Ultrasonic plaque character and outcome after lower limb angioplasty

Abstract

Purpose: The value of ultrasonic plaque characteristics in identifying patients at “high-risk” of restenosis after percutaneous transluminal angioplasty (PTA) was studied. Methods: Thirty-one arterial stenoses (6 common iliac, 2 external iliac, 1 profunda femoris, 21 superficial femoral, and 1 popliteal) in 17 patients who underwent angioplasty were studied by means of duplex scanning. With a computer-based program, B-mode images were digitized and normalized using 2 reference points, blood and adventitia. A grey level of 0 to 5 was allocated for the lumen (blood) and 180 to 190 for the adventitia on a linear gray scale of 0 to 255 (0 = absolutely black; 255 = absolutely white), and the overall plaque gray-scale median (GSM) of the pixels of the plaque was used as a measure of plaque echodensity. After PTA, follow-up of stenoses was done on day 1, weekly for 8 weeks, at 3 months, 6 months, and 1 year. The total plaque thickness (sum of anterior and posterior components), minimal luminal diameter (MLD), and peak systolic velocity ratio (PSVR) were measured for all stenoses. An increase of more than 2 in the PSVR was the duplex criterion used to signify restenosis. Results: The GSM of the stenoses before angioplasty ranged from 6 to 71 (mean, 31.3 ± 17.9); 17 stenoses had a GSM less than 25 (mean, 18.7 ± 5.3), and 14 had a GSM more than 25 (mean, 46.4 ± 15.8). When the GSM was less than 25, the absolute reduction in plaque thickness on day 1 post-PTA was 3.3 ± 1.8 mm, in contrast to 1.8 ± 1.6 mm when GSM was more than 25 ( P < .03). The restenosis rate (PSVR more than 2) was 41% at 6 months and remained unchanged at 1 year. When the GSM was less than 25, restenosis occurred in 11% of lesions, in comparison with 78% when the GSM was more than 25 ( P < .001). Conclusion: Plaque echodensity can be used to evaluate stenoses before PTA, to predict initial success and identify a subgroup that has a high prevalence of restenosis. The identification of a group at “high-risk” of restenosis can improve the selection of patients for the procedure and also be used in prospective studies on the prevention of restenosis. (J Vasc Surg 1999;29:110-21.)