Treatment of vasospasm with a 480-nm pulsed-dye laser

Abstract

Laser energy at a wavelength of 480 nm was applied in 1-microseconds pulses of 3 to 10 mJ to two models of vasospasm. Rabbit common carotid arteries (CCA's) were constricted chronically by the application of human blood within a silicone sheath. Peak vasospasm developed 24 to 48 hours later, and persisted for up to 6 days. Endovascular laser treatment was delivered to 40 CCA's via a 200-microns diameter silica quartz fiber introduced through the femoral artery. The CCA caliber increased from 60% of the pre-vasospasm control diameter to a minimum post-laser diameter of 83% of control. No instances of laser-induced perforation or of arterial thrombosis were observed for up to 60 days after treatment. Prophylactic laser application to nine normal vessels was able to attenuate the development of vasospasm if blood was applied immediately thereafter (88% vs. 59% of control diameter, p less than 0.02), but not if blood was applied 7 days later. Studies in 16 normal CCA's established that there was a considerable margin between the laser energy required to induce dilatation and that which caused perforation, providing that the fiber remained relatively central within the artery. Morphological examination demonstrated focal loss of endothelial cells immediately after laser application, followed approximately 7 days later by the development of areas of intimal hyperplasia. Only minimal changes were observed in the medial or adventitial layers. In a second study, the basilar artery of seven dogs was constricted chronically by two intracisternal injections of autologous blood 3 days apart. Five dogs received endovascular laser treatment 7 or 10 days after the first injection, when basilar artery diameter was reduced to a mean of 61% and 77% of control, respectively. Immediately following treatment, basilar artery diameter increased to 104% and 102% of resting diameter, respectively. Both untreated and laser-treated arteries were smaller than the control diameter at 30 days (80% and 82%, respectively), but in each group the vasodilatory response to hypercapnia was preserved. These findings indicate that 1-microsecond laser pulses are well tolerated by systemic and cerebral arteries in two different animal models, and suggest that the 480-nm pulsed-dye laser may have an application for the treatment or prophylaxis of cerebral vasospasm.

Pathological effects of angioplasty on vasospastic carotid arteries in a rabbit model

“…A similar model of vasospasm was used by MacFarlane and colleagues. 10 They found a 53% reduction in arterial diameter 2 days after clot placement and a return to normal caliber by 6 days. Results of placement of empty sheaths were not reported in their findings.…”

“…12 In the present study, a rabbit model of vasospasm was used to investigate the effects of angioplasty. 10 The goals of this study were to define the effect of angioplasty on vasospastic rabbit carotid arteries as it is observed on angiography, to determine if angioplasty causes arterial fibrosis or endothelial proliferation after induction of vasospasm by periarterial blood clot placement, and to define the pathological and ultrastructural effects of angioplasty on these arteries. The endpoints determined in this study included vasospasm exhibited on angiography, amino acid analysis, and histopathological examination of arteries for evidence of changes in smooth muscle and in the extracellular matrix.…”

Diverse effects of a 445 nm diode laser on isometric contraction of the rat aorta

“…Blue lasers (360-480 nm) are used for skin (acne) and cancer therapy [5,6]. In addition, a previous study demonstrated that a 480 nm laser could be used for treating vasospasms [7]. However, the effects of visible laser on blood vessels are controversial.…”