NEW TECHNOLOGIES FOR THE TREATMENT OF OBSTRUCTIVE ARTERIAL-DISEASE

The well-known limitations of balloon angioplasty include unpredictable abrupt closure, chronic total occlusion, diffuse disease, and restenosis, among other factors. These limitations have prompted the development of new technologic approaches to angioplasty including laser applications for plaque ablation, mechanical device applications for plaque removal/debridement, and stent devices for structural maintenance of vascular lumen patency. Devices which directly apply laser energy for ablation of plaque material include a balloon-centered laser angioplasty system, excimer laser ablation catheter systems, and a fluorescence-guided spectral feedback laser system. Experience with these devices indicates that plaque can be successfully ablated by using laser energy. Vessel perforation and dissection are complications reported with these devices and the effects of laser angioplasty on restenosis remain unclear. Indirect application of laser energy has been tested by using a "hot tip" catheter and a laser balloon angioplasty system. Although the hot tip device has received FDA approval for use in peripheral arteries, it appears to have very limited applications in the coronary arteries. Laser balloon angioplasty appears to be beneficial in the setting of threatened acute closure; the device continues to be evaluated for potential beneficial impact on restenosis. Mechanical atherectomy catheters are designed to remove atherosclerotic plaque from the arterial system and include the AtheroCath, the Transluminal Extraction Catheter (TEC), and the Pullback Atherectomy Catheter (PAC). The Rotablator is an atheroablation device which debrides the obstructing plaque material with distal embolization of the particulate debris. Successful removal/debridement of atherosclerotic plaque has been demonstrated with the AtheroCath, Rotablator, and the TEC device. Pre-clinical studies demonstrate successful removal of plaque material with the PAC device. Despite the theoretic advantage of removing plaque material when performing angioplasty with these devices, there has been little or no reduction in restenosis rates based on a significant experience with the AtheroCath and the Rotablator. Intravascular stent devices including one self-expanding device design and two balloon-expandable device designs have been employed successfully in the elective setting to treat recurrent restenosis lesions. Two of the devices have been successfully tested in the setting of threatened acute closure. Early follow-up studies suggest some improvement in restenosis rates in certain clinical settings following intravascular stenting. Acute and subacute thrombosis remain substantial problems for stent devices and very aggressive anticoagulation regimens are necessary to minimize the adverse events. In summary, a number of a new technologic approaches for treatment of atherosclerotic lesions have been developed and are undergoing significant clinical evaluation. Collectively, these techniques appear to be leading to an improvement in angioplasty results although significant limitations for these devices are also being recognized.