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PubMed1999

Long-term histological and electrophysiological results of an inactive epiretinal electrode array implantation in dogs.

PURPOSE: Short-term pattern electrical stimulation of the retina via multielectrode arrays in humans blind from photoreceptor loss has shown that ambulatory vision and limited character recognition is possible. To develop an implantable retinal prosthesis that would provide useful vision, these results need to be sustained over a prolonged period of retinal electrical stimulation. As a first step toward this goal, the biocompatibility and the feasibility of surgically implanting an electrically inactive electrode array onto the retinal surface was tested. METHODS: A 5 x 5 electrode array (25 platinum disc-shaped electrodes in a silicone matrix) was implanted onto the retinal surface using retinal tacks in each of the 4 mixed-breed sighted dogs. Color fundus photography, fluorescein angiography, electroretinography, and visual evoked potentials were obtained preoperatively, at 1-week intervals for 2 weeks postoperatively, then at 2-week intervals up to 2 months postoperatively, and thereafter at 1-month intervals. One dog was killed at 2 months after implantation and a second dog after 3 months of implantation. Histologic evaluation of the retinas was performed. The remaining two dogs continue to be followed beyond 6 months after the implantation surgery. RESULTS: No retinal detachment, infection, or uncontrolled intraocular bleeding occurred in any of the animals. Retinal tacks and the retinal array remained firmly affixed to the retina throughout the follow-up period. Hyperpigmentation of the retinal pigment epithelium was observed only around the site of retinal tack insertion. No fibrous encapsulation of the implant or intraocular inflammation was visible. A- and b-wave amplitudes of the electroretinogram were depressed at the first postoperative week testing but recovered over the ensuing 1 week and were not statistically different from the normal unoperated fellow eye throughout the postoperative period. N1 and P1 wave amplitudes of the visual evoked potentials were not significantly different from the normal fellow eyes at any of the postoperative test intervals. Fluorescein angiography showed that the entire retina including the area under the electrode array remained well perfused. Similarly, histologic evaluation revealed near total preservation of the retina underlying the electrode array. CONCLUSIONS: Implantation of an electrode array on the epiretinal side (i.e., side closest to the ganglion cell layer) is surgically feasible, with insignificant damage to the underlying retina. The platinum and silicone arrays as well as the metal tacks are biocompatible. With the success of implanting an electrically inactive device onto the retinal surface for prolonged periods, the effects of long-term retinal electrical stimulation are now ready to be tested as the next step toward developing a prototype retinal prosthesis for human use.

Animals↗
PubMedDate not supplied

A comparison of flow convergence with other transthoracic echocardiographic indexes of prosthetic mitral regurgitation.

Prosthetic shadowing of the left atrium may prevent detection of mitral regurgitation during transthoracic echocardiography. In 60 patients with mitral valves, Carpentier-Edwards (n = 20), St. Jude (n = 22), and cage-ball (n = 18), we blindly evaluated the accuracy of three transthoracic Doppler signs of significant (> 2+) mitral regurgitation: (1) color Doppler flow convergence, (2) a color Doppler jet of significant regurgitation in the left atrium, and (3) an intense continuous wave Doppler signal. All 60 patients had transesophageal echocardiography, 26 had cardiac catheterization, and 28 had surgery. The sensitivity and specificity of flow convergence for significant regurgitation by transesophageal echocardiography was 73% and 70%, respectively, compared with 33% and 93% for left atrial color Doppler, and 15% and 97% for continuous wave Doppler. The sensitivity of flow convergence in Carpentier-Edwards, St. Jude, and cage-ball valves was 80%, 73%, and 67%, respectively; whereas the sensitivity of left atrial color Doppler was 70%, 27%, and 0%, and the sensitivity of continuous wave Doppler was 33%, 0%, and 13%. Flow convergence was the only sign of significant regurgitation in 12 of 30 patients (40%); 10 of these patients had mechanical valves. We conclude flow convergence is a more sensitive, though less specific, predictor of significant mitral regurgitation than color Doppler, spatial mapping of the left atrium, and continuous wave Doppler, especially when a mechanical valve is present.

Adult↗
PubMed2001

Anatomical post design meets quartz fiber technology: rationale and case report.

