Dynamic Performance of an Oil Starved Squeeze Film Damper Combined With a Cylindrical Roller Bearing.

Squeeze film dampers (SFDs) are widely used to dissipate mechanical energy caused by rotor vibrations as well as to improve overall stability of the rotor system. Especially turbomachine rotors, supported on little damped rolling element bearings (REBs), are primarily sensitive to unbalance excitation and thus high amplitude vibrations. To ensure safe operation, potential failure modes, such as an oil starved damper state, need to be well examined prior to the introduction in the ultimate industrial application. Hence, the aim of this research project is to evaluate the performance of the rotor support for a complete oil starvation of the SFD. An academic rotor dynamic test bench has been developed and briefly presented. Experimental testing has been conducted for two static radial load cases resembling the full load and idle condition of a certain turbomachine. Evidently, the measurement results exposed severe vibration problems. Even a split first whirl mode arises due to a pronounced anisotropic bearing stiffness. Moreover, for the least radially loaded bearing, highly nonlinear behavior emerged at elevated unbalance excitation. Consequently, the rollers start to rattle which will have a negative effect on the overall bearing lifetime. To explain the nature of the nonlinear behavior, advanced quasi-static bearing simulations are exploited. A number of possible solutions are proposed in order to help mitigate the vibration issues.

5-Year clinical follow-up of the COBRA (complex coronary bifurcation lesions: Randomized comparison of a strategy using a dedicated self-expanding biolimus A9-eluting stent vs. a culotte strategy using everolimus-eluting stents) study.

OBJECTIVES: We evaluated healing responses with optical coherence tomography, and long-term clinical outcomes after treatment with a dedicated stent versus a conventional culotte technique. BACKGROUND: Dedicated bifurcation stents have been proposed as an alternative treatment for coronary bifurcation lesions. The long-term performance of dedicated stents versus conventional dual-stent techniques for the treatment of complex coronary bifurcation lesions is unknown. METHODS: Forty patients with true coronary bifurcation lesions were randomized to treatment with a dedicated Axxess bifurcation stent in the proximal main vessel and additional Biomatrix stents in branches versus culotte stenting using Xience stents. RESULTS: The percentage of uncovered struts in each bifurcation segment at 9 months (primary endpoint) was similar between groups. Five-year clinical follow-up was available for all patients and included major adverse cardiac events [MACE; a composite of cardiac death, myocardial infarction (MI) and ischemia-driven target lesion revascularization (TLR)], target-vessel (TVR) and non-target-vessel revascularization (non-TVR), non-TLR and stent thrombosis. At 5 years, in the culotte group, one patient had undergone TLR and another suffered a clinical MI, resulting in 10% MACE versus none in the Axxess group. TVR (5% vs. 10%, P = 0.54) and non-TVR (5% vs. 20%, P = 0.39) rates were similar between the Axxess and culotte groups, respectively. There was no stent thrombosis. CONCLUSION: Compared with culotte stenting with Xience, complex coronary bifurcation stenting using a dedicated strategy combining the Axxess and Biomatrix stents results in similar stent strut coverage at 9 months, and excellent clinical outcomes at 5 years.

Evaluation of automatic dose rate control for flat panel imaging using a spatial frequency domain figure of merit.

