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Evaluation of reversible ischaemia and understanding the physiological significance of known coronary lesions is one of the most important applications of functional cardiac testing. Myocardial perfusion abnormalities during stress are important predictors of clinical outcome and appear to be superior to the angiographic evaluation of the coronary anatomy alone.1–3
The classical ischaemic cascade illustrated in fig 1 demonstrates that one of the first indicators of an imbalance between myocardial oxygen demand and supply is a reduction in myocardial perfusion. Myocardial contrast echocardiography (MCE) has the ability to demonstrate both myocardial blood volume and velocity on a regional basis. The combination of these two parameters has been shown to represent myocardial blood flow4–7 and we can assume that this is directly proportional to myocardial perfusion. The excellent spatial resolution of MCE affords significant advantages over nuclear techniques. Cost, availability, and patient preference also means that stress MCE has the potential to be a more appropriate investigation than stress cardiac magnetic resonance imaging in the evaluation of reversible ischaemia.
PRINCIPLES OF STRESS MCE
Ischaemia, as generated during stress in myocardial segments subtended by epicardial coronary vessels with flow limiting lesions, results in a relative reduction in myocardial blood flow.8,9 Myocardial blood flow is directly proportional to the product of blood volume and velocity.9–12 Both these parameters can be readily evaluated and appreciated during stress MCE, using a variety of techniques. Myocardial contrast signal intensity is directly proportional to blood volume. Relative reduction in blood volume during ischaemia will cause a reduction in the …