"Optimally spaced" excimer laser coronary catheters: Performance analysis

Background: Excimer laser angioplasty is a percutaneous treatment modality for management of selected patients with severe obstructive coronary artery disease. This technology entails application of multifiber catheters that vaporize intra-arterial plaque and thrombus with the 308-nm wavelength ligh t. A coronary laser catheter ("OS") with increased space between its optic fibers (90 mu) at the tip was recently developed. The previous design used a closely packed fiber bundle ("CP") with a smaller space between the fiber s (77 mu). We sought to determine the ablation characteristics of the new, OS design. Methods: Experiments testing the new catheter and comparing it t o the existing catheter included: (1) measurement of the laser output beam sizes and divergences; (2) evaluation of particulate matter generation duri ng ablation of atherosclerotic tissue; (3) measurement of ablation hole siz es and tissue penetration rates; (4) histopathologic examination of laser-i nduced in vivo vessel wall injury. Results: The new OS catheters produce a wider beam with higher divergence than the traditional CP catheters (6.7 de grees vs. 4,7, respectively). Testing two different levels of energy reveal ed the generation of a reduced number of particulate matter and shallower p enetration depth with the OS catheter compared with traditional CP catheter s, The OS catheters created a larger diameter of ablated hole than the CP c atheters (for 2.0-mm catheters: 2.7 mm(2) vs. 1.5 mm(2), respectively, p = 0.01], Lasing with the OS catheters with slow advancement rates (0.2-0.5 mm /sec) resulted in creation of significantly larger-diameter holes than thos e produced at higher speeds (1-3 mm/sec), The in vivo vessel wall injury sc ores were similar among the two types of catheters tested. Conclusions: A n ew design of spaced optical fibers for coronary laser catheters provides in creased tissue ablation in comparison to the traditional closely packed fib ers catheter, Slow advancement rates during lasing with the new OS catheter are crucial for achievement of adequate plaque debulking.