MECHANISMS OF LUMEN ENLARGEMENT AFTER EXCIMER-LASER CORONARY ANGIOPLASTY - AN INTRAVASCULAR ULTRASOUND STUDY

Background The mechanisms of excimer laser coronary angioplasty (ELCA) have never been studied in human coronary arteries in vivo. Methods a nd Results ELCA was used to treat 202 lesions in 190 patients. Forty-n ine lesions in 48 patients were studied by use of sequential (before a nd after ELCA and after adjunctive device therapy) intravascular ultra sound (IVUS). External elastic membrane (EEM), lumen, and plaque+media (P+M=EEM-lumen) cross-sectional areas (CSAs) and lesion arcs of calci um were measured before and after ELCA and after adjunct device use. L umen improvement after ELCA (1.4+/-0.5 to 2.7+/-0.8 mm(2)) was the res ult of both tissue ablation (decrease in P+M CSA from 16.8+/-7.1 to 15 .9+/-6.7 mm(2), P<.0001) and vessel expansion (increase in EEM CSA fro m 18.2+/-7.1 to 18.6+/-6.8 mm(2), P=.0245), with no change in calcium. The decrease in P+M CSA was 39% of the CSA of the laser catheter used . Dissections were present in 39% of lesions, 84% within superficial c alcium; fibrocalcific deposits developed a ''fragmented'' appearance. Conclusions ELCA increased lumen CSA by both atheroablation and vessel expansion without calcium ablation. Superficial fibrocalcific deposit s developed a characteristic fragmented appearance. These findings sup port both photoablation and forced vessel expansion as mechanisms of l umen enlargement and plaque dissection after ELCA.