Correlation of Angiographic Late Loss With Neointimal Proliferation in Stents Evaluated by OCT and Histology in Porcine Coronary Arteries

ObjectivesWe aimed to evaluate the correlation of angiographic late loss (LL) with the degree of in-stent neointimal proliferation assessed by optical coherence tomography (OCT) and histology.BackgroundAngiographic LL is the most common endpoint used in clinical trials for the evaluation of the efficacy of drug-eluting stents (DES). However, there are few data in regards to the accuracy of angiographic LL in the evaluation of DES displaying lower degrees of neointimal proliferation.MethodsA total of 49 stents (36 DES and 13 bare-metal stents) were deployed in coronary arteries of 23 domestic swine and followed up for 28 or 90 days, thus obtaining different degrees of neointimal proliferation. Each stent was divided into 8 to 9 segments along the longitudinal axis to match corresponding histological cross sections. Angiographic LL was calculated at each segment throughout the entire length of the stent and compared with in-stent neointimal thickness (NT) obtained by OCT and histology.ResultsA total of 382 angiographic segments were suitable for matched comparison with both OCT and histological findings. The mean LL at follow-up was 0.60 ± 0.57 mm (range: −0.46 to 2.3 mm) for all segments. Approximately 13.9% of stent segments had a LL between −0.5 and 0 mm, and 22.5% had a LL greater than 1.0 mm. The correlation between OCT and histology for the evaluation of NT was adequate regardless the level of angiographic LL. In addition, overall correlations between angiographic LL and NT by OCT or histology were adequate (R = 0.77 and 0.63, respectively). However, angiographic LL showed a poor correlation with NT by OCT or histology at a value <0.55 mm (R = 0.38 and 0.15, respectively).ConclusionsAngiographic LL below a threshold value of 0.55 mm correlates poorly with NT obtained by OCT and histology. These results suggest a cautious interpretation is needed to evaluate angiographic endpoints in DES trials in which LL values below this threshold are reported.