The clinical manifestations of coronary artery disease result from an impairment of blood flow by coronary obstructive lesions. As a diagnostic technique, coronary angiography provides essential information regarding the presence, location, and extent of such epicardial lesions but remains an imperfect tool for diagnosing their functional significance.<sup>71 White C.W., Wright C.B., Doty D.B. , et al. Does visual interpretation of the coronary arteriogram predict the physiologic importance of a coronary stenosis? N Engl J Med 1984 ;  310 : 819  [cross-ref]

Cliquez ici pour aller à la section Références</sup> Angiographic images only indirectly visualize plaque and are subject to interobserver variability in interpretation.<sup>75 Zir L.M., Miller S.W., Dinsmore R.E. , et al. Interobserver variability in coronary angiography Circulation 1976 ;  53 : 627

Cliquez ici pour aller à la section Références</sup> Uncertainty regarding lesional functional significance and, therefore, the need for intervention can be especially problematic among stenoses with intermediate severity or complex morphology.

To address these limitations, adjunctive techniques have been developed to improve on conventional angiography. Computer-assisted quantitative angiographic analysis (QCA) and intravascular ultrasound enhance the ability to define lesion geometry. Although these techniques provide detailed geometric analyses of coronary lesions, both remain limited to morphologic data, and physiologic consequences must be extrapolated using assumptions based on fluid dynamic principles that are difficult to apply to the coronary arteries of patients. Methods directed at the measurement of coronary blood flow have offered a potential advantage by targeting coronary physiology directly. The development of catheter-based ultrasound technology for quantitative measurement of blood flow has made physiologic coronary analyses practicable in patients. By miniaturization of this technology and refinement of signal processing, the Doppler-tipped angioplasty guide wire (FloWire, Cardiometrics, Inc, Mountain View, CA) has emerged as a significant advance, providing a clinically useful tool for the evaluation of coronary pathophysiology during cardiac catheterization and intervention. This article focuses on information supporting clinical application of coronary flow velocity measurements using the flow velocity guide wire.