Background: Relation between metallic allergy and in-stent restenosis (ISR) has been inconclusive. We hypothesized that mechanism of restenosis is different between initial stent implantation and dilatation for ISR. Thus, we studied metallic allergy and restenosis in these two different situations separately.
Methods and results: We performed follow-up angiography and patch test for metallic allergy in a total of 174 stented consecutive patients, 109 patients (63%) for restudy of initial stent implantation and 65 patients (37%) for restudy of treatment following ISR. The positive rate of patch test in initial stent implantation was not significantly different between with or without restenosis (10% vs. 9%; p=ns). Whereas, following dilatation of ISR, the incidence of positive patch test was significantly higher in patients with recurrence of restenosis than those without the recurrence (39% vs. 12%; p=0.02). Multivariate analysis revealed that the positive patch test (Odd Ratio 4.39, p=0.02) and diffuse typed ISR (Odd Ratio 3.68, p=0.03) were significant predictors of recurrent restenosis.
Conclusions: Metal allergy does not have any correlation with the restenosis after initial stent implantation. However, metal allergy is frequently observed in patients with recurrence of ISR. Metal allergy may contribute to a mechanism in the repeat recurrence of ISR, but not to restenosis after initial stent implantation.