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At least 685 records · Page 38Linked to original sources
PubMed2000

Establishment of a parabiotic rat model by anastomosis of common carotid artery.

A cross circulation model was established by replacing mutual blood between two rats by anastomoses of each common carotid artery. In this model, parabiotic rats were shown to replace their mutual blood completely without any artificial materials or instruments, such as silicon tubes or pumps. The rate of blood exchange was measured by intravenous injection of Evans blue dye without the use of the radioactive materials that were so far commonly used. The partial alteration of blood circulation through microvascular surgery may reveal the mechanisms of organ tropism of bacteria, protozoa, and parasites. Microvascular surgery is available for reconstruction and analysis of organ functions as well as for clinical use in organplasty.

Anastomosis, Surgical↗
PubMed1995

The relationship between arm-ankle pressure difference and peak systolic velocity in patients with stenotic lower extremity vein grafts.

The relationship between the measured arm-ankle pressure difference (AAPD), or the ankle/arm index (AAI), and the focal peak systolic velocity (PSV) at stenotic sites of infrainguinal vein grafts has not been determined. We attempted to relate these two parameters. We used Doppler systolic pressures and duplex ultrasonography to study 35 infrainguinal vein bypass grafts followed in a surveillance protocol. The following graft groups were identified: grafts in nondiabetic patients (n = 26), grafts in diabetic patients (n = 9), nonrevised stenotic grafts (n = 14), revised stenotic grafts (n = 14), and normal grafts (n = 7). AAPD and AAI were measured in both lower extremities. Pressure gradients across graft stenoses were indirectly estimated using the modified Bernoulli equation (delta P =4V2). Measured AAPDs and estimated pressure gradients showed moderate correlation in nondiabetic (r = 0.58) and diabetic (r = 0.63) patients. Correlation was fair (r = 0.3) prior to graft revision. There was no correlation (r = 0.1) in the nonrevised stenotic grafts. For individual patients with stenotic grafts who were followed in consecutive visits, the correlation varied from none to good (r range 0.01 to 0.71). We conclude that there is a lack of consistent correlation between the measured AAPD, or AAI, and the estimated stenotic graft pressure gradient. This finding illustrates the limitation of the AAI as a monitoring test to predict failure of stenotic infrainguinal vein grafts.

Ankle↗
PubMed2002

Mitral regurgitation without supravalvular aortic stenosis in Williams syndrome.

Isolated mitral regurgitation without supravalvular aortic stenosis is rarely identified in Williams syndrome. We describe the case of a 24-year-old man with isolated mitral regurgitation in Williams syndrome. Severe regurgitation due to prolapse of the anterior leaflet was noted in an echocardiogram and color Doppler, and a left ventriculogram showed grade IV regurgitation. No pressure gradient between the left ventricle and the ascending aorta was found. Mitral regurgitation had been noted since his birth, and pediatricians suspected Williams syndrome because of postnatal growth deficiency, mental deficiency, unusual personality, and unusual facial features in his childhood. The diagnosis was confirmed by demonstration of the hemizygous deletion of 7q11.23 in the karyotype by the fluorescent in situ hybridization technique after his admission to our department. The patient underwent mitral valve replacement, and microscopic examination of the excised valve revealed myxomatous degeneration.

Adult↗
PubMed2005

Changes in surface characteristics of dental resin composites after polishing.

The objectives of this study were (1) to determine in vitro changes in surface roughness and color of dental resin composites after application of three finishing and polishing systems; (2) to evaluate the difference in color stability after immersion in a dye solution after polishing; and (3) to evaluate the effects of surface condition, especially roughness, on measured color depending on the color measuring geometries of specular component excluded (SCE) and specular component included (SCI). Color and surface roughness (R(a)) of resin composites of four brands of A2 shade and one brand of Yellow Enamel shade were measured after polymerization, after polishing with Enhance (Dentsply), Sof-Lex (3M ESPE), or Super-Snap (Shofu) composite finishing and polishing systems. Color was also measured after immersion in 2% methylene blue solution. Color was measured according to the CIELAB color scale. Color changes (DeltaE*(ab)) after polishing/staining and by the measuring geometry were calculated by the equation; DeltaE*(ab) = [(DeltaL*)(2) + (Deltaa*)(2) + (Deltab*)(2)](1/2). Ra value was measured with a surface roughness tester. DeltaE*(ab) and DeltaL* values after polishing and after staining varied among polishing systems when measured with SCE geometry. Composites polished with Super-Snap and Sof-Lex systems showed higher DeltaE*(ab) and DeltaL* values than those polished with Enhance polishing system with SCE geometry. DeltaE*(ab) and DeltaL* values between specimens with different surface conditions measured with SCE geometry were significantly higher than those with SCI (p < 0.01). Changes in R(a) value after polishing was insignificant in most cases.

