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Cardiac alternans

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https://www.readbyqxmd.com/read/28324970/development-of-data-acquisition-components-for-simultaneous-recording-of-3d-epicardial-and-surface-ecg-signals-in-the-langendorff-perfusion-apparatus
#1
Ryan Wade Selby, Anup Jonchhe, Chen Kaplan, Coeli M Lopes, Behnaz Ghoraani
Sudden Cardiac Death (SCD) claims 7 million lives per year. The importance of myocardial electrogram (EGM) repolarization alternans and surface electrocardiogram (ECG) T-wave alternans is gaining traction for understanding the underlying SCD mechanisms. However, the relationship between the 3D spatial distribution of myocardial EGMs and surface ECG with respect to SCD has yet to be investigated. To make this happen, a modified data acquisition system has been developed and fabricated in conjunction with the Langendorff perfusion system to enable simultaneous recording and analysis of the 3D spatial distribution of myocardial EGMs and the surface ECG...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28314848/effects-of-late-sodium-current-blockade-on-ventricular-refibrillation-in-a-rabbit-model
#2
Mohammed Ali Azam, Nima Zamiri, Stéphane Massé, Marjan Kusha, Patrick F H Lai, Govind K Nair, Nigel S Tan, Christopher Labos, Kumaraswamy Nanthakumar
BACKGROUND: After defibrillation of initial ventricular fibrillation (VF), it is crucial to prevent refibrillation to ensure successful resuscitation outcomes. Inability of the late Na(+) current to inactivate leads to intracellular Ca(2+) dysregulation and arrhythmias. Our aim was to determine the effects of ranolazine and GS-967, inhibitors of the late Na(+) current, on ventricular refibrillation. METHODS AND RESULTS: Long-duration VF was induced electrically in Langendorff-perfused rabbit hearts (n=22) and terminated with a defibrillator after 6 minutes...
March 2017: Circulation. Arrhythmia and Electrophysiology
https://www.readbyqxmd.com/read/28284506/sudden-cardiac-death-the-role-of-imaging
#3
Pieter van der Bijl, Victoria Delgado, Jeroen J Bax
Sudden cardiac death (SCD) is defined as "a non-traumatic, unexpected, fatal event occurring within one hour of the onset of symptoms in an apparently healthy subject", and it causes a fifth of all deaths worldwide. It often occurs in individuals not previously known with cardiac disease, which makes prevention challenging. The mechanism underlying SCD is thought to be a trigger (e.g. ischemia) acting upon a substrate (e.g. scar), causing a lethal arrhythmia. Primary prevention refers to patients at high risk of SCD and secondary prevention to those who have had an aborted episode of SCD...
March 6, 2017: International Journal of Cardiology
https://www.readbyqxmd.com/read/28268303/effects-and-underlying-mechanisms-of-refractory-period-pacing-on-repolarization-dynamics-in-the-human-heart
#4
Diogo Santos, Michele Orini, Xin Zhou, Alfonso Bueno-Orovio, Ben Hanson, Peter Taggart, Martin Hayward, Blanca Rodriguez, Pier Lambiase
Repolarization alternans is related to the initiation of life threatening cardiac arrhythmias. Experimental and computational studies suggest that the abolishment of alternans using dynamic pacing protocols may prevent abnormal heart rhythms. In a recent animal study, refractory period pacing (RPP) on every other beat has shown promising results in alternans reduction. However, the cellular mechanisms underlying this therapy and its efficiency in human patients remain unclear. In this study, in vivo unipolar electrograms acquired during RPP from 240 epicardial sites from one patient were analysed...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28268301/pro-arrhythmic-effect-of-heart-rate-variability-during-periodic-pacing
#5
Kanchan Kulkarni, Steven W Lee, Elena G Tolkacheva
Clinically, healthy hearts have been associated with a high ventricular heart rate variability (HRV) while diseased hearts have been known to exhibit low ventricular HRV. Hence, low HRV is suggested to be a marker of cardiac ventricular arrhythmias. Over the past few years, there has been considerable amount of interest in incorporating HRV in pacing to emulate healthy heart conditions and re-stabilize the electrical activity in diseased hearts. Recently, we used single cell numerical simulations to demonstrate that HRV incorporated into periodic pacing promotes alternans formation and thus, can be pro-arrhythmic...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28257761/membrane-potential-determines-calcium-alternans-through-modulation-of-sr-ca-2-load-and-l-type-ca-2-current
#6
Giedrius Kanaporis, Lothar A Blatter
Alternans is a risk factor for cardiac arrhythmia, including atrial fibrillation. At the cellular level alternans is observed as beat-to-beat alternations in contraction, action potential (AP) morphology and magnitude of the Ca(2+) transient (CaT). It is widely accepted that the bi-directional interplay between membrane voltage and Ca(2+) is crucial for the development of alternans, however recently the attention has shifted to instabilities in cellular Ca(2+) handling, while the role of AP alternation remains poorly understood...
