Contrast Echocardiography: Latest Developments and Clinical Utility

Abstract

Ultrasound enhancing agents (UEAs) are being utilized for a growing number of applications with real-time very low mechanical index (MI) techniques in clinical cardiology today. This article will review recent developments on the safety of UEAs and their effectiveness in myocardial perfusion imaging, three-dimensional quantification of left ventricular function, and vascular imaging. UEAs are now being utilized in all age groups, with new indications that add incremental value to the currently approved by the Food and Drug Administration. These include the incremental value in cardiac imaging, where the off-label analysis of myocardial perfusion observed with UEAs adds to the enhanced endocardial border delineation. In carotid artery imaging, UEAs improve the detection of plaque but also can examine plaque neovascularization. Vascular surgeons now utilize UEAs in the evaluation of endovascular repair to detect endoleaks without the need of ionizing radiation. Newer applications are emerging in the detection of left atrial appendage thrombi and quantification of myocardial blood flow and volume in transplant patients.

Contrast echocardiography in daily clinical practice

“…In summary, the two techniques are called low-MI and high-MI imaging, respectively. The real-time low-MI (<0.3) techniques are those that are more routinely used in clinical practice [3]. …”

“…Therefore, backscattered signals from the myocardial tissue, which produces a linear response, will be cancelled out. Power modulation is considered a highly sensitive technique but has lower resolution and image quality [3]. Pulse inversion Doppler , as was explained in high-MI imaging, can also be used in the real-time low-MI MCE.…”

“…However, because it can only receive even harmonics, there will be attenuation artifact, particularly in the basal myocardial segments. The contrast pulse sequencing (Siemens, USA ) is another multiphase technique that uses both alternate amplitude and polarity resulting in high image quality and sensitivity but is still subject to attenuation ([3]; Figs. 4 and 5).…”

Update on the safety and efficacy of commercial ultrasound contrast agents in cardiac applications

“…Therefore, it is recommended that a non-linear imaging technique combined with a low harmonic or a very low real-time perfusion (mechanical index <0.2) pulse sequence scheme be performed for all injections (14). Very low real-time perfusion MI techniques, including pulse inversion Doppler, power modulation, and contrast pulse sequencing, have been developed to improve the visualization of the microbubble response and to eliminate background tissue signals (15). …”

Frequency Dependence of Petechial Hemorrhage and Cardiomyocyte Injury Induced during Myocardial Contrast Echocardiography

“…The MCE perfusion imaging concept has clinically useful applications (Porter and Xie, 2015), although MCE has not gained wide clinical acceptance (Pathan and Marwick, 2015). In addition, the bioeffects and their implications for the MI concept present fundamental problems for medical ultrasound dosimetry and safety guidance.…”