1,720,979 research outputs found
Determinants of myocardial work indices in women
No full textBy incorporating myocardial deformation and afterload, novel echocardiographic myocardial work indices appear to be advantageous compared to load-dependent left ventricular (LV) deformation analyses. As such, these indices may provide a more accurate and, above all, load-independent estimation of LV function in patients with chronically increased afterload. To date however, data on the relation of these indices to clinical and conventional echocardiographic parameters are scarce. Purpose: Our aim was to evaluate the relationship between myocardial work indices and age, body mass index (BMI), NTproBNP, the clinical history of arterial hypertension and diastolic dysfunction as well as selected conventional echocardiographic parameters in women. We analyzed echocardiographic data of women included in the Berlin Female Risk Evaluation (BEFRI) trial. Global Work Index (GWI), Global Constructive Work (GCW), Global Wasted Work (GWW), and Global Work Efficiency (GWE) were calculated using commercially available software based on noninvasive pressure-strain loops. The impact of selected clinical and echocardiographic characteristics on myocardial work parameters was investigated by uni- and multivariate regression analyses. A total of 224 women were included in the final analysis. One hundred fifty-five of them were normotensive and 69 had a history of arterial hypertension. Diastolic dysfunction was more prevalent in subjects with arterial hypertension. Study participants with arterial hypertension showed higher GWI and GCW, whereas GWW and GWE did not significantly differ between groups. GCW and GWW were lower and GWE higher in the presence of normal diastolic function. In multivariate regression analyses, arterial hypertension, LV GLS, and interventricular septal thickness were significantly associated with GWI. GCW showed significant associations with the clinical history of arterial hypertension, LV GLS, age, and IVRT. Similarly, LV GLS, IVRT, and mitral inflow E wave deceleration time were identified to be significant determinants of GWW and GWE. Our data confirm that, in a randomly selected sample of the general urban female population, myocardial work parameters are predominantly determined by LV GLS. In addition, the presence of arterial hypertension was identified to be a significant determinant of GWI and GCW, but not for GWW and GWE. Finally, a prolonged LV relaxation time was significantly associated with GWW and GWE, suggesting more wasted myocardial work and lower GWE values with increasing LV relaxation time.This study was supported by the DZHK (German Centre for Cardiovascular Research) and by the BMBF (German Ministry of Education and Research)
Konventionelle Echokardiographie und Strain Imaging für die Vorhersage des kurzfristigen Verlaufs von idiopathischer dilatativer Kardiomyopathie
No full textIn the light of continuous prolongation of the waiting time on heart
transplantation (HTx) lists, the need for reliable predictors of the time
course of heart failure (HF) has become increasingly important. Thus, the aim
of our study was to evaluate the prognostic value of echocardiography
including 2D strain imaging in patients with end-stage idiopathic dilated
cardiomyopathy (IDCM). The study population comprised 38 consecutive stable
IDCM patients referred for HTx. At the baseline all of them underwent standard
echocardiography, during which views for radial, circumferential and
longitudinal strain and strain rate measurements were stored. Strain imaging
was used to acquire radial, circumferential and longitudinal endsystolic
strains (ESS), peak systolic strain rates (SSRmax), as well as early and late
diastolic strain rate (DSRE and DSRA, respectively). Dyssynchrony indexes were
also calculated from strain images. For quantification of systolic
intraventricular dyssynchrony the coefficient of variance of time interval
from the beginning of QRS complex to peak systolic strain at separate segments
was used. Echocardiographic parameters were analyzed to find significant
differences between the groups. Their value in predicting the time course of
HF during the following 6 months was tested. During the first 6 months after
inclusion in the study, 18 patients remained stable; the other 20 showed
severe cardiac deterioration and finally 14 of them underwent ventricular
assist implantation and 6 died, although initially there were no significant
differences in peak oxygen consumption, left ventricular size, ejection
fraction or other parameters describing systolic function. However, at the
baseline, patients who remained stable had lower NT-proBNP values and less
altered diastolic function in comparison to those with rapid HF progression.
