2008 Computers in Cardiology最新文献

{"title":"Model-based analysis of Na-K+ pump influence on potassium depuration during Acetate Free Biofiltration (AFB)","authors":"A. Ciandrini, S. Severi, S. Cavalcanti, F. Grandi, S. Santoro","doi":"10.1109/CIC.2008.4749181","DOIUrl":"https://doi.org/10.1109/CIC.2008.4749181","url":null,"abstract":"Potassium ion (K⁺) kinetics in intra and extracellular compartments during hemodialysis was studied by means of a double-pool computer model which included potassium-dependent active transport (Na-K-ATPase pump) in thirty-four patients (21M/13F; aged 66 plusmn 22 years old, dry weight 68 plusmn 18 kg, height 160 plusmn 15 cm) on renal replacement therapy with thrice weekly 4 hour double-needle hemodialysis. Each patient was studied during acetate free biofiltration (AFB) with a constant K⁺ dialysate concentration (K_CONST therapy) and with a time-varying (profiled) K⁺ dialysate concentration (K_PROF therapy). The two therapies induced different levels of K⁺ plasma concentration (K_CONST: 3.6plusmn0.8 vs. K_PROF: 4.0plusmn0.7 mmol/L, time-averaged values, p<0.01). The computer model was tuned to accurately fit plasmatic K⁺ measured in the course of K_CONST and K_PROF therapies and was then used to simulate the kinetics of intra and extracellular K⁺. Model-based analysis showed that almost all the K⁺ removal in the first 90 minutes of dialysis was mainly derived from the extracellular compartment. The different K⁺ time course in the dialysate and the consequently different Na-K pump activity resulted in a different sharing of removed potassium mass at the end of dialysis: 55+17% from the extracellular compartment in K⁺ _PROF vs. 41plusmn14% in K⁺ _CONST. These results suggest that the Na-K pump plays a major role in K⁺ apportionment between extracellular and intracellular compartments, and potassium dialysate concentration strongly influences pump activity. For this reason the computer-model here presented may represent a useful tool to quantitatively assess the impact of dialysate potassium on K⁺ kinetics in intra and extracellular compartments and to design dialysate potassium content tailored to the patient's needs.","PeriodicalId":194782,"journal":{"name":"2008 Computers in Cardiology","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125774623","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Efficient and fast ECG baseline wander reduction without distortion of important clinical information","authors":"S. Hargittai","doi":"10.1109/CIC.2008.4749173","DOIUrl":"https://doi.org/10.1109/CIC.2008.4749173","url":null,"abstract":"Baseline wander makes manual and automatic analysis of ECG records difficult, especially the measuring of ST-segment deviation. Since the spectrum of baseline wander and low frequency component of ECG signal usually overlaps, removing of baseline wander can cause distortion of important clinical information, particularly ST-segment distortion. The use of digital linear phase high-pass filter minimizes this undesirable effect, but it requires large computational complexity. A multirate architecture with linear phase low-pass filter working at low sampling rate is presented for removal of the baseline wander. Design tradeoff between transition band width and filter delay was considered. We determined the optimal decimation factor with respect to complexity and filter delay. For testing and assessment of behavior of baseline filter we used test signals, normal and wide QRS complexes with different heat rate.","PeriodicalId":194782,"journal":{"name":"2008 Computers in Cardiology","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125989802","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Linear and nonlinear parametric model identification to assess granger causality in short-term cardiovascular interactions","authors":"L. Faes, G. Nollo, K.H. Chon","doi":"10.1109/CIC.2008.4749161","DOIUrl":"https://doi.org/10.1109/CIC.2008.4749161","url":null,"abstract":"We assessed directional relationships between short RR interval and systolic arterial pressure (SAP) variability series according to the concept of Granger causality. Causality was quantified as the predictability improvement (PI) of a time series obtained when samples of the other series were used for prediction, i.e. moving from autoregressive (AR) to AR exogenous (ARX) prediction. AR and ARX predictions were performed both by linear and nonlinear parametric models. The PIs of RR given SAP and of SAP given RR, measuring baroreflex and mechanical couplings, were calculated in 15 healthy subjects in the resting supine and upright tilt positions. Using nonlinear models we found a bilateral interaction between the two series, unbalanced towards the mechanical direction at rest and balanced after tilt. The utilization of linear AR and ARX models led to higher prediction accuracy but comparable trends of predictability and causality measures.","PeriodicalId":194782,"journal":{"name":"2008 Computers