AN EXPLANATION FOR DISCREPANCY BETWEEN ANGIOGRAPHIC AND INTRAVASCULARULTRASOUND MEASUREMENTS AFTER PERCUTANEOUS TRANSLUMINAL CORONARY ANGIOPLASTY

Objectives. This study attempted to determine why there is a discrepan cy between angiographic and intravascular ultrasound measurements afte r coronary balloon angioplasty. Background. Previous studies have show n a poor correlation between angiographic and intravascular ultrasound measurements after percutaneous coronary balloon angioplasty. Methods . After successful balloon angioplasty, 91 lesions in 84 patients were studied by intravascular ultrasound. Plaque morphology on intravascul ar ultrasound was classified as demonstrating a superficial injury if there was either no fracture or only a small tear that did not extend to the media versus a deep injury defined as the presence of a plaque fracture that reached the media. Measurements of minimal lumen diamete r were compared between angiography and intravascular ultrasound. Resu lts. On ultrasound imaging, a superficial injury pattern was observed in 44 lesions, whereas a deep injury was seen in 47 lesions. There wer e no statistical differences at baseline in patient or lesion characte ristics. In the superficial injury group there was a significant corre lation between angiography and intravascular ultrasound for minimal lu men diameter (r = 0.67) and lumen cross-sectional area (r = 0.69). In the deep injury group there was a poor correlation for minimal lumen d iameter (r = 0.05) and lumen cross-sectional area (r = 0.28). After ba lloon angioplasty, the angiographic appearance showed a normal contour in 34%, the presence of dissection in 38% or a hazy appearance in 23% . On ultrasound imaging after angioplasty, the superficial injury grou p comprised 65% of lesions with a normal angiographic appearance and 6 7% of lesions with a hazy appearance, whereas 77% of lesions with an a ngiographic diagnosis of dissection were in the deep injury group by u ltrasound (p = 0.0005). Conclusions. These observations suggest that t he discrepancies between angiographic and ultrasound measurements are due to differences in plaque morphology created by balloon dilation. S uperficial injuries demonstrate similar results by angiography or ultr asound, whereas a deep injury to the plaque produces a difference in m easurements between angiography and ultrasound. When angiography revea ls a dissection, there is a high probability that intravascular ultras ound will demonstrate a plaque fracture extending to the media.