Current automatic dose rate controls (ADRCs) of dynamic x-ray imaging systems adjust their acquisition parameters in response to changes in patient thickness in order to achieve a constant signal level in the image receptor. This work compares a 3 parameter (3P) ADRC control to a more flexible 5-parameter (5P) method to meet this goal. A phantom composed of 15 composite poly(methyl) methacrylate (PMMA)/aluminium (Al) plates was imaged on a Siemens Artis Q dynamic system using standard 3P and 5P ADRC techniques. Phantom thickness covered a water equivalent thickness (WET) range of 2.5 cm to 37.5 cm. Acquisition parameter settings (tube potential, tube current, pulse length, copper filtration and focus size) and phantom entrance air kerma rate (EAKR) were recorded as the thickness changed. Signal difference to noise ratio (SDNR) was measured using a 0.3 mm iron insert centred in the PMMA stack, positioned at the system isocentre. SDNR was then multiplied by modulation transfer function (MTF) based correction factors for focal spot penumbral blurring and motion blurring, to give a spatial frequency dependent parameter, SDNR(u). These MTF correction factors were evaluated for an object motion of 25 mm s-1 and at a spatial frequency of 1.4 mm-1 in the object plane, typical for cardiac imaging. The figure of merit (FOM) was calculated as SDNR(u)²/EAKR for the two ADRC regimes. Using 5P versus 3P technique showed clear improvements over all thicknesses. Averaged over clinically relevant adult WET values (20 cm-37.5 cm), EAKR was reduced by 13% and 27% for fluoroscopy and acquisition modes, respectively, while the SDNR(u) based FOM increased by 16% and 34% for fluoroscopy and acquisition. In conclusion, the generalized FOM, taking into account the influence of focus size and object motion, showed benefit in terms of image quality and patient dose for the 5-parameter control over 3-parameter method for the ADRC programming of dynamic x-ray imaging systems.

Complex bifurcation lesions: Randomized comparison of a fully bioresorbable modified t stenting strategy versus bifurcation reconstruction with a dedicated self-expanding stent in combination with bioresorbable scaffolds, an OCT study: Rationale and design of the COBRA II trial.

OBJECTIVE: There is an ongoing controversy regarding the efficacy and safety of different percutaneous stenting techniques for coronary bifurcation lesions needing >1 stent. The promise of safe vessel restoration with bioresorbable scaffolds (BRS) may not be transferable to complex double BRS bifurcation techniques, and permanent metallic scaffolding of the bifurcation core may be needed. We identified modified-T stenting as the most promising fully bioresorbable 2-stent strategy in a preclinical setting. The objective of this study is to assess acute performance and compare long-term vessel healing with this strategy, versus an approach combining BRS with a dedicated metallic drug-eluting bifurcation stent. STUDY DESIGN: In a single center, 60 consecutive patients with true and complex coronary bifurcation lesions will be randomly assigned to treatment with the dedicated self-expanding Axxess™ biolimus-eluting bifurcation stent in the proximal main vessel and additional Absorb™ everolimus-eluting BRS in the branches versus a modified T technique using Absorb™ only. Angiography and optical coherence tomography (OCT) will be performed immediately after implantation and at 30 months, and clinical follow-up is foreseen up to 5 years after implantation. The primary endpoint is the change in minimal luminal area assessed with OCT from baseline to 30 months in pre-specified bifurcation segments. CONCLUSION: To date the use of Absorb™ BRS in complex coronary bifurcations has not been evaluated in a randomized clinical trial setting. The COBRA II study will examine the role and safety of a double BRS strategy in coronary bifurcations, alone or in combination with a metallic dedicated bifurcation device. © 2016 Wiley Periodicals, Inc.

Comparison of sirolimus eluting stent with bioresorbable polymer to everolimus eluting stent with permanent polymer in bifurcation lesions: Results from CENTURY II trial.

OBJECTIVE: To demonstrate the safety and efficacy of a new sirolimus eluting stent with bioresorbable polymer, Ultimaster, (BP-SES) compared with everolimus-eluting, permanent polymer, Xience stent (PP-EES) in bifurcation lesions with respect to the freedom from Target Lesion Failure at 1-year. METHODS: Within 1,119 patients enrolled in the CENTURY II randomized controlled multicenter trial, 194 patients were treated for bifurcation lesions and randomized to either BP-SES (n = 95) or PP-EES (n = 99). The primary endpoint was freedom from target lesion failure (TLF) composite endpoint [cardiac death, MI not clearly attributable to a non-target vessel, and clinically driven target lesion revascularization (TLR)] at 1-year. RESULTS: Baseline patient demographic, angiographic, and stenting characteristics were similar in both study arms. A single stent technique with provisional or "cross over" stenting were the most widely used in both arms (93.2% BP-SES vs. 92.4% PP-EES). Freedom from TLF at 1-year was 94.7% for BP-SES and 91.9% for PP-EES (P for noninferiority 0.031). The rate of clinically driven target lesion revascularization (TLR) at 1-year was 3.2% for BP-SES and 3.0% for PP-EES (P = 0.95). There were no significant differences detected in any of the individual clinical endpoints or other secondary clinical endpoints between the study arms at 1-year follow up. CONCLUSIONS: The new bioresorbable polymer sirolimus-eluting stent showed safety and efficacy profiles similar to durable polymer everolimus-eluting in the treatment of patients with bifurcation lesions at 1-year follow up. © 2015 Wiley Periodicals, Inc.

T-Wave Alternans Is Linked to Microvascular Obstruction and to Recurrent Coronary Ischemia After Myocardial Infarction.

The purpose of this study is to investigate the relationship between T-wave alternans (TWA), infarct size and microvascular obstruction (MVO) and recurrent cardiac morbidity after ST elevation myocardial infarction (STEMI). One hundred six patients underwent TWA testing 1-12 months and 57 patients underwent cardiac magnetic resonance imaging (MRI) in the first 2-4 days after STEMI. During follow-up (3.5 ± 0.5 years), death (n = 2), ventricular tachycardia (n = 3), supraventricular tachycardia (n = 4), heart failure (n = 3) and recurrent coronary ischemia (n = 25) were observed. After multivariate analysis, positive TWA (HR2.59, CI1.10-6.11, p0.024) and larger MVO (HR1.08, CI1.01-1.16, p0.034) were associated with recurrent angina or ACS. Presence of MVO was correlated with TWA (Spearman rho 0.404, p0.002) and the impairment of LVEF (-0.524, p < 0.001). Patients after STEMI remain at a high risk of symptoms of coronary ischemia. The presence of MVO and TWA 1-12 months after STEMI is related to each other and to recurrent angina or ACS.

Automatic segmentation of in-vivo intra-coronary optical coherence tomography images to assess stent strut apposition and coverage.

The implantation of intracoronary stents is currently the standard approach for the treatment of coronary atherosclerotic disease. The widespread adoption of this technology has boosted an intensive research activity in this domain, with continuous improvements in the design of these devices, aiming at reducing problems of restenosis (re-narrowing of the stented segment) and thrombosis (sudden occlusion due to thrombus formation). Recently, a new, light-based intracoronary imaging modality, optical coherence tomography (OCT), was developed and introduced into clinical practice. Due to its very high axial resolution (10-15 µm), it allows for in vivo evaluation of both stent strut apposition and neointima coverage (a marker of healing of the treated segment). As such, it provides valuable information on proper stent deployment, on the behaviour of different stent types in-vivo and on the effect of new types of stents (e.g. drug-eluting stents) on vessel wall healing. However, the major drawback of the current OCT methodology is that analysis of these images requires a tremendous amount of-currently manual-post-processing. In this manuscript, an algorithm is presented that allows for fully automated analysis of stent strut apposition and coverage in coronary arteries. The vessel lumen and stent struts are automatically detected and segmented through analysis of the intensity profiles of the A-lines. From these data, apposition and coverage can then be measured automatically. The algorithm was validated using manual assessments by two experienced operators as a reference. High Pearson's correlation coefficients were found (R = 0.96-0.97) between the automated and manual measurements while Bland-Altman analysis showed no significant bias with good limits of agreement. As such, it was shown that the presented algorithm provides a robust and fast tool to automatically estimate apposition and coverage of stent struts in in-vivo OCT pullbacks. This will be important for the integration of this technology in clinical routine and for the analysis of datasets of larger clinical trials.