in Cardiology","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130204645","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Propagation of electrical excitation in isolated rabbit hearts: Influence of stimulation protocol and spatial coupling","authors":"S. Bauer, S. Fruhner, I. Romero, H. Engel, M. Bar","doi":"10.1109/CIC.2008.4749037","DOIUrl":"https://doi.org/10.1109/CIC.2008.4749037","url":null,"abstract":"Propagation of electrical excitation in the rabbit heart was computed using a simple realistic ionic model. Excitation was initiated by two different stimulation protocols. The simulations were compared to surface electrograms obtained from autonomously beating rabbit hearts in Langendorff perfusion. Additionally the influence of a gap junction blocking drug (palmitoleic acid) was investigated. After filtering the data, they were characterized by surface propagation speed maps. Under influence of the drug the propagation speeds decreased by 10-20% while the QRS time increased by approximately 10%. The first observation could be confirmed by simulations where the speeds were lowered by 10-30%. The QRS time showed a larger increase by up to 33%. The first protocol with a stimulation near the apex showed a more realistic shape of the QRS complex and reproduced the QRS time more accurately. The second, Purkinje type protocol yielded better agreement concerning the propagation speeds.","PeriodicalId":194782,"journal":{"name":"2008 Computers in Cardiology","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133206647","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Self risk assessment and monitoring for cardiovascular disease patients based on service-oriented architecture","authors":"J. Pan, Km Chen","doi":"10.1109/CIC.2008.4749122","DOIUrl":"https://doi.org/10.1109/CIC.2008.4749122","url":null,"abstract":"Risk assessment of cardiovascular disease (CVD) relies on a complex computation from several critical risk factors. To a patient, such factors can be examined at different health providers at different time. In order to efficient access patientpsilas risk factor information from these distributed health service providers, we developed a CVD risk assessment and monitoring system, named CRAMS, that based on the service-oriented architecture. With open standards, such as XML and SOAP, the service-oriented architecture supports interoperability between different platform and application. The distributed health service providers register in CRAMS and provide specific patient information as user demand. In this study, the Framingham heart study is served as the target of risk factors and risk computation model.","PeriodicalId":194782,"journal":{"name":"2008 Computers in Cardiology","volume":"148 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115542036","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Inhomogeneous human torso model of magnetohydrodynamic blood flow potentials generated in the MR environment","authors":"G. Nijm, S. Swiryn, A. Larson, A. Sahakian","doi":"10.1109/CIC.2008.4748964","DOIUrl":"https://doi.org/10.1109/CIC.2008.4748964","url":null,"abstract":"Magnetohydrodynamic (MHD) voltages resulting from blood flow in a magnetic field contribute to the ECG acquired in the MR environment. These MHD voltages may result in triggering problems for MR image acquisition, since the ECG is typically used for gating. Comsol Multiphysics software was used to model blood flow through the aorta in an inhomogeneous 3D human torso model in a 3.0 Tesla static magnetic field. These voltages were compared with experimentally acquired MHD voltages as well as MHD voltages computed using a simplified torso model. The maximum MHD voltage magnitude was 0.2 mV for the experimental data, 3.04 mV for the simplified model and 0.285 mV for the inhomogeneous torso model. Modeling MHD voltages using an inhomogeneous torso model may aid in optimizing ECG electrode placement for cardiac MRI. In addition, analysis of MHD not only as interference, but also as a physiological signal, may provide blood flow information.","PeriodicalId":194782,"journal":{"name":"2008 Computers in Cardiology","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124234546","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Real-time discrimination of multiple cardiac arrhythmias for wearable systems based on neural networks","authors":"G. Valenza, A. Lanatà, M. Ferro, E. Scilingo","doi":"10.1109/CIC.2008.4749226","DOIUrl":"https://doi.org/10.1109/CIC.2008.4749226","url":null,"abstract":"This paper aims at developing a wearable system able to recognize the most significant cardiac arrhythmias through an efficient algorithm, in terms of low computational cost and memory usage, implementable in a portable, real-rime hardware. In addition, it must respect the specifications of good specificity and sensitivity, in order to permit a positive clinical validation. The hardware is constituted of a general propose