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Biomedical subjects

T David

Publications and source records attributed to T David.

At least 37 records · Page 2Linked to original sources
PubMed2000

Computational models of blood flow in the circle of Willis.

A two-dimensional, steady state model of the circle of Willis has been developed. To simulate the peripheral resistance of the cerebrovascular tree, blocks of porous media were used. Their effective resistance was kept constant, disregarding the effects of arterial auto-regulation. The model was then used to simulate different common abnormalities of the circle of Willis while a range of varying boundary conditions was imposed to the right internal carotid artery (ICA). The total flux was tabulated and compared favourably with both clinical measurements and other models of the circle of Willis. Relevant fluid dynamics effects were also observed and analysed. The present model demonstrates that the use of CFD can produce physiological results if the appropriate boundary conditions are used. We can provide clinicians with a priority list of the severity of the flux reduction for the considered abnormalities for different degrees of stenosis of the right ICA. From this study it is apparent that the redistribution of blood via the circle of Willis is mainly driven by changes in the vascular resistance of the brain rather than in the local arterial geometry. The use of valid peripheral resistances allows for a more realistic model of the circle of Willis but also highlights the need for more accurate means to estimate the vascular resistance of a patient.

Animals↗
PubMed2000

[Cysticercosis in Guadeloupe].

We report two cases of cysticercosis proved by histology, one in the brain, the other in the orbit. The first case was observed in a traveller, heavy smoker, serologically negative to cysticercosis in whom an isolated cerebral tumoral metastasis was suspected and resected. The lesion was centered by a typical cysticercus of Taenia solium. The second was a periorbital intramuscular nodule observed in a child who had never left our island. The fibroinflammatory nodule was centered by a cysticercus with a scolex without rostellum and without suckers. Its histological aspect led us to the diagnosis of cysticercosis. Three species of Taenia are discussed : T. solium, T. crassiceps and T. bovis. This case shows that the human transmission of the disease may exist in Guadeloupe.

Animals↗
PubMed1999

[Phototherapeutic keratectomy in the treatment of Groenouw's type I corneal dystrophy].

PURPOSE: This study was designed to investigate the therapeutic potential of phototherapeutic keratectomy (PTK) for the treatment of corneal granular dystrophy. PATIENTS AND METHODS: PTK was performed with the Excimed UV 200, (Summit Technology, Inc) on a series of 27 eyes of 22 patients with corneal granular dystrophy. Mean patients' age was 34.6 years. The mean follow-up period was 31 months (ranged from 6 to 52 months). The changes in best corrected visual acuity and spherical equivalent were evaluated at 6, 12, 18 and 24 months. RESULTS: All of patients achieved visual improvement. Mean preoperative best corrected visual acuity (BCVA) was 20/100 and mean postoperative BCVA was 20/30 at one year. The mean hyperopic shift caused by tissue ablation was +/- 2.8 D after one year. CONCLUSION: Corneal grafting was the standard treatment for visually disabling granular dystrophy, but PTK has significant advantages over this procedure and must now be the standard method of managing corneal granular dystrophy when intervention is required.

Adult↗
PubMed1999

[Fuchs' uveitic syndrome in a patient with ocular toxoplasmosis].

We report a case of Fuchs' uveitic syndrome associated with toxoplasmic chorioretinis scars, and a positive Desmonts' coefficient. This allows us to emphasize ocular toxoplasmosis as a main association to be searched for clinically. In the cases in which this association is found, it would be warranted, if a high level of specific antitoxoplasmic antibodies is demonstrated in aqueous humor, to consider toxoplasmosis as one of the potential etiopathogenic factors of the Fuchs' uveitic syndrome.

Adult↗
PubMed1999

Will stentless valves be durable? The Toronto valve (TSPV) at 5 to 6 years.

The early hemodynamic benefits of stentless aortic valves have been well documented. The issue of long-term functional integrity remains unanswered. We report the clinical results of a multicenter registry with prospective data on 621 patients monitored for 7.1 years. Patient data were collected and analyzed at St Jude Medical Inc, St Paul, Minnesota. In all, 66% of patients were male; the average age was 65.9 years +/-11.0 years, with 39% older than 70 years. Native aortic valves were bicuspid in 40.6%, 91.5% were calcified and 65.7% stenotic. Most valves implanted (83.1%) were sizes 25, 27, or 29 mm. Concomitant coronary bypass was performed in 42% of patients. Total follow-up time for the 621 patients was 1,944.5 valve years (mean 3.1 years per patient). At 5 years, 86.1% (n = 137) and at 6 years 80.4% (n = 51) were in New York Heart Association class I, and 78% had no or trivial atrial insufficiency. The average mean systolic gradient for all valves at 6 years was 4.0 mm Hg, and the peak gradient was 8.6 mm Hg. The effective orifice area varied from 1.4 cm2 (23-mm valve) to 2.7 cm2 (29-mm valve). The decrease in left ventricular mass index was significant and sustained. Actuarial survival at 6 years was 84.2%, and freedom from cardiac-related deaths was 90.1%. Freedom from valve-related deaths was 95.7%, and freedom from prosthetic endocarditis was 98.6%. There were no instances of primary tissue valve failure during follow-up, with 97.2% freedom from reoperation. The early hemodynamic benefits of the TSPV are well maintained during more than 6 years of follow-up, without evident valvular dysfunction. Longer follow-up time is required to validate durability, but there is increasing evidence for well-maintained structural and functional integrity.

Actuarial Analysis↗
PubMed1998

Hemodynamics and left ventricular mass regression following implantation of the Toronto SPV stentless porcine valve.