February 28, 2017: Journal of Molecular and Cellular Cardiology
https://www.readbyqxmd.com/read/28227084/development-of-data-acquisition-components-for-simultaneous-recording-of-3d-epicardial-and-surface-ecg-signals-in-the-langendorff-perfusion-apparatus
#7
Ryan Wade Selby, Anup Jonchhe, Chen Kaplan, Coeli M Lopes, Behnaz Ghoraani, Ryan Wade Selby, Anup Jonchhe, Chen Kaplan, Coeli M Lopes, Behnaz Ghoraani, Chen Kaplan, Behnaz Ghoraani, Anup Jonchhe, Coeli M Lopes, Ryan Wade Selby
Sudden Cardiac Death (SCD) claims 7 million lives per year. The importance of myocardial electrogram (EGM) repolarization alternans and surface electrocardiogram (ECG) T-wave alternans is gaining traction for understanding the underlying SCD mechanisms. However, the relationship between the 3D spatial distribution of myocardial EGMs and surface ECG with respect to SCD has yet to be investigated. To make this happen, a modified data acquisition system has been developed and fabricated in conjunction with the Langendorff perfusion system to enable simultaneous recording and analysis of the 3D spatial distribution of myocardial EGMs and the surface ECG...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28226462/effects-and-underlying-mechanisms-of-refractory-period-pacing-on-repolarization-dynamics-in-the-human-heart
#8
Diogo Santos, Michele Orini, Xin Zhou, Alfonso Bueno-Orovio, Ben Hanson, Peter Taggart, Martin Hayward, Blanca Rodriguez, Pier Lambiase, Diogo Santos, Michele Orini, Xin Zhou, Alfonso Bueno-Orovio, Ben Hanson, Peter Taggart, Martin Hayward, Blanca Rodriguez, Pier Lambiase, Ben Hanson, Diogo Santos, Martin Hayward, Pier Lambiase, Alfonso Bueno-Orovio, Blanca Rodriguez, Michele Orini, Xin Zhou, Peter Taggart
Repolarization alternans is related to the initiation of life threatening cardiac arrhythmias. Experimental and computational studies suggest that the abolishment of alternans using dynamic pacing protocols may prevent abnormal heart rhythms. In a recent animal study, refractory period pacing (RPP) on every other beat has shown promising results in alternans reduction. However, the cellular mechanisms underlying this therapy and its efficiency in human patients remain unclear. In this study, in vivo unipolar electrograms acquired during RPP from 240 epicardial sites from one patient were analysed...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28226460/pro-arrhythmic-effect-of-heart-rate-variability-during-periodic-pacing
#9
Kanchan Kulkarni, Steven W Lee, Elena G Tolkacheva, Kanchan Kulkarni, Steven W Lee, Elena G Tolkacheva, Elena G Tolkacheva, Steven W Lee, Kanchan Kulkarni
Clinically, healthy hearts have been associated with a high ventricular heart rate variability (HRV) while diseased hearts have been known to exhibit low ventricular HRV. Hence, low HRV is suggested to be a marker of cardiac ventricular arrhythmias. Over the past few years, there has been considerable amount of interest in incorporating HRV in pacing to emulate healthy heart conditions and re-stabilize the electrical activity in diseased hearts. Recently, we used single cell numerical simulations to demonstrate that HRV incorporated into periodic pacing promotes alternans formation and thus, can be pro-arrhythmic...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28102901/risk-of-arrhythmic-death-in-ischemic-heart-disease-a-prospective-controlled-observer-blind-risk-stratification-over-10%C3%A2-years
#10
Thomas Pezawas, André Diedrich, David Robertson, Robert Winker, Bernhard Richter, Li Wang, Herwig Schmidinger
BACKGROUND: Risk of arrhythmic death is considered highest in ischemic heart disease with severe left ventricular ejection fraction (LVEF) reduction. Non-invasive testing should improve decision-making of prophylactic defibrillator (ICD) implantation. DESIGN: We enrolled 120 patients with ischemic heart disease and LVEF < 50% and 30 control subjects without ischemic heart disease and normal LVEF. An initial assessment, a second assessment after 3 years and a final follow-up comprised of pharmacological baroreflex testing (BRS), short-term spectral [low-frequency (LF) to high-frequency (HF) ratio] and long-term time-domain analysis of heart rate variability (SDNN), exercise Microvolt T-wave alternans (MTWA) and others...
