7 research outputs found
The function of right ventricle in patients with arterial hypertension
No full textArterial hypertension is nowadays one of the biggest health problems worldwide consisting the main risk factor for cardiovascular disease. Long-term hypertension leads to increased afterload, diastolic dysfunction and concentric hypertrophy of the left ventricular walls. In addition to the effect on the left ventricle, arterial hypertension also affects the function of the right ventricle by increasing the thickness of the interventricular septum and the right ventricular free wall. The role of the renin-angiotensin-aldosterone system (RAAS) in the pathophysiology of arterial hypertension is well established and RAAS inhibition consists a primary therapeutic goal in the management of hypertension. Two kinds of RAAS inhibitors are widely used in the management of hypertension, the angiotensin converting enzyme inhibitors (ACEi) and the angiotensin receptor-1 blockers (ARBs). RAAS inhibitors have been shown not only to reduce blood pressure but to reduce left ventricular hypertrophy and hypertension induced myocardial fibrosis as well. The effects of hypertension and antihypertensive treatment on left ventricular function have been widely studied. However, limited data exist regarding the effects of antihypertensive treatment on the right ventricular function in patients with systematic hypertension. The current thesis is the first that aims to explore the effect of hypertension and antihypertensive treatment with RAAS inhibitors on the function of the right ventricle by using old and new echocardiographic modalities, specifically by tissue Doppler imaging, strain and strain rate in patients who have never before been treated with antihypertensive agents. The study population consisted of 40 patients recently diagnosed with essential arterial hypertension. These patients were drawn by the population of the hypertensives that visited the Arterial Hypertension Clinic of the first Propaedeutic Department of AHEPA Hospital, Thessaloniki. Patients with secondary hypertension, coronary artery disease, valvulopathies, cardiomyopathy, heart failure, congenital heart disease, atrial fibrillation or other arrhythmia, diabetes mellitus, renal failure, liver failure, chronic pulmonary disease, history of malignancy, malignant obesity or systematic use of drugs that affect blood pressure (such as non steroid anti-inflammatory drugs and corticosteroids) were excluded from the study. Selected patients underwent echocardiographic examination at the echocardiography laboratory of the first Cardiology Department of AHEPA Hospital. Subsequently, they were administered antihypertensive treatment with an ACE inhibitor or an ARB. After 9 months of follow up the patients underwent a second echocardiographic examination. All patients underwent a complete echocardiographic examination with special focus on the right ventricle. Data were stored into digital magneto-optical discs and were analyzed off line. After the acquisition of the demographic, clinical and echocardiographic data, statistical analysis of the parameters at the baseline and 9 months after antihypertensive treatment was done. Results are as follows: Among the classical echocardiographic parameters of the right ventricle, the only one that changed was the right ventricular free wall thickness, which was reduced after 9 months of treatment, in concordance with the reduction of the interventricular septum thickness and the left ventricular mass index. There was a positive correlation between the E/A ratio of the transmitral flow and the E/A ratio of the transtricuspid flow both at the baseline and after 9 months of treatment. A correlation between the systolic and the diastolic blood pressure reduction and a poor