Summary
A preprint reports that a peripheral stent designed to accommodate leg movement was associated with less neointimal growth and inflammation in minipigs. The animal study followed two groups for three and six months.
A peripheral stent designed to better accommodate the bending and compression that occur when a leg moves was associated with less tissue growth inside the artery and a smaller inflammatory response in a study of 16 Yucatan minipigs. The findings, reported in a bioRxiv preprint, suggest that how a stent deforms with the artery may influence healing after implantation.
Stents are mesh-like devices used to support narrowed arteries. In the femoropopliteal artery, which runs through the thigh and knee, limb movement can produce bending, twisting, compression and pinching. Tissue can also grow inside an artery after stenting; this neointimal hyperplasia can narrow the opening and contribute to restenosis.
How the stents were compared
The researchers used computational optimization to design a nitinol stent intended to maintain contact with the artery while reducing wall stress and narrowing of the lumen during leg-flexion deformation. They compared it with a commercial stent described as having representative biomechanical behaviour.
The study used two independent groups of eight minipigs, followed for three or six months. Each animal received the optimized stent in one leg and the commercial comparator in the other. Computed tomography angiography measured deformation in the living animals; micro-CT and tissue analysis were used to assess narrowing, neointimal growth, inflammatory cells and tissue composition.
The optimized stent accommodated greater axial shortening: 11.2±2.7% versus 6.6±2.1% at three months (p=0.003), and 13.7±4.4% versus 6.8±2.3% at six months (p=0.004).
Less neointimal growth at both timepoints
The measured volume of intimal hyperplasia was lower with the optimized stent at both follow-ups. At three months, the reported values were 227.5±85.2 mm³ compared with 350.0±130.5 mm³ for the commercial stent (p=0.002). At six months, they were 183.6±46.2 mm³ compared with 261.2±60.6 mm³ (p=0.001). Maximum, mean and median stenosis were also significantly lower with the optimized device at both timepoints.
At three months, macrophage counts were 51% lower and total inflammatory-cell counts were 45% lower with the optimized stent. Histologic tissue area was 28% lower at three months and 12% lower at six months. The fraction of tissue positive for αSMA was higher with the optimized stent at both follow-ups, while elastin, glycosaminoglycan and collagen fractions were similar between devices.
Taken together, the results associate improved accommodation of leg movement with a smaller inflammatory and neointimal response through six months. The broadly similar matrix fractions indicate that the difference in tissue amount was not accompanied by a reported shift in those measured matrix components.
This is preclinical evidence from a small animal study, not a clinical trial in people. The report is a preprint, and whether the same design advantage would improve outcomes for patients requires evaluation in human studies.