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Biomedical subjects

S H Duda

Publications and source records attributed to S H Duda.

At least 109 records · Page 6Linked to original sources
PubMed1992

Holmium:YAG laser angioplasty. Experimental ablation of vascular tissue via flexible ring catheters.

This experimental study was designed to define the potential value of a mid-infrared holmium laser in the free running mode for angioplasty. Immediately after removal, fresh normal and diseased human cadaveric arteries were irradiated under saline with a Ho:YAG laser (wavelength 2.13 microns). The laser was pulsed at 3 Hz, 250 microseconds pulse width and fluences of 10 to 40 J/cm2. The laser beam was coupled to ring catheters with multiple low-OH quartz fibers. The tip of the delivery device was held in direct contact with the vessel surface with the laser beam oriented perpendicularly. Ablation of atherosclerotic plaque was accomplished at an ablation threshold of 10 J/cm2. The ablation rate was 2.1 to 8.3 microns/pulse. Removal of calcified plaque was only partially effective. There were marked thermal effects with vacuolizations extending up to 1505 +/- 178 microns into the adjacent tissue. Laser light at the mid-infrared wavelength of 2.13 microns is supposed to be attractive as it is readily absorbed in water and can easily be transmitted through optical fibers. However, Q-switching seems to be essential to minimize thermal side effects and to make effective ablation of calcium possible.

Angioplasty, Laser↗
PubMed1991

[Peripheral excimer laser angioplasty. The indications, methods and clinical results].

Between March 1989 and January 1990, percutaneous transluminal excimer laser angioplasty was performed in 61 patients (40 men and 21 females; mean age 66 [41-86] years) with 65 peripheral arterial occlusions (iliac: 11, femoropopliteal: 48, tibial: 5, left subclavian artery: 1). The average ankle-arm index before treatment was 0.45 (0.2-0.8) for iliac, 0.52 (0-0.7) for femoropopliteal and 0.3 (0.1-0.4) for tibial occlusion. Recanalization was successful in 58 occlusions, but additional balloon dilatation was necessary in 54. The mean residual stenosis degree after laser application was 54%, after balloon dilatation 22%. Postangioplasty thromboembolism occurred in five patients. Intravascular stents were implanted in 11 patients because of extensive dissection or high-grade restenosis. After four weeks the clinical findings were improved in 54 of the 58 patients, in 47 even after six months. At that point the average ankle-arm index was 0.88 (0.5-1.1) after iliac, 0.79 (0.6-1.15) after femoropopliteal and 0.6 (0.4-0.7) after tibial recanalization.

Adult↗
PubMed1991

Laser angioplasty of peripheral arterial occlusive disease.

To evaluate the impact of laser ablation of arteriosclerotic material on the long-term results of transluminal angioplasty, 103 patients were treated by laser-assisted recanalization of peripheral arterial occlusion and followed-up for 6 and 12 months. Two pulsed laser systems (308 nm-excimer laser and 504 nm-dye laser) were tested. Laser energy was transmitted via wire-guided 4.5-, 7- and 9-French multifiber catheters. Stand-alone laser angioplasty was possible in 22% of the patients, especially in the popliteal and the lower-limb arteries. Compared to the results of balloon dilatation in the literature, the clinical success rate at 6 and 12 months after the treatment was better in occlusions with a length between 6 and 10 cm, however no improvement was seen in either shorter or longer occlusion. Due to the limited size of percutaneously applicable catheters, laser treatment and pretreatment seemed to be of most benefit in distal femoropopliteal arteries and in lower-limb arteries. Clinical improvement after revascularization depends on a sufficient run-off in branching vessels distal to the recanalized artery segment.

Adult↗
PubMed1991

Dye laser-assisted angioplasty with multifiber catheters: short-term results in the treatment of 29 peripheral arterial occlusions.

