Development of novel short-term heating angioplasty: Assessment of artery collagen/elastin ratio and its contribution to artery dilatation

We have proposed a new thermal angioplasty device, Photo-thermo dynamic balloon (PTDB), for stenotic artery treatment. The PTDB provides short-term (<15s) and uniform heating during the balloon dilatation by the combination of efficient laser-driven heat generation and continuous fluid perfusion in the balloon. We have demonstrated previously that sufficient artery lumen dilatation was attained by the PTDB, but the correlation between the artery tissue composition and the PTDB dilatation characteristic has not been investigated. In this study, we aimed to reveal the influence of artery collagen/elastin ratio on the PTDB dilatation characteristic. We investigated the assessment method of the relative artery collagen/elastin ratio by artery fluorescence measurement. We obtained that the fluorescence spectrum of the artery collagen and elastin fiber could be separated from each other by optimized two pairs of wavelengths; Ex. 295nm and Em. 340nm for collagen detection, Ex. 360nm and Em. 445nm for elastin detection. By the artery fluorescence intensity measurement with these wavelengths, we measured the relative artery collagen/elastin ratio of extracted porcine carotid artery, femoral artery, coronary artery, and ascending aorta. The PTDB dilatation was performed in ex vivo with a prototype PTDB catheter with following conditions; 10s in heating duration, 65°C in peak balloon temperature, and 2atm in dilatation pressure. The artery lumen dilatation ratio with the PTDB dilatation was increased monotonically with the relative artery collagen/elastin ratio. Therefore, we concluded that the artery fluorescence measurement is effective method to assess the relative artery collagen/elastin ratio and to predict the PTDB dilatation effect in various arteries. We think that the PTDB dilatation might be available for treatment of collagen-rich artery, i.e., stiff artery.