Endodontically treated teeth frequently require a post and core to serve as a foundation for the coronal restoration. Remaining tooth structure, physical properties of the post material, post shape, and cement type all contribute to the success of the restoration. Post adaptation to the canal walls also represents an important element in the biomechanical performance of the prosthetic restoration. A double taper post system made of quartz fiber and epoxy was developed to conform more precisely to the shape of endodontically treated canals. Immediate benefits of this post system include minimal tooth structure removal during canal reshaping, greater post-to-canal adaptation in the apical and coronal half of the canal, and good post retention. The use of a quartz fiber/epoxy material with a lower modulus of elasticity also reduces the incidence of root fracture. Furthermore, the esthetic nature of the colors offered with this post system (translucent and off-white) provide a favorable foundation for eliminating discoloration caused by a metallic post placed under all-ceramic crown systems.

Adult↗
PubMed1990

Echocardiographic evaluation of prosthetic cardiac valves.

Comprehensive echocardiographic examination of patients with prosthetic cardiac valves using M-mode, two-dimensional, conventional, and color Doppler echocardiography represents an invaluable clinical tool in the serial follow-up of these patients. A thorough knowledge of these techniques and their limitations allows accurate assessment and prevention of misdiagnoses.

Echocardiography↗
PubMed2001

Hemodynamic evaluation of a new stentless autologous pericardial mitral valve.

BACKGROUND: There is no satisfactory mitral valve prosthesis. An ideal mitral valve substitute should be biologic, nonantigenic, and anatomically correct. METHODS: We developed a stentless, chordal-supported (including anterior basal stay chords) mitral valve made with glutaraldehyde-treated autologous pericardium. Eight such prostheses were implanted in sheep. RESULTS: Seven animals survived the operation and were studied postoperatively immediately, at 1 week, and at 1 month. Simultaneous left ventricular and left atrial pressures showed peak and mean transvalvular pressure gradients of 6+/-2 mm Hg and 1+/-1 mm Hg, respectively. Echocardiography performed intraoperatively and then 1 week and 1 month postoperatively showed normal valve leaflet movements. Color and pulsed Doppler echocardiography showed no sign of transvalvular stenosis or regurgitation. Effective orifice area was 5.39+/-0.35 cm2 at intraoperative, 5.51+/-0.29 cm2 1 week after operation (n = 5), and 5.51+/-.28 cm2 1 month after operation (n = 3). Three animals were sacrificed at 19 days and at 1 and 3 months. One animal is alive at 10 months. CONCLUSIONS: This new stentless pericardial mitral valve performed satisfactorily with low gradients and no regurgitation. Possible advantages of this pericardial valve are excellent hemodynamics, ease of construction and implantation, lack of immunogenicity, and low cost. Similarly designed valves but with a shorter nonglutaraldehyde treatment time have been used in 3 sheep monitored for more than 3 months.

Animals↗
PubMed2003

Morphological analysis of aortic root in eccentric aortic regurgitation using anyplane two-dimensional images produced by transesophageal three-dimensional echocardiography.

BACKGROUND AND AIM OF THE STUDY: Evaluation of leaflet dysfunction in aortic valve repair is important. In eccentric aortic regurgitation (AR), it is unclear whether leaflet dysfunction other than prolapse exists. The study aim was to validate the hypothesis that eccentric AR correlates with leaflet dysfunction. METHODS: Both anyplane 2-D images produced by a 3-D reconstruction system and surgical views for 21 patients with eccentric AR (11 with aortic valve prolapse, group A; 10 without prolapse, group B) were analyzed prospectively. Vertical height from annulus to coaptation point (termed AC), and distance from coaptation point to sinotubular junction (CS) were measured at early diastole. RESULTS: For group A, AC and CS values were 1.3 +/- 2.2 mm and 25.9 +/- 3.4 mm respectively for leaflets of eccentric AR jet origin, and 3.8 +/- 0.4 mm and 22.7 +/- 2.1 mm for other leaflets. For group B, AC and CS values were 4.7 +/- 0.9 mm and 39.8 +/- 7.0 mm for leaflets of eccentric AR jet origin, and 7.8 +/- 0.9 mm and 31.9 +/- 5.7 mm for other leaflets. The AC for leaflets of eccentric AR jet origin was smaller than AC for other leaflets (p < 0.01) between both groups. There was no difference between CS for leaflets of eccentric AR jet origin and other leaflets in group A, but CS for leaflets of eccentric AR jet origin was larger than for other leaflets in group B (p <0.01). AC and CS values for leaflets of eccentric AR jet origin in group B were larger than those for group A. Leaflets of eccentric AR jet origin were always shifted toward the direction of the base in the anyplane images, and elongated in the surgical view. CONCLUSION: Anyplane 2-D images obtained by 3-D echocardiography showed that aortic leaflets of eccentric AR jet origin shifted towards the direction of the base with or without prolapse, and were accompanied by dysfunction. Color flow Doppler determination of the eccentricity of AR jet origin was useful in predicting aortic valve dysfunction.