microcontroller, which is able to acquire electro-cardiogram signal (ECG), perform analog to digital conversion and extract QRS complex. The algorithm classifies QRS complexes as normal or pathologic by means of selected features obtained from discrete fourier transform (DFT). Furthermore, a spatial wavelet pre-filter is also investigated to obtain an enhanced QRS complex discrimination. In particular, pattern recognition of QRS complex is performed from binding minimal architecture of neural network as Kohonen self organizing map (KSOM). Experimental results were validated by means of MIT-BIH arrhythmias database obtaining specificity and sensitivity up to 98%.","PeriodicalId":194782,"journal":{"name":"2008 Computers in Cardiology","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115001419","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Novel method of automatic auscultation for blood pressure measurement using pulses in cuff pressure and korotkoff sound","authors":"D. Park, H. Oh, J.H. Kang, I.Y. Kim, Y. Chee, J.S. Lee","doi":"10.1109/CIC.2008.4749007","DOIUrl":"https://doi.org/10.1109/CIC.2008.4749007","url":null,"abstract":"In the NIBP (Non-Invasive Blood Pressure) measurement, we need well trained observer and there are differences in reading values between observers. We suggest new automated auscultation algorithms to select the proper epoch of K-sound for each heart beat. The sound for each epoch is converted into frequency domain and total power was calculated. We decided SBP(Systolic Blood Pressure) point when there was abrupt jump from the baseline. DBP (Diastolic blood pressure) was decided when there was the biggest drop in total power of successive beats. For the validation of our suggested method, human observer assessed SBP/DBP according to EHS (European Hypertension Society) recommendation. The mean differences between the automatic method and traditional auscultation method were 2.0 mmHg for SBP and 3.1 mmHg for DBP. We also took the paired t-test with the two results, and there was no statistically significant difference between these two methods.","PeriodicalId":194782,"journal":{"name":"2008 Computers in Cardiology","volume":"53 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114698980","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"QT dispersion induced by local temperature variations","authors":"A. Guill, I. Trapero, E. Roses, J. Millet, A. Tormos, F. Pelechano, L. Such-Miquel, A. Martinez-Climent, L. Such, F. Chorro","doi":"10.1109/CIC.2008.4749137","DOIUrl":"https://doi.org/10.1109/CIC.2008.4749137","url":null,"abstract":"Abnormally long and short QT intervals (QTi) have been shown to be associated with an increased risk for life-threatening ventricular arrhythmias and sudden cardiac death. Because of its electrophysiological effects temperature can influence this parameter. Therefore hypothermia or/and hyperthermia can be used for modulate QTi in studies with experimental models. In this work, a novel electrode-device to perform epicardial mapping and simultaneous thermal modifications is presented. In ten preparations of isolated rabbit hearts (Langendorff-perfused) changes in QTi was analyzed in two different left ventricular areas. One area was thermally modified, while the other remained in basal conditions, the QTi were measured in both areas. During hypothermia the differences between them increased mainly due to the prolongation of the QTi in altered area. hyperthermia had the opposite effect.","PeriodicalId":194782,"journal":{"name":"2008 Computers in Cardiology","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114922893","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Linear and nonlinear heart rate variability risk stratification in heart failure patients","authors":"Andreas Voss, R. Schroeder, M. Vallverdú, I. Cygankiewicz, Rafael Vázquez, A. B. D. Luna, P. Caminal","doi":"10.1109/CIC.2008.4749102","DOIUrl":"https://doi.org/10.1109/CIC.2008.4749102","url":null,"abstract":"Chronic heart failure (CHF) is a major and growing public health concern (~23 million people worldwide) with five-year survival rates of 25% in men and 38% in women. Objective of this study was to investigate whether linear and nonlinear heart rate variability (HRV) indices enhance risk prediction in patients with CHF. To discriminate between low risk (stable condition, N = 459) and high risk (cardiac death, N = 50) CHF patient groups, nonlinear indices from compression entropy (CE), detrended fluctuation analysis (DFA), symbolic dynamics (SD) and standard linear HRV analysis were calculated from 24 h Holter ECG recordings. Indices from nonlinear dynamics (CE, DFA, SD: p < 0.001) contribute together with clinical parameters NYHA and LVEF to an enhanced risk stratification in CHF patients.","PeriodicalId":194782,"journal":{"name":"2008 Computers in Cardiology","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117000906","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}