In-vitro study of the effects of Congo Red on the ablation of atherosclerotic plaque

摘要

The possible application of the vital dye Congo Red to enhance the selective ablation of plaque was investigated. Fresh healthy human aorta samples and samples with varying degrees of atherosclerotic disease were incubated for 3 minutes in a 0.25 mg/ml solution of Congo Red in saline, washed and then irradiated either in air or under saline using an argon laser ($lambda $EQ 488 and 514.5 nm, spotsize $EQ 1.1 mm). The experiments were repeated with undyed healthy and diseased tissue samples. The effect of Congo Red staining on ablation was evaluated by comparing the minimum irradiance and the average amount of time needed to create ablation onset, which was defined as a 'pop' sound followed by carbonization of tissue in air. Ablation thresholds in air for dyed normal tissue, fatty and fibrous plaque were lowered by 42, 60 and 66% respectively. The average time to start ablation dropped from 40 to 2 s, 13 to 1 s and 20 to 14 s respectively. When tissue samples were submerged under saline, Congo Red paradoxically reduced the difference between the ablation threshold of healthy tissue and fatty threshold. During the initial irradiation a concentration of dye around the irradiation spot was observed. This unusual finding may be due to the transport of dye during irradiation. This may explain the observed effect that tissue adjacent to the initial irradiation site had a lowered ablation threshold. By examining the complex mechanisms involved in dye enhanced ablation in may be possible to select a combination of dye and irradiation parameters to achieve selective ablation of plaque.