Aortic Valve↗
PubMed2006

Flow reduction in high-flow arteriovenous access using intraoperative flow monitoring.

PURPOSE: This study used intraoperative monitoring of the access flow to evaluate the results of flow reduction in the management of high-flow arteriovenous access-related symptoms of distal ischemia and cardiac insufficiency. METHODS: A retrospective study was conducted of 95 patients (78 with ischemia, 17 with cardiac failure) who underwent flow reduction between 1999 and 2005. A preoperatively measured access flow-volume rate > 800 mL/min for autogenous accesses (n = 77) and > 1200 mL/min for prosthetic accesses (n = 18) was the selection criterion for the use of a flow reduction procedure. Flow reduction was achieved using a spindle-like narrowing suture near the anastomosis and final placement of a polytetrafluoroethylene strip while a flow meter was used for intraoperatively measuring the access flow. The desired postoperative flow was 400 mL/min for autogenous and 600 mL/min for prosthetic accesses. RESULTS: The mean preoperative access flow was 1469 +/- 633 mL/min in patients with ischemia and 2084 +/- 463 mL/min in patients with cardiac failure, without significant differences between access types. The flow was reduced to 499 +/- 175 mL/min for autogenous accesses and to 676 +/- 47 mL/min for prosthetic accesses. The mean follow-up was 25 months (range, 1 to 73 months). Complete long-term relief of symptoms was observed in 86% of patients with ischemia and in 96% of patients with cardiac failure. Reconstruction significantly increased the digital-brachial index (0.41 +/- 0.12 vs 0.74 +/- 0.11; P < .05) and mean distal arterial pressure (47 +/- 17 mm Hg vs 79 +/- 21 mm Hg; P < .05) in patients with ischemia. Primary patency rates were significantly better for reconstructed autogenous accesses compared with rates of prosthetic accesses (91% +/- 4% vs 58% +/- 12% at 12 months; 81% +/- 6% vs 41% +/- 14% at 36 months; P < .001). The low patency of reconstructed prosthetic accesses is due to the high thrombosis risk of accesses that have a flow < 700 mL/min. CONCLUSIONS: Flow reduction using intraoperative access flow monitoring is an effective and durable technique allowing for the correction of distal ischemia and cardiac insufficiency in patients with a high-flow autogenous access. The desired postoperative access flow of 400 mL/min is not associated with an increased risk of thrombosis. Flow reduction of prosthetic access is as effective; however, a higher access flow than the desired 600 mL/min seems to be necessary to achieve an acceptable patency in prosthetic accesses.

Arteries↗
PubMed1998

A comparative evaluation of femorofemoral crossover bypass and iliofemoral bypass for unilateral iliac artery occlusive disease.

The purpose of this study was to compare the results of extra-anatomic femorofemoral crossover bypass grafting to the anatomic iliofemoral bypass grafting procedure in the treatment of patients with unilateral iliac artery occlusive disease with respect to patency and limb salvage. The records of all patients with unilateral iliac artery disease who underwent revascularization between January 1988 and December 1995 at the University of Iowa Hospitals and Clinics (UIHC) were retrospectively reviewed; 108 patients were identified and divided into two groups. Group I (n=68; male/female=44/24) was composed of all patients who underwent a femorofemoral crossover extra-anatomic bypass. All patients who underwent an iliofemoral anatomic bypass constituted group II (n=40; male/female=24/16). The mean age for group I was 60 years (range 28-87) and for group II, 54 years (range 14-86). The medical risk factors between both groups were comparable. Except for the higher incidence of gangrene in group II the indications for surgery were comparable between both groups. A polytetrafluoroethylene graft was used in 88% of group I patients and in 90% of group II patients (NS). In the remaining patients, an autogenous vein conduit was used. Two patients from group I (2.9%) died in the perioperative period (NS). Graft patency was assessed by clinical evaluation, Doppler-derived ankle/brachial indices, and color duplex imaging. The cumulative primary and secondary patency rates, limb salvage, and patient survival were calculated by use of life table analysis (SE<0.1). The need for simultaneous outflow and inflow procedures at the time of surgery was comparable between both groups. The proportion of patients who underwent further revascularization during follow-up was also comparable. The 5-year primary and secondary graft patency rates were 81.7% and 90.3%, in group I and 61.3% and 80.5% in group II. Although the difference between both groups was not significant there was a tendency toward higher rates with femorofemoral bypass. The 5-year survival rates of 80.3% for group I and 73.3% for group II were comparable. These data suggest that there is no significant difference in the long-term results between the femorofemoral crossover bypass grafts and iliofemoral grafts. Both procedures result in acceptable patency and limb salvage rates. The femorofemoral bypass is, however, more attractive, for it can be performed under local anesthesia if needed and does not involve the creation of the retroperitoneal incision necessary with the iliofemoral bypass.

