Clinically significant arterial spasm can complicate percutaneous coronary and vascular interventions. We investigated the effects of pulsed dye laser irradiation using an anesthetized rabbit model of femoral artery vasoconstriction. Pulsed dye laser irradiation *(585 nm, 2 µsec pulse duration, 2 Hz for 10 seconds) was delivered via a 320µ core ball-tip optical fiber introduced perpendicularly through a femoral artery sidebranch. Laser Irradiation (LI) was delivered at incremental energies of 2.5-10 mJ/pulse. Artery internal dimensions were measured continuously using 12.5 HMHz ultrasonic imaging. Eight rabbits were studied in each of the three groups.
Group I: LI was delivered to vessels with surgically induced vasoconstriction increasing vessel diameter from 0.65±0.32 mm to 1.65±0.23 mm (p<0.01). After dilation with LI, the vessel was resistant to vasoconstriction by a topical phenylephrine (0.05mg/ml) bath (decreased in diameter from 1.65±0.23mm to 1.63±0.24 mm compared to control vessels decreasing from 1.25 ±0.23 mm to .032±0.18 mm p<0.001).
Group II:LI delivered to vessels pretreated with topical phenylephrine reversed vasoconstriction (increase in diameter from 032±0.18mm to 1.63±0.16mm, p<0.001.)
Group III: After pretreatment with a lidocaine and nitroglycerin bath to produce maximum vasodilation, LI was delivered with no significant effect on vessel diameter. However, in contrast to group I, these vessels remained sensitive to phenylephrine vasoconstriction (decrease in diameter from 1.70 ±0.35 mm to 0.52± 0.26mm, p<0.001.)
Conclusion: LI can reverse surgically and pharmacologically-induced vasoconstriction rendering the vessel refractory to phenylephrine. However, when LI is delivered to a predilated vessel, this responsiveness to phenylephrine is preserved. Thus, preexisting vasoconstriction must be present for laser-induced arterial paresis to occur.
Schwengel RH, Scott HJ, Beauman GJ, Mergner WJ, Gregory KW, Ziskind AA: "Pulsed dye laser irradiation can reverse and prevent surgical and pharmacologic vasoconstriction," Lasers in Surgery and Medicine (Suppl.) 4:19,1992.