Mechanisms of late lumen loss after antiproliferative percutaneous coronary intervention using beta-irradiation in a porcine model of restenosis.

Background: The short-term results for the prevention of coronary restenosis after intravascular brachytherapy (IVBT) and use of drug-eluting stents (DESs) are excellent. The long-term results either lack or present with late complications (e.g., late thrombosis and late catch-up phenomenon leading to late restenosis even years after the initial procedure). Both IVBT and DESs mediate their potent antirestenotic effects via a cytostatic mechanism, but the cardiovascular pathology at late time points after the use of these antiproliferative therapies is incompletely understood. This study investigated the long-term effects of antiproliferative beta-irradiation in a clinically relevant porcine coronary model to address the pathophysiology of late coronary restenosis after antiproliferative vascular interventions.

Methods: We performed percutaneous transluminal coronary angioplasty (PTCA) in two major coronary arteries in 12 domestic crossbred pigs. One of the two balloon-injured segments was randomly assigned to receive immediate beta-irradiation (PTCA+IVBT group) using a noncentered delivery catheter (20 Gy; Novoste Beta-Cath System, Novoste, Norcross, GA, USA). The animals were sacrificed after 14 days (n=6) or 3 months (n=6).

Results: The luminal area in the PTCA+IVBT group decreased significantly 3 months after the intervention as compared with that in the PTCA group (PTCA 3.45+/-0.46 mm2 vs. PTCA+IVBT 1.22+/-0.26 mm2; P=.0017). This lumen loss was primarily due to shrinkage of the external elastic lamina area (negative arterial remodeling; PTCA 5.22+/-0.27 mm2 vs. PTCA+IVBT 3.42+/-0.45 mm2; P=.0064), which was accompanied by an increase in the adventitial area (PTCA 3.07+/-0.2 mm2 vs. PTCA+IVBT 5.41+/-0.5 mm2; P=.0049).

Conclusions: The application of antiproliferative radiation in a porcine coronary model caused an early beneficial effect (reduction of intimal-medial lesion and luminal gain) that was followed by a late lumen loss primarily due to negative arterial remodeling. This mechanism may in part help us understand the pathophysiology of late adverse events occurring after IVBT.