Adolescent↗
PubMed1989

[Transthoracic color Doppler echocardiography in the diagnosis of insufficiency of heart valve prostheses. A comparison with conventional Doppler sonography].

Color-coded and conventional pulsed wave/continuous wave Doppler detection of valvular or paravalvular regurgitation in 59 patients with 67 cardiac valve prostheses were compared; 21 patients had known regurgitation determined by auscultation. Analysis of the color-coded Doppler findings was made from videotape and blinded as to patient identity and clinical findings. Conventional Doppler Sonography detected 36 instances of aortic and 3 of mitral prosthetic regurgitation. Color-coded Doppler investigation detected 27 instances of aortic and 1 of mitral prosthetic regurgitation resulting in a sensitivity of 72% and specificity of 100% as compared to conventional Doppler sonography. All 21 patients with a regurgitant murmur had pathological conventional Doppler findings, but 3 of them did not show regurgitant flow in the color-coded Doppler examination. The apical four chamber view contributed most to the colour-coded Doppler detection of regurgitant flow, followed by the parasternal long axis view.

Adult↗
PubMed2002

Retrofitting crowns to an existing removable partial denture clasp: a simple technique.

The fabrication of a new crown to replace an existing abutment tooth for a removable partial denture is one of the most labor-intensive chairside and laboratory procedures. The process can become more complicated when the patient requests a tooth-colored esthetic restoration. Numerous techniques are described in the literature, some for all-metallic restorations and others for metal-ceramic restorations. This article describes a simplified technique that makes use of a polymer ceramic material.

Crowns↗
PubMed1990

Doppler echocardiography. Role in emergency diagnosis of cardiac valve disease.

Doppler echocardiography provides crucial information in the evaluation of a patient with suspected significant heart valve dysfunction. Doppler studies can provide quantitative data on the gradients across the stenotic valves and in many cases derive the actual valve area (with use of the pressure half-time method for stenotic atrioventricular valves or the continuity equation for semilunar valves). When combined with two-dimensional echocardiographic studies, Doppler studies may discern the cause of valve dysfunction. In valvular regurgitation, semi-quantitative estimation of the severity of the problem can be obtained by pulsed Doppler flow mapping or color Doppler echocardiography. These methods show great value for rapid evaluation of valve dysfunction in the emergency setting.

Adult↗
PubMed1988

Pulsed, continuous, and color flow Doppler echocardiographic assessment of normal and abnormal Ionescu-Shiley pericardial valves.

We studied the value of pulsed, continuous, and color flow Doppler echocardiography for identifying normal and abnormal function in 51 Ionescu-Shiley bovine pericardial valves. In 15 patients with clinically normal functioning mitral valves, the peak and mean pressure gradients as calculated by the modified Bernoulli equation were 8.5 +/- 4.9 mmHg (mean +/- SD) and 2.6 +/- 2.9 mmHg, respectively. The mitral valve area as calculated by the pressure half-time method was 2.2 +/- 0.6 cm2. In 18 patients with normally functioning aortic valves, the peak and mean pressure gradients were 22.9 +/- 9.0 mmHg and 11.1 +/- 5.0 mmHg, respectively. In five patients with suspected mitral prosthetic dysfunction, two-dimensional and Doppler echocardiography showed: two had mitral stenosis with a mean gradient of 14.2 mmHg and mean mitral valve area of 1.0 cm2, two had severe mitral regurgitation, and one was thickened but nonstenotic. In 13 patients with suspected aortic prosthetic dysfunction, two-dimensional and Doppler echocardiography showed: two patients had markedly thickened leaflets and mean aortic gradient of 41.5 mmHg, two patients had mild aortic regurgitation, four patients had severe aortic regurgitation, and five patients had systolic murmurs secondary to pathology unrelated to the prosthetic aortic valve. Of the three patients with severe aortic regurgitation who had color Doppler, the site and direction of the regurgitant jet was correctly identified in all compared to intraoperative assessment. Pulsed, continuous, and color flow Doppler are useful as noninvasive techniques in assessing Ionescu-Shiley valve hemodynamics and function.

