The wear phenomena and wear characteristics of reciprocating sliding wear with superimposed lateral vibrations were investigated using a ball-on-disc tribometer. The tribometer enabled two orthogonal ...oscillations, whereas one oscillation had a constant amplitude of 1mm (primary oscillation) and the other one had a variable amplitude from 0 to 20.2μm (secondary oscillation). Ball and disc were made of AISI 52100 steel. The ball surface was polished and the disc surface was unidirectionally grinded parallel to the direction of primary oscillation. Two regimes with different wear rates were found, being separated by a characteristic transition amplitude of 2.7±0.4μm in the secondary oscillation. This transition correlated with a change of wear mechanisms from tribochemically to mechanically dominated wear. A wear model based on surface topography and particle motion was developed. The wear model is able to predict the value of the transition amplitude by means of characteristic topographical data and the size of wear particles.
Aims We sought to assess the feasibility of catheter-based mitral valve repair using the MitraClip system in high-surgical-risk patients with mitral regurgitation (MR) ≥grade 3+. Methods and results ...MitraClip therapy was performed in 51 consecutive patients 73 ± 10 years; 34 (67%) men with symptomatic functional n = 35 (69%) or organic MR n = 16 (31%). Mean logistic EuroSCORE was 29 ± 22%; Society of Thoracic Surgeons score was 15 ± 11. Left ventricular (LV) ejection fraction was 36 ± 17%. In 35 patients (69%), adverse mitral valve morphology and/or severe LV dysfunction were present. MitraClip implantation was successful in 49 patients (96%). Most patients n = 34/49 (69%) were treated with a single clip, whereas 14 patients (29%) received two clips and one patient received three clips. Mean device and fluoroscopy times were 105 ± 65 min and 44 ± 28 min, respectively. Procedure-related reduction in MR severity was one grade in 16 patients (31%), two grades in 24 patients (47%), and three grades in 9 patients (18%). Forty-four of the 49 successfully treated patients (90%) showed clinical improvement at discharge NYHA functional class ≥III in 48 patients (98%) before and 16 patients (33%) after the procedure (P < 0.0001). There were no procedure-related major adverse events and no in-hospital mortality. Conclusion Mitral valve repair using the MitraClip system was shown to be feasible in patients at high surgical risk primarily determined by an adverse mitral valve morphology and/or severe LV dysfunction.
The 4th universal definition of myocardial infarction consensus document is a further development of the document from 2012. It highlights the discrimination between myocardial injury and infarction ...and in particular the periprocedural occurrence of increased troponin levels. The chapter on cardiac biomarkers deals with the problems of comparison of various troponin assays and the kinetics of troponin in acute myocardial infarction. The definition of the 5 types of myocardial infarction underwent only minor changes. In the chapter on ECG interpretation high-risk constellations are described. A total of six new chapters were added to the consensus document including the takotsubo syndrome and myocardial infarction with non-obstructive coronary arteries (MINOCA), which are briefly discussed.
Zusammenfassung
Die 4. Allgemeine Definition des Myokardinfarkts ist eine Weiterentwicklung der Version aus dem Jahr 2012. Sie legt besonderen Wert auf die Abgrenzung zwischen Myokardschaden und ...Myokardinfarkt, insbesondere bei periprozedural auftretenden Troponinerhöhungen. Im Kapitel „Biomarker“ wird auf die Problematik der Vergleichbarkeit verschiedener Troponinassays und auf die Troponinverlaufskurve beim akuten Myokardinfarkt eingegangen. Die Definition der 5 Infarkttypen erfuhr geringe Veränderungen. Im Kapitel „EKG-Interpretation“ werden Hochrisikokonstellationen beschrieben. 6 neue Kapitel wurden in die aktuelle Definition eingebracht, darunter das Tako-Tsubo-Syndrom und MINOCA („myocardial infarction with non-obstructive coronary arteries“), auf die kurz eingegangen wird.
