Distal endothelial function and vascular morphology after catheter-based radiation in pig coronary arteries

Purpose

Endovascular irradiation inhibits neointimal hyperplasia in ballooned and stented arteries but impacts both diseased and adjacent normal tissue. Little is known about the effects of irradiation on downstream vasculature. In this study, we investigated vascular function and structure of pig coronary arteries distal to sites of endoluminal irradiation.

Materials and methods

Vasomotor responses of distal arteries to contraction of KCl and PGF_2α and endothelium-dependent (substance P and A23187) and -independent (sodium nitroprusside) relaxation were studied in naı̈ve, sham-treated, irradiated, stented, and stented plus irradiated vessels. Light and scanning electron microscopy were used to assess vascular morphology.

Results

Relaxations to substance P and A23187 at 1 month post treatment were significantly decreased in the irradiated group, whereas contractile response to PGF_2α was significantly increased. Hemorrhage, mural thrombus, and inflammation were present at the upstream-irradiated site; inflammatory cells were also present adherent to the endothelium in the distal segments.

Conclusions

Distal vasomotor function reflects an influence from the nature of a proximal intervention. The effect of irradiation on downstream conduit arteries to increase the threshold of contractility and suppress endothelium-dependent relaxation may be related to the presence of inflammatory cells at both the upstream-instrumented site as well as the distal location.