Academic Medical Centers↗
PubMed1989

Color flow duplex screening of infrainguinal grafts combining low- and high-velocity criteria.

The aim of this prospective study was to evaluate the ability of duplex ultrasonography to identify infrainguinal grafts at high risk for failure. The criteria used identified low flow by low peak systolic velocity (less than 45 cm/s) and stenosis by high velocity (greater than 300 cm/s) or by velocity at the stenosis three times the velocity in the adjacent normal graft. A total of 114 patent grafts were scanned and compared with concurrent angiograms. Duplex scanning correctly identified 18 high-risk grafts by low-flow criteria and an additional 21 by stenosis criteria. There was one false-negative finding (sensitivity 98 percent). The velocity ratio of the stenosis to the adjacent graft was useful in estimating the degree of stenosis. Color flow duplex imaging reduced examination time through visual feedback by highlighting the graft and areas of high velocity. These results indicate that color flow duplex scanning, combining low- and high-peak systolic criteria, is a very sensitive screening test in the early detection of failing grafts.

Blood Vessel Prosthesis↗
PubMed1989

Microwave techniques for fabrication of provisional facial prostheses.

Timely rehabilitation of facial defects necessitates provisional prostheses during the period following surgery. The possibilities of using microwave radiation in the drying of gypsum casts, the preparation of stone molds, the curing of silicone elastomers, and the extrinsic coloring of silicone prostheses are presented. Microwave radiation has the potential for saving time, energy, and resources during the fabrication of provisional facial prostheses.

Biocompatible Materials↗
PubMed1997

Carotid endarterectomy for recurrent stenosis.

PURPOSE: The purpose of this study was to report our results in the surgical management of recurrent carotid stenosis (RCS) after carotid endarterectomy (CEA). METHODS: In a 20-year period, we performed 1209 CEAs; 82 operations (6.8%) were for RCS. There were 33 men and 36 women, with an average age of 66.3 years. Nine patients underwent two redo CEAs and two patients underwent three redo CEAs for either bilateral recurrence or a second recurrence on the same side. Overall, 10 patients were identified with a second recurrence. RESULTS: The average time to presentation with RCS was 65 months (range, 3 to 361 months). The majority of patients (66%) were symptomatic, 34% had transient ischemic attacks, 17% had amaurosis fugax, 9% had strokes, and 6% had nonhemispheric symptoms. Before repair, angiograms were obtained. Patch repair was performed in 61 procedures (74%), 41 with vein, 11 with Dacron, and nine with polytetrafluoroethylene. Autogenous or synthetic bypass grafts were used in 20 procedures (24%), vein in eight, Dacron in two, and polytetrafluoroethylene in 10. In one patient, an occluded internal carotid artery was ligated and an endarterectomy of the external carotid artery was performed without a patch. The operative stroke rate was 4.8%. Minor complications included transient or permanent cranial nerve deficits in 7.3% and wound hematomas in 2.4%. CONCLUSION: Although repeat endarterectomy to treat RCS is technically more demanding, it can be performed safely. Long-term follow-up examination shows that a second recurrence may develop, and we recommend serial noninvasive testing.

Aged↗
PubMedDate not supplied

[The subclavian-carotid bypass as a method for treating obstruction of the common carotid].

Common carotid artery occlusion is a relatively uncommon lesion (0.5-5% of patients with cerebral ischaemia). Cerebral revascularization is possible only in case of patent carotid bifurcation, three patients, all of them symptomatic (2 TIA's and 1 amaurosis fugax) with a complete common carotid artery occlusion have been treated with a subclavian-carotid artery by-pass (2 PTFE, 1 reversed saphenous vein). Among the patients one death occurred in the fourth postoperative day by bronchopneumonia, no stroke was detected, in the remaining two, the by-pass was patent one year and respectively three years post-operatively. In case of common carotid artery occlusion, visualization of bifurcation is usually better obtained through a color-duplex than arteriography. Several operations have been proposed in these patients (retrograde thrombectomy, carotid to carotid by-pass, carotid-subclavian reimplantation), but subclavian to carotid by-pass is the most safe and common used procedure.

Aged↗
PubMed1989

[Exertional dyspnea, chest pain, dizziness].

A 66 year old patient with chest pain and exertional dyspnea is described. Auscultation and physical examination showed signs of aortic stenosis combined with aortic insufficiency. Electrocardiography revealed left ventricular hypertrophy with associated ST-segment and T-wave abnormalities. Color blood flow imaging confirmed severe combined aortic stenosis and regurgitation, the hemodynamic evaluation demonstrated the indication for aortic valve replacement.

Aged↗