correlation between the reduction of the systolic pressure and the reduction of the interventricular septum thickness were also observed. The myocardial performance index (Tei index) of the right ventricle was reduced after 9 months of treatment, in concordance with the Tei index of the left ventricle. The reduction of the Tei index of the left and the right ventricle did not correlate neither with the reductions in the interventricular septum thickness and the right ventricular free wall thickness, nor with the reductions in systolic and diastolic blood pressure. The right ventricular systolic strain was increased in absolute value, after 9 months of treatment with RAAS inhibitors, both at the basal and at the mid segments of the right ventricular free wall, while no correlation was found between the change in the systolic and diastolic pressure and the change in maximal systolic strain. From the analysis of the results we came into the following conclusions: - A reduction of the right ventricular free wall thickness was observed, as well as a reduction of the interventricular septum thickness in patients with mild essential hypertension, after 9 months of antihypertensive treatment. -There was an improvement of the impaired diastolic function of the right ventricle with a reduction in the myocardial performance index (Tei index), after 9 months of antihypertensive treatment. - Using the echocardiographic modality of strain, an improvement of the systolic function of the right ventricle was observed after antihypertensive treatment in the early stages of hypertension. - The RAAS inhibition with ACE inhibitors or ARBs has improved the function of the right ventricle, as measured by contemporary echocardiographic modalities, in patients with mild hypertension. - The above beneficial effects of RAAS inhibition seem to be independent of the reduction in blood pressure and they may be possibly attributed to the reduction of the structural myocardial lesions.Η αρτηριακή υπέρταση αποτελεί σήμερα ένα από τα μεγαλύτερα προβλήματα της παγκόσμιας υγείας και το βασικότερο παράγοντα κινδύνου για εμφάνιση καρδιαγγειακής νόσου. Η μακροχρόνια αυξημένη ΑΠ οδηγεί σε αύξηση του μεταφορτίου, διαστολική δυσλειτουργία και συγκεντρική υπερτροφία των τοιχωμάτων της αριστερής κοιλίας. Παράλληλα με την επίδραση στην αριστερή κοιλία η αρτηριακή υπέρταση επηρεάζει δυσμενώς και τη διαστολική λειτουργία της δεξιάς κοιλίας, μέσω της πάχυνσης του μεσοκοιλιακού διαφράγματος και του ελεύθερου τοιχώματός της. Ο ρόλος του ΣΡΑΑ στην παθοφυσιολογία της αρτηριακής υπέρτασης είναι τεκμηριωμένος και η αναστολή του αποτελεί πρωτεύοντα θεραπευτικό στόχο στην αντιμετώπιση της υπέρτασης. Δύο είδη αναστολέων του ΣΡΑΑ χρησιμοποιούνται ευρέως στην αντιμετώπιση της υπέρτασης, οι αναστολείς του μετατρεπτικού ενζύμου της αγγειοτενσίνης (αΜΕΑ) και οι αναστολείς των υποδοχέων 1 της αγγειοτενσίνης (αναστολείς ΑΤ-1). Οι αναστολείς του ΣΡΑΑ φαίνεται ότι εκτός από το να μειώνουν την ΑΠ περιορίζουν την υπερτροφία της αριστερής κοιλίας και ελαττώνουν την επαγόμενη από την υπέρταση μυοκαρδιακή ίνωση. Η επίδραση της υπέρτασης και της αντιυπερτασικής αγωγής στη λειτουργικότητα της αριστερής κοιλίας έχει μελετηθεί εκτενώς. Εντούτοις, υπάρχουν περιορισμένα δεδομένα σχετικά με την επίδραση της αντιυπερτασικής αγωγής στη λειτουργικότητα της δεξιάς κοιλίας σε ασθενείς με συστηματική υπέρταση. Η παρούσα διδακτορική διατριβή αποτελεί την πρώτη ερευνητική εργασία με σκοπό να μελετήσει την επίδραση της υπέρτασης και της αντιυπερτασικής αγωγής με αναστολείς του ΣΡΑΑ στη λειτουργικότητα της δεξιάς κοιλίας με όλες τις προυπάρχουσες καθώς και με νεότερες υπερηχογραφικές μεθόδους και συγκεκριμένα με το ιστικό Doppler, το strain και το strain rate, σε ασθενείς που δεν έχουν λάβει καμία αντιυπερτασική αγωγή στο παρελθόν. Υλικό της μελέτης