Determining Light Dose for Photodynamic Therapy of Atherosclerotic Lesions in the Yucatan Miniswine

Abstract

Purpose:

To determine the light dose required for photodynamic therapy of atherosclerotic lesions in the miniswine.

Methods:

Aortic atherosclerosis was created in seven Yucatan miniswine by a combination of balloon endothelial injury and 2% cholesterol and 15% lard for 7 weeks. Six animals received the photosensitizer Photofrin^R 2.5 mg/kg, while an additional swine received no drug. After 24 hours, the abdominal aorta was exposed and the aorta opened longitudinally in each animal. Three 1-cm spots were illuminated with energy densities of 60, 120, and 240 J/cm² from an argon-pumped dye laser tuned to 630 nm with a laser output of 1 W. Four weeks later, the animals were killed, abdominal aortae removed, and intimal thickness determined by morphometry.

Results:

The percentage intimal thickness (mean ± SD) was 36.7 ± 27.1, 9.1 ± 5.0, and 6.4 ± 8.1 for the three energy densities, respectively. Although both 120 and 240 J/cm² energy densities produced significant (p < 0.05) reduction in atheroma, considerable damage to the underlying media was also observed in the 240 J/cm² group.

Conclusions:

A Photofrin dose of 2.5 mg/kg and 120 J/cm² light are necessary for adequate ablation of atheroma while avoiding extensive medial damage.