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PubMedDate not supplied

Transluminal aortic valve placement. A feasibility study with a newly designed collapsible aortic valve.

Percutaneous stents are used in vascular applications in conjunction with angioplasty and in combination with graft material for repair of abdominal aneurysms. The authors have designed a collapsible bioprosthetic aortic valve for placement by a transluminal catheter technique. This trileaflet stent valve is composed of stainless steel and bovine pericardium. Stent valves, 23 and 29 mm, were tested in a pulse duplicator system with rigid rings from 21 to 31 mm in 2 mm increments. At a mean flow of 3.1 L/min (+/-0.7), normal systemic aortic pressure was generated with a transvalvular gradient of 14.9 +/- 7 mmHg (mean +/- SD). Regurgitation fraction ranged from 10 to 18% (mean 13.8 +/- 3%) in the best ring size. Valves with the best hemodynamic profile were used for implantation in three 70 kg pigs in an open chest model. The valve was collapsed in a 24 Fr catheter designed to allow slow, controlled release. After resection of the native leaflets, the new valve was placed in the subcoronary position. No additional sutures were used for securing the valve. Two animals were successfully weaned from cardiopulmonary bypass and maintained systemic pressures of 100/45 (+/-10) and 116/70 (+/-15) mmHg, respectively. Intraoperative color echocardiography revealed minimal regurgitation, central flow, full apposition of all leaflets, and no interference with coronary blood flow. Both animals were sacrificed after being off bypass for 2 hr. Postmortem examination revealed the valves to be securely anchored. The third animal was weaned from cardiopulmonary bypass but developed refractory ventricular fibrillation because of valve dislodgment due to structural failure. Although long term survival data are needed, development of a hemodynamically acceptable prosthetic aortic valve for transluminal placement is feasible.

Animals↗
PubMedDate not supplied

Long-term echocardiographic follow-up of patients with a tricuspid bioprosthesis.

To clarify the long-term results of bioprosthetic valve function in the tricuspid position, 29 consecutive patients who underwent tricuspid valve replacement (TVR) were evaluated. There were 20 girls/women and 9 boys/men, with ages ranging from 6 to 61 years (mean 41.4 years). The bioprosthetic valves included Hancock in 2, and Carpentier-Edwards in 27. The follow-up period ranged from 32 to 145 months (mean 89 months). Regurgitant flow of the tricuspid bioprosthesis was studied by color Doppler echocardiography. Peak velocity (Vp) and pressure half time (PHT) were measured by continuous wave Doppler echocardiography. Operative mortality was 13.7% (4/29), with the actuarial survival rate, including operative deaths, 75% at 10 years. Valve thrombosis developed in one patient 4 years after TVR. Color Doppler showed regurgitation in 7 of the 20 patients who were completely followed up, but they were all asymptomatic and required no special intervention. Cusp tear or calcification requiring reoperation was not observed in this study, including 8 patients younger than 35 years of age. The Vp was significantly slower, and PHT was significantly prolonged, in the tricuspid rather than the mitral position. These data demonstrate that bioprosthetic valves in the tricuspid position can be used safely. Doppler examination should be performed taking these different flow dynamics into account.

Adolescent↗
PubMedDate not supplied

Color Doppler echocardiographic assessment of Sorin mitral prosthetic valve.

Doppler echocardiographic characteristics of 57 normally functioning Sorin prosthetic valves (a tilting valve) in the mitral position were studied in the early postoperative period. The three valve sizes (in mm) studied were: 25 (n = 15), 27 (n = 32) and 29 (n = 10). The mean gradients (mmHg) and the valve area (Sq cm) calculated by pressure half time method) for the three valve sizes were 3.46 +/- 1.69 and 2.49 +/- 0.26; 3.46 +/- 1.25 and 2.57 +/- 0.44; and 3.2 +/- 1.23 and 2.55 +/- 0.41; respectively. There was no significant difference in gradients and valve area between the three sizes, variations in pressure half time and therefore the calculated valve area was large. Color Doppler evaluation revealed a bifid nonturbulent jet directed anteriorly towards the interventricular septum. 12 patients (20%) had mild valvar and 7 (12%) had paravalvar mitral regurgitation (mild in 5 and moderate in 2) without any associated prosthetic valve dysfunction. The paravalvar regurgitation persisted in all the 5 patients restudied at 5-12 months postoperatively. Sorin prosthetic valves have similar gradients and valve area when compared to other disc valves. The incidence of of paravalvar regurgitation was slightly higher in our series. The limitations of Doppler derived gradients and area of prosthetic valve are discussed.

