Collateral Blood Flow and Myocardial Viability

To the Editor: Sabia et al. (Dec. 24 issue)¹ used myocardial contrast echocardiography to assess collateral flow, on the basis of experimental validation studies. The accuracy of this method in determining collateral flow in humans with chronic coronary occlusion has, to my knowledge, never been demonstrated. Nevertheless, total occlusion of a coronary artery is a “stable” coronary condition that would have allowed a comparison of the distribution of the microbubbles in collateral-dependent areas with the results of other techniques for the assessment of myocardial flow, such as perfusion scintigraphy. The choice of angiographic grading of collateral vessels is unclear and…