An explanation for discrepancy between angiographic and intravascular ultrasound measurements after percutaneous transluminal coronary angioplasty

Objectives. This study attempted to determine why there is discrepancy between angiographic and intravascular ultrasound measurements after coronary balloon angioplasty. Background. Previous studies have shown 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 intravascular ultrasound was classified as demonstrating superficial injury if there was either no fracture or only small tear that did not extend to the medi versus deep injury defined as the presence of plaque fracture that reached the media. Measurements of minimal lumen diameter were compared between angiography and intravascular ultrasound. Results. On ultrasound imaging, superficial injury pattern was observed in 44 lesions, whereas deep injury was seen in 47 lesions. There were no statistical differences at baseline in patient or lesion characteristics. In the superficial injury group there was significant correlation between angiography and intravascular ultrasound for minimal lumen diameter (r = 0.67) and lumen cross-sectional are (r = 0.69). In the deep injury group there was poor correlation for minimal lumen diameter (r = 0.05) and lumen cross-sectional are (r = 0.28). After balloon angioplasty, the angiographic appearance showed normal contour in 34%, the presence of dissection in 38% or hazy appearance in 23%. On ultrasound imaging after angioplasty, the superficial injury group comprised 65% of lesions with normal angiographic appearance and 67% of lesions with hazy appearance, whereas 77% of lesions with an angiographic diagnosis of dissection were in the deep injury group by ultrasound (p = 0.0005). Conclusions. These observations suggest that the discrepancies between angiographic and ultrasound measurements are due to differences in plaque morphology created by balloon dilation. Superficial injuries demonstrate similar results by angiography or ultrasound, whereas deep injury to the plaque produces difference in measurements between angiography and ultrasound. When angiography reveals dissection, there is high probability that intravascular ultrasound will demonstrate plaque fracture extending to the media.