Adolescent↗
PubMed2004

Prosthodontic management of ridge deficiencies.

The treatment goals in prosthodontics and dental laboratory technology are to provide patients with long-term predictable and esthetic outcomes. The periodontal tissues define the framework that will maintain ridge height, thickness, color, texture, and gingival-tooth frame. The loss of teeth, residual ridge resorption and the loss of gingival tissues continue to affect long-term and esthetic treatment outcomes. Prosthodontic treatment requires consideration of the potential negative tissue effect that time and normal biologic change might have on the completed prosthetic design. This article describes alternative restorative solutions for clinical conditions that have traditionally been managed by surgery, removable prosthodontics, or esthetically compromised fixed restorations. Different clinical conditions for tooth-retained and implant-retained fixed partial dentures as well as the laboratory technology describing construction of these different restorations will be discussed.

Alveolar Bone Loss↗
PubMed2001

Usefulness of transesophageal echocardiographic monitoring to improve the outcome of stent-graft treatment of thoracic aortic aneurysms.

The stent-graft procedure is becoming an alternative to surgery for treatment of many diseases of the descending thoracic aorta. This study evaluated the role of transesophageal echocardiography (TEE), used in combination with fluoroscopy and angiography, in monitoring the outcome of stent-graft placement. Twenty-two consecutive patients were submitted to stent-graft positioning in the descending aorta for various pathologies (7 patients had type B aortic dissections, 6 had thoracic aneurysms, 2 had thoraco-abdominal aneurysms, and 7 had post-traumatic aortic aneurysms). Before stent-graft deployment, TEE changed the proximal site of stent positioning initially identified by angiography in 33% of patients (5 of 15) with aortic aneurysms because of calcifications or atheromas that could interfere with stent adhesion to the aortic wall and that were not seen on angiography. In 28% of patients (2 of 7) with aortic dissection, TEE showed the guidewire in the false lumen, allowing an immediate repositioning. After stent-graft deployment, color Doppler TEE showed a perigraft leak in 7 patients, whereas angiography detected a perigraft leak in only 2 patients (p = 0.02). In 4 of these patients, further balloon expansions resulted in resolution of the leak. In the remaining 3 patients, additional stent-graft positioning was necessary. Considering the total patient cohort, TEE yielded relevant information, resulting in procedure changes in 59% (13 of 22). In conclusion, TEE provided additional information with respect to angiography in all phases of stent-graft treatment, improving immediate outcome and reducing complications.

Adult↗
PubMed1992

Single-plane transesophageal echocardiography for assessing function of mechanical or bioprosthetic valves in the aortic valve position.