Stentless tissue valves may provide more favorable hemodynamics than conventional stented valves. Hemodynamic findings from a large multicenter trial have not been previously reported. The present report describes the hemodynamic findings from a multinational, multicenter study after implantation of the Toronto SPV valve. A total of 577 patients underwent aortic valve replacement with the Toronto SPV valve at 12 sites in 3 countries. Echocardiograms were recorded in the early postoperative period, 3 to 6 months after surgery, 1 year after surgery, and yearly thereafter, with follow-up to 3 years. Gradients decreased and effective orifice area increased in the months after surgery. One year after surgery, mean gradient for valve sizes 20 to 22, 23, 25, 27, and 29 mm was 7.3 +/- 4.4, 7.4 +/- 4.5, 6.1 +/- 3.3, 4.9 +/- 2.4, and 4.0 +/- 2.1 mm Hg, respectively; effective orifice area was 1.3 +/- 0.7, 1.5 +/- 0.5, 1.7 +/- 0.4, 2.0 +/- 0.4, and 2.4 +/- 0.6 cm2, respectively. There was a very low prevalence of significant aortic regurgitation at all time periods. There was significant left ventricular (LV) mass regression between the early and 3- to 6-month periods and between the 3- to 6-month and 1-year postoperative periods. The Toronto SPV valve has an excellent hemodynamic profile supported by significant regression of LV hypertrophy in the year after implantation. Data through 3 years demonstrates maintenance of low gradients and freedom from significant aortic regurgitation.

Aged↗
PubMed1998

A model for the fluid motion of vitreous humour of the human eye during saccadic movement.

During saccadic motion the eyewall moves in a manner similar to a sinusoid or at least can be represented by a sine Fourier series. Motion of the vitreous is induced by the saccade and the vitreo-retinal interface is subjected to a time-dependent shear. This force may be a significant factor for retinal tearing in the neighbourhood of small retinal holes or tears. An analytical viscoelastic model and a numerical, Newtonian model of the motion of the vitreous are presented and compared. Under sinusoidal boundary motion the analytical model shows that a viscous wave propagates inward toward the axis of rotation and the characteristic length of this wave is a function of the Womersley number. The numerical solution indicates that the vitreous moves similarly to the analytical result with small secondary motion; however, this motion allows complete recirculation of the vitreous over large timescales. Excellent agreement is found between the analytical and numerical models. The time-dependent fluid shear is evaluated and from the analytical solution the maximum value of this is found to be proportional to R0 square root of v(omega)3, where R0 is the eye radius, v the modified complex viscosity and omega the sinusoidal frequency. This indicates that myopes have a larger shear force exerted on them by virtue of the larger eye size. Further work is directed toward a model which links the stress found in the sclera to that exerted on the vitreo-retinal interface by the vitreous fluid motion.

Biophysical Phenomena↗
PubMed1998

A prospective randomized trial of topical soluble 0.1% indomethacin versus 0.1% diclofenac versus placebo for the control of pain following excimer laser photorefractive keratectomy.

BACKGROUND AND OBJECTIVE: To compare the safety and efficacy of topical nonsteroidal antiinflammatory drugs (NSAIDs) for the control of pain after excimer laser photorefractive keratectomy (PRK). PATIENTS AND METHODS: One hundred twenty informed patients were enrolled in a double-masked, randomized, comparative study and assigned to either 0.1% indomethacin, 0.1% diclofenac, or placebo treatment. Subjective postoperative pain, symptoms, re-epithelialization rate, and systemic medications were monitored for 2 days following photoablation. RESULTS: Compared with the placebo, 0.1% indomethacin solution significantly reduced pain on the day of surgery (D0) (P < .05), whereas 0.1% diclofenac did not reach a significant level (P = .46). At D0, analgesic intake by the oral route was significantly greater in the placebo group (P < .05). Severe photophobia was significantly less frequent in the group treated with 0.1% indomethacin (P < .05). Corneal wound healing was significantly delayed in the patients treated with 0.1% diclofenac at D2 as compared with other groups (P = .04). CONCLUSION: Topical 0.1% indomethacin solution helps control the pain induced by excimer laser photoablation of the cornea without any detrimental effect to the corneal epithelial wound healing.

Administration, Topical↗
PubMed1998

[Acute open-angle glaucoma in a woman with AS hemoglobinopathy].

A 64-year-old black woman presented unilateral acute ocular hypertension. Gonioscopy showed a blood clot obstructing Schlemm's canal. Intraocular pressure returned to normal values after resorption of the blood clot. Hemoglobin electrophoresis found a sickle-cell trait, raising the hypothesis that the obstruction of outflow was probably due to the mechanism of sickling.

Acute Disease↗
PubMed1998

[Reis-Buckler dystrophy: therapeutic photo-ablation with the excimer laser].

PURPOSE: Reis-Buckler's corneal dystrophy consist of superficial reticulated opacities with recurring attacks of corneal erosion. Lamellar and penetrating keratoplasties were the traditional surgical means of improving recurrent erosions and vision but the dystrophy recurs following surgery. Phototherapeutic keratectomy (PTK) is now the standard method of managing this anterior corneal disease when intervention is required. MATERIAL AND METHODS: We have treated ten eyes with Reis-Buckler's dystrophy using Excimer laser PTK. RESULTS: All of patients achieved visual improvement (preoperative corrected visual acuity: average 0.3 +/- 0.2 SD, postoperative at one month 0.6 +/- 0.3 SD and 0.7 +/- 0.2 SD at one year. The refractive shift changed from a spherical equivalent of -0.92 D to a postoperative refraction of +1.80 D at one month and +1.65 D at one year.

Adult↗