Intraoperative demonstration of coronary collateral flow using myocardial contrast two-dimensional echocardiography

The extent of coronary collateral vessels and their significance are controversial issues.¹ The controversy regarding collaterals in man is related, to a large extent, to the lack of an appropriate method to assess collateral function in vivo. The most frequently used technique of assessing collateral blood vessels is coronary angiography. This technique, however, can only detect vessels >100 to 200 μ in diameter.¹ It has been shown in animals, particularly dogs, that most of the collateral vessels are <100 μ in diameter.¹ Furthermore, the angiographic assessment of collateral vessels is unrelated to the functional capacity of these channels.¹. Myocardial contrast echocardiography is a new technique capable of demonstrating myocardial perfusion in humans.² This technique uses the intracoronary or intraaortic injection of microbubbles of air. The size of these microbubbles is similar to that of red blood cells, as is their intravascular rheology.³ The appearance of these microbubbles within regions of the myocardium remote from the site of injection should, therefore, reflect collateral flow. This technique has been shown to demonstrate collateral flow in dogs.⁴.