Iatrogenic left main coronary artery dissection.

We present a case of iatrogenic left main coronary artery dissection, successfully treated by prompt bail-out stenting, and provide a brief discussion on its occurrence and treatment, as well as the immediate and long-term outcome of percutaneous coronary intervention, including our own single-centre experience, for this potentially catastrophic complication.

[Implementation of reperfusion therapy in ST segment elevation myocardial infarction (STEMI). A policy statement from the Belgian Society of Cardiology and its working group of acute cardiology and interventional cardiology]. / Mise en pratique du traitement de reperfusion dans les infarctus du myocarde avec élévation du segment ST (STEMI). Recommandations actualisées de la Société Belge de Cardiologie et de ses groupes de travail: le Groupe Interdisciplinaire de Cardiologie Aiguë (BIWAC) et le Groupe de Cardiologie Interventionnelle (BWGIC).

Myocardial infarction remains a major healthcare problem. Reperfusion therapy has been shown to influence favourably short- and long-term patient survival. The authors reviewed the data of early recognition of STEMI (ST Elevation Myocardial Infarction), the reperfusion modalities including a flowchart management, as proposed by the Belgian working groups (BIWAC and BWGIC), and the lessons learned from European and American registries. Primary PCI often remains the treatment of choice. A national policy is still required to implement the guidelines and improve clinical practice for our STEMI patients.

[Implementation of reperfusion therapy in ST segment elevation myocardial infarction (STEMI). A policy statement from the Belgian Society of Cardiology and its working group of acute cardiology and interventional cardiology]. / Mise en pratique du traitement de reperfusion dans les infarctus du myocarde avec élévation du segment ST.

Myocardial infarction remains a major healthcare problem. Reperfusion therapy has been shown to influence favourably short- and long-term patient survival. The authors reviewed the data of early recognition of STEMI (ST Elevation Myocardial Infarction), the reperfusion modalities including a flowchart management, as proposed by the Belgian working groups (BIWAC and BWGIC), and the lessons learned from European and American registries. Primary PCI often remains the treatment of choice. A national policy is still required to implement the guidelines and improve clinical practice for our STEMI patients.

A large-scale multicentre study of patient skin doses in interventional cardiology: dose-area product action levels and dose reference levels.

For 318 patients in 8 different Belgian hospitals, the entire skin-dose distribution was mapped using a grid of 70 thermoluminescence dosimeters per patient, allowing an accurate determination of the maximum skin dose (MSD). Dose-area product (DAP) values, exposure parameters and geometry, together with procedure, patient and cardiologist characteristics, were also registered. Procedures were divided into two groups: diagnostic procedures (coronary angiography) and therapeutic procedures (dilatation, stent, combined procedures (e.g. coronary angiography + dilatation + stent)). The mean value of the MSD was 0.310 Gy for diagnostic and 0.699 Gy for therapeutic procedures. The most critical projection for receiving the MSD is the LAO90 (left anterior oblique) geometry. In 3% of cases, the MSD exceeded the 2 Gy dose threshold for deterministic effects. Action levels in terms of DAP values as the basis for a strategy for follow-up of patients for deterministic radiation skin effects were derived from measured MSD and cumulative DAP values. Two DAP action levels are proposed. A first DAP action level of 125 Gy cm(2) corresponding to the dose threshold of 2 Gy would imply an optional radiopathological follow-up depending on the cardiologist's decision. A second DAP action level of 250 Gy cm(2) corresponding to the 3 Gy skin dose would imply a systematic follow-up. Dose reference levels - 71.3 Gy cm(2) for diagnostic and 106.0 Gy cm(2) for therapeutic procedures - were derived from the 75 percentile of the DAP distributions. As a conclusion, we propose that total DAP is registered in patient's record file, as it can serve to improve the follow-up of patients for radiation-induced skin injuries.

