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The use of 2-dimensional intravascular ultrasound (2-D IVUS) to improve the outcome of coronary stenting has gained clinical acceptance, and recently 3-D IVUS has been introduced to clinical practice. However, there have been no comprehensive studies comparing the measurements of the coronary dimensions after stenting obtained by the different approaches of IVUS and quantitative coronary angiography. We examined the minimal luminal cross-sectional area of 38 stents using 2-D IVUS, 3-D IVUS, and 2 standard methods of quantitative coronary angiography, edge detection (ED) and videodensitometry (VD). Correlations between 2-D IVUS and ED (r = 0.72; p < 0.0001), VD (r = 0.87; p < 0.0001), and 3-D IVUS (r = 0.81; p < 0.0001) were higher than the correlations seen between 3-D IVUS and ED (r = 0.58; p < 0.0005) and VD (r = 0.70; p < 0.0001). The measurements by 2-D and 3-D IVUS (8.32 +/- 2.50 mm2 and 8.05 +/- 2.66 mm2) were larger than the values obtained by the quantitative angiographic techniques ED and VD (7.55 +/- 2.22 mm2 and 7.27 +/- 2.21 mm2). Thus, concordance was seen among all of the 4 techniques, confirming the validity of using IVUS for determination of the minimal luminal cross-sectional area after coronary stenting. A particularly good correlation was found between VD and IVUS, perhaps because measurement of the luminal area is the basic quantification approach of both techniques, whereas the lower correlations of ED with IVUS and VD may be explained by the dependence of ED on the angiographic projections used, which is especially important in eccentric stent configurations.

Stent use has been increasing steadily over the last 5 years and might be viewed as the "second wind" of angioplasty. A large number of different stents are now available, and many trials have been designed to assess their safety and efficacy. But do comparisons of the various stents serve a useful purpose-i.e., do they address real medical questions? Many issues remain unresolved, such as who should and should not be stented, what the actual costs are of this modality, and what the future holds in terms of multifunctional devices. In addition, research is under way to explore such areas as techniques for stent guidance, the role of anticoagulation and adjunctive therapies, treatment of patient subsets (e.g., those with ischemic syndromes or challenging coronary anatomy), and synergistic approaches (e.g., directional atherectomy, radiotherapy, laser angioplasty). The results of such studies are likely to change the face of interventional cardiology.