James Richard Spears

Percutaneous coronary laser balloon angioplasty: Initial results of a multicenter experience

A multicenter clinical trial was initiated to test the potential safety and short-term efficacy of a percutaneous coronary application of laser balloon angioplasty, which has been shown experimentally to alleviate the common causes (dissection, recoil, thrombus) of suboptimal luminal results of conventional balloon angioplasty. Fifty-five patients, the majority (62%) of whom had relatively high risk lesions, were treated in 10 centers with a laser balloon that was identical in size (3 x 20 mm) to a balloon used for conventional balloon angioplasty performed on the same lesion immediately before laser balloon angioplasty. One or more neodymium:yttrium aluminum garnet (Nd:YAG) (1,060 nm) laser doses of 250 to 450 J were each delivered over a 20 s duration per exposure. Immediately and 1 day after laser balloon angioplasty no significant adverse effects on the arterial lumen were noted in any patient. By computerized image analysis of cineangiograms initial conventional balloon angioplasty failed to achieve a minimal luminal diameter greater than 1.5 mm in 14 patients (25%), including 3 patients with acute closure. However, after subsequent laser balloon angioplasty, minimal luminal diameter exceeded this value in all patients including this subgroup. Overall, minimal luminal diameter increased from 1.74 +/- 0.46 mm after conventional balloon angioplasty to 2.32 +/- 0.31 mm after laser balloon angioplasty (p less than 0.001) with no change found on 1 day and 1 month follow-up angiograms. Thus, laser balloon angioplasty is a safe, effective procedure for improving luminal dimensions after conventional balloon angioplasty.

Nucleation in small capillary tubes

Abstract In this paper, the classical theory of nucleation is extended to describe heterogeneous nucleation in small capillary tubes, of diameters of less than 100 μm. The effect of confinement within progressively finer capillary tubes is to increase the required superheat or applied tension before nucleation is observed and is particularly pronounced when the liquid has been pre-compressed under high pressure. Thus, by reducing the tube diameter, the nucleation thresholds or concentrations of gases which remain dissolved in carrier liquids transported along capillaries can be raised. The extended theory requires a pair of experimentally-determined coefficients which account for physico-chemical effects on nucleation at the tube surface. It then yields results for capillary tubes of a range of diameters in good agreement with: (i) experimental measurements of the degree of supersaturation of water with oxygen which can be achieved without nucleation during decompression; and (ii) measurements of the temperature at which nucleation of pure water is observed.

A NOVEL SURFACTANT-FREE SMALL OXYGEN MICROBUBBLE ECHO CONTRAST AGENT

Current echo contrast agents, including agitated saline, have limitations. We developed a microbubble contrast agent comprised solely of oxygen and normal saline (NS), based on a novel surfactant-free generation method termed Controlled Nucleation from Gas Supersaturated Solutions (CNSS). To study