αποτέλεσαν 40 ασθενείς με πρόσφατη διάγνωση ιδιοπαθούς αρτηριακής υπέρτασης. Οι ασθενείς αυτοί επιλέχθηκαν από τον πληθυσμό των υπερτασικών που προσήλθε στα Τακτικά Εξωτερικά Ιατρεία Αρτηριακής Υπέρτασης της Α΄ Προπαιδευτικής Κλινικής ΑΠΘ του Νοσοκομείου ΑΧΕΠΑ. Από τη μελέτη αποκλείστηκαν ασθενείς με δευτεροπαθή υπέρταση, στεφανιαία νόσο, βαλβιδοπάθεια, μυοκαρδιοπάθεια, καρδιακή ανεπάρκεια, συγγενή καρδιοπάθεια, κολπική μαρμαρυγή ή άλλη αρρυθμία, σακχαρώδη διαβήτη, νεφρική ανεπάρκεια, ηπατική ανεπάρκεια, χρόνια πνευμονική νόσο, ιστορικό κακοήθειας, κακοήθη παχυσαρκία ή συστηματική λήψη φαρμάκων που επιδρούν στην αρτηριακή πίεση (όπως μη στεροειδή αντιφλεγμονώδη και κορτικοειδή). Οι ασθενείς που πληρούσαν τα παραπάνω κριτήρια, υποβλήθηκαν σε υπερηχοκαρδιογραφικό έλεγχο στο Εργαστήριο Ηχοκαρδιογραφίας της Α΄ Καρδιολογικής Κλινικής ΑΠΘ του Νοσοκομείου ΑΧΕΠΑ. Στη συνέχεια χορηγήθηκε αντιυπερτασική αγωγή με έναν αναστολέα ΜΕΑ ή με έναν ανταγωνιστή των υποδοχέων αγγειοτενσίνης με στόχο τη ρύθμιση της αρτηριακής πίεσης. Μετά από 9 μήνες παρακολούθησης οι ασθενείς υποβλήθηκαν εκ νέου σε υπερηχοκαρδιογραφικό έλεγχο. Όλοι οι ασθενείς υποβλήθηκαν σε πλήρη υπερηχοκαρδιογραφικό έλεγχο και το ενδιαφέρον εστιάστηκε στη δεξιά κοιλία. Τα δεδομένα καταγράφηκαν, αποθηκεύτηκαν και οι μετρήσεις έγιναν σε δεύτερο χρόνο. Μετά την καταγραφή των δημογραφικών, κλινικών και υπερηχογραφικών δεδομένων, ακολούθησε η στατιστική ανάλυση και επεξεργασία των παραμέτρων πριν από την έναρξη της αντιυπερτασικής αγωγής και 9 μήνες μετά. Τα αποτελέσματα έχουν ως εξής: Από τις κλασσικές υπερηχογραφικές παραμέτρους, η μόνη που παρουσίασε μεταβολή ήταν το πάχος του ελεύθερου τοιχώματος της δεξιάς κοιλίας, το οποίο ελαττώθηκε μετά την 9μηνη θεραπεία, κατά αντιστοιχία της ελάττωσης του πάχους του μεσοκοιλιακού διαφράγματος και του δείκτη μάζας της αριστερής κοιλίας. Παρατηρήθηκε θετική συσχέτιση ανάμεσα στο λόγο Ε/Α της διαμιτροειδικής και της διατριγλωχινικής ροής τόσο κατά την αρχική μελέτη, όσο και μετά 9 μήνες θεραπεία. Επίσης παρατηρήθηκε συσχέτιση ανάμεσα στη μείωση της συστολικής και της διαστολικής αρτηριακής πίεσης και ασθενής συσχέτιση της μείωσης της συστολικής αρτηριακής πίεσης με την ελάττωση του πάχους του μεσοκοιλιακού διαφράγματος. Ο δείκτης μυοκαρδιακής απόδοσης (Τei index) της δεξιάς κοιλίας ελαττώθηκε μετά 9 μήνες αντιυπερτασικής αγωγής, κατά αντιστοιχία του Tei index της αριστερής κοιλίας που ήταν αυξημένος αρχικά ενώ ελαττώθηκε σημαντικά μετά 9 μήνες θεραπείας. Η ελάττωση του Tei index της αριστερής και της δεξιάς κοιλίας δεν παρουσίασε συσχέτιση με την αλλαγή στο πάχος του μεσοκοιλιακού ή του ελεύθερου τοιχώματος της δεξιάς κοιλίας, αλλά ούτε και με τη μείωση της συστολικής και διαστολικής αρτηριακής πίεσης. Τέλος το συστολικό strain της δεξιάς κοιλίας αυξήθηκε κατ’ απόλυτη τιμή μετά 9 μήνες θεραπείας με αναστολείς του ΣΡΑΑ τόσο στο βασικό τμήμα όσο και στη μεσότητα του ελεύθερου τοιχώματος της δεξιάς κοιλίας, ενώ δεν βρέθηκε συσχέτιση μεταξύ της μεταβολής της συστολικής ή της διαστολικής πίεσης και της μεταβολής της μέγιστης αυτής συστολικής παραμόρφωσης. Από την ανάλυση των αποτελεσμάτων προκύπτουν τα εξής συμπεράσματα: - Παρατηρήθηκε μείωση του πάχους του ελεύθερου τοιχώματος της δεξιάς κοιλίας, παράλληλα με τη μείωση του πάχους του μεσοκοιλιακού διαφράγματος σε ασθενείς με ήπια ιδιοπαθή αρτηριακή υπέρταση, μετά από 9μηνη αντιυπερτασική αγωγή. - Βελτίωση της επηρεασμένης διαστολικής λειτουργίας της δεξιάς κοιλίας με ελάττωση του δείκτη μυοκαρδιακής απόδοσης (Tei index), μετά από 9μηνη αντιυπερτασική αγωγή. - Με την υπερηχογραφική τεχνική του strain, διαπιστώθηκε βελτίωση της συστολικής λειτουργίας της δεξιάς κοιλίας σε πρώιμα στάδια αρτηριακής υπέρτασης και μετά από φαρμακευτική αγωγή. - Η αναστολή του ΣΡΑΑ με τη χορήγηση αναστολέων ΜΕΑ ή αποκλειστών αγγειοτενσίνης βελτίωσε τη λειτουργικότητα της δεξιάς κοιλίας, όπως αυτή καταγράφηκε με σύγχρονες υπερηχογραφικές μεθόδους, σε ασθενείς με ήπια υπέρταση. - Οι παραπάνω ευεργετικές δράσεις της αναστολής του ΣΡΑΑ φαίνεται ότι είναι ανεξάρτητες από τη μείωση της αρτηριακής πίεσης και πιθανόν αποδίδονται στην βελτίωση των δομικών αλλοιώσεων του μυοκαρδίου
