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Laser balloon angioplasty: Effect of constant temperature versus constant power on tissue weld strength
Author(s) -
Anand Raj K.,
Sinclair I. Nigel,
Jenkins Ronald D.,
Hiehle John F.,
James Leslie,
Spears J. Richard
Publication year - 1988
Publication title -
lasers in surgery and medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 112
eISSN - 1096-9101
pISSN - 0196-8092
DOI - 10.1002/lsm.1900080109
Subject(s) - laser , materials science , balloon , restenosis , welding , angioplasty , laser power scaling , biomedical engineering , optics , composite material , surgery , medicine , cardiology , stent , physics
Abstract Thermal fusion of intimal plaque with the arterial wall during coronary balloon angioplasty may significantly reduce the incidence of abrupt closure and may reduce the occurrence of delayed restenosis by improvement of luminal size and shape. Although Nd:YAG laser energy has been shown to be effective in the thermal fusion of plaque‐arterial wall separations in vitro, the most efficient manner of energy delivery for rapid achievement of therapeutically useful equilibrium tissue temperature during laser exposure has not been defined. A comparison of weld strength achieved was therefore made between two formats of laser delivery: constant power vs. decremental power with an initial high dose followed by the minimal serial decrements necessary to maintain tissue temperature constant for 15 seconds. One hundred sixty‐six tissue discs of human postmortem aorta of 11 mm diameter were studied. Intimal plaque was separated from the media, the two layers were juxtaposed, a force of 4 pounds was applied, and a fiberoptic‐delivered laser beam was directed perpendicular to the tissue over a 3‐mm‐diameter nominal spot size. Weld strength was measured as the shear force required to separate completely the two tissue layers. The mean weld strength (75 g) achieved by use of the decremental power format was significantly higher (P < .01) than the mean strength (32 g and 56 g) achieved by using constant power for 20 and 30 seconds, respectively. The total laser energy used for the decremental power format was 235 joules, which was significantly less than the 320 and 480 joules used when constant power exposure for 20 and 30 seconds, respectively, was employed, despite the fact that the peak tissue temperature was similar for all three groups. It is concluded, therefore, that the use of decremental power to achieve quickly and, thereafter, to maintain a constant temperature provides better tissue weld strength at a lesser energy cost and hence is superior to the use of constant power.