Stephen T. DeJesus

Pulsed ultraviolet laser irradiation produces endothelium-independent relaxation of vascular smooth muscle.

Recent studies have shown that continuous wave laser irradiation induces contraction of vascular smooth muscle, except at powers far below the threshold for tissue ablation. To determine the corresponding effects of pulsed laser irradiation on vascular smooth muscle tone, vascular rings of rabbit thoracic aorta were mounted isometrically with 1 g tension in Krebs-bicarbonate buffer and irradiated with 308 or 351 nm from an excimer laser through a 400-microns optical fiber. A total of 250 exposures were performed with 1-6.5 mJ/pulse (fluence = 0.8-5.5 J/cm2), 10-50 Hz, and cumulative exposures of 10-120 seconds. Excimer laser irradiation in combinations of pulse energy (PE), repetition rate (RR), and cumulative exposure below, at, or above threshold for tissue ablation consistently produced relaxation unassociated with contraction in each of the 250 exposures. For the total 250 exposures, the magnitude of relaxation (reduction in recorded tension, Rmax) was 55 +/- 4% (mean +/- SEM) of maximum vasomotor reactivity recorded in the specimen in response to administration of serotonin. Rmax varied directly with both PE and RR. When PE was increased from 1 to 5 mJ/pulse (n = 13), Rmax increased from 57 +/- 19% to 80 +/- 19% (p less than 0.0001); when RR was increased from 10 to 50 Hz (n = 10), Rmax increased from 27 +/- 8 to 46 +/- 8 (p less than 0.0001). Rmax varied independently of endothelial integrity (assessed anatomically and pharmacologically) and wavelength (308 vs. 351 nm). Simultaneously recorded tissue-temperature profiles disclosed that during pulsed laser irradiation, tissue temperature rise did not exceed 5 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

Vascular spasm complicates continuous wave but not pulsed laser irradiation

Preliminary clinical experience with laser angioplasty has suggested that arterial spasm may complicate attempts to employ laser light to accomplish vascular recanalization. The present study was designed to investigate the role of energy profile on the development of arterial spasm during laser angioplasty. Laser irradiation was delivered percutaneously in vivo to New Zealand white rabbits and to Yucatan microswine with or without atherosclerotic lesions induced by a combination of balloon endothelial denudation and atherogenic diet. Continuous wave (CW) laser irradiation from an argon ion gas laser (wavelength 488 to 514 nm) was applied to 23 arteries, while 16 arteries were irradiated using a pulsed xenon chloride (308 nm) or xenon fluoride (351 nm) excimer laser. Arterial spasm, defined as greater than 50% reduction in luminal diameter narrowing, complicated delivery of laser light to 17 (74%) of the 23 arteries irradiated with the CW argon laser. Spasm was consistently observed at powers greater than 2 W, at cumulative exposures greater than 200 seconds, and at total energy greater than 200 joules. Spasm was typically diffuse (including the length of the vessel) and protracted (lasting up to 120 minutes). Intra-arterial nitroglycerin (up to 300 micrograms) produced only temporary and incomplete resolution of laser-induced spasm. In contrast, spasm was never observed in any of the 16 arteries in which laser angioplasty was performed using a pulsed laser (0.95 to 6.37 joules/cm2, 10 to 50 Hz, 48 to 370 seconds). Thus CW but not pulsed laser angioplasty may be complicated by arterial spasm.(ABSTRACT TRUNCATED AT 250 WORDS)

Failure of angiography to diagnose thermal perforation complicating laser angioplasty in a rabbit

Abstract Perforation of the vascular wall underlying the site of intended recanalization constitutes the principal risk of laser angioplasty. 1–3 In clinical trials of percutaneous laser angioplasty, absence of contrast extravasation on angiographic examination after laser treatment is usually interpreted to indicate that laser angioplasty was uncomplicated by vessel wall perforation. 1–3 We describe failure of angiography to diagnose necropsy-proved thermal perforation complicating laser recanalization of experimentally induced atherosclerotic narrowing in a rabbit.

Determination of gasoline fuel properties by Raman spectroscopy

We have demonstrated a correlation between laser Raman scattering features and the octane rating of gasolines and aromatic content of hydrocarbon fuels; our initial success measuring octane and aromatic content is very encouraging and forms the basis for our proposed research program. It is our aim to use this technology to develop an inexpensive, portable, field-deployable device that would allow on-site testing and/or verification of octane labeling of gasoline products at the pump, along with the environmentally significant properties, Reid vapor pressure and aromatic content.

Embolic Potential Of Cardiovascular Laser Irradiation

Calcified human coronary arterial segments obtained at necropsy were irradiated in vitro with continuous wave (CW) argon laser (n=16) and a pulsed (P) excimer laser (n=28). CW laser irradiation accomplished little debridement of calcified plaque. P laser irradiation accomplished extensive ablation of calcific plaque, but was associated with more particulate photoproducts. The quantity and size of the resultant particles varied as a function of the pulse energy employed. Reduction in pulse energy from 80 to 15 mJ/pulse decreased the quantity of particulate debris by 50% and eliminated the largest (>700 microns) particles.