Laser angioplasty of peripheral arteries: basic principles, current clinical studies, and future directions

Abstract

Percutaneous transluminal angioplasty (PTA) is a routine procedure for the treatment of peripheral arterial disease. However, its main limitation is late restenosis occurring at a 1-year rate of 6%-60%. Restenosis arises from injury to the arterial wall including overstretching, compression and rupture of the atherosclerotic plaque during balloon inflation. It is hypothesized that better long-term angioplasty results are observed if atherosclerotic plaques are removed rather than compressed and fractured. Laser angioplasty is one method to remove atherosclerotic plaques. We discuss the principles of lasers, physical properties of laser light, history of laser angioplasty and effects of laser radiation on tissues. Large clinical studies using laser angioplasty are critically assessed. In comparison to conventional PTA, there are some advantages of laser angioplasty: easier passage through chronic and calcified occlusions and according to some studies, better short- and medium-term results regarding limb salvage and management of in-stent restenoses.

Figure 1

Effects of different lasers on human postmortem atherosclerotic coronary arteries: light microscopic findings (own experiments, hematoxylin and eosin staining). Left: a crater after irradiation by argon laser (energy 30 J, beam transmitted through a 250 μm core diameter quartz optical fiber) reveals thermal injury. A superficial zone of coagulation necrosis and a subjacent zone of polymorphous lacunae are present (magnification ×150). Right: After excimer laser irradiation (wavelength 193 nm, energy 100 mJ/pulse, 15 ns pulse duration, 1 Hz repetition rate, energy density 1.5 J cm⁻², 250 pulses applied, radiation focused by means of a lens), no thermal damage is evident. The surface of the crater has sharp edges and tissue architecture is preserved (magnification ×120).

Figure 2

Laser system consists of a laser (1), a connector (2), a laser catheter with optical fiber(s) transmitting the laser energy into the artery (3) and a catheter tip (4).