Coronary Angiography

Abstract

The introduction of selective coronary angiography by Mason Sones in 1958 stands as a milestone in clinical cardiology. The procedure continues as a cornerstone in the evaluation of the coronary arteries and is indicated not only to diagnose coronary artery disease (CAD) but also to assess its severity. These data are then integrated with other clinical information to help guide treatment decisions. Traditionally, assessment of coronary lesion severity has been accomplished by a visual estimate obtained from simple inspection of the angiogram. Although this method of assigning CAD diagnosis, and more specifically attempting to quantify its severity, has long been recognized to have important limitations, 1 simple visual estimation remains the most commonly used form of lesion evaluation and is taken by many operators to be their reference standard. Article see p 1793 It is important to understand that among the many factors contributing to limit coronary blood flow (eg, diastolic pressure time, microvascular resistance), the minimal luminal cross-sectional area available for flow is critically important. At rest, blood flow remains unchanged until the cross-sectional area reduction is very severe (ie, >80% stenosis) and increases resistance (Figure 1). Maximal blood flow, however, becomes impaired when the reduction in cross-sectional area approximates 50%, and this became the definition of significant CAD. This reduction in area also operates over the length of the lesion, so lumen area reduction actually represents only 1 factor in a complex geometry within a lesion that is difficult to measure in the clinical setting. For this reason, and because experimental models centered on the idealized focal stenosis, clinicians substituted an approximation of the most severeappearing obstruction. However, CAD patients frequently have long or multiple stenoses in the same coronary artery. Our laboratory and others have shown that compared with a single focal stenosis, multiple consecutive stenoses and an increase in stenosis length result in a greater reduction in maximal flow. 2–6 Because the area reduction over the length of the complex lesion and multiple lesions was difficult to measure precisely even with multiple views, clinicians defaulted to estimating the maximal percent diameter narrowing in the worst view. Additionally, considerable variability occurs in the relation between myocardial flow and percent diameter stenosis, 7 suggesting that other factors (eg, microvascular dysfunction) also operate. Nevertheless, percent diameter stenosis is most commonly used to define the presence of obstructive CAD.