Thus, stable patients had significantly lower flow Doppler and strain imaging
derived E/A ratios, longer transmitral E wave deceleration time and higher
late diastolic strain rate (DSRA) values). They also had significantly lower
systolic circumferential and longitudinal dyssynchrony indexes and higher
longitudinal systolic strain and strain rate values. Diastolic parameters
correlated strongly with NT-proBNP, which is known to be elevated in patients
with HF, whereas systolic dyssynchrony indexes showed moderate correlations
with this marker. No correlations between peak oxygen consumption and
echocardiographic parameters were observed. At certain cut-off values flow
Doppler and strain imaging derived diastolic parameters, as well as systolic
dyssynchrony indexes showed high predictive values for cardiac stability over
the next 6 months. Highest positive predictive values for rapid HF progression
were found for transmitral E decelaration time (DT) <100ms, late diastolic
strain rate (DSRA) 2
(88%, 89% and 85%, respectively). Thus in patients with advanced idiopathic
DCM and similar LVEF (<30%), further cardiac stability appeared to be related
to the severity of alterations in LV systolic synchronicity and diastolic
function. Transmitral flow Doppler and strain imaging parameters can be
recommended as short-term prognostic factors in these patients. Moreover,
strain imaging is a highly reproducible, not time consuming and a very useful
method, as it allows a better understanding of HF pathophysiology and throws
light on the progress of this syndrome in individual patients. This extensive
approach to the problem is essential while making decisions of vital
importance, such as patient listing for high-urgency Tx.Der Mangel an Spenderorganen verlängert zunehmend die Wartezeiten auf den
Transplantations-Listen. Der klinische Verlauf nach Herztransplantation (HTx)
- Listung ist bei Patienten mit idiopathischer dilatativer Kardiomyopathie
(IDCM) unterschiedlich und schwer vorhersehbar. Die frühzeitige Erkennung
einer potentiell vitalen Gefährdung könnte das Outcome der Patienten
wesentlich verbessern. Deswegen war unser Ziel echokardiographische Parameter
mit prognostischem Wert für die kurzfristige Vorhersage des klinischen
Verlaufs bei schwerer IDCM zu suchen. Für unsere Studie haben wir 38 stabile
Patienten mit End-Stage IDCM, die für HTx gelistet sind, aufgenommen. Am
Ausgang wurde für alle Patienten die konventionelle Echokardiographie und das
2D Strain Imaging durchgeführt. Von den 2D Strain Imaging Bildern haben wir
radialen, zirkumferenziellen und longitudinalen endsystolischen Strain (ESS),
maximalen systolischen Strain Rate (SSRmax), frühen und späten diastolischen
Strain Rate (DSRE und DSRA,). Um die Dyssynchronizität des linken Ventrikels
zu bewerten haben wir den Variationskoeffizient der Zeit zwischen QRS Beginn
und maximalem Strain in den unterschiedlichen Segmenten berechnet.
Prognostischer Wert von diesen Parametern wurde für die 6 Monate des Verlauf
von IDCM überprüft. Nach 6 Monaten sind 18 von den Patienten klinisch stabil
geblieben und 20 haben sich klinisch verschlechtert, obwohl es am Anfang der
Studie keine signifikanten Unterschiede hinsichtlich maximalem
Sauerstoffverbrauch, Dimensionen und Ejektions Fraktion des linken Ventrikels
oder anderen konventionellen systolischen Parametern gab. Allerdings hatten
die Patienten, die stabil geblieben sind, am Ausgang eine bessere diastolische
Funktion. Sie haben ein kleineres E/A Verhältnis, längere E Dezelerationszeit,
sowie größere spät diastolische Strain Rate (DSRA) als die Patienten, dessen
Zustand sich später verschlechterte, gehabt. Außerdem war die
zirkumferenzielle und longitudinale Dyssynchronizität mehr ausgeprägt in die
Gruppe von instabilen Patienten. Wir haben starke Korrelationen zwischen
diastolischen Parametern und NT-proBNP gefunden. Die Korrelationen zwischen
dem Dyssynchronizitätsparameter und NT-proBNP waren mittelmäßig.
