Myocardial contrast echocardiography has the potential for the assessment of coronary microvascular reserve

Coronary vasodilators increase coronary flow by increasing myocardial blood volume. Diseases affecting the coronary microvasculature will affect vasodilator-induced changes in coronary flow by inhibiting changes in myocardial blood volume. In such cases, when myocardial time-intensity curves after administration of a vasodilator are compared with those at baseline, a less than anticipated increase in microbubble transit rates will be noted. As long as we understand what we are measuring in the context of where and how we inject the bubbles, we can begin to define the role of myocardial contrast echocardiography in assessing changes in coronary microvascular reserve. It is also conceivable that because myocardial contrast echocardiography can assess changes in myocardial flow/volume relations rather than just changes in flow, this technique could be used to provide additional insights into the mechanisms of action of different coronary vasodilators and into the pathophysiology of various diseases affecting the coronary microvasculature. Finally, with the advent of commercially available microbubbles, robust on- and off-line analysis algorithms and intracardiac imaging, myocardial contrast echocardiography may become an invaluable adjunct to coronary angiography for determining the pathophysiologic significance of coronary disease in individual patients.