Laser energy at a wavelength of 480 nm was applied in 1 µs pulses of 3 to 10 mJ to two models of vasospasm. Rabbit common carotid arteries (CCA) were constricted chronically by the application of human blood within a silicone sheath. Peak spasm developed 24-48 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 vessel were 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 dilation 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 of hypercapnia was preserved. These finding indicate that 1-microsecond laser pulses are well tolerated by systemic and cerebral arterial in two different animal models and suggest that the 480-nm pulsed-dye laser may have an application for the treatment of prophylaxis of cerebral vasospasm.
MacFarlane R, Teramura A, Owen CJ, Chase S, De la Torre, Gregory KW, Parrish JA, Zervas NT: Treatment of vasospasm with 480 nm pulsed-dye laser. Journal Neurosurgery 75:613-622, 1991.