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Cardiac alternans

Alba Martin-Yebra, Violeta Monasterio, Iwona Cygankiewicz, Antoni Bayes-de-Luna, Enrico G Caiani, Pablo Laguna, Juan Pablo Martinez
OBJECTIVE: We proposed and evaluated a method for correcting possible phase shifts provoked by the presence of ventricular premature contractions (VPCs) for a better assessment of T-wave alternans (TWA). Methods: First, we synthesized ECG signals with artificial TWA in the presence of different noise sources. Then, we assessed the prognostic value for sudden cardiac death (SCD) of the long-term average of TWA amplitude (the index of average alternans, ) in ambulatory ECG signals from congestive heart failure (CHF) and evaluated whether it is sensitive to the presence of VPCs...
March 2018: IEEE Transactions on Bio-medical Engineering
James Winter, Martin J Bishop, Catherine D E Wilder, Christopher O'Shea, Davor Pavlovic, Michael J Shattock
Rationale: Arrhythmogenic cardiac alternans are thought to be an important determinant for the initiation of ventricular fibrillation. There is limited information on the effects of sympathetic nerve stimulation (SNS) on alternans in the intact heart and the conclusions of existing studies, focused on investigating electrical alternans, are conflicted. Meanwhile, several lines of evidence implicate instabilities in Ca handling, not electrical restitution, as the primary mechanism underpinning alternans. Despite this, there have been no studies on Ca alternans and SNS in the intact heart...
2018: Frontiers in Physiology
Chia-Ti Tsai, Ming-Wei Kuo, Jiunn-Lee Lin, Alice L Yu, John Yu
Heart failure is a major cardiovascular disease and is associated with significant morbidity and mortality. Sudden cardiac death (SCD) in heart failure is a disastrous cardiovascular phenomenon. However, few studies have examined the genetic background that determines susceptibility to heart failure and SCD. We found that deficiency of a newly identified gene, Yulink, promoted cardiac alternans in zebrafish cardiomyocytes, and genetic knockdown (KD) resulted in pericardial edema, decreased cardiac output, and premature ventricular contractions...
January 11, 2018: FASEB Journal: Official Publication of the Federation of American Societies for Experimental Biology
Kanchan Kulkarni, Steven W Lee, Ryan Kluck, Elena G Tolkacheva
Cardiac alternans, a beat-to-beat alternation in action potential duration (APD), can lead to fatal arrhythmias. During periodic pacing, changes in diastolic interval (DI) depend on subsequent changes in APD, thus enhancing cardiac instabilities through a 'feedback' mechanism. Recently, an anti-arrhythmic Constant DI pacing protocol was proposed and shown to be effective in suppressing alternans in 0D and 1D in silico studies. However, previous experimental validation of Constant DI pacing in the heart has been unsuccessful due to the spatio-temporal complexity of 2D cardiac tissue and the technical challenges in its real-time implementation...
January 22, 2018: Annals of Biomedical Engineering
Daisuke Sato, Rose E Dixon, Luis F Santana, Manuel F Navedo
In ventricular myocytes, membrane depolarization during the action potential (AP) causes synchronous activation of multiple L-type CaV1.2 channels (LTCCs), which trigger the release of calcium (Ca2+) from the sarcoplasmic reticulum (SR). This results in an increase in intracellular Ca2+ (Cai) that initiates contraction. During pulsus alternans, cardiac contraction is unstable, going from weak to strong in successive beats despite a constant heart rate. These cardiac alternans can be caused by the instability of membrane potential (Vm) due to steep AP duration (APD) restitution (Vm-driven alternans), instability of Cai cycling (Ca2+-driven alternans), or both, and may be modulated by functional coupling between clustered CaV1...
January 16, 2018: PLoS Computational Biology
Vrishti M Phadumdeo, Seth H Weinberg
Heart rate continuously varies due to autonomic regulation, stochasticity in pacemaking, and circadian rhythm, collectively termed heart rate variability (HRV), during normal physiological conditions. Low HRV is clinically associated with an elevated risk of cardiac arrhythmias. Alternans, a beat-to-beat alternation in action potential duration (APD) and/or intracellular calcium (Ca) transient, is a well-known risk factor associated with cardiac arrhythmias that is typically studied under conditions of a constant pacing rate, i...
January 11, 2018: Journal of Theoretical Biology
Hasti Sanandajifar, Sarosh P Batlivala
A previously healthy 21-month-old presented with new-onset dilated cardiomyopathy. Evaluation noted pulsus alternans, with beat-to-beat alternations in aortic pulse wave amplitude, both clinically and on diagnostic studies. Pulsus alternans is an infrequent, complex pathophysiologic