Effects of plaque composition on vascular remodelling after angioplasty in the MultiVitamins and Probucol (MVP) trial.

Background: The antioxidant probucol reduced coronary restenosis in the MultiVitamins and Probucol (MVP) trial by improving vascular remodelling. Whether calcification limits the extent of adaptive vessel enlargement is not known.
Objective: To determine whether plaque composition at the dilated site affects probucol-induced vascular remodelling after angioplasty.
Patients and Methods: Beginning 30 days before percutaneous transluminal coronary angioplasty (PTCA), 317 patients received either probucol, vitamins, probucol and vitamins, or placebo. Patients were then treated for six months after PTCA. Intravascular ultrasound (IVUS) was performed post-PTCA and at follow-up in 94 patients (111 segments). The cross-section for serial analysis was the one at the angioplasty site with the smallest lumen area at follow-up. Quantitative analysis consisted of measurements of lumen area and external elastic membrane (EEM) area. The selected cross-section was also divided into five regions according to the type of plaque present (calcific, fibrotic, hypoechoic, fibrohypoechoic or normal). Plaque characterization scores (PCS) (PCS for arc, area, inner perimeter and outer perimeter) were calculated using weighting factors.
Results: There were no interactions between potential PCS covariates and probucol main effect on changes in lumenal, EEM and wall area. There were no significant PCS covariates in the model for change in EEM as they were all removed using a backward stepwise procedure. The last potential covariate (area PCS) had a significance level of P=0.48. In contrast, probucol significantly influenced the change in EEM over time (P=0.003).
Conclusion: Plaque composition at the dilated site does not appear to influence probucol-induced vascular remodelling after angioplasty.