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 and Results ELCA was used to treat 202 lesions in 190 patients. Forty-nine lesions in 48 patients were studied by use of sequential (before and after ELCA and after adjunctive device therapy) intravascular ultrasound (IVUS). External elastic membrane (EEM), lumen, and plaque+media (P+M=EEM-lumen) cross-sectional areas (CSAs) and lesion arcs of calcium were measured before and after ELCA and after adjunct device use. Lumen improvement after ELCA (1.4+/-0.5 to 2.7+/-0.8 mm(2)) was the result 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 from 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 calcium; fibrocalcific deposits developed a ''fragmented'' appearance. Conclusions ELCA increased lumen CSA by both atheroablation and vessel expansion without calcium ablation. Superficial fibrocalcific deposits developed a characteristic fragmented appearance. These findings support both photoablation and forced vessel expansion as mechanisms of lumen enlargement and plaque dissection after ELCA.