The use of pulsed dye laser energy for angioplasty offers the possibility of ablating atherosclerotic plaques without thermal damage to the adjacent arterial wall. However, to be of value, systems that deliver the energy safely and effectively are required. We tested multifiber catheters in 504-nm pulsed dye laser angioplasty for treatment of peripheral arterial occlusions. Flexible multifiber catheters consist of 12 (7-French) and 19 (9-French) concentrically arranged 200-microns quartz fibers allowing guidewire-directed use. Laser-assisted angioplasty was performed in 2- to 13-cm- (mean, 7.5-cm) long occlusions of iliac (six) and femoropopliteal (23) arteries in patients with symptomatic occlusive vascular disease. Angiograms were obtained before and after laser ablation, after subsequent balloon dilatation, and if signs or symptoms indicated restenosis, during follow-up. The laser procedure was impossible to perform in three (10%) of 29 patients; this was related to unsuccessful passage of the wire in one patient and to inability to advance the laser catheter across the lesion in two patients. In one other patient, reocclusion occurred 1 day after angioplasty. Stand-alone laser angioplasty relieved residual stenosis of less than 30% in six (26%) of 23 femoropopliteal arteries, making balloon dilatation dispensable. Immediate clinical improvement was achieved in 26 (90%) of 29 patients. Laser treatment caused no perforation and no embolization, but minor dissections occurred in 36% of the patients. Our experience suggests that pulsed dye laser angioplasty via multifiber catheters converts arterial occlusions into stenoses. With the exception of angioplasty in distal femoropopliteal arteries, additional balloon dilatation is necessary to complete recanalization.

Aged↗
PubMed1991

[Pancreas].

Explore the source record for details and available documents.

Acute Disease↗
PubMed1990

[Excimer laser angioplasty. I. The tissue effects of a ring catheter system on peripheral arterial vessels].

We have carried out an experimental study using a new laser catheter on 28 cadaver femoral arteries in 14 subjects and on six aortas. This ring catheter system consists of 12 circular quartz fibres with a central lumen and allows the application of energies up to 20 mJ through a 7F flexible catheter in vivo. The laser emits ultraviolet light of a wave-length of 308 nm, in pulses of 60 ns and a frequency of 2-40 Hz. The energy within a single fibre is 5 J/cm2 and exceeds the intensity required to ablate calcifications. Histologically it has been shown that, depending on the type of tissue, 1 to 2.4 microns of tissue per pulse is removed. Experimentally, rate of progress in a calcified occlusive lesion in the femoral artery, using 20 Hz and energy transmission of 20 mJ, was 3 to 5 mm per minute. Perforation of vessel wall if the catheter tip was at right angles to it depended on the degree of atherosclerosis and was between nine and 116 seconds. Marginally, there was only minimal thermal damage.

Angioplasty, Balloon↗
PubMed1990

[Excimer laser angioplasty. II: Initial clinical experience with peripheral arterial occlusive diseases].

First clinical experiences in the treatment of chronically occluded arteries with 7F-multi-fiber catheter systems transmitting pulsed laser light are presented. 16 patients (7 stadium IIb, 4 stadium III, 5 stadium IVa Fontain) underwent the procedure. 14 of 16 lesions (distance: 0.5-10 cm), most of them with visible calcification, could be recanalized successfully. After the catheter had passed lesions several times, remaining stenoses of 48% (mean value) could be reduced by balloon angioplasty. By moving the catheter with less speed than the experimentally determined speed of laser light ablation and by guiding it over a safety wire, perforation and embolization could be avoided. In one case, occlusion material was pressed into collateral vessels and in two cases groin hematomas had to be observed.

Aged↗
PubMed1990

Laser ring catheters in excimer laser angioplasty.

