Response of very small (2 mm) porcine coronary arteries to balloon angioplasty and stent implantation

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Abstract
Objective: To investigate the response of very small coronary arteries to stent deployment and balloon angioplasty.Setting: Normal porcine coronary arteries.Methods: 24 pigs underwent intervention to two main coronary arteries, in segments 2.0 mm in diameter, with balloons whose diameter was 2.5 mm at standard pressure. Twelve arteries received a BiodivYsio small vessel (SV) stent; 12 an NIR SV stent; 12 standard BiodivYsio stent, and 12 balloon only. The arteries were harvested at 28 days, fixed, embedded in plastic, and cut and ground in cross section. The injury score and histomorphometry were assessed.Results: The BiodivYsio SV stent was associated with 20% less injury (p = 0.16), a 30% larger lumen (p = 0.13), and a 25% smaller neointima (p = 0.03) than the NIR SV stent, despite identical oversize. The standard BiodivYsio stent exhibited less recoil but 29% greater injury (p = 0.01), 59% more neointima (p = 0.00), and 18% less lumen (p = 0.27) than the BiodivYsio SV. Of all interventions, balloon only was associated with little injury, little neointima, major vessel shrinkage, and the largest lumen.Conclusion: Despite uniform oversize dilatation, both injury and response varied widely in very small porcine coronary arteries, depending on whether a stent or balloon was used, the stent design, and the number and/or thickness of struts. The response to different stent designs is considerable and is related to the degree of injury.