Difference in neointimal proliferation between ruptured and non-ruptured segments after bare metal stent implantation

The difference in neointimal stent coverage (NSC) between ruptured segments and adjacent nonruptured segments in infarct-related lesions (IRL) of acute myocardial infarction after bare metal stent (BMS) implantation was evaluated using coronary angioscopy. Serial angioscopic observations were performed for 19 IRLs immediately after the implantation of a BMS and at 1-month and 6-month follow-up. Stented segments were divided into the ruptured segment and the nonruptured segment based on the presence of a thrombus. The grade of NSC was divided into 0 = complete exposure, 1 = partial coverage, or 2 = complete coverage. The grade of plaque color was classified semiquantitatively as 0 = white, 1 = light yellow, or 2 = intense yellow. The existence of a thrombus was also determined. The grade of NSC in the ruptured segment was lower than that of the nonruptured segment at each follow-up. The grade of plaque color at the 1-month follow-up was higher in the ruptured segment than in the nonruptured segment. At 6 months, the grade of plaque color was similar between the ruptured and nonruptured segments. In all cases, thrombi existed in the ruptured segments immediately after stenting. Although thrombi still remained frequently at 1-month, most had disappeared at the 6-month follow-up. Neointimal proliferation of the ruptured segment in IRL advanced slowly in comparison to the adjacent nonruptured segment. The presence of an atherosclerotic yellow plaque and a thrombus may affect the delayed neointimal coverage after BMS implantation.