New contrast agents and technologies for myocardial contrast echocardiography.

Myocardial contrast echocardiography is a new method for evaluating myocardial perfusion. However, it relies on the marriage of two evolving technologies; ultrasound contrast agents and ultrasound imaging instrumentation. To date, these technologies have only been available to a limited number of researchers throughout the world. Within the next 12 months, both agents and specialised ultrasound instruments will be commercially available, making this new methodology open to widespread clinical application. Moreover, echocardiographic evaluation of myocardial perfusion should have a major role in the management of both chronic and acute ischaemic situations, myocardial infarction, and assessment of myocardial viability. This review examines the current and likely future status of both contrast agents and machines in this context. In addition, the probable clinical role of the methodology, as a potential replacement for nuclear techniques, is discussed In patients with coronary artery disease the study of myocardial perfusion is of great clinical relevance and is currently investigated by nuclear medicine techniques. Nuclear cardiology, however, is limited by contamination risks, by a limited availability of the equipment, and by considerable expense. Furthermore, the current role of nuclear medicine in cardiology is mainly confined to stable patients, while acutely ill patients rarely benefit from the information regarding myocardial perfusion. An alternative method of studying myocardial perfusion is echocardiography following the injection of ultrasound contrast agents directly into the coronary circulation.'2 This invasive approach, however, is limited to applications within the cardiac catheterisation laboratory. To overcome this limitation, investigators, pharmaceutical companies, and ultrasound industries have sought to develop a method that could achieve myocardial enhancement following peripheral venous injection of ultrasound contrast agents. Wider use of this methodology might have an important impact on clinical cardiology, as myocardial perfusion could be evaluated noninvasively, requiring only the use of widely available ultrasound scanners that have been suitably adapted. Additionally, the study of myocardial perfusion by contrast echocardiography would make information on perfusion available to a large population of patients in different settings, from the emergency room to the outpatient clinic. This non-invasive approach to myocardial contrast echocardiography stands on three main pillars: new ultrasound contrast agents, new equipment, and clinical models for myocardial perfusion studies.