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Circulation, Vol 85, 756-768, Copyright © 1992 by American Heart Association
D Gal, SK Chokshi, M Mosseri, RH Clarke and JM Isner
BACKGROUND. Previous in vitro experiments performed in our laboratory have
shown that low-level laser energy may produce prompt reduction in isometric
tension of vascular smooth muscle. The present study was designed to extend
these previous in vitro findings to an in vivo model and thereby
investigate the hypothesis that laser light delivered percutaneously in
vivo could successfully reverse arterial spasm. METHODS AND RESULTS. Spasm
defined as greater than 50% reversible reduction in luminal diameter
persisting for greater than or equal to 5 minutes was successfully provoked
by injection of histamine (100-400 micrograms/kg) in 13 arteries among 10
atherosclerotic Yucatan microswine; the magnitude of histamine-induced
vasoconstriction was then documented angiographically by repeated
injections of contrast media for as long as 30 minutes (controls). After
return of angiographic luminal diameter to baseline, spasm was reproduced
with a second injection of histamine into the same artery. Representative
wavelengths generated by ultraviolet (UV), visible, and infrared lasers
were then delivered percutaneously via conventional fiberoptics to the site
of spasm, and angiographic assessment was repeated for as long as 30
minutes (treatment trial). In three arteries treated with UV (351 nm) light
from an excimer laser, angiographic luminal diameter narrowing decreased
from 100% to 23.9%, 50.0% to 9.3%, and 76.0% to 42.3%, respectively. The
magnitude of laser-induced increase in luminal diameter was 50.2 +/- 22.7%,
which was significantly greater than the magnitude of relaxation observed
spontaneously during the control trials (10.9 +/- 9.8%, p = 0.02). Visible
light from a helium-neon (632 nm) laser accomplished complete reversal of
histamine-induced spasm in two of four arteries; in the remaining two
arteries, luminal diameter narrowing percentages were reduced from 57.0% to
20.0% and from 76.5% to 30.8%, respectively. The magnitude of helium-neon
laser-induced relaxation (55.8 +/- 17.9%) was again significantly greater
than that observed during the control trials (0.9 +/- 1.9%, p = 0.01).
Finally, infrared irradiation from a diode-pumped neodymium:yttrium
aluminum garnet (1,064 nm) laser decreased histamine-induced luminal
diameter narrowing in three arteries from 100% to 21.4%, 56.0% to 8.7%, and
68.3% to 35.3%, respectively. The magnitude of infrared laser-induced
improvement in luminal diameter narrowing was 53.0 +/- 23.3%, which was
significantly greater than that observed during the control trials (12.9
+/- 10.7%, p = 0.01). In three additional arteries, fiberoptic sham trials
(without laser irradiation) failed to produce relaxation of
histamine-induced spasm. CONCLUSIONS. These findings document for the first
time that light-induced relaxation of vascular smooth muscle, previously
documented in vitro, may be reproduced in vivo.
ARTICLES
Percutaneous delivery of low-level laser energy reverses histamine- induced spasm in atherosclerotic Yucatan microswine
Tufts University School of Medicine, Department of Biomedical Research, St. Elizabeth's Hospital, Boston, Mass. 02135.
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