Myocardial contrast echocardiography in the assessment of patients with chronic coronary artery disease

The development of new contrast agents and new imaging methods has lead to an emerging field of applications for myocardial contrast echocardiography (MCE) in patients suffering from chronic ischemic heart disease. Echo contrast allows the assessment of myocardial perfusion (MP) by imaging the coronary microcirculation. Several echocardiographic modalities are available, the main difference between them being the acoustic power needed to perform the study. MP is evaluated by assessing the changes in myocardial videointensity that occur after intravenous contrast injection. Evaluation of these patients is performed by using different techniques. Evaluation of coronary stenosis may be performed by using stress tests or without its use. Coronary artery stenosis >50% of the coronary luminal diameter reveals a decreased hyperemic response when myocardial oxygen demand is increased. Different methods to evaluate the presence of relevant coronary stenosis have been developed: evaluation of myocardial blood flow reserve, evaluation of myocardial blood volume, and evaluation of the transmural distribution of myocardial blood flow. The combination of wall motion analysis with MCE assessment has been demonstrated to achieve the best balance between sensitivity (86%) and specificity (88%), with the highest accuracy (86%). Without the need of any stress, the ratio systolic/diastolic myocardial blood volume has been described to increase with the presence of a epicardial coronary stenosis and it may be measured by MCE. Myocardial viability is also one of the potentials of MCE. Microvascular integrity, demonstrated by MCE, is an indicator of preserved viability and predicts functional recovery that has been validated in the setting of chronic left ventricular dysfunction secondary to chronic coronary artery disease and in the setting of post acute myocardial infarction left ventricular dysfunction. In conclusion: contrast echocardiography provides an interesting tool that offers the potential of a complete evaluation of patients with chronic coronary artery disease. This includes both diagnostic and prognostic evaluation.