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Heart rate variability and motion artifact are two major obstacles to the photoplethysmographic (PPG) signal analysis, which is a very promising tool to derive useful information about the hemodynamics as well as autonomic nerve system. This paper suggests employing a truncation/extrapolation method on the PPG signal or its first order derivative to overcome the heart rate variability problem while...
The maintenance of adequate anesthesia is very important for animal studies. This goal could be achieved if the pharmacokinetics of the anesthetic is known and a well-controlled instrument system is used. To this end, a graphic control system is developed to study the effects of sodium pentobarbital on anesthesia. Hemodynamic signals such as mean blood pressure, pulse pressure, heart rate were analyzed...
In this study a telemedicine system based on embedded computer system is presented, which is designed specially for the need of immediate medical treatment in remote areas. In the system embedded Linux is cut down, customized and ported into the monitor terminal. Data interchange between the monitor center and the terminal via Internet and GPRS is introduced. This system which is convenient, portable...
The aims of the present study were to examine the effect of heptanol on electrical coupling during ischemia, and to assess whether changes in electrical coupling by heptanol is associated with its cardiac protection. Perfused isolated rat hearts were subjected to a 24 min infusion of heptanol (0.05, 0.1, 0.5 or 1.0 mmol/L) followed by 70 min of global no-flow ischemia or by 20 min of regional ischemia...
Two series of experiments were performed in the perfused isolated rat heart to determine whether stimulation of kappa-opioid receptor with U50,488H, a selective kappa-opioid receptor agonist, produces any changes in electrical coupling during prolonged ischemia and whether these changes in electrical coupling is associated with the cardioprotection induced by U50,488H. It was found that U50,488H concentration...
We have developed a computational model for the rat cardiac ventricular cell by using electrophysiology data. Our control model (Pandit et al., 2001). The model represents the bioelectric activity in the left ventricular cells in adult male rats. We have described the differences in the membrane properties within the left ventricle to simulate the action potential variations of the endocardial and...
In this study, we investigate the role of sinoatrial node (SAN) cellular heterogeneity in normal cardiac pacemaker function. Using detailed ionic models of electrical activity in SAN and atrial myocytes, we have formulated a number of models of SAN heterogeneity based on discrete-region (in which central and peripheral SAN type cell are separated into discrete regions), gradient and mosaic models...
Action potential duration (APD) alternans is believed to be a loss of stability and contributes much to the reentry arrhythmias. The purpose of this study is to analyze the stability conditions for one-dimension model and higher dimension model. These criterions are concluded by linear stability analysis in nonlinear dynamics. They should be useful for finding of cardiac control algorithms in low...
While biosignal analysis has been a mainstay in many medical applications for a number of decades, notably in cardiology, problems remain in the analysis of high volume data and in comparison among time series. Effective comparisons can determine if the state of a particular patient has changed significantly. These comparisons are useful in both long-term and short-term monitoring. Methods will vary...
This paper presents simulation study of the action potential waveforms of different ventricular cell types based on experimental studies of transmural electrophysiological heterogeneities in control and failing human hearts. The results show that prolonged action potential duration (APD) and APD rate-adaptation are markedly transmural heterogeneous in heart failure than those in controlled heart which...
Methods have been developed for modeling cardiac activation which accounts for detailed myocardial geometric structures derived from specific tissue samples. This modeling allows both study and analysis of the effects of cleavage planes and other structural barriers to myocardial current flow. Specialized numerical and computational procedures have been developed to enable this modeling. The results...
Continuous flow blood pumps, such as axial flow and centrifugal pumps, have been gaining interest as circulatory devices for total artificial hearts (TAHs) and a biventricular assist device (BVAD) because of their smaller size and simpler structure compared to pulsatile pumps. However, continuous flow pumps are more prone to suction of the left ventricle than pulsatile pumps are. Sudden increases...
In clinical first-pass myocardial perfusion studies, physiological and patient motions are inevitable. Such motions impair the sensitivity and reliability in assessing myocardial perfusion abnormalities. The current study aims to correct the misregistration of myocardium during first-pass perfusion imaging by using a normalized mutual information approach. Multi-slice registrations were performed...
This is a review of the state of the art in two important modalities thermal and electrical properties of living tissues - that are complementary from the point of view of medical diagnostics. Advantages and limitations of IR thermal imaging and electroimpedance measurements, including tomography procedures are discussed. Properties of both modalities are compared from the point of view of skin burn...
A simulation-based training resource was developed for electrophysiology. The resource focuses on computational modeling of cellular bioelectric activity and is called the interactive cell modeling tool. iCell can be used as a simulation-based teaching and learning tool for electrophysiology. The site consists of JAVA models of various cardiac cells and neurons, and provides simulation data of their...
Wearable technology has been used in various health-related fields to develop advanced monitoring solutions. However, the monitoring function alone cannot meet all the requirements of personal customizing machine-supported exercise that have biosignal-based controls. In this paper, we propose a new wearable unit design equipped with measurement and control functions to support the personal customization...
Coronary artery disease (CAD) is a major cause of mortality in the western world. Although progress has been made in recent years for the noninvasive diagnosis of CAD, a widely available, inexpensive and effective diagnostic solution remains elusive. We have developed a novel ultrasound-based technology to detect and analyze the myocardial vibrations associated with diastolic murmurs produced by CAD...
We searched for possible associations between various measures of severity of sleep-disordered breathing (SDB) and indices of cardiac autonomic function in older subjects (>60 years). Twenty four overnight unattended home-based polysomnograms obtained from the Sleep Heart Health Study were analyzed using spectral analysis. For each subject, six autonomic indices reflecting heart rate variability...
We constructed an impedance spectroscopy measurement system based on frequency response analyzer. Using four-terminal method, we measured impedance spectroscopy of rabbit different tissues in vitro within 5 to 360 minutes after excision at the frequency range from 1Hz to 1MHz. According to the measurement results, we analyzed the changes of characteristic parameters (Ro, Rinfin, fc and alpha) of different...
Quantitative assessment of the motion and deformation variability of the heart has important implications for the understanding, diagnosis, and treatment of cardiac diseases. Various existing image-based approaches typically rely on linear constraining models which are however physically implausible. In this paper, we present a biomechanically constrained framework for the estimation of left ventricle...
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