Intracoronary irradiation: dose response for the prevention of restenosis in swine.
OBJECTIVE
Restenosis after percutaneous transluminal coronary angioplasty represents, in part, a proliferative response of vascular smooth muscle at the site of injury. We have previously shown that high-dose radiation (20 Gy), delivered via an intracoronary 192Ir source, causes focal medial fibrosis and markedly impairs the restenosis process after balloon angioplasty in swine. This study sought to delineate the dose-response characteristics of this effect.


METHODS
Forty juvenile swine underwent coronary angiography; a segment of the left coronary artery was chosen as a target for balloon injury. In 30 swine, a 2 cm ribbon of 192Ir was positioned at the target segment and 20, 15, or 10 Gy were delivered to the vessel wall (10 animals/dose). Subsequently, overdilatation balloon angioplasty was performed at the irradiated segment. In 10 control swine, overdilatation balloon angioplasty was performed without previous irradiation. Thirty-eight animals survived until sacrifice at 30 +/- 3 days. Histopathological analysis was performed by a pathologist in a blinded manner. The area of maximal luminal compromise within the target segment was analyzed via computer-assisted planimetry.


RESULTS
Neointimal area was decreased by 71.4% at 20 Gy and by 58.3% at 15 Gy compared with control animals (p < 0.05 for both). A stimulatory effect on smooth muscle cell proliferation was noted at 10 Gy, with a 123% increase in neointimal area compared with controls (p < 0.05). Mean percent area stenosis was also reduced by 63% at 20 Gy and by 74.8% at 15 Gy compared with controls (p < 0.05 for both).


CONCLUSIONS
Intracoronary irradiation prior to overstretch balloon angioplasty markedly reduces neointima formation; this effect is dose dependent, with evidence of a significant stimulatory effect at 10 Gy. The effective therapeutic dose range for the prevention of restenosis in this model begins at approximately 15 Gy delivered to the vessel wall.
Weinberger
J
J
Department of Medicine, College of Physicians & Surgeons of Columbia University, New York, NY 10032, USA.
Amols
H
H
Ennis
R D
RD
Schwartz
A
A
Wiedermann
J G
JG
Marboe
C
C
D015906:Angioplasty, Balloon, Coronary; D000818:Animals; D001918:Brachytherapy / Q000379:methods*; D003327:Coronary Disease / Q000473:pathology / Q000517:prevention & control / Q000532:radiotherapy* / Q000628:therapy; D003331:Coronary Vessels / Q000293:injuries / Q000473:pathology / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D006965:Hyperplasia / Q000209:etiology / Q000473:pathology; D007496:Iridium Radioisotopes / Q000627:therapeutic use*; D011879:Radiotherapy Dosage; D012008:Recurrence; D013552:Swine; D017539:Tunica Intima / Q000293:injuries / Q000473:pathology / Q000528:radiation effects*
D007496:Iridium Radioisotopes