The assessment of perfusion by myocardial contrast echocardiography has evolved from the early contrast agents, including agitated saline solutions and hydrogen peroxide, to the current second-generation contrast agents. Unlike the first-generation contrast agents, which are composed of air, the newer, second-generation agents contain gases with a higher molecular weight and less solubility and diffusivity, improving microbubble persistence. The newer contrast agents are capable of transpulmonary passage and opacification of the left-heart chambers and the myocardial microcirculation after intravenous administration. Also, innovative imaging techniques using harmonics and triggered imaging have minimized tissue signal and improved signal-to-noise ratio, making the assessment of myocardial perfusion possible. Currently, microbubbles are being designed for specific research or clinical use by exploiting certain characteristics of the microbubble such as the shell, surface characteristics, and/or gas content. Some novel applications of microbubble technology include tissue-targeted gene therapy, drug delivery, ultrasoundenhanced thrombolysis, and the assessment of endothelial function and integrity. This review focuses on the composition, physical properties, and acoustic characteristics of the currently available myocardial contrast agents and those under clinical investigation. In addition, the clinical trials involving these agents will also be discussed.
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine