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Biomedical subjects

Peter Wilde

Publications and source records attributed to Peter Wilde.

11 recordsLinked to original sources
PubMed2006

Multislice computed tomography coronary angiography in patients admitted with a suspected acute coronary syndrome.

OBJECTIVES: The aim of this prospective clinical study was to assess the accuracy and clinical relevance of multislice computed tomography coronary angiography (MSCTCA) in patients presenting with acute chest pain. BACKGROUND: Multislice computed tomography coronary angiography has shown ability to detect accurately coronary artery disease (CAD) in selected elective patient groups. METHODS: One hundred and twenty patients presenting with acute chest pain (<24 h) underwent MSCTCA (Siemens Sensation 16) before a scheduled inpatient conventional coronary angiogram (CCA). Exclusion criteria included patients with STEMI, non-sinus rhythm, contraindication to beta blockers and renal impairment. Blinded visual assessment of MSCTCA to detect CAD was performed on an 11-segment model. The accuracy of MSCTCA was compared to CCA to detect significant stenoses (> or =50%). RESULTS: One hundred and thirteen patients underwent both investigations. The prevalence of significant CAD was 74%. 1,243 native segments were assessed by MSCTCA. The overall ability of MSCTCA to detect the presence of > or =1 significant stenosis in all native segments had a sensitivity of 92% (95%CI 83-97%), specificity of 55% (95%CI 35-74%), positive predictive value of 86% (95%CI 76-93%) and negative predictive value of 70% (95%CI 47-87%). 22% of all segments (mostly distal) were non-analyzable. Coronary calcification was a major cause of false positivity. CONCLUSION: In a prospective study of unselected patients presenting with acute chest pain, the diagnostic accuracy of 16-slice CT coronary angiography was moderate and less than reported from studies in elective patients. The clinical relevance of this technology to screen patients with acute chest pain is limited.

Acute Coronary Syndrome↗
PubMed2006

Structure modification in hen egg yolk low density lipoproteins layers between 30 and 45 mN/m observed by AFM.

We have studied the structure of films made by low density lipoproteins (LDL) from hen egg yolk, which are composed of apoproteins, neutral lipids and phospholipids. These LDL have been deposited on air-water interface to form a monolayer which has been compressed to measure an isotherm using Langmuir balance. This isotherm presented three transitions (neutral lipid (surface pressure, pi=19 mN/m), apoprotein-lipid (pi=41 mN/m) and phospholipid (pi=51 mN/m) transitions). We have studied only the apoprotein-lipid transition. In order to observe the LDL film structure before (pi=30 mN/m) and after (pi=45 mN/m) the apoprotein-lipid transition, the formed films were transferred and visualised by atomic force microscopy (AFM). Our results have shown that the structures observed in the LDL film were different depending on the surface pressure. The apoproteins and neutral lipids appeared to be miscible up to the apoprotein-lipid transition, when demixing occurred. The structures observed after the apoprotein-lipid transition should be due to the demixing between apoproteins and neutral lipids. On the other hand, apoproteins and phospholipids seemed miscible whatever the surface pressure. Hence, the first transition (pi=19 mN/m) should be attributed to the free neutral lipid collapse; the second transition (pi=41 mN/m) should be attributed to the demixing of apoprotein-neutral lipid complexes; and the last transition (pi=51 mN/m) should be attributed to phospholipid collapse or to demixing of apoprotein-phospholipid complexes.

Animals↗
PubMed2006

Comparison of radiation doses from multislice computed tomography coronary angiography and conventional diagnostic angiography.

OBJECTIVES: The aim of this study was to quantify and compare effective doses from conventional angiography and multislice computed tomography (MSCT) coronary angiography using a 16-slice scanner. BACKGROUND: Multislice computed tomography is now a viable modality for cardiac imaging. However, for any diagnostic use of ionizing radiation, the risk to the patient must be considered and justified. METHODS: Multislice computed tomography angiography and conventional angiography were used to assess 180 patients with suspected coronary artery disease. Estimates of effective dose were derived from exposure data recorded for each patient examination. For each modality, a comparable calculation technique was used, based on Monte Carlo modeling of the standard Cristy phantom. RESULTS: In a subset of 91 directly comparable patients the mean effective dose for MSCT coronary angiography was 14.7 mSv (SD 2.2) and that for conventional angiography was 5.6 mSv (SD 3.6). A significant difference in effective dose was seen between the two protocols. CONCLUSIONS: The mean effective dose for MSCT coronary angiography was significantly higher than that for conventional angiography. As MSCT cardiac scanners become increasingly available, operators must be aware of the radiation dose and the factors that affect it.