January 19, 2017: European Journal of Clinical Investigation
https://www.readbyqxmd.com/read/28028806/from-channels-to-systems-ca-2-sensitive-k-currents-alternans-and-cardiac-arrhythmia
#11
Christopher L-H Huang
No abstract text is available yet for this article.
December 28, 2016: Journal of Physiology
https://www.readbyqxmd.com/read/27916321/exercise-induced-quantitative-microvolt-t-wave-alternans-in-hypertrophic-cardiomyopathy
#12
Murillo de Oliveira Antunes, Nelson Samesima, Horacio Gomes Pereira Filho, Afonso Yoshikiro Matsumoto, Richard L Verrier, Carlos Alberto Pastore, Edmundo Arteaga-Fernández, Charles Mady
BACKGROUND/PURPOSE: Patients with hypertrophic cardiomyopathy (HCM) have elevated risk for sudden cardiac death (SCD). Our study aimed to quantitatively characterize microvolt T-wave alternans (TWA), a potential arrhythmia risk stratification tool, in this HCM patient population. METHODS: TWA was analyzed with the quantitative modified moving average (MMA) in 132 HCM patients undergoing treadmill exercise testing, grouped according to Maron score risk factors as high-risk (H-Risk, n=67,), or low-risk (L-Risk, n=65, without these risk factors)...
March 2017: Journal of Electrocardiology
https://www.readbyqxmd.com/read/27914945/effects-of-zacopride-a-moderate-ik1-channel-agonist-on-triggered-arrhythmia-and-contractility-in-human-ventricular-myocardium
#13
Mohammad T Elnakish, Benjamin D Canan, Ahmet Kilic, Peter J Mohler, Paul M L Janssen
Ventricular tachycardia is the leading cause of sudden arrhythmic death in the U.S. Recently, the moderate IK1 channel activator, zacopride, was shown to suppress triggered ventricular tachycardia in rats. Nonetheless, concerns were raised about the possibility of pro-arrhythmic activity after IK1 channel stimulation based on the promising anti-arrhythmic strategy of IK1 blockade in other animal models. Therefore, the goal of the current study was to investigate the ex-vivo effects of zacopride on triggered arrhythmia and contractility in ventricular human myocardium in order to validate data that was solely obtained from animal models...
January 2017: Pharmacological Research: the Official Journal of the Italian Pharmacological Society
https://www.readbyqxmd.com/read/27902841/dynamical-effects-of-calcium-sensitive-potassium-currents-on-voltage-and-calcium-alternans
#14
Matthew Kennedy, Donald M Bers, Nipavan Chiamvimonvat, Daisuke Sato
KEY POINTS: A mathematical model of a small conductance Ca(2)(+) -activated potassium (SK) channel was developed and incorporated into a physiologically detailed ventricular myocyte model. Ca(2+) -sensitive K(+) currents promote negative intracellular Ca(2+) to membrane voltage (CAi(2+) → Vm ) coupling. Increase of Ca(2+) -sensitive K(+) currents can be responsible for electromechanically discordant alternans and quasiperiodic oscillations at the cellular level. At the tissue level, Turing-type instability can occur when Ca(2+) -sensitive K(+) currents are increased...
November 30, 2016: Journal of Physiology
https://www.readbyqxmd.com/read/27879279/heart-rate-turbulence-is-a-powerful-predictor-of-cardiac-death-and-ventricular-arrhythmias-in-postmyocardial-infarction-and-heart-failure-patients-a-systematic-review-and-meta-analysis
#15
Marcello Disertori, Michela Masè, Marta Rigoni, Giandomenico Nollo, Flavia Ravelli
BACKGROUND: Heart rate turbulence (HRT) has been proposed as a candidate marker of altered autonomic tone, and some studies showed its prognostic value for both cardiac death (CD) and sudden death. Nevertheless, HRT is not currently used in the clinical practice. METHODS AND RESULTS: We performed a systematic review and meta-analysis of the predictive value of HRT for the end points of total mortality, CD, and fatal and nonfatal ventricular arrhythmias in postacute myocardial infarction and heart failure patients...