To assess the value and limitations of single-plane transesophageal echocardiography in the evaluation of prosthetic aortic valve function, 89 patients (69 mechanical and 20 bioprosthetic aortic valves) were studied by combined transthoracic and transesophageal 2-dimensional and color flow Doppler echocardiography. In the assessment of aortic regurgitation, the transthoracic and transesophageal echocardiographic findings were concordant in 71 of 89 patients (80%). In 8 patients, the degree of aortic regurgitation was underestimated by the transthoracic approach; in each case the quality of the transthoracic echocardiogram was poor. In 10 patients, transesophageal echocardiography failed to detect trivial aortic regurgitation due to acoustic shadowing of the left ventricular outflow tract from a mechanical valve in the mitral valve position. Transesophageal echocardiography was superior to transthoracic echocardiography in diagnosing perivalvular abscess, subaortic perforation, valvular dehiscence, torn or thickened bioprosthetic aortic valve cusps, and in clearly distinguishing perivalvular from valvular aortic regurgitation. Transesophageal echocardiography correctly diagnosed bioprosthetic valve obstruction in 1 patient, but failed to diagnose mechanical valve obstruction in another. In conclusion, transesophageal echocardiography offers no advantage over the transthoracic approach in the detection and quantification of prosthetic aortic regurgitation unless the transthoracic image quality is poor. Transesophageal echocardiography is limited in detecting mechanical valve obstruction and in detecting aortic regurgitation in the presence of a mechanical prosthesis in the mitral valve position. However, it is superior to transthoracic echocardiography in identifying perivalvular pathology, differentiating perivalvular from valvular regurgitation and in defining the anatomic abnormality responsible for the prosthetic valve dysfunction. Combined transthoracic and transesophageal examination provides complete anatomic and hemodynamic assessment of prosthetic aortic valve function.

Adolescent↗
PubMed1988

Clinical and experimental evaluation of aortic polytetrafluoroethylene grafts for aneurysm replacement.

The aortic expanded polytetrafluoroethylene bifurcation graft has a unique taper design. This was studied in an in vitro model using hydrogen bubbles and colored dyes to assess its hemodynamic significance compared with a conventional nontapered graft model. Under conditions of nonpulsatile flow the only significant differences were seen with a high percentage of occlusions of one outflow limb. Clinical experience with this new graft for infrarenal aneurysm replacement was accumulated in 163 elective cases and 53 emergency cases. The results with this new graft were compared with those obtained in the same time frame with alternative Dacron grafts. No detrimental problems with the graft have appeared in its use up to 78 months following aneurysm bypass or replacement.

Aged↗
PubMedDate not supplied

Perivalvular extension of infection in patients with infectious endocarditis.

Perivalvular extension of infection is a not-infrequent and potentially fatal complication of bacterial endocarditis. Because the efficacy of various modalities in the diagnosis of such complications is not well established, a selective review of the published literature on this issue is worthwhile. The electrocardiogram is the easiest study to obtain. It is quite specific in identifying perivalvular extension of infection when conduction system disease is demonstrated but has a low degree of sensitivity overall. Transthoracic two-dimensional echocardiography, transesophageal echocardiography, and color-flow Doppler echocardiography are the most practical and useful techniques for diagnosis of perivalvular extension of infection. Magnetic resonance imaging also appears to be an effective tool in this setting; however, because of a paucity of clinical data, its precise utility has not yet been determined. Nuclear medicine studies and computed tomography play a minimal role. Cardiac catheterization is as useful as the echocardiographic techniques but is invasive, not as readily available, and significantly riskier in terms of complications. An approach to the diagnosis of perivalvular extension of infection is proposed on the basis of the literature review.

Abscess↗
PubMed2004

A technique for standardized evaluation of soft and hard peri-implant tissues in partially edentulous patients.

BACKGROUND: There is a growing need to evaluate the esthetics of implant-supported crowns and bridges. An important tool for such an evaluation is standardized assessment of the soft and hard peri-implant tissue levels. METHODS: A simple acrylic device has been developed for reliable and reproducible assessment of soft and hard peri-implant tissues using standardized color slides and standardized dental x-rays. With this device, changes in both the soft and hard tissues around implant-supported crowns can be evaluated as a function of time. The reproducibility of the technique was tested on color slides as well as on dental x-rays in a series of implant-supported crowns and their neighboring teeth. RESULTS: The reproducibility of this technique was excellent. The measuring errors for repeated measurements of the soft and hard tissues were 0.14 +/- 0.02 mm and 0.13 +/- 0.01 mm, respectively. CONCLUSIONS: The device is a reliable tool to assess changes in both soft and hard tissues around crowns and implants over time. Likewise, it is suggested that this technique also can be used to objectively assess soft and hard tissue changes around natural teeth with or without prosthetic restorations.