Biocompatible Materials↗
PubMed1995

Early experience with the Toronto stentless porcine valve.

Stentless porcine valves in the aortic position offer many theoretic advantages, but their clinical performance has not been adequately defined. We evaluated the clinical and echocardiographic results of 103 patients who had aortic valve replacement with the Toronto stentless porcine valve over a 2-year period. There were 67 men with a mean age of 68 years. The predominant native valve lesion was aortic stenosis (64%), and 4 patients had prosthetic valve dysfunction. Forty-two patients had concomitant procedures. The 30-day mortality rate was 3.3% (n = 2) for isolated valve replacement and 5.8% (n = 6) for the series. The sole determinant of early death was poor left ventricular function. There were three late deaths due to non-valve-related complications over a median follow-up of 11.87 months. In addition, prosthetic valve endocarditis developed in 1 patient, necessitating a homograft valve replacement at 6 weeks. Doppler echocardiography performed at 3 to 6 months showed low peak and mean transvalvular gradients, with no substantial change at 1 year. None of the patients showed signs of clinically significant aortic regurgitation, although echocardiography demonstrated trivial or mild regurgitation in 12 patients at discharge or early follow-up, which was less marked or absent at 1 year. We conclude that the Toronto stentless porcine valve appears to offer promising early results.

Adult↗
PubMed1992

Effects of environmental factors on maxillofacial elastomers: Part II--Report of survey.

Part II of a four-part report presents an international survey that was conducted to determine the most frequently used materials in the fabrication of facial and somatoprostheses. The survey also solicited information about advantages and disadvantages, methods of coloring, and the perceived properties of an "ideal" material. The results of the survey indicated that the majority of prosthodontists and prosthetists are using room temperature-vulcanized silicone products, intrinsically colored with dry earth pigments or artist's pigments. The need for further research in materials for external prostheses was clearly indicated.

Color↗
PubMed2006

Austrian triad with sinus of Valsalva aneurysm and rupture.

An interesting case of a young patient presenting with Austrian's Triad: pneumococcal pneumonia, pneumococcal meningitis, and pneumococcal endocarditis. On echocardiogram the patient was noted to have a noncoronary sinus of Valsalva aneurysm and vegetations on the aortic cusps resulting in disruption of valvular integrity and severe aortic insufficiency. Color Doppler also revealed rupture of the aneurysm into the right atrium. The patient was taken to surgery where the noncoronary cusp was noted to be completely replaced with vegetative lesions. The aortic valve was replaced with a No. 21 Carpentier-Edwards bioprosthetic valve (Edwards Lifesciences, Irvine, CA), and the noncoronary sinus of Valsalva was repaired with concomitant closure of the fistula using glutaraldehyde autologous pericardium.

Adult↗
PubMed2003

In vivo repopulation of xenogeneic and allogeneic acellular valve matrix conduits in the pulmonary circulation.

BACKGROUND: Approaches to in vivo repopulation of acellularized valve matrix constructs have been described recently. However, early calcification of acellularized matrices repopulated in vivo remains a major obstacle. We hypothesised that the matrix composition has a significant influence on the onset of early calcification. Therefore, we evaluated the calcification of acellularized allogenic ovine (AVMC) and xenogenic porcine (XVMC) valve matrix conduits in the pulmonary circulation in a sheep model. METHODS: Porcine (n = 3) and sheep (n = 3) pulmonary valve conduits were acellularized by trypsin/EDTA digestion and then implanted into healthy sheep in pulmonary valve position using extracorporeal bypass support. Transthoracic echocardiography (TTE) was performed at 12 and 24 weeks after the implantation. The animals were sacrificed at week 24 or earlier when severe calcification of the valve conduit became evident by TTE. The valves were examined histologically and biochemically. RESULTS: All AVMC revealed severe calcification after 12 weeks with focal endothelial cell clustering and no interstitial valve tissue reconstitution. In contrast, after 24 weeks XVMC indicated mild calcification on histologic examination (von Kossa staining) with histologic reconstitution of valve tissue and confluent endothelial surface coverage. Furthermore, immunohistologic analysis revealed reconstitution of surface endothelial cell monolayer (von Willebrand factor), and interstitial myofibroblasts (Vimentin/Desmin). CONCLUSIONS: Porcine acellularized XVMC are resistant to early calcification during in vivo reseeding. Furthermore, XVMC are repopulated in vivo with valve-specific cell types within 24 weeks resembling native valve tissue.

