Biomedical subjects

D S Choy

Publications and source records attributed to D S Choy.

At least 55 records · Page 3Linked to original sources

PubMed1986

[Transfemoral catheter-laser thromboendarterectomy of the carotid artery].

Argon laser irradiation via a transfemorally introduced catheter successfully vapourized both fresh thrombi and stenosing plaques in the carotid artery of seven cadavers and two patients. Fresh thrombi were recanalized throughout their length, while the arteriosclerotic plaques were partially reduced. No particles larger than 7 micron were demonstrated in the eluant flushing fluid, indicating that peripheral emboli need not be feared with this technique.

Arteriosclerosis↗

PubMed1986

Argon laser recanalization of three totally occluded human right coronary arteries.

We report the successful recanalization, in vivo, of three totally occluded human right coronary arteries with an argon laser catheter during coronary artery bypass surgery. The laser catheter and technique of laser recanalization are described. At 15 days postoperatively, two of the laser-treated arteries were reoccluded angiographically. The third patient refused postoperative angiography.

Cardiac Catheterization↗

PubMed1986

Laser revascularization, 1985: state of the art.

Progress in the young field of laser recanalization of occluded arteries and applications in cardiovascular disease to which many investigators have contributed is briefly summarized. Specific problems remaining to be solved are set forth. In conclusion, the author makes a cautious prediction of success for the percutaneous laser catheter within the next 5 years.

Arterial Occlusive Diseases↗

PubMed1985

Vascular recanalization with the argon laser: the role of blood in the transmission of laser energy.

Successful revascularization of stenosed arteries with the argon laser optical fiber catheter requires delivery of high-power-density energy to the lesion. Because of the high energy absorption by hemoglobin at the argon laser wavelengths, which would attenuate transmission of laser energy to the obstruction, we measured argon laser transmission through blood at different concentrations. We found that no transmission occurred through 1 mm of whole blood with hematocrit of 42 and that blood must be diluted to a hematocrit below 1 for laser energy to be delivered. Successful use of the intravascular argon laser is dependent on the creation of a transmission medium by displacement of blood by saline or other non-absorbing substance.

Arterial Occlusive Diseases↗

PubMed1985

Absence of distal emboli during in vivo laser recanalization.

We used an argon laser to recanalize occluded arteries in vivo and to determine the extent of any particulate matter resulting from the procedure that might cause embolization. Thrombosis was achieved by balloon de-endothelialization and thrombin injection in 12 canine femoral or carotid arteries in six dogs. The resulting totally occlusive thrombi (2.5-8.5 cm in length) were laser treated in situ 2-29 days after formation, using laser tip power outputs of 0.8-3.4 W. The treated arterial segment was perfused before, during, and after the recanalization procedure with 1,000 ml of heparinized saline. All saline passing through the artery was collected and studied by filtration through 20-micron pore filter paper; 50-ml unfiltered aliquots were studied by automated, calibrated cell counting and microscopically after centrifugation and staining. All vessels except one were completely recanalized. Filtration yielded a thin reddish, dust-like residue. No large fragments were found in 11 of 12 effluents. The residue after centrifugation was almost entirely composed of erythrocytes plus one to four 20-30-micron strands of amorphous cellular material per high-power field. Cell counting showed that 99.1% of the material in the effluents was smaller than 9.37 micron. These results demonstrate the presence of some filterable debris following laser recanalization of intraarterial thrombi, but it probably lacks any physiologic significance. Further study of this effect of laser recanalization is needed.

Animals↗

PubMed1985

Complete patency in thrombus-occluded arteries two weeks after laser recanalization.

The potential problem of rethrombosis after laser recanalization was studied in 16 thrombus-occluded canine femoral arteries. Balloon de-endothelialization and thrombin-human blood injection produced adherent, completely occlusive thrombi 4.13 +/- 1.54 cm in length; laser exposure of the thrombi occurred at 18.35 +/- 22.1 hours. The argon laser catheter was introduced via a proximal arteriotomy and a power of 3.83 +/- 0.58 W delivered for 411.3 +/- 296.87 seconds. Follow-up period was 14 days. All arteries were patent immediately after and 14 days following lasing, as demonstrated by angiography. There was no vessel perforation. Seven of the dogs were maintained on aspirin and dipyridamole 4 days before and throughout the study, but there were no differences in thrombus length, laser power, or duration of laser exposure between these dogs and those receiving no anti-platelet therapy. Control thrombosed arteries (without laser energy application) showed no autolysis within 14 days in all dogs and up to 95 days in three dogs followed for this period of time. These data show that rethrombosis of totally occluded, thrombosed arteries is not present up to 2 weeks later after laser recanalization, with or without the aid of anti-platelet therapy.

Animals↗

PubMed1985

Embolization and vessel wall perforation in argon laser recanalization.

The primary concerns in the development of a laser catheter for intravascular use are the potential hazards of vessel wall perforation and distal embolization. We present evidence, using technetium 99-labeled thrombi in two rabbit aortas and one human cadaver coronary artery, that distal embolization does not occur after argon laser recanalization. Also, no vessel wall perforation was observed during recanalization of 15 thrombosed rabbit aortas and 1 inferior vena cava, used because of their extremely thin walls. Laser recanalization of three peripheral arteries with atherosclerotic plaque obstruction, in amputated human legs, showed no evidence of vessel wall perforation. The incidence of vessel wall perforation can be minimized by preferential use of the argon laser, strict maintainance of a coaxial relationship between the laser catheter and the vessel, and exercising care during the actual lasing process. Distal embolization does not appear to be an important consideration.

Animals↗

PubMed1984

Human coronary laser recanalization.

Five patients undergoing distal saphenous vein bypass had an attempt at intraoperative laser vaporization of a proximal coronary stenosis. Laser treatment of three patients was technically successful. One patient's successfully treated native vessel was competing with the graft at angiographic restudy 25 days after the procedure. This first human intraoperative laser recanalization trial generated questions regarding the energy source, power parameters, and catheter modifications required for satisfactory clinical laser therapy. The trial is directing future experiments toward more efficient and complete laser vaporization of atherosclerotic plaques in the human coronary vasculature.

Aged↗

PubMed1983

Effective treatment for smoking cessation.

An effective method of cigarette smoking cessation using acupuncture is described. From May 1976 to December 1982, 514 patients were treated. Of 339 evaluable patients, 297 stopped smoking, for a success rate of 88 percent. In a two-year follow-up, the rate of relapse was 31 percent. The possible mechanisms by which this technique works are discussed.

Acupuncture Therapy↗

PubMed1982

Transluminal laser catheter angioplasty.

The first transluminal laser angioplasty in animals is reported herein. An Argon laser and a specialized coronary arterial catheter with a fiberoptic wave guide were used. Immediate histologic changes consisted of a moderate degree of intimal necrosis and some loss of elastic tissue. At 5 days the intima was repaired, but focal elastic tissue loss persisted.

Angioplasty, Balloon↗

PubMed1982

Laser coronary angioplasty: experience with 9 cadaver hearts.

Experience with laser angioplasty in 16 coronary arteries in 9 cadaver hearts is presented. Coronary obstructions were due to experimentally created thrombi as well as to naturally occurring calcified plaques. Successful laser angioplasty was achieved in 14 of 15 arteries. One artery was sacrificed to determine factors necessary for deliberate perforation of the arterial wall. This procedure required more than 30 seconds of laser energy at 3.0 W with the catheter tip almost perpendicular to the wall. Penetration of the arterial wall occurred only in the second left anterior descending artery which was plaque-occluded because of operator inexperience.

Angioplasty, Balloon↗

PubMed1982