Investigation of the Optimum Connection of a Fish Pond with the Adjacent Main Riverine Flow
No full textAbstractThe optimum design of the opening through which a fish refuge pond communicates laterally to the main flow of a river was investigated. The study was based on the realization of physical and mathematical models. The physical modeling was realized via laboratory experiments which included the use of an open channel with a lateral reservoir. The flow characteristics measurements were realized with the PIV method. The mathematical simulations were based on the development of a 2DH hydrodynamic model and a quasi 3D sediment transport model. The study led to the optimum technical design of the system
Experimental and Numerical Study of Turbulent Flow in Open Channels with Impermeable and Porous Bed
No full textAbstractIn order to experimentally and numerically investigate turbulent flow in an open channel with porous (vegetated) and impermeable bed 2D Particle Image Velocimetry (PIV) and a Computational Fluid Dynamical (CFD) model were used. PIV is an optical method of flow visualisation that is used to obtain instantaneous velocity measurements on a plane of a flow field. The CFD model is based on the CFX computer package, a high-performance general purpose fluid dynamics program that has been applied to solve wide-ranging fluid flow problems.In order to validate the results of the numerical model, the CFX based results were compared with experimental data from PIV measurements. The comparison is carried out for two cases: a) impermeable bed and b) porous bed. For the simulation of the porous bed a grass-like of flexible vegetation of 2 cm thickness was used. Vertical distributions of velocities above the impermeable bed and above the vegetation for the porous bed for the same different total depths were evaluated
Effects of renin-angiotensin system inhibition on right ventricular function in patients with mild essential hypertension
No full text Introduction: Systemic hypertension is known to affect both left and right ventricular (RV) function. Little is known about the effect of the renin—angiotensin system (RAS) inhibition on global RV function in patients with essential hypertension. Materials and methods: Forty patients (17 male, mean age 47 ± 10 years) with mild hypertension free of cardiovascular disease were assessed by echocardiography at baseline and after nine months of antihypertensive treatment with RAS inhibitors. Tissue Doppler imaging derived myocardial performance index (MPI) of the left and right ventricle was used as an index of global ventricular function. Results: Both left ventricular (LV) and RV MPI were increased at baseline and were reduced after treatment (LV MPI reduced from 0.42 ± 0.06 to 0.39 ± 0.05, p < 0.001 and RV MPI was reduced from 0.34 ± 0.06 to 0.32 ± 0.05, p < 0.005). There was a positive correlation between mitral and tricuspid E/A ratio both at baseline and at month nine after treatment ( r = 0.661, p < 0.001 and r = 0.503, p < 0.005 respectively). LV mass index and interventricular septum thickness were decreased after treatment. No correlation was found between MPI improvement and blood pressure reduction. Conclusions: RAS inhibition in patients with mild hypertension results in an improvement of RV global function which is unrelated to the reduction in blood pressure. </jats:p
The evolution of root-zone moisture capacities after deforestation:A step towards hydrological predictions under change?
