Myocardial electrical impedance mapping of ischemic sheep hearts and healing aneurysms.

Fallert, Michael A.; Mirotznik, Mark S.; Downing, Stephen W.; Savage, Edward B.; Foster, Kenneth R.; Josephson, Mark E.; Bogen, Daniel K.

doi:10.1161/01.cir.87.1.199

Cited by 105 publications

(80 citation statements)

References 39 publications

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“…According to [6], the extracellular conductivity of infarcted myocardium is increased by a factor of 1.75, whereas the intracellular conductivity is fully suppressed due to the closure of gap junctions.…”

Section: Forward Problem Of Electrocardiographymentioning

confidence: 99%

Model-based approach to the localization of infarction

Farina

Dössel

2007

2007 Computers in Cardiology

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A model-based approach to noninvasively determine the location and size of the infarction scar is proposed, that in addition helps to estimate the risk of arrhythmias.The approach is based on the optimization of an electrophysiological heart model with an introduced infarction scar to fit the multichannel ECG measured on the surface of the patient's thorax. This model delivers the distributions of transmembrane voltages (TMV) within the ventricles during a single heart cycle.The forward problem of electrocardiography is solved in order to obtain the simulated ECG of the patient. This ECG is compared with the measured one, the difference is used as the criterion for optimization of model parameters, which include the site and size of infarction scar. IntroductionMortality of patients in the immediate postinfarction period, as well as during the first year after myocardial infarction, is most often due to sudden death from ventricular fibrillation [1]. Thus the development of a cardiac model, which would allow to estimate the probability of arrhythmia for a specific patient, must include a correct implementation of ischemia and/or infarction.The aim of this work is to build a model of the patient's heart that contains infarction scar. It is optimized until the simulated multichannel ECG is as near as possible to the measured one. It is assumed that the location and size of infarction obtained in this manner corresponds to the real one. Taking part in the PhysioNet Challenge 2007 [2] should prove or disprove this assumption.Within the scope of the Challenge, 4 data sets were proposed for patients suffering from different infarctions. Each of the data sets contained anatomical information about the heart and the locations of 352 electrodes on the surface of the patient's thorax. Corresponding 352-channel ECGs were also provided. The first two data sets were considered as training and contained the information about the parameters of infarction scar. The main task of the Challenge consisted in the estimation of location and size of infarction scar for the latter two patients based on the pro- Figure 1. Model of the heart used in this work. Atria, ventricles and excitation conduction system are shown. vided data. Methods Cellular automatonA cellular automaton based model of the heart is employed in this work. The anatomy of the heart has been taken from the Visible Male Project [3]. The cardiac geometry is defined on a regular mesh with the resolution of 1 × 1 × 1 mm 3 . This model contains ventricles and atria, sinus and AV-nodes. An excitation conduction system is generated as a tree-shaped structure, with two branches going from the AV-node towards the apex of both ventricles, afterwards giving rise to multiple branches of Purkinje fibers connected to the ventricular endocardium through a large amount of junctions (see figure 1).The cellular automaton is implemented as follows. If an excitation appears in some voxel, it is transferred to all the neighboring voxels containing excitable tissue. The velocity o...

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Section: Forward Problem Of Electrocardiographymentioning

confidence: 99%

Model-based approach to the localization of infarction

Farina

Dössel

2007

2007 Computers in Cardiology

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“…17 Currently, however, no optical method exists-apart from polarized-light-based techniques-for assessing the structure of myocardium, particularly with regards to the structural remodeling that occurs with infarction and regeneration, with the potential to be employed in vivo on bulk tissues. Other nonoptical modalities such as ultrasound elastography 21 and electrical impedance mapping 22 do provide information on the structural state of the myocardium. However, neither of these techniques provides information on the organizational structure of the tissue, but rather on the elastic and conductive properties, respectively.…”