December 2016: Circulation. Arrhythmia and Electrophysiology
https://www.readbyqxmd.com/read/27778458/t-wave-alternans-heart-rate-turbulence-and-ventricular-ectopy-in-standard-versus-daily-hemodialysis-results-from-the-fhn-daily-trial
#16
RANDOMIZED CONTROLLED TRIAL
Rachel M Kaplan, Charles A Herzog, Brett Larive, Haris Subacius, Bruce D Nearing, Richard Verrier, Rod S Passman
BACKGROUND: Hemodialysis (HD) patients are at high risk of sudden cardiac death (SCD). HD 6-times/week (6x/wk) may reduce SCD risk compared to usual 3-times/week HD (3x/wk) by mechanisms unknown. T-wave alternans (TWA), heart rate turbulence (HRT), and ventricular ectopy (VE) are elevated in HD patients, but their response to 6x/wk HD has not been assessed. METHODS: Baseline and 1-year Holter recordings were analyzed from enrollees in the Frequent Hemodialysis Network Daily Trial, a randomized trial comparing 3x/wk to 6x/wk in 245 chronic HD patients...
November 2016: Annals of Noninvasive Electrocardiology
https://www.readbyqxmd.com/read/27777148/eleclazine-an-inhibitor-of-the-cardiac-late-sodium-current-is-superior-to-flecainide-in-suppressing-catecholamine-induced-ventricular-tachycardia-and-t-wave-alternans-in-an-intact-porcine-model
#17
Danilo Bacic, Juliana Saran Carneiro, Afonso Alves Bento, Bruce D Nearing, Sridharan Rajamani, Luiz Belardinelli, Richard L Verrier
BACKGROUND: The capacity of catecholamines to induce ventricular tachycardia (VT) is well documented. OBJECTIVE: The effectiveness of the novel cardiac late sodium inhibitor eleclazine in suppressing catecholamine-induced VT in a large animal model was compared with that of flecainide. METHODS: In 13 closed-chest anesthetized Yorkshire pigs, spontaneous VT and surges in T-wave alternans (TWA) level measured using the Modified Moving Average method were induced by epinephrine (2...
October 21, 2016: Heart Rhythm: the Official Journal of the Heart Rhythm Society
https://www.readbyqxmd.com/read/27765387/t-wave-alternans-an-ominous-marker-for-malignant-cardiac-arrhythmias
#18
Gurunath Parale, Chinmay Parale
No abstract text is available yet for this article.
October 17, 2016: European Journal of Internal Medicine
https://www.readbyqxmd.com/read/27761166/cardiac-dynamics-alternans-and-arrhythmogenesis
#19
REVIEW
Gary Tse, Sheung Ting Wong, Vivian Tse, Yee Ting Lee, Hiu Yu Lin, Jie Ming Yeo
Pre-existing heterogeneities present in cardiac tissue are essential for maintaining the normal electrical and mechanical functions of the heart. Exacerbation of such heterogeneities or the emergence of dynamic factors can produce repolarization alternans, which are beat-to-beat alternations in the action potential time course. Traditionally, this was explained by restitution, but additional factors, such as cardiac memory, calcium handling dynamics, refractory period restitution, and mechano-electric feedback, are increasingly recognized as the underlying causes...
October 2016: Journal of Arrhythmia
https://www.readbyqxmd.com/read/27749895/a-parsimonious-model-of-the-rabbit-action-potential-elucidates-the-minimal-physiological-requirements-for-alternans-and-spiral-wave-breakup
#20
Richard A Gray, Pras Pathmanathan
Elucidating the underlying mechanisms of fatal cardiac arrhythmias requires a tight integration of electrophysiological experiments, models, and theory. Existing models of transmembrane action potential (AP) are complex (resulting in over parameterization) and varied (leading to dissimilar predictions). Thus, simpler models are needed to elucidate the "minimal physiological requirements" to reproduce significant observable phenomena using as few parameters as possible. Moreover, models have been derived from experimental studies from a variety of species under a range of environmental conditions (for example, all existing rabbit AP models incorporate a formulation of the rapid sodium current, INa, based on 30 year old data from chick embryo cell aggregates)...
October 2016: PLoS Computational Biology
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