Artificial cardiac pacemaker | EPFL Graph Search

An artificial cardiac pacemaker (artificial pacemaker, and sometimes just pacemaker, although the term is also used to refer to the body's natural cardiac pacemaker) is a medical device, nowadays always implanted, that generates electrical pulses delivered by electrodes to one or more of the chambers of the heart, the upper atria or lower ventricles. Each pulse causes the targeted chamber(s) to contract and pump blood, thus regulating the function of the electrical conduction system of the heart. The primary purpose of a pacemaker is to maintain an adequate heart rate, either because the heart's natural pacemaker is not fast enough, or because there is a block in the heart's electrical conduction system. Modern pacemakers are externally programmable and allow a cardiologist, particularly a cardiac electrophysiologist, to select the optimal pacing modes for individual patients. Most pacemakers are on demand, in which the stimulation of the heart is based on the dynamic demand of the

S-pace Maker. ; Logements et commerces dans le centre historique de Florence (I)

Ivan Venticinque

L'insertion de nouvelles constructions dans le contexte historique a toujours été l'objet d'un débat animé et loin d'être conclu. La grande difficulté qu'il y a à inclure toute nouvelle architecture, causée par la multitude de contraintes sociales, réglementaires et théoriques, a mené la plupart des centres villes historiques italiens dans une impasse architecturale et urbanistique. Dans l'idée que la ville doit continuer à se construire sur elle-même, comme cela a été fait depuis toujours, par une régénération continue, dans le plein respect des préexistences et des nouvelles exigences, l'analyse détaillée du contexte historique particulier du centre-ville de Florence, donne les indices permettant d'esquisser une stratégie pour que cela advienne. La force culturelle reconnue aux héritages historiques, architecturaux et urbanistiques permet en effet d'utiliser les contraintes et exemples du passé plutôt que de les nier. Avec une intervention dans la Piazza Torquato Tasso, le projet propose une réponse personnelle en réinsérant dans la ville historique toutes les activités humaines afin de la revivifier et de la revitaliser. Le système structurel du projet calque la trame du tissu, en aménageant des logements et des commerces qui s'adaptent mieux aux exigences de vie plus contemporaines.

2011

New/Surface-Modified Biocompatible Polymer for ICD Lead Insulation

Rubin Berek Pisarek

The average lifetime of an implanted pacemaker or defibrillator cable (lead) is approximately 10 years. One of the main lead failure mechanisms is deterioration of the insulation, which can be caused by chemical, biological, and mechanical processes. Each time lead failure occurs, an operation for its prompt replacement is required, in order to guarantee the patients' well-being. Since lead failure poses a health risk for the patients, and replacement operations are costly, this study aims at the improvement of one of the materials which is used by the cardiac pacing industry. Silicone polymers are commonly used for pacemaker and defibrillator lead insulation. Previous studies showed that some modified polyurethane polymers exhibit very different as well as favorable mechanical surface properties, as compared to their unmodified counterparts. This was due to the fact that polymeric blocs within the network can migrate to the materials' surface, and thereby act as surface-modifying end-groups (SMEs). In this study, a commercially available silicone system was modified by introducing two different SMEs and using two different approaches. In one approach the SMEs were covalently bonded to the silicone backbone, and in the second approach carrier molecules with the SMEs attached to them were admixed to the silicone. The carriers themselves had a siloxane backbone. The tensile properties, tear strength, and hardness were measured in order to describe the material as compared to commercially available mixtures, and to improve the mixing ratio of the components. Protein adhesion, water uptake, and surface wettability were evaluated to investigate the effect of the SMEs on the surface properties of the novel silicone formulations. While the mechanical properties of the silicone mixtures are comparable to but not competitive with the commercially available materials, contact angle measurement showed a significant reduction of the surface hydrophobicity: The initial contact angle of ∼114° could be reduced to ∼55°. It was concluded that the two novel SMEs can be used in order to make initially hydrophobic silicone hydrophilic.

EPFL2011

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

New/Surface-Modified Biocompatible Polymer for ICD Lead Insulation

Rubin Berek Pisarek

EPFL2011