Section: Introductionmentioning

confidence: 99%

Polarization birefringence measurements for characterizing the myocardium, including healthy, infarcted, and stem-cell-regenerated tissues

et al. 2010

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Abstract. Myocardial infarction leads to structural remodeling of the myocardium, in particular to the loss of cardiomyocytes due to necrosis and an increase in collagen with scar formation. Stem cell regenerative treatments have been shown to alter this remodeling process, resulting in improved cardiac function. As healthy myocardial tissue is highly fibrous and anisotropic, it exhibits optical linear birefringence due to the different refractive indices parallel and perpendicular to the fibers. Accordingly, changes in myocardial structure associated with infarction and treatment-induced remodeling will alter the anisotropy exhibited by the tissue. Polarization-based linear birefringence is measured on the myocardium of adult rat hearts after myocardial infarction and compared with hearts that had received mesenchymal stem cell treatment. Both point measurement and imaging data show a decrease in birefringence in the region of infarction, with a partial rebound back toward the healthy values following regenerative treatment with stem cells. These results demonstrate the ability of optical polarimetry to characterize the micro-organizational state of the myocardium via its measured anisotropy, and the potential of this approach for monitoring regenerative treatments of myocardial infarction.

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“…At the macroscopic level (1-10 mm), a gradual change in fiber direction over more than 120 is found, going from epicardium to endocardium (about 20 over the first tenth of wall thickness) [1]. This structure makes it difficult to obtain the longitudinal and transversal specific impedance from the measurements made with four intramural needle electrodes [2]. Some authors [3], [4] have reported longitudinal and transversal resistivities, and also in [5] a special probe and an analytical method for separating transversal and longitudinal resistivities were introduced, but other authors have been unable to differentiate the anisotropy [6], [2].…”

Section: Introductionmentioning

confidence: 99%

“…This structure makes it difficult to obtain the longitudinal and transversal specific impedance from the measurements made with four intramural needle electrodes [2]. Some authors [3], [4] have reported longitudinal and transversal resistivities, and also in [5] a special probe and an analytical method for separating transversal and longitudinal resistivities were introduced, but other authors have been unable to differentiate the anisotropy [6], [2]. Given the difficulty of separating the two components, especially for in situ measurements, we did not use this distinction a priori.…”

Section: Introductionmentioning

confidence: 99%

Transmural Versus Nontransmural In Situ Electrical Impedance Spectrum for Healthy, Ischemic, and Healed Myocardium

Salazar

Bardia

Casas

et al. 2004

IEEE Trans. Biomed. Eng.

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Abstract-Electrical properties of myocardial tissue are anisotropic due to the complex structure of the myocardial fiber orientation and the distribution of gap junctions. For this reason, measured myocardial impedance may differ depending on the current distribution and direction with respect to myocardial fiber orientation and, consequently, according to the measurement method. The objective of this study is to compare the specific impedance spectra of the myocardium measured using two different methods. One method consisted of transmural measurements using an intracavitary catheter and the other method consisted of nontransmural measurements using a four-needle probe inserted into the epicardium. Using both methods, we provide the in situ specific impedance spectrum (magnitude and phase angle) of normal, ischemic, and infarcted pig myocardium tissue from 1 kHz to 1 MHz. Magnitude spectra showed no significant differences between the measurement techniques. However, the phase angle spectra showed significant differences for normal and ischemic tissues according to the measurement technique. The main difference is encountered after 60 min of acute ischemia in the phase angle spectrum. Healed myocardial tissue showed a small and flat phase angle spectrum in both methods due to the low content of cells in the transmural infarct scar. In conclusion, both transmural and nontransmural measurements of phase angle spectrum allow the differentiation among normal, ischemic, and infarcted tissue.

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Myocardial electrical impedance mapping of ischemic sheep hearts and healing aneurysms.

Cited by 105 publications

References 39 publications

Model-based approach to the localization of infarction

Model-based approach to the localization of infarction

Polarization birefringence measurements for characterizing the myocardium, including healthy, infarcted, and stem-cell-regenerated tissues

Transmural Versus Nontransmural In Situ Electrical Impedance Spectrum for Healthy, Ischemic, and Healed Myocardium

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