Echokardiographische Parameter haben nicht mit maximalem Sauerstoffverbrauch
korreliert. Diastolische sowie Dyssynchronizitätsparameter haben starken
prädiktiven Werten für die kurzfristige Stabilität der Patienten mit IDCM. Die
besten positiven prädiktiven Werte für klinische Verschlechterung haben E
Dezelarationszeit (DT) <100ms, spät diastolische Strain Rate (DSRA) <0.3/s und
von 2D Strain Imaging bewertetes E/A (DSRE/A) >2 (entsprechend 88%, 89% and
85%). Die Stabilität von IDCM Patienten scheint abhängig von diastolischer
Funktion und Synchronizität des linken Ventrikels zu sein. Tranmitrales Fluss
Doppler und 2D Strain Imaging sind wenig Zeit verbrauchende und gut
reproduzierbare Methoden, die den kurzfristigen Verlauf von diesen Patienten
vorhersagen können. Die beiden Methoden könnten durch frühzeitige Erkennung
einer potentiell vitalen Gefährdung das Outcome der Patienten wesentlich
verbessern
De intraventriculaire relatie tussen rek en verkorting, een nieuwe echocardiografische parameter van linker ventrikel contractiliteit
No full textThe goal of this Ph.D. project was to propose and clinically validate anon-invasive echocardiographic estimate of intrinsic left ventricular (LV) contractility. Indeed, such an index is currently missing in clinical routine, even though it could be very useful in multiple clinical settings, as for example in monitoring heart failure treatment, in selectingpatients with valvular heart disease for surgical treatment or in detecting early cardiac damage in patients with systemic disease. Before describing the studies that were undertaken to reach this goal, thebasic mechanisms of cardiac contraction, needed to understand the concept of intrinsic cardiac contractility, are described and a short overview of the main contractility parameters proposed so far is given in the first part of this thesis manuscript. Besides that, the general principles and possible clinical applications of the echocardiographic myocardialdeformation imaging methods that were employed in all the studies of this project are explained. In the second part of the thesis a novel non-invasive echocardiographic estimate of intrinsic left ventricular contractility is described. This index is based on the dependency of regional systolic LV strain (SS) on late diastolic stretch (preS), which was measured as a relative change of LV segmental length during atrial contraction from adapted myocardial deformation imaging curves. In analogy to the Frank Starling concept and to the experimental studies, the preS SS relationship got steeper with a pharmacologically induced increase of LV contractility, flattened after the exposure to a cardiotoxic drug and remained the same during the preload induced increase of LV systolic function. We have also found that in spite of increasing late diastolic stretch in the elderly, the slope of this relationship does not change with age. Further on, it was shown that the intraventricular distribution of passive late diastolic stretch is very consistent between individuals. As the flatter LV walls were stretched more than the more spherical walls, we have suggested that regional heterogeneity of passive LV deformation is related to the regional differences of wall stress. Our results have also shown that the spatial intraventricular distribution of regional systolic strain is very similar to that of passive diastolic stretch, which confirmed that a major part of intraventricular systolic strain variability could be explained by segmental differences in diastolic stretch as a direct consequence of the Frank Starling mechanism. Last but not least, we wanted to extend the stretch-strain methodology from TDI to a more widely used 2D speckle tracking (ST) and to the novel and very promising 3D strain estimation (SE) method. Hereto, a clinical validation of the chosen 3DSE was performed first. In this study 3DSE was compared to the widely clinically accepted 2DST method. After showing good agreement between global and fair agreement between regional strain values obtained with those two techniques, aseparate pilot study was performed to test the suitability of the 2D and3D myocardial deformation imaging approaches for the extraction of the stretch strain relationship. With both of those techniques individual longitudinal preS SS relationships obtained in healthy LVs at rest were similar to what we have previously observed with TDI. However, the slopes and intercepts of circumferential stretch strain relationships were widely spread. Only averaging the segmental deformation values improved the correlation between preS and SS and gave the same regression equation as observed with the longitudinal strain component. We attributed this to the high intramural gradient of the circumferential strain component, and concluded that differently from the longitudinal, the circumferential stretch strain relationship is not suitable for individual use. Of course, whether, 2D and 3D derived longitudinal stretch strain is capable to detect changes in global LV contractility still remains to be tested in the future. Besides that, an experimental validation study, which would also reveal the effect of afterload on this index remains to be performed in the future.status: Publishe
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Machine learning of the spatio-temporal characteristics of echocardiographic deformation curves for infarct classification
No full textThe aim of this study was to analyze the whole temporal profiles of the segmental deformation curves of the left ventricle (LV) and describe their interrelations to obtain more detailed information concerning global LV function in order to be able to identify abnormal changes in LV mechanics. The temporal characteristics of the segmental LV deformation curves were compactly described using an efficient decomposition into major patterns of variation through a statistical method, called Principal Component Analysis (PCA). In order to describe the spatial relations between the segmental traces, the PCA-derived temporal features of all LV segments were concatenated. The obtained set of features was then used to build an automatic classification system. The proposed methodology was applied to a group of 60 MRI-delayed enhancement confirmed infarct patients and 60 controls in order to detect myocardial infarction. An average classification accuracy of 87% with corresponding sensitivity and specificity rates of 89% and 85%, respectively was obtained by the proposed methodology applied on the strain rate curves. This classification performance was better than that obtained with the same methodology applied on the strain curves, reading of two expert cardiologists as well as comparative classification systems using only the spatial distribution of the end-systolic strain and peak-systolic strain rate values. This study shows the potential of machine learning in the field of cardiac deformation imaging where an efficient representation of the spatio-temporal characteristics of the segmental deformation curves allowed automatic classification of infarcted from control hearts with high accuracy
- …
