Fréquence cardiaque | EPFL Graph Search

La fréquence cardiaque est le nombre de battements cardiaques (ou pulsations) par unité de temps (généralement la minute). C'est une notion quantitative qui peut aussi se définir en nombre de cycles par seconde, par l'inverse de la période. Par abus de langage, on confond souvent la fréquence cardiaque avec le rythme cardiaque ou le pouls. Le rythme cardiaque est une notion qualitative qui désigne la manière avec laquelle s'effectue une révolution cardiaque, la manière dont les cycles se succèdent. Le rythme cardiaque est le mécanisme à l’origine de la contraction des ventricules. Le pouls désigne quant à lui la perception au toucher de l'artère battante, permettant, certes d'évaluer les battements cardiaques, mais d'apporter également d'autres renseignements. Selon les espèces animales, la fréquence cardiaque est très inégale. Ainsi chez la baleine, le plus gros mammifère actuel, la fréquence cardiaque est inférieure à par minute ; chez l'homme, elle est d'environ par minute ;

Evaluation and extension of an automated system to diagnose the health of premature babies

Camille Joggi

Premature babies are not fully equipped to deal with the outside world. Their immature bodies make them highly at risk to a large number of physiological complications. Therefore, while they are still immature, premature babies are taken care of in neonatology intensive care units, where they are kept in a controlled and protective environment. In these units, the babies' vital parameters, such as their heart rate and temperature, are tightly monitored. The devices used to record this data are fitted with alarms that are triggered automatically when something wrong is detected. However, the alarm systems currently used are often unable to discriminate between real physiological problems and artefacts that should be ignored (e.g. when a measurement device drops-out). As a result, these systems produce a high rate of false alarms, where the alarm is triggered when nothing is clinically wrong. The can have unwanted consequences: first, it creates a noisy environment, which may disturb the babies; second, it can lead to the alarm being ignored when there is actually something wrong. In order to address this problem, my host laboratory has constructed a system that can automatically infer the state of health of premature babies in neonatology units, based on their recorded physiological data. The new system is designed to be able to deal with artefactual changes in the measurements, hopefully resulting in a reduced number of false alarms. In this thesis, I describe my contribution to this project, which is twofold. The first part deals with the problem of evaluating the performance of the system. To do this, I developed an online feedback process, where clinicians could provide information about the true clinical interpretation of the physiological data, which could be compared to the output of the system. The feedbacks provided by the clinicians were then analysed to investigate how the system could be improved. The second part of my thesis was motivated be early feedbacks from the clinicians, which indicated that the system was unable to deal with changes in the humidity measurements that occurred when the incubator door was opened and closed. To address this, I extended the current system, so that it was able to account for these changes, thereby increasing its capability to detect "true" physiological problems during the period after the incubator door is closed.

2011

p-Aminobenzamidine attenuates cardiovascular dysfunctions in spontaneously hypertensive rats

Allancer Divino De Carvalho Nunes, Fabiana Pereira Da Costa Fraga, Nikolaos Stergiopulos

Aims:Diminazene aceturate, a putative ACE2 activator, is susceptible to cleavage resulting in the formation of paminobenzamidine (PAB). This study aimed to investigate the effects of PAB in addressing cardiovascular dysfunctions in spontaneously hypertensive rats (SHR). Main methods:Acute effects of PAB on mean arterial pressure (MAP), heart rate (HR), and aortic (AVC) and mesenteric vascular conductance (MVC) were evaluated in anesthetized SHR. Isolated aortic rings and the Langendorff technique were used to investigate the acute and chronic effects of PAB in the artery and heart. Chronic treatment with PAB (1 mg/kg, gavage) was carried out for 60 days. During this period, systolic blood pressure (SBP) and HR were measured by tail-cuff plethysmography. After the treatment, the left ventricle was collected for histology analyses, western blotting, and ACE2 activity. Key findings:Bolus infusion of PAB acutely reduced MAP and increased both AVC and MVC in SHR. Additionally, PAB induced coronary and aorta vasodilation in isolated organs from Wistar and SHR in an endothelialdependent manner. The chronic PAB treatment in SHR significantly attenuated the increase of SBP and improved the aorta vasorelaxation induced by acetylcholine and bradykinin-induced coronary vasodilation. In addition, chronic treatment with PAB attenuated the cardiomyocyte hypertrophy and extracellular matrix deposition in hearts from SHR. PAB did not alter the protein expression of the AT1, AT2, Mas, ACE, ACE2, or ACE2 activity. Significance:PAB induced beneficial effects on cardiovascular dysfunctions induced by hypertension, suggesting that this molecule could be used in the development of new drugs for the treatment of cardiovascular diseases.

PERGAMON-ELSEVIER SCIENCE LTD2022

Reduced order models for the simulation of pathological heart valves

Lidia Stepanova

Numerical modeling of the human cardiovascular system (CVS) represents an active branch of research which allows the medical specialists to advance in understanding of underlined processes of blood circulation and the heart work at any scale, moreover, it helps to analyze the potential problems which can arise in the CVS by modifying the parameters inside the mathematical models. Due to inability to capture in details the pressure and flow parameters without invasion into heart chambers, the process of diagnosing heart diseases can become very complicated, the limited data on atrial pressure and cardiogram results can give only overall representation of the heart condition and the exactness of the diagnosis is based mainly on experience of the doctor. Nevertheless, the development of numerical models of CVS helps to get better understanding on processes which can cause particular disease (reverse flow leakage in heart chambers, improper contraction of heart muscles due to infarction of tissue). Mathematical model allows the analysis of all physical values of the system during the heart beat as well as possibility to adjust individual parameters specific to each patient. Therefore, it becomes an efficient tool for doctors to diagnose properly the heart disease, to assign the necessary treatment and surgery, and to predict the effect of implanting cardiac-assist devices.

2013

Evaluation and extension of an automated system to diagnose the health of premature babies

Camille Joggi

2011