Acrylic Resins↗
PubMed1992

A prospective study on intermittent pneumatic compression in the prevention of deep vein thrombosis in patients undergoing total hip or total knee replacement.

Three hundred and forty-six consecutive patients undergoing total hip or total knee replacement were prospectively studied to evaluate the effectiveness of intermittent pneumatic compression of the legs for the prevention of postoperative deep vein thrombosis. All patients were serially studied using impedance plethysmography and duplex ultrasound with color flow preoperatively and on the fourth and seventh postoperative day. The incidence of postoperative deep vein thrombosis in this series was 4 percent. Each patient with a postoperative duplex ultrasound had positive impedance plethysmography. Of the 14 patients who had postoperative deep vein thrombosis, seven had positive test results on postoperative day four and seven had positive tests on postoperative day seven. No patients were symptomatic. The results suggest that the high incidence of postoperative deep vein thrombosis after extensive orthopedic operation is significantly lowered by the use of intermittent pneumatic compression. Intermittent pneumatic compression, therefore, may be the preferred approach in prophylaxis of postoperative deep vein thrombosis.

Hip Prosthesis↗
PubMed1996

A quantitative method for comparing and evaluating manual prosthetic socket modifications.

Manually designed prosthetic sockets are difficult to evaluate since the hand-sculpting modification process does not retain the initial shape for comparison. A quantitative method for defining and comparing manual socket modifications was developed and integrated into the CADVIEW software package. The numerical comparison procedure consisted of a) digitizing premodification and post-modification models of a prosthetic socket, b) aligning these two shapes to a common axis (calculate cross section centroids, determine line of best fit through the centroids, rotate and move the line of best fit to a common axis), and c) displaying the differences in shape both numerically and using a color-coded three dimensional image. Alignment technique testing showed a between-radial-point average error of 2.5 mm using automatic alignment and 1.4 mm after further manual alignment adjustment. The between socket difference values were used to outline individual modifications and save these outlines to disk. Modification outlines from a series of patients were averaged to determine a prosthetist's general modification style. Averaged results from two prosthetists qualitatively supported the effectiveness of this procedure. This alignment and comparison system should help transfer hand-sculpting skills to prosthetic CAD/CAM systems, clinical research, and education for new clinicians.

Amputation Stumps↗
PubMed1989

[Dental application of superplastic forming for titanium complete denture bases].

In order to investigate the application of superplastic in forming dental prosthesis, the sheets of titanium and its alloy were deformed to the complete denture bases by using a trial hot press and ceramic die. The results are summarized as follows: 1) By the hot press. It was possible to deform the sheet at a deformation speed ranging from 1 x 10(-3) to 3 x 10(-2) mm/sec at a temperature up to 900 degrees C under a vacuum down to 10(-3) Torr. 2) The trial ceramic die was prepared by sintering the green of the CaO-TiO2-ZrO2-MgCl2 system at 1150 degrees C for 6 hours in the atmosphere. The compressive strength, the thermal expansion, and the surface roughness of the test piece of the die were 11 kg/cm2, 0.8%, Ra = 1.4 microns and Rz = 6.8 microns, respectively. 3) Both the sheet of pure chemical titanium and commercial superplastic titanium alloy Ti-6Al-4V were deformed under the conditions of about 0.1 mm/min, 850 degrees C, and 10(-3) Torr. The deformed surface of the complete denture bases appeared to be nearly the same metallic color of each raw sheet and the pattern was the same as the detail of the die. The oxygen enriched layer of the article determined by EPMA was far thinner than that of a dental cast.

Dental Alloys↗
PubMed2001

Physicochemical and biomechanical examination of surfaces of retrieved polyethylene heads from total hip prostheses with rotating polyethylene head system.

