New ultrasound contrast agents for left ventricular and myocardial opacification.

Until recently, the use of contrast agents with 2-dimensional echocardiography has been limited to the detection of intracardiac shunts or abnormal venous connections. The advent of commercially available transpulmonary contrast agents and progress in imaging technology changed this situation. New indications for contrast echocardiography include improved assessment of ventricular function by endocardial border enhancement and the assessment of myocardial perfusion. The major advantage of novel contrast agents is their persistence in circulation, due to the content of a gas that is poorly soluble in plasma or a specific microcapsule wall composition. These features, in conjunction with advanced imaging techniques (intermittent harmonic imaging, harmonic power Doppler, pulse inversion Doppler) allow the detection of minute amounts of the agents in myocardium. There are more than 10 echocardiographic contrast agents undergoing clinical or late preclinical tests. Apart from commercially available Albunex, Levovist, Optison, such agents as EchoGen, Quantison, NC100100 and PESDA have been successfully used in humans. Initial clinical data demonstrating the feasibility of myocardial perfusion studies in patients have been presented for PESDA, Optison, Quantison and NC100100. Early attempts are being made for therapeutic applications of microbubbles, including ultrasound-intensified thrombolysis, tissue targeting and drug delivery. Rapid progress in microbubble technology and imaging techniques has raised a wide interest of the clinicians for contrast echocardiography, which may soon become an established technique for the evaluation of myocardial perfusion, competitive for radionuclide imaging.