Global ETD Search
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Showing 1 to 15 of 15 for “"alternans"”.
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Relating cardiac electrical and mechanical alternans to ventricular stability
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1987.
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Spatial Variation of Cardiac Restitution and the Onset of Alternans
… is correlated statistically with the onset of alternans, a possible precursor to fibrillation in the human heart.</p><p>An optical imaging system using novel illumination based on LEDs is used to determine the spatial dependence of action potential duration (APD) and the slope of the dynamic …
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P-wave electrical alternans as an indicator of paroxysmal atrial fibrillation
P-wave electrical alternans is a beat to beat alternation in the morphology of the P-wave, the wave in an electrocardiogram corresponding to atrial depolarization. In this investigation, software to measure p-wave alternans was developed and then tested on simulated data and on real data previously …
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Exploring alternans characteristics of electrocardiogram for prediction of Paroxysmal Atrial Fibrillation
… was to investigate if P-wave and PQ segment alternans can be used to detect and predict Paroxysmal Atrial Fibrillation (PAF) from an Electrocardiogram (ECG). The work involved implementing an algorithm for computing alternans information for a region of ECG, applying the algorithm to derive …
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Bifurcations in the Echebarria-Karma Modulation Equation for Cardiac Alternans in One Dimension
<p>While alternans in a single cardiac cell appears through a simple</p><p>period-doubling bifurcation, in extended tissue the exact nature</p><p>of the bifurcation is unclear. In particular, the phase of</p><p>alternans can exhibit wave-like spatial dependence, either</p><p>stationary or …
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The relationship between repolarisation alternans and the production of ventricular arrhythmia in heart failure
Microvolt T-wave alternans is thought to predict the risk of ventricular arrhythmias in patients with heart disease, although recent clinical studies have conflicting results. Understanding the cellular basis for alternans may not only inform more effective utilisation of the clinical test, but …
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A snapshot of color: Exploring the ecological and genetic basis of color variation in the Neotropical tortoise beetle, Chelymorpha alternans (chrysomelidae:cassidinae)
… of the Neotropical tortoise beetle, Chelymorpha alternans, across the Isthmus of Panama? 2) What is the inheritance hierarchy of alleles for color polymorphisms in Chelymorpha alternans? 3) Do mating preferences for particular color morphs influence the maintenance of color polymorphisms in C. …
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Metabifurcation analysis of a phenomenological ventricular cell model
… however, it has been shown that cardiac alternans is closely related to arrhythmia[35]. Therefore, predicting alternans could be the _rst step in preventing arrhythmia. Fenton and Karma(1998)[10] came up with the Fenton-Karma model (the F-K model) with three variables and 13 parameters …
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Arrhythmia mechanisms in acute ischaemia and chronic infarction in rabbit heart
… were observed during occlusion. T-wave alternans behaviour was observed frequently during local ischaemia and associated with alternans of optical action potentials (OAPs) in the ischaemic border zone (BZ) and in ischaemic zone (IZ). T-wave alternans amplitude was not maintained during …
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A comprehensive assessment of variations in electrocardiogram morphology in risk assessment of cardiovascular death post-acute coronary syndrome
… rate turbulence, deceleration capacity, T-wave alternans, and morphologic variability. This thesis introduces new ECG-based metrics that can be used to risk-stratify post-ACS patients for future cardiovascular death and evaluates the clinical utility of the existing electrocardiogram based …
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Atrial arrhythmogenesis in a murine model of mitochondrial insufficiency
… AF. However in the present work the incidence of alternans or steepness of the restitution curves did not correlate with arrhythmic tendency. Loose patch clamp measurements demonstrated that Pgc-1β−/− atria had significantly lower inward Na+ currents than that of WT preparations, correlating to …
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Mechanisms of ventricular arrhythmogenesis in the age dependent Pgc-1β -/- model of mitochondrial dysfunction.
… as evidenced by the presence of electrical alternans. Finally, patch-clamp studies are performed to confirm the hypotheses of the earlier experiments and their effect on cellular currents in a physiological environment which show a physiological deficit in sodium current density. At all …
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Electrocardiographic predictors of clinical outcome in ST-elevation myocardial infarction
… morphology, dynamics of ST-segment and T-wave alternans (TWA) were calculated, and myocardial area at risk (MaR) and infarct size (IS) were assessed. Predictors and prognostic impact of early VF in STEMI was assessed in a register-based study of 1,718 consecutive patients admitted for primary …
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Augmentations vs. Restoration: A computational study of the effects of bacterial sodium channels on cardiac conduction.
… reductions in action potential duration removed alternans present in the restitution curves for single cells. To study how BacNav affected arrhythmias, BacNav was incorporated into one-dimensional cables and two-dimensional tissues with source-load mismatches present, premature stimuli that could …
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Biogeography and biosystematics of plum curculio, Conotrachelus nenuphar (Herbst)/Wolbachia interactions
… from the neotropical beetle, Chelymorpha alternans Boheman (Keller et al. 2004). The wCne2 sequence was 98.5% identical to the flower bug, Orius nagaii Yasunaga (Miura and Tagami, unpublished). The wCne3 sequence was 100% identical to Wolbachia sequenced from the tephritid fruit fly, Dacus …