No full textThe core component of many hydrological systems, the moisture storage capacity available to vegetation, is impossible to observe directly at the catchment scale and is typically treated as a calibration parameter or obtained from a priori available soil characteristics combined with estimates of rooting depth. Often this parameter is considered to remain constant in time. Using long-term data (30-40 years) from three experimental catchments that underwent significant land cover change, we tested the hypotheses that: (1) the root-zone storage capacity significantly changes after deforestation, (2) changes in the root-zone storage capacity can to a large extent explain post-treatment changes to the hydrological regimes and that (3) a time-dynamic formulation of the root-zone storage can improve the performance of a hydrological model.A recently introduced method to estimate catchment-scale root-zone storage capacities based on climate data (i.e. observed rainfall and an estimate of transpiration) was used to reproduce the temporal evolution of root-zone storage capacity under change. Briefly, the maximum deficit that arises from the difference between cumulative daily precipitation and transpiration can be considered as a proxy for root-zone storage capacity. This value was compared to the value obtained from four different conceptual hydrological models that were calibrated for consecutive 2-year windows. It was found that water-balance-derived root-zone storage capacities were similar to the values obtained from calibration of the hydrological models. A sharp decline in root-zone storage capacity was observed after deforestation, followed by a gradual recovery, for two of the three catchments. Trend analysis suggested hydrological recovery periods between 5 and 13 years after deforestation. In a proof-of-concept analysis, one of the hydrological models was adapted to allow dynamically changing root-zone storage capacities, following the observed changes due to deforestation. Although the overall performance of the modified model did not considerably change, in 51% of all the evaluated hydrological signatures, considering all three catchments, improvements were observed when adding a time-variant representation of the root-zone storage to the model. In summary, it is shown that root-zone moisture storage capacities can be highly affected by deforestation and climatic influences and that a simple method exclusively based on climate data can not only provide robust, catchment-scale estimates of this critical parameter, but also reflect its time-dynamic behaviour after deforestation.</p
Constraining conceptual hydrological models with multiple information sources
No full textThe calibration of hydrological models without streamflow observations is problematic, and the simultaneous, combined use of remotely sensed products for this purpose has not been exhaustively tested thus far. Our hypothesis is that the combined use of products can 1) reduce the parameter search space and 2) improve the representation of internal model dynamics and hydrological signatures.Five different conceptual hydrological models were applied to 27 catchments across Europe. A parameter selection process, similar to a likelihood weighting procedure, was applied for 1023 possible combinations of ten different data sources, ranging from using 1 to all 10 of these products. Distances between the two empirical distributions of model performance metrics with and without using a specific product, were determined to assess the added value of a specific product. In a similar way, the performance of the models to reproduce 27 hydrological signatures was evaluated relative to the unconstrained model.Significant reductions in the parameter space were obtained when combinations included AMSR‐E and ASCAT soil moisture, GRACE total water storage anomalies, as well as, in snow dominated catchments, the MODIS snow cover products. The evaporation products of LSA‐SAF and MOD16 were less effective for deriving meaningful, well constrained posterior parameter distributions. The hydrological signature analysis indicated that most models profited from constraining with an increasing number of data sources.Concluding, constraining models with multiple data sources simultaneously was shown to be valuable for at least four of the five hydrological models to determine model parameters in absence of streamflow
Clinical characteristics and management of patients with diabetes mellitus and stable coronary artery disease in daily clinical practice. The SCAD–DM Registry
No full textBackground: Patients with diabetes mellitus (DM) and coronary artery disease (CAD) represent a high-risk population, where comorbidities are common and the progression of coronary heart disease is relatively rapid and extensive. The present survey, conducted nationwide in a Eurozone country, Greece, with a properly organized national health system, aimed to record specific data from a significant number of patients with diabetes and documented stable CAD (SCAD). Methods and results: We conducted our survey across the country, in private and public primary, secondary, and tertiary care centers. A total of 1900 patients aged 71 ± 10 years old who suffered from both DM and chronic coronary syndromes were registered. Of the patients registered, 574 (30.24%) were women. It was found that 506 (26.6%) of the 1900 surveyed patients showed typical angina symptoms, while another 560 (29.5%) patients had developed angina-equivalent symptoms according to their history. Additionally, 324 (17%) patients had atypical symptoms that could not easily be attributed to existing CAD and the remaining 510 (26.8%) of the 1900 patients did not exhibit any angina symptoms during their daily activities. Functional testing for myocardial ischemia was not performed in 833 patients (43.8%). Myocardial scintigraphy was the most commonly used noninvasive technique (644 patients, 34%), while 492 patients (25.9%) had an exercise test and 159 (8.4%) underwent stress echocardiography. Conclusion: Real-world data in this specific high-risk population of diabetic patients with SCAD offer the opportunity to identify and improve diagnostic and therapeutic practice in the healthcare system of a European Union country
