECG recordings, and stained cardiomyocytes were counted in frozen sections.
The continuous burst mode produced variable PCs and stained cells above a 0.3-MPa PRPA. The triggered bursts above 0.3 MPa and pulse envelopes above 1.2 MPa produced statistically significant (P < .01) PCs and stained cardiomyocytes.
Irreversible cardiomyocyte injury was associated with the development of PCs for the burst mode and occurred at substantially lower PRPAs than for pulsed ultrasound.
已有研究报道，心肌对比超声心动图的心电图（ECG）信号中存在过早复合波（PCs），而在较低的峰值稀疏压力振幅（PRPA）下，采用气体造影剂的突发模式（物理治疗）超声也会出现 PCs。对于对比超声心动图，不可逆性心肌损伤与心律失常有关。本研究旨在确定心肌损伤是否与较低 PRPA 下突发模式诱导的 PCs 有关。
将麻醉大鼠置于水浴中的聚焦 1.5MHz 超声下。通过腹腔内注射伊文思蓝染料来标记受损的心肌细胞，并静脉内输注全氟丙烷脂质微球超声造影剂。连续突发模式模拟物理治疗超声。在舒张末期以 1:4 的比例触发间歇 2 毫秒的突发或模拟诊断超声的脉冲包络。在心电图记录上观察到过早复合波，并在冷冻切片上计数染色的心肌细胞。
连续突发模式在 0.3MPa 以上的 PRPA 时产生了可变的 PCs 和染色细胞。在 0.3MPa 以上的触发突发和 1.2MPa 以上的脉冲包络会产生统计学上显著的（P<.01） PCs 和染色的心肌细胞。
与脉冲超声相比，突发模式下不可逆性心肌损伤与 PCs 的发生相关，且发生在明显较低的 PRPA 下。
