Restenosis after coronary angioplasty: The paradox of increased lumen diameter and restenosis

Restenosis after coronary angioplasty is the single complication that most limits this revascularization procedure in clinical practice. The process is largely unpredictable and the lesion-related factors predisposing to restenosis are poorly understood, with little consensus in published reports. In this study using detailed quantitative angiographic measurements to assess 490 lesions, the simple lesion characteristics associated with restenosis were defined and the relation to the restenosis process documented. Restenosis was defined as an absolute deterioration in the minimal lumen diameter by ≥ 0.72 mm, a criterion based on the 95% confidence intervals for repeat angiographic measurements. This was chosen in an attempt to separate spurious changes due to a poor angiographic result and the variability of angiographic measurements from significant changes due to the restenosis process. The principal determinants of restenosis were found to be a large improvement in the minimal lumen diameter at the time of dilation (1.13 mm for the restenosis group compared with 0.86 mm for the no restenosis group [p < 0.0001]) and an optimal postangioplasty result (minimal lumen diameter 2.28 mm in the restenosis group compared with 2.05 mm [p < 0.001] in the no restenosis group, corresponding to a 25% and a 30% diameter stenosis, respectively [p < 0.0001]). These observations reported for the first time suggest that the distinction needs to be made between a "clinical restenosis" of ≥ 50% diameter stenosis and the "restenosis process" as measured by the absolute changes occurring during and after angioplasty. They lend support to the hypothesis that the degree of mechanical stretch produced by the dilating balloon on the vessel wall may be important in stimulating the restenosis process. This is in contradiction to deductions obtained if restenosis is based on "clinical restenosis," which suggests that restenosis is associated primarily with a poor angioplasty result. More important, it indicates that there is potential for misinterpreting the results of restenosis studies if the observations are based solely on conventional restenosis criteria without knowledge of the absolute changes occurring during and after the angioplasty procedure.