Background: Intracoronary radiation (IR) studies have shown reduction of neointima formation (NF). Extrapolation of animal studies with beta-radiation to clinical trials have shown variable results, which may be related to dosimetry, centering issues, and/or shielding of beta-rays by the stent metal. We examined the effect of yttrium-90 (90Y), a pure beta-emitter delivered via an automatic afterloader to a centering catheter, on the inhibition of NF in balloon-injured (BI) porcine coronary arteries as well as in arteries receiving 90Y either prior to or following stent implantation (SI).
Methods: Twenty-three swine (44 coronary arteries) were studied. In the first study, IR (18 Gy at 1.2 mm from the balloon surface) was administered in 17 arteries following BI, while eight control arteries were subjected to BI only. In the second study, 10 swine (19 coronary arteries) underwent SI. IR (18 Gy) was administered in six arteries before and in eight arteries after SI, while five control arteries received SI only. The animals were sacrificed 2 weeks after BI and 4 weeks after SI. Their coronaries were perfusion fixed and stained, and vessel parameters (intimal area [IA] and medial fracture length [FL]) were analyzed by computer-aided histomorphometry.
Results: Arteries subjected to IR following BI had less NF compared to controls (IA/FL = 0.14 +/- 0.2 mm vs. 0.49 +/- 0.2 mm; P = 0.003). IA was reduced significantly in the arteries receiving radiation before and after SI compared to controls (0.92 +/- 0.98 and 0.00 +/- 0/00 vs. 2.72 +/- 1.2 mm2; P = 0.014), despite similar SI in all groups.
Conclusions: IR with 90Y delivered via a centering catheter is safe and effective with complete and homogenous inhibition of NF in the context of BI or SI in the porcine coronary model.