In order to assess whether hydrodynamic lubrication occurs in total hip prostheses with a rotating polyethylene (PE) head system (R-THP), several physicochemical, morphological, and biomechanical tests were carried out. R-THPs have been used in more than 1000 patients since 1970, and 12 PE heads, retrieved from 10 patients after an average of 24.5 years since total hip arthroplasty (THA), were employed for the tests. The weight-bearing area of the PE surface was light yellow in color and considerably oxidized, but no wear scars were observed. In the non-weight-bearing area, in contrast, discoloration and oxidation were hard to detect. The weight-bearing surface of the PE head became smoother with time after THA, and the friction coefficient did not differ significantly from that of an unused PE head. The radial clearance between head and socket decreased at a temperature of 17 degrees C, which is equivalent to the difference between room temperature and the temperature of the human body. Scanning electron microscopy showed a fine undulating pattern, which suggested that hydrodynamic lubrication could occur in the rotating PE head system.

Adult↗
PubMed1998

Application of proximal isovelocity surface area method to determine prosthetic mitral valve area.

BACKGROUND: In this study, we investigated the accuracy of orifice area determination of the prosthetic valve (Biocor) by using proximal isovelocity surface area method (PISA). Thirty-two patients (26 women, 6 men; mean age 44 +/- 8.1 years) were studied. Eleven patients were in normal sinus rhythm and the rest were in atrial fibrillation. Associated valvular lesions were mild aortic regurgitation in 12 patients and moderate tricuspid regurgitation in 19 patients. Sizes of prosthetic valves were 27 to 31, and implantation duration was 4 to 8 years. METHODS AND RESULTS: We analyzed the flow convergence zone proximal to the valve orifice with the concept of a hemispheric model. Mitral valve area (MVA) calculation was formulated by MVA = 2pi r2 x Va/Vm x (Vm/Vm-Va), where Vm is the maximal mitral velocity and Vm/Vm - Va is a correction factor to account for flattening of isotachs near the prosthetic orifice. MVA calculations by PISA were compared with pressure half-time (PHT), continuity equation (CONT), and color flow area (CFA) methods. Mitral valve areas were 2.17 +/- 0.17 cm2, 2.22 +/- 0.21 cm2, 2.19 +/- 0.22 cm2, and 2.16 +/- 0.17 cm2 in PISA, CFA, PHT, and CONT methods, respectively. Values in the comparison of MVA measurements by different methods were PISA vs PHT, r =.86; PISA vs CFA, r =.77; and PISA vs CONT, r =.89. CONCLUSIONS: The PISA method gives reliable estimates of large orifices such as prosthetic valves. Although the best correlation was seen with the CONT method, results of this study also confirmed that the PISA method can be applied with reasonable accuracy.

Adult↗
PubMed1997

Blood velocity patterns after aortic valve replacement with a pulmonary autograft.

OBJECTIVE: Besides several other advantages, aortic valve replacement with a pulmonary autograft may result in improved hemodynamic characteristics compared to other valve replacement procedures. However, this plausible assumption has never been verified. Therefore, the aim of this study was to determine turbulent blood velocity energies in the ascending aorta after aortic valve replacement with a pulmonary autograft. METHODS: Blood velocity measurements were performed using a specialized pulsed Doppler ultrasound technique in the ascending aorta immediately after weaning from extracorporeal circulation. Six patients were included in the study. Determination of radial velocity components in 17 measuring points evenly distributed in the cross sectional area allowed computation of turbulence energies and a quantitative display of the spatial and temporal turbulence energy distribution during systole. RESULTS: The maximum turbulence energies were below 13 N/m2 in all patients and in all measuring positions in the cross sectional area. Color coded mapping of the spatial and temporal turbulence energy distribution displayed no consistent areas with markedly enhanced turbulence. These data are moderately elevated compared to turbulence energy values for normal aortic valves, which are below 4 N/m2, while artificial or xenovalves typically show values in the range of 40-60 N/m2. CONCLUSIONS: Turbulence energy levels after aortic valve replacement with a pulmonary autograft are considerably lower than those found for artificial aortic valves. From a fluid dynamic point of view this procedure provides excellent hemodynamic conditions in the ascending aorta.