Percutaneous excimer laser angioplasty is dependent on a reliable and effective energy transmission through fiberoptic devices. Compared with bare fibers, ring catheters provide improved flexibility and a central channel for insertion of guide wires. Peripheral laser catheters (7-9 F) were used in 32 patients with arterial occlusive disease in the lower limbs. The technical success rate was 91%. Vessel wall dissections occurred in nine cases but caused no clinical sequelae in the preliminary follow-up period (1-6 months). The clinical application of the catheter devices proved to be safe.

Aged↗
PubMed1988

[Megacalycosis in childhood].

Congenital megacalycosis is a renal dysplasia characterised by hypoplasia of the medullary pyramids and associated non-obstructive dilatation of the calyces. Calyceal dilatation promotes via disturbed urodynamics the manifestation of chronic interstitial nephritis and calculus formation. Therapy is primarily not necessary, but in the presence of stone development and chronic infections surgical procedures may become indispensable. Pathogenesis, diagnosis, differential diagnosis and therapy of megacalycosis in two children are discussed.

Adolescent↗
PubMed1988

[Determination of hematocrit and iodine concentrations following intravenous bolus administration of ionic and nonionic monomeric and dimeric contrast media--an animal experimental study].

A monomeric ionic (meglumine diatrizoate), a monomeric non-ionic (iopromide) and a dimeric non-ionic contrast medium were intravenously administered (V. jugularis) to 15 rabbits. Blood iodine concentration as well as haematocrit were determined from blood samples taken from the femoral artery immediately after injection until the 90th second p.i. The contrast media showed clear differences concerning the haematocrit, i.e. the isotonic non-ionic dimer induced its lowest decrease. The direct determination of the blood iodine concentration revealed no significant deviations between the contrast media studied. Only non-ionic dimers are iso-osmolar with plasma at the iodine concentrations employed in diagnostic radiology. Compared with monomeric compounds this study provides fundamental evidence that isotonic, non-ionic dimeric contrast media cause only slight effects on blood cells. This confirms experimentally the clinically reported good tolerance of dimeric contrast media in patients.

Animals↗
PubMed1987

Surgical therapy of congenital distal urethral stenoses in girls by meatoplasty.

In girls there are three distinct morphological kinds of congenital distal urethral stenoses in the broad sense. Incomplete meatal stenoses are the most frequent of these. Calibration of the urethra appeared to be the most reliable diagnostic tool in revealing distal urethral obstructions. To relieve the urodynamically interfering urethral stenoses we developed a resecting surgical technique. In a retrospective study the follow-up after meatoplasty of 163 girls with recurrent urinary tract infections was analysed. The long-term success rate totals up to 83.5%.

Adolescent↗
PubMedDate not supplied

Mn-DPDP-enhanced MR imaging of malignant liver lesions: efficacy and safety in 20 patients.

Twenty patients with malignant liver lesions underwent magnetic resonance (MR) imaging with manganese (II) DPDP [N,N'-dipyridoxylethylenediamine-N,N'-diacetate 5,5'-bis(phosphate)] to evaluate the safety and efficacy of the contrast agent. In two groups of 10 patients each, 5 mumol/kg Mn-DPDP was administered intravenously (3 mL/min) at a concentration of either 50 or 10 mumol/mL. T1- and T2-weighted images were obtained with a 1.5-T imager. Six patients reported a total of eight instances of side effects (flush, feeling of warmth, metallic taste) of which seven occurred at the 50 mumol/mL concentration. A significant decrease in alkaline phosphatase levels 2 hours after injection was recorded. On T1-weighted images, the 10 mumol/mL formulation yielded significantly greater increases in contrast-to-noise ratio (79.8%-137.5%) than the 50 mumol/mL formulation (46.2%-86.6%). In a blinded reader study of 10 patients with one to five lesions each, no lesion was missed on Mn-DPDP--enhanced T1-weighted images; however, four false-positive foci were identified. The authors conclude that slow administration of 5 mumol/kg Mn-DPDP at a concentration of 10 mumol/mL is safe and efficient enough to proceed to further clinical trials.

Adult↗