Animals↗
PubMed1998

In vitro testing of bioprostheses: influence of mechanical stresses and lipids on calcification.

BACKGROUND: Structural valve deterioration of bioprostheses is mainly caused by the progressive development of calcification. Mechanical stresses or lipid deposits in porcine aortic leaflets have been proposed as major factors contributing to the calcification process. METHODS: A new test protocol consisting of nondestructive holographic interferometry, which allows a quantitative deformation analysis of heart valves, and accelerated dynamic in vitro calcification was used. The rapid calcification fluid contained a final combined calcium and phosphorus concentration of 130 (mg/dL)2 in barbital buffer solution. The calcification of 32 bioprostheses donated by different manufacturers (SJM Bioimplant, Biocor standard, Biocor No-React, Carpentier-Edwards SAV, Bravo, pericardial prototype) was assessed after up to 25 x 10(6) cycles by microradiography and the areas of calcification were compared with the holographic interferograms. The distribution of lipid droplets of four porcine prostheses were visualized by Sudan III stain before the calcification process. RESULTS: Most of the tested bioprostheses had areas presenting with stress concentrations, and the dynamic in vitro testing resulted in leaflet calcification corresponding to the holographic irregularities. A strong correlation between calcification and stress distribution or lipid accumulation was found (r = 0.72; r = 0.81, respectively). After 19 x 10(6) cycles, the Carpentier-Edwards SAV and the pericardial valves had significantly less calcification than other prostheses tested (p = 0.003), but the variation among individual prostheses from the same manufacturer was even more pronounced. CONCLUSIONS: Mechanical stresses or lipid accumulation seems to play an important role in the calcification process of bioprostheses. Quality control of bioprosthetic valves using holographic interferometry has the potential to predict calcification before implantation.

Aortic Valve↗
PubMed1999

Aortic valve replacement: is the stentless xenograft an alternative to the homograft? Midterm results.

BACKGROUND: This study was performed to assess the midterm clinical results after aortic valve replacement (AVR) with stentless xenograft (SX) compared with cryopreserved aortic or pulmonary homografts (HX). METHODS: In 139 patients (<60 years) undergoing elective AVR, 59 HX and 80 SX were inserted. All patients were followed clinically and by color flow Doppler echocardiography for 45+/-12 months (range 31-58 months). RESULTS: There were 5 in-hospital deaths (3.5%): 4 HX and 1 SX (p = NS). The mean gradient was 6+/-2 mm Hg in HX versus 13+/-6 mm Hg in SX (p<0.001) and remained unchanged during follow-up. Actuarial survival (HX 77%, SX 80%), freedom from endocarditis (HX 91%, SX 99%), freedom from thromboembolic events (HX 98%, SX 90%), and freedom from reoperation (HX 98%, SX 100%) were comparable between groups after 58 months. CONCLUSIONS: Despite slightly higher transvalvular gradients, the stentless aortic valve achieved excellent midterm results, when compared with homografts.

Actuarial Analysis↗
PubMed1998

Association of increased QT dispersion with coronary atherosclerosis in patients with aortic stenosis.