Adult↗
PubMed2000

Tissue response to an expanded polytetrafluoroethylene external valve support device: a histologic study in dogs.

Expanded polytetrafluoroethylene (ePTFE) external valve support devices (EVS) have been used successfully in patients to restore valve function in leg veins with incompetent valves when incompetence is due to dilatation of the vein walls or elongation of the valve leaflet edges. To assess tissue response to these devices, the authors implanted 12 of them in dogs, wrapping the devices around veins in the head and neck. The dogs recovered from the implantation procedure uneventfully, and the veins remained patent on color flow Doppler scanning. Gross and histologic evaluations of vein segments and attached EVS devices after sacrifice of the dogs 30 days postoperatively showed that the ePTFE devices did not affect vein patency or the cellular composition or architecture of vein walls. There were no adverse tissue reactions to the EVS and no thrombus formation in the veins to which the EVS had been applied. Tissue attachment to the EVS was apparent in all specimens. These histologic results support clinical experiences indicating that the ePTFE EVS device is safe to use in external valvuloplasty for the treatment of venous incompetence.

Animals↗
PubMed1999

A new approach to restorative dentistry: fabricating ceramic restorations using CEREC CAD/CAM.

Ceramic materials provide an alternative when choosing a tooth-colored restoration. Currently, posterior composite restorations can be used to achieve esthetic restorations; however, they have many disadvantages with regard to wear, polymerization shrinkage, discoloration, marginal leakage, and technique sensitivity. The use of CEREC CAD/CAM enables the dentist to place feldspathic porcelain (Vitablocs Mark II) and machinable glass ceramic (Dicor MGC) restorations in a single visit. When compared to composite materials, these materials closely approximate the physical properties of enamel in compressive and tensile strength and wear resistance. This study evaluated 50 CEREC CAD/CAM restorations after 4 years in service. Restorations ranged from Class I to 7/8s crown preparations.

Adult↗
PubMed2004

Small-diameter prosthetic H-graft portacaval shunts in the treatment of portal hypertension.

BACKGROUND: Portasystemic shunts, especially total shunts, are effective tools for reducing portal pressure and controlling variceal bleeding but lead to high risk of encephalopathy and accelerating liver failure. The purpose of this study is to evaluate the clinical effects of small-diameter expanded polytetrafluoroethylene (ePTFE) H-graft portacaval shunts in the treatment of portal hypertension. METHODS: Thirty-one patients with portal hypertension were treated with ePTFE small-diameter H-graft portacaval shunts from December 1995 to April 2002. Twenty-one had externally ringed grafts and 10 had non-ringed grafts; 20 had 10 mm diameter grafts and 11 had 8 mm grafts. The left gastric artery and coronary vein were ligated in 22 patients. Additionally, 6 patients underwent pericardial devascularization, and splenectomies were performed on 30 patients. RESULTS: An average decrease of free portal pressure (FPP) from (32.13 +/- 4.86) cmH2O before shunting to (12.55 +/- 5.57) cmH2O after shunting was observed. Portal blood flow was reduced by 1/3 compared with the levels measured before shunting. Twenty-eight patients survived after the operation, and no upper gastrointestinal rebleeding occurred in the follow-up period (40.2 months on average). We lost contact with one patient. Color Doppler ultrasonography and/or portography revealed the shunts to be patent in 28 cases and occluded in 2 (6.4%) cases. Encephalopathy developed in 4 patients (12.9%). CONCLUSION: Small-diameter ePTFE H-graft portacaval shunts can effectively reduce portal pressure. Moreover, the majority of the hepatopetal flow from the portal vein can be adequately maintained. The reinforced shunts may achieve a higher rate of patency. Morbidity from encephalopathy was less frequent than in patients receiving total shunts. Small-diameter H-graft portacaval shunts are also effective in preventing recurrent variceal bleeding.

Adult↗