The aim of the study was to examine the differences between conventional and DES in the swine model, and associate them with the degree of vessel injury induced during implantation.
Factors that may modify the biological response to different intravascular devices in this experimental model must actually be taken into account before transferring the experimental study conclusions to human beings.Īlthough the relationship between vessel injury and restenosis has been described, 16 preclinical studies do not always provide this data given that is difficult to acquire such information. In this respect, preclinical assessment must include a histomorphometric study of the stents 28 days after implantation. 14, 15 This is why pre-marketing experimental models examining the endothelial reaction and intimal reaction to new devices have become more important. Despite the encouraging results from clinical trials, 6, 7, 8, 9, 10 due to their mechanism of action DES have lately been reported to provoke high rates of delayed thrombosis secondary to problems such as withdrawal from antiplatelet therapy, 11 delayed malapposition, 12 lack of endothelisation 13 or chronic inflammation. This proliferative response is the main determining factor for long-term stent outcomes, and has been considerably reduced with the advent of drug-eluting stents (DES). Healthy coronary arteries in a swine model is currently considered the standard for evaluating different platforms, polymers, and drugs for stents, given the anatomical and physiological similarity with the human model, and because its biological processes develop rapidly.This similarity also extends to the myocardial tissue repair system, 1, 2, 3 and the proliferative response or restenosis following coronary stent implantation. ConclusionesĮn el modelo porcino de coronarias sanas, la integridad de la lámina elástica interna no permite apreciar diferencias en la respuesta proliferativa entre stent farmacoactivo y convencional la diferencia se establece sólo cuando el daño vascular es más profundo. En cambio, en el grupo de rotura de la lámina elástica interna sí se encontraron diferencias significativas (área de neoíntima, 1,2 frente a 2,9 mm 2 p=0,001 y porcentaje de reestenosis, 16,63 frente a 30,4 % p=0,001).
ResultadosĮn el grupo de integridad de lámina elástica interna no se encontraron diferencias significativas entre stents farmacoactivos y stents convencionales para las variables área de neoíntima y porcentaje de reestenosis (1,3 frente a 2 mm 2 p=0,6 y 14 frente a 22,2 % p=0,5). Se clasificó el grado de daño vascular en función de integridad o rotura de la túnica limitante elástica interna. A los 28días se procedió a eutanasia y análisis histomorfométrico. MétodosĮn 20 hembras de cerdos de la raza Large White de 2meses de edad se implantó de forma aleatoria un total de 60 stents distribuidos en dos grupos: convencionales (n=20) y farmacoactivos (paclitaxel) (n=40). El objetivo de este estudio es comparar la histomorfometría vascular coronaria tras el implante de stents sin recubrir o stents farmacoactivos en un modelo porcino. Los stents farmacoactivos son una herramienta útil para prevenir la reestenosis, pero los mecanismos involucrados en la respuesta proliferativa tras su implante aún no son conocidos en su totalidad. In our swine model, we did not find any differences between proliferative response of drug-eluting stents and bare metal stents when the internal elastic lamina is intact differences are only found when vascular injury is deeper. We assessed statistically significant differences for the ruptured internal elastic lamina group, (neointimal area 1.2 vs 2.9 mm 2 P=.001 and % restenosis 16.63 vs 30.4 % P=.001). There were no differences between drug-eluting stents and bare metal stents in the intact internal elastic lamina group regarding neointimal area or % restenosis (1.3 ) vs 2.0 mm 2 P=.6 and 14.0 vs 22.2 % P=.5). We defined the vessel injury score in accordance to whether the internal elastic lamina was intact or ruptured. After 28 days, euthanasia and histomorphometry were performed. Sixty stents were randomly implanted in 20 Large White female pigs with a ratio of baremetal/drug-eluting stents of 1:2. The aim of this study is to compare the coronary vascular histomorphometry after implanting drug-eluting stents and bare metal stents in a swine model.
Drug-eluting stents are useful for preventing restenosis, but the patho-physiological processes involved in the proliferative response after implantation are still not known in detail.