Biomedical subjects

L A Stern

Publications and source records attributed to L A Stern.

3 recordsLinked to original sources

PubMed2000

Transformations in methane hydrates.

Detailed study of pure methane hydrate in a diamond cell with in situ optical, Raman, and x-ray microprobe techniques reveals two previously unknown structures, structure II and structure H, at high pressures. The structure II methane hydrate at 250 MPa has a cubic unit cell of a = 17.158(2) A and volume V = 5051.3(13) A(3); structure H at 600 MPa has a hexagonal unit cell of a = 11.980(2) A, c = 9.992(3) A, and V = 1241.9(5) A(3). The compositions of these two investigated phases are still not known. With the effects of pressure and the presence of other gases in the structure, the structure II phase is likely to dominate over the known structure I methane hydrate within deep hydrate-bearing sediments underlying continental margins.

Journal Article↗

PubMed1992

Angioscopy in endovascular surgery: recent technical advances to enhance intervention selection and failure analysis.

Recent technical and procedural modifications have greatly enhanced the usefulness of angioscopy during angioplasty. A pulsed irrigation system, proximal and distal blood flow control by pressure, and attention to sheath/vessel diameter ratio were incorporated into a study in which angioscopy was used for pretreatment assessment in 23 patients with symptomatic peripheral vascular disease presenting for initial (8 patients) evaluation or repeat treatment (15 patients) following a previous vascular procedure. Twenty-five lesions were examined with a 2.3 mm flexible angioscope equipped with an irrigating lumen; there were no complications attributable to angioscopy. The angioscope was useful in the characterization of lesions for selection of the recanalization technique. Lesions more amenable to initial atherectomy were visualized in 12 patients; 7 occlusions were successfully treated with laser/balloon angioplasty, with angioscopy assisting in probe and/or wire passage in 4 cases. Three late reocclusions were identified angioscopically as due solely to thrombosis, indicating the need for thrombolytic therapy. Angioscopy also identified 4 cases of incomplete recanalization despite a satisfactory arteriographic image. Angioscopy was also used to evaluate stenotic lesions unaccompanied by thrombus formation in patients previously treated with laser-assisted angioplasty. Histologic evaluation of the biopsied plaques identified intimal hyperplasia as the etiology, matching identically similar specimens harvested from a lesion treated with balloon dilation only.

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PubMed1990

Intraoperative coronary excimer laser angioplasty: preliminary clinical experience.

Diffuse coronary artery atherosclerosis is generally recognized as a deterrent to successful revascularization if it cannot be adequately treated. Mechanical endarterectomy can be useful, but it is not the optimal solution owing to the associated higher incidences of perioperative infarction and mortality. The use of laser energy as an endarterectomy tool appears promising. To investigate the application of excimer laser radiation to intraoperative coronary artery endarterectomy, 15 stenotic lesions in 13 patients were treated with excimer irradiation during coronary artery bypass grafting. Eleven (73%) of the lesions were enlarged by the excimer probe (6 of the successes were in calcified lesions). The 4 arteries not enlarged by the excimer laser all demonstrated calcified lesions. There were 3 perforations and 2 dissections, all but 1 in heavily calcified arteries. The results of this phase 1 safety and efficacy study indicate that excimer irradiation can recanalize most arteries, including total and subtotal occlusions and some calcified lesions. Further evaluation with better delivery systems is needed to determine whether the perforation rate can be reduced.

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