Fundamental microtribological properties such as the interaction force between surfaces, friction, and wear are studied by performing atomic and lateral force microscopy measurements on Au(001) under ...ultrahigh vacuum conditions. The system tip/sample surface is treated as a model-like micromechanical system in sliding motion. The adhesion force appears to be a substantial contribution to the interaction force between tip and sample surface. The wear of the Au(001) surface is estimated and its impact is discussed, identifying elastic deformation as the main dissipative contribution to the friction process. Combining the results of the friction study with those of the adhesion force measurements, the friction behavior of the microsystem is favored to be explained by a sliding single-asperity contact.
The impact of incomplete stent apposition (ISA) after drug-eluting stent implantation determined by intravascular ultrasound (IVUS) on late clinical events is not well defined.
To evaluate the ...clinical impact of ISA after sirolimus-eluting stent (SES) placement during a follow-up period of 4 years.
Pooled analysis from the RAVEL, E-SIRIUS and SIRIUS trials, three randomised, multicentre studies comparing SES and bare-metal stents (BMS).
IVUS at angiographic follow-up was available in 325 patients (SES: n = 180, BMS: n = 145). IVUS images were reviewed for the presence of ISA defined as one or more unapposed stent struts. Clinical follow-up was available for a 4-year period in all patients. Frequency, predictors and clinical sequel of ISA at follow-up after SES and BMS implantation were determined.
ISA at follow-up was more common after SES (n = 45 (25%)) than after BMS (n = 12 (8.3%), p<0.001). Canadian Cardiology Society class III or IV angina at stent implantation (odds ratio (OR) = 4.69, 95% CI 2.15 to 10.23, p<0.001) and absence of diabetes (OR = 3.42, 95% CI 1.05 to 11.1, p = 0.041) were predictors of ISA at follow-up after SES placement. Rate of myocardial infarction tended to be slightly higher for ISA than for non-ISA patients. When SES patients only were considered, major adverse cardiac event free survival at 4 years was identical for those with and without ISA at follow-up (11.1% vs 16.3%, p = 0.48).
ISA at follow-up is more common after SES implantation than after BMS implantation. Considering the current very sensitive IVUS definition, ISA appears to be an IVUS finding without significant impact on the incidence of major adverse cardiac events even during long-term follow-up.
Over the past 25 years carotid artery stenting (CAS) has emerged as an alternative to carotid endarterectomy (CEA). Most of all younger patients and symptomatic patients with contralateral carotid ...artery occlusion particularly benefit from CAS. To achieve an optimal result with CAS, patient selection and even more important, knowledge and experience of the interventionist is crucial. The periprocedural complication rate of CAS in large experienced centers is lower (2-3%) than those in randomized trials. Several different devices are now available which allow the procedure to be tailored according to patient anatomy and lesion complexity. Complications like hyperperfusion syndrome and intracerebral bleeding, rupture of side branches of the external or internal carotid artery as well as problems caused by slow flow can be widely avoided by adequate experience.
Technik der Karotis-PTA Schofer, J.; Bijuklic, K.
Herz,
11/2013, Letnik:
38, Številka:
7
Journal Article
Recenzirano
Zusammenfassung
Die Stentbehandlung von Stenosen der A. carotis (CAS) ist zu einer Alternative für die Karotisendatherektomie (CEA) herangereift. Vor allem jüngere Patienten und symptomatische ...Patienten mit einer kontralateralen Okklusion der A. carotis profitieren von einer CAS-Prozedur. Die Auswahl des geeigneten Patienten, ausreichende Erfahrung mit verschiedenen Techniken der Prozedur sowie die Kenntnis der Strategien zur Vermeidung und Beherrschung von Komplikationen sind unabdingbare Voraussetzung für eine erfolgreiche Prozedur. In Zentren mit großer Erfahrung liegt die periprozedurale Komplikationsrate heutzutage mit 2–3% deutlich unter der in randomisierten Studien berichteten. Mit fachgerechter Anwendung der verschiedenen zur Verfügung stehenden Devices lässt sich die Prozedur auf den individuellen Patienten zuschneiden. Komplikationen wie Hyperperfusion und intrazerebrale Blutung, Ruptur von Seitenästen der A. carotis externa oder der A. carotis interna sowie Probleme, die durch „slow flow“ entstehen, lassen sich mit ausreichender Erfahrung weitgehend vermeiden.
PDF