An investigation of flat panel equipment variables on image quality with a dedicated cardiac phantom.

Image quality (IQ) evaluation plays a key role in the process of optimization of new x-ray systems. Ideally, this process should be supported by real clinical images, but ethical issues and differences in anatomy and pathology of patients make it impossible. Phantom studies might overcome these issues. This paper presents the IQ evaluation of 30 cineangiographic films acquired with a cardiac flat panel system. The phantom used simulates the anatomy of the heart and allows the circulation of contrast agent boluses through coronary arteries. Variables investigated with influence on IQ and radiation dose are: tube potential, detector dose, added Copper filters, dynamic density optimization (DDO) and viewing angle. The IQ evaluation consisted of scoring 4 simulated calcified lesions located on different coronary artery segments in terms of degree of visualization. Eight cardiologists rated the lesions using a five-point scale ((1) lesion not visible to (5) very good visibility). Radiation doses associated to the angiograms are expressed in terms of incident air kerma (IAK) and effective dose that has been calculated with PCXMX software (STUK, Finland) from the exposure settings assuming a standard sized patient of 70 Kg. Mean IQ scores ranged from 1.68 to 4.88. The highest IQ scores were obtained for the angiograms acquired with tube potential 80 kVp, no added Cu filters, DDO 60%, RAO and LAO views and the highest entrance detector dose that has been used in the present study, namely 0.17 microGy/im. Radiation doses (IAK approximately 40 mGy and effective dose of 1 mSv) were estimated for angiograms acquired at 15 frames s(-1), detector field-of-view 20 cm, and a length of 5 s. The following parameters improved the IQ factor significantly: a change in tube potential from 96 to 80 kVp, detector dose from 0.10 microGy/im to 0.17 microGy/im, the absence of Copper filtration. DDO variable which is a post-processing parameter should be carefully evaluated because it alters the quality of the images independently of radiation exposure settings. The SAM anthropomorphic phantom has the advantage of visualization of stenotic lesions during the injection of a contrast agent and using an anatomical background. In the future, this phantom could potentially bridge the gap between physics tests and the clinical reality in the catheterization laboratory.

Prediction of the sound field above a patchwork of absorbing materials.

The aim of this paper is to investigate the acoustic performance of sound absorbing materials through a numerical wave based prediction technique. The final goal of this work is to get insight into the acoustic behavior of a combination of sound absorbing patches. In order to address a wide frequency range, a model based on the Trefftz approach is adopted. In this approach, the dynamic field variables are expressed in terms of global wave function expansions that satisfy the governing dynamic equations exactly. Therefore, approximation errors are associated only with the boundary conditions of the considered problem. This results in a computationally efficient technique. The main advantage of this method is the fact that the sound absorbing patches do not have to be locally reacting. In this article, the wave based method is described and experimentally validated for the case of normal incidence sound absorption identification in a standing wave tube. Afterwards, the method is applied to simulate some interesting setups of absorbing materials.

Radiation dose survey in a paediatric cardiac catheterisation laboratory equipped with flat-panel detectors.

Flat-panel X-ray detectors for fluoroscopy represent a modern imaging equipment that is being implemented in paediatric cardiac catheterisation laboratories. Infants and children represent a group of patients with a high radiosensitivity. A survey of 273 (126 diagnostic and 147 therapeutic) paediatric catheterisations was performed to investigate the radiation doses delivered by the new X-ray system. Statistical parameters (75th, 50th and 25th percentiles) of dose-area product (DAP) and fluoroscopy time are reported for patients divided into six age groups: 0-30 d, >1-12 m, >1-3, >3-5, >5-10 and >10-15 y. For accurate risk estimation, effective dose (E) has been determined for all patients using the PCXMC software. For diagnostic procedures, the third quartile of E ranges from 11.3 mSv for newborns to 7 mSv for children of 10-15 y. Therapeutic procedures are more complex than diagnostic. Consequently, the third quartile of E is 22.6 mSv (0-30 d), 18.6 (>1-12 m), 13.3 (>1-3 y), 21.5 (>3-5 y), 17.8 (>5-10 y) and 34.1 mSv (>10-15 y). Dose conversion factors, which relate the DAP and E, have been estimated for each age group. The results of this study may serve as a first step in the optimisation process, in order to make full use of the dose reduction potential of flat-panel systems.