To evaluate correlates between electrocardiographic QT dispersion and coronary atherosclerosis in patients with aortic stenosis before aortic valve replacement, 39 consecutive patients >40 years old with symptomatic aortic stenosis and coronary diameter narrowing > or =50% measured by digital angiographic study were included. An additional matched group with insignificant coronary lesions (<50%) consisted of 39 patients for comparisons. Matching by age, sex heart rate and incidence of chest pain resulted in two comparable groups with identical baseline characteristics. Preoperative transthoracic echocardiography and electrocardiograms were performed in all subjects. QT dispersion was defined as the difference between maximal and minimal QT interval measurements occurring among any of the 12 leads on a standard electrocardiogram. No subject had fewer than nine measurable leads. There were no significant differences of risk factors of coronary artery disease between the two groups. From a conditional multivariate logistic regression analysis, independent predictors of development of coronary artery disease in aortic stenosis were only QTc dispersion (odds ratio= 1.255, P=0.01). A wide QTc dispersion > or =70 ins) correlated with the presence of angiographically significant coronary artery disease with a sensitivity and specificity of 72% and 79%. The positive accuracy of having significant coronary artery disease in the presence of QTc dispersion > or =70 ms was 78%. The negative predictive value was 74%. In conclusion, electrocardiographic QTc dispersion may provide important clinical information. A wide QTc dispersion in patients with aortic stenosis is associated with a high incidence of coronary artery disease. These findings warrant further investigation in a large trial.

Aged↗
PubMed2003

Self-expandable valved stent of large size: off-bypass implantation in pulmonary position.

OBJECTIVE: To evaluate the feasibility of the off-bypass implantation of a self-expandable valved stent of large size in pulmonary position. MATERIALS AND METHODS: A glutaraldehyde preserved valved bovine jugular xenograft with internal diameter = 22 mm, mounted in two rings of nitinol 'Z' stent, expandable from 7 to 24 mm of internal diameter, was acutely evaluated in 6 adult pigs, mean body weight 55.6 kg (range 47-67 kg). Through a stent-graft delivery system (24 French) the self expandable valved stent was implanted off-bypass in pulmonary valve position by trans-ventricular approach through median sternotomy. RESULTS: The mean diameter of the main pulmonary artery measured was 21.7 +/- 1.6 mm. The mean length of the self expandable valved stent was 23.1 +/- 0.7 mm, the mean internal diameter 21.6 +/- 0.7 mm and the mean external diameter 26.3 +/- 0.7 mm. The mean peak pressure gradient recorded across the valve was 6.33 +/- 2.8 mmHg (range 4.5-9.6 mmHg) at Doppler echocardiography, and 4.5 +/- 3.1 mmHg (range 0-7 mmHg) at invasive measurement, with a pulmonary blood flow of 3.03 +/- 0.05 l/min. Intra-vascular ultrasound showed complete opening and closure of the valve (mean area reduction from 315.08 +/- 54.13 to 0 mm2). CONCLUSIONS: (a) Off-bypass implantation of self-expandable valved stent is feasible in pulmonary position; (b) off-bypass surgical approach allows for valved stent implantation of adult size with adequate hemodynamic functioning; and (c) intra-vascular ultrasound makes implantation and evaluation easy and reproducible.

Animals↗
PubMed1995

In vivo analysis and three-dimensional visualisation of blood flow patterns at vascular end-to-side anastomoses.

OBJECTIVES: The aim of this study was to describe the velocity fields at distal vascular end-to-side anastomoses with different anastomosis angles in vivo. MATERIALS AND METHODS: The abdominal aorta of ten 90 kg pigs was exposed from the superior mesenteric artery to the trifurcation. A segment of the aorta was bypassed using a polyurethane graft. Three anastomosis angles: 90 degrees (n = 3), 45 degrees (n = 3) and 15 degrees (n = 4) were studied. The bypass length, the anatomical position and the geometry of the anastomoses were standardised. During measurements, the proximal outflow segment was occluded and the flow rate was controlled by reversible iliac artery cross-clamping. Using a colour Doppler system the velocity fields were measured at various positions in the anastomosis. The colour Doppler velocity data were transferred to a computer for dynamic three-dimensional visualisation of the velocity profiles. RESULTS: The angulation was reproduced within 10%. During the experiment, the flow rate was kept constant with Reynold's numbers typical for peripheral arteries. In the 90 degrees anastomoses very disturbed flow fields were seen. The 45 degrees anastomoses were characterised by: (1) low antegrade and retrograde velocities at the heel and (2) a zone of reverse and oscillating velocities at the toe and at one diameter downstream of the toe (1DDD) during deceleration. In the 15 degrees anastomoses no flow disturbances were seen either at the toe or at 1DDD. The velocity profiles were close to parabolic at peak flow at both positions. CONCLUSIONS: It is concluded that the 15 degrees anastomosis is preferable from a haemodynamic point of view.

Anastomosis, Surgical↗