Coronary Angiography↗
PubMed2005

The role of interactions in defining the structure of mixed protein-surfactant interfaces.

The behaviour of dispersed systems is often controlled by the composition of the interface between the different phases. Because of the inherent differences between proteins and surfactants, when both are present at the interface complex pseudo two-dimensional structures can be formed. This review brings together work that allows these structures to be explained in terms of the interactions involved. The significance of both the interactions and the structures is discussed in terms of the effect on bulk properties in colloidal systems.

Adsorption↗
PubMed2005

A statherin and calcium enriched layer at the air interface of human parotid saliva.

Parotid saliva placed in 35-mm-diameter tissue culture dishes developed increasing surface viscoelasticity at the interface with air. A surface layer became visible with time, and was collected and analysed by protein electrophoresis which indicated that a single protein (pI 4.2; molecular mass approx. 6 kDa) predominated. Western blot analysis demonstrated that the major protein band reacted with an antiserum directed against the C-terminal of the calcium-binding salivary protein statherin. Matrix-assisted laser-desorption ionization-time-of-flight MS analysis gave a molecular mass of 5380 Da for the protein, corresponding to the molecular mass of statherin. Staining of film protein in electrophoresis gels was compared with statherin synthesized on a solid phase, and the mean statherin content of film formed from 1 ml of parotid saliva was measured as 7 nmol. The mean calcium content of the surface layer was 250 nmol. Surface rheology was greatly decreased in the presence of EDTA, whereas surface tension of saliva was unaffected by calcium chelation, suggesting that protein accumulated at the surface was unaffected. The results suggest that a layer rich in statherin forms at the interface of saliva and air, and that the surface rheology developed is dependent upon protein interactions mediated by calcium. The surface layer may enhance the function of saliva as a protective layer on the mucosal surfaces and teeth.

Air↗
PubMed2005

Eight years survival after partial left ventriculectomy.

Remodelling the left ventricle by partial left ventriculectomy (PLV) has been proposed as an alternative surgical treatment for end-stage heart failure. We present the case of a patient with dilated idiopathic cardiomyopathy who underwent PLV and remains in NYHA functional Class I eight years after the surgery.

Aged↗
PubMed2004

Proteins and emulsifiers at liquid interfaces.

The interfacial properties of proteins and emulsifiers have been studied extensively in the field of food colloid research. Emulsions form the basis of a huge range of food products and are generally stabilised by either protein and/or emulsifiers. Proteins have been shown to stabilise emulsions by forming a viscoelastic, adsorbed layer on the oil droplets, which form a physical barrier to coalescence. Emulsifiers can be oil or water soluble, forming a fluid, close-packed layer at the interface with a low interfacial tension. This results in an emulsion with a small droplet size distribution, stabilised by the fluid Gibbs-Marangoni mechanism or weak electrostatic repulsion. In real food emulsions, there is usually a mixture of proteins and emulsifiers competing for the interfacial area. This can produce a finer emulsion, however, the emulsifiers break down the viscoelastic protein-adsorbed layer, resulting in an emulsion with reduced stability. We present a review recent work that aims to characterise the composition, structure and physical properties of mixed protein-emulsifier interfaces, in an effort to understand the mechanisms behind the stability behaviour of food emulsion systems.

Colloids↗
PubMed2004

Midterm results after septal reshaping for anteroseptal scars.

