Evaluation of coronary steal in myocardium supplied by coronary collaterals: the role of speckle tracking analysis in resting and stress echocardiography.

Coronary steal could develop in patients with chronic coronary artery disease (CAD) with collateral circulation, and adversely affect ventricular function and long-term clinical outcome. Poorly developed collaterals are more prone than well-developed collaterals to withdrawing their blood support to the collateralized myocardium due to higher collateral pathway resistance and lower vasodilatory reserve of the collateral bed. Even with well-developed coronary collaterals, coronary steal could still occur when perfusion pressure in the donor artery becomes low, or the recipient microvasculature is maximally dilated with exhaustion of vasodilatory reserve. The evaluation of distinctive coronary collateral function with or without steal provides important therapeutic and prognostic information in patients with chronic CAD. However, due to lack of reliable assessment methods, the detection and quantitative measurement of coronary steal remains a challenge. In this article, we present typical clinical scenarios to illustrate the major mechanisms underlying coronary steal in patients with chronic CAD and coronary collateral circulation, and review invasive and noninvasive methods currently available to assess coronary steal in myocardium supplied by coronary collaterals. We specifically focus on recent advances in the resting and stress echocardiography with speckle tracking techniques.