Cardiac compression by a thymic cyst.

A patient with a giant thymic cyst, causing cardiac compression, is presented. Thymic cysts are uncommon and often asymptomatic.

La hiperglicemia de ingreso se asocia a mayor mortalidad en pacientes con infarto agudo al miocardio y supradesnivel del ST sometidos a angioplastía primaria / Hyperglycemia is associated to increased mortality rate in patients with acute myocardial infarction undergoing primary angioplasty

Antecedentes: La hiperglicemia es habitual en los pacientes graves, tales como quienes cursan con un infarto al miocardio con supradesnivel del ST (IAMSDST). Los registros han demostrado que la hiperglicemia de ingreso es un marcador certero de mortalidad durante un IAM, especialmente en aquellos no diagnosticados previamente como diabéticos. Objetivos: El objetivo de este estudio fue establecer la relación entre los niveles de glicemia al ingreso y la mortalidad intrahospitalaria de pacientes cursando IAMSDST sometidos a angioplastía primaria. Métodos: Se analizaron 273 pacientes consecutivos sometidos a angioplastía primaria o de rescate (después de trombolisis fallida) entre junio de 2003 y mayo de 2005. En 234 de ellos se midió la glicemia dentro de las primeras 6 horas del ingreso. Se dividió a los pacientes en cuatro grupos según la glicemia: hasta 125 mg/dl, 126-150 mg/dl, 151-200 mg/dl y, mayor a200 mg/dl. Se registró la mortalidad intrahospitalaria y la ocurrencia de eventos cardíacos mayores (MACE: muerte, infarto no fatal, revascularización). Resultados: La mortalidad total fue de 9,4 por ciento y la ocurrencia de MACE fue 13,6 por ciento. La mortalidad aumentó significativamente conforme aumentaba la glicemia. Los pacientes con niveles altos de glicemia presentaron un riesgo mayor de shock cardiogénico. Los niveles de glicemia se correlacionaron con el tamaño del infarto medido como niveles de CK total (p<0.001). El análisis multivariado señaló como marcadores independientes de mortalidad intrahospitalaria a la disfunción ventricular (p=0,006) y a la glicemia mayor de 150 mg/dl (p=0,023)Conclusión: Los niveles de glicemia al ingreso se asocian a mayor mortalidad intrahospitalaria en pacientes con IAMSDST sometidos a angioplastía primaria.

Radiation dose levels during interventional cardiology procedures in a tertiary care hospital.

The aim of our investigation was to prospectively measure the patient radiation exposure from different cardiological procedures performed in the Catheterisation laboratory of the University Hospital Gasthuisberg in Leuven. The following local reference values were proposed: 40, 47 and 80 Gycm2 for coronary angiography (CA) or angioplasty (PTCA and stent implantation for elective patients), radio frequency ablation with angiographic images and CA plus ad hoc PTCA, respectively.

Image quality criteria in cardiology.

Image quality evaluation plays a key role in the process of optimisation in radiological procedures. Image quality criteria for cardiac cine-angiography were recently agreed as part of a European Research Project, and a scoring system based on these criteria has been developed to allow an 'objective' measurement of the quality of cardiac angiograms. Two studies aimed at the evaluation of the methodology have been completed, demonstrating that the method can be applied to cardiac images and translated into a scoring system that yields reproducible data. Based on the results of these studies, quality criteria have been further reviewed by DIMOND III panel and the updated version is presented in this paper.