BACKGROUND: Midterm clinical and morphologic results of the septal-reshaping exclusion of anteroseptal dyskinetic or akinetic areas were evaluated. METHODS: From January to June 2003, 44 patients with myocardial infarction following left anterior descending coronary artery (LAD) occlusion underwent septal reshaping. The mean (+/- SD) New York Heart Association (NYHA) class of the patients at admission was 2.7 +/- 0.9. Angina was referred in 21 cases. The incision was started at the apex and directed parallel to the LAD toward the base of the heart. The septum was rebuilt with 1 or 2 U-stitches passed from the inside to join the anterior wall to the septum by starting as high as possible where the scar began and continuing in an oblique direction toward the new apex. An oval polyethylene terephthalate fiber (Dacron) patch was then sutured from the septum (at the end of the direct suture through the border with the inferior septum) to the anterior wall (between the healthy wall and the scarred wall) and up to the new apex. RESULTS: The 30-day mortality rate was 2.2% (1 patient, due to the failure of a previously implanted defibrillator). Three patients experienced acute renal failure. No patient had restrictive syndrome. After a mean follow-up period of 8.5 +/- 4.9 months (range, 4-22 months), the mean NYHA class improved from 2.7 +/- 0.9 to 1.6 +/- 0.5 (P < .001). The 18- month survival rate and the probability of being alive in NYHA class I or II were 93.2% +/- 2.0% and 90.9% +/- 4.3%, respectively. Echocardiographic results showed reductions in the left ventricle volume with a normalization of the stroke volume. The diastolic longitudinal length remained unchanged, and the diastolic sphericity index was reduced but not significantly. CONCLUSIONS: At 1 year after surgery, the good clinical and morphologic results demonstrate the safety and effectiveness of septal reshaping for anteroseptal scars.

Adult↗
PubMed2002

A physicochemical investigation of two phosphatidylcholine/bile salt interfaces: implications for lipase activation.

Within the gastrointestinal tract ingested lipids are broken down into their constituent mono-acylglycerides and fatty acids by the enzyme family of lipases. In this study we have investigated the interfacial composition and structure of two phospholipid/bile salt (BS) systems that display significant differences in the duration of the lag phase of porcine pancreatic lipase kinetics. The interfacial tension of the single BSs, and their binary mixtures with phospholipid is reported at an n-tetradecane/water interface as a function of phospholipid mole fraction and total surfactant concentration. The structuring of the interface was probed by characterisation of the thin liquid film formation, thickness and stability. Lateral interactions were quantified by measurement of the diffusion coefficient of a probe fluorophore. We conclude that interfacial tension was not a factor in lag time duration as there was no significant difference in the minimum interfacial tension for the phosphatidylcholine (PC)/sodium taurocholate and the PC/sodium taurodeoxycholate system. No correlation was found between lag phase duration and the physiochemical properties of the interface, i.e. lateral diffusion, thin liquid film formation or interfacial tension. This is in agreement with our previous study that the lag time duration was directly related to the phospholipid content of the interface.

Animals↗
PubMed2002

Comparison of exercise and dobutamine echocardiography in the haemodynamic assessment of small size mechanical aortic valve prostheses.

OBJECTIVE: Doppler echocardiographic evaluation of prosthetic heart valve function is usually performed at rest although this situation is not representative of patients' daily activities. Following aortic valve replacement, patients most likely to remain symptomatic are those with a small aortic root and dobutamine or exercise echocardiography has been proposed to elicit the presence of abnormal haemodynamics or persistently elevated transvalvular gradients in these patients. This study was carried out to compare dobutamine echocardiography with a symptom limited treadmill exercise echocardiography in patients following aortic valve replacement with a small size (19 mm) St. Jude Mechanical valve prosthesis. METHODS: The study population consisted of ten unselected patients following aortic valve replacement. Dobutamine was infused intravenously starting at 5 microg/kg/min and increasing by 5 microg/kg/min at 15 min interval up to 20 microg/kg/min. Heart rate, blood pressure, cardiac output (CO), peak and mean gradients as well as effective orifice area (EOA) were measured. These parameters were also measured following a symptom limited treadmill exercise. RESULTS: Dobutamine stress increased heart rate (HR) and CO by 50 and 74%, respectively (both P<0.0002), and mean transvalvular gradient from 22+/-4.1 mmHg at rest to 40.0+/-10 mmHg at maximum stress (P<0.001). With exercise, HR and CO increased by 48 and 70%, respectively while mean transvalvular gradient increased from 22+/-3.1 mmHg at rest to 38.0+/-6.4 mmHg (P<0.0001). The maximum increase in HR, CO and mean transvalvular gradient with dobutamine and exercise were similar however. There was no significant change in the EOA with either dobutamine or exercise. CONCLUSION: The result suggests that both treadmill exercise and dobutamine stress echocardiography are equally effective for the hemodynamic evaluation of small aortic valve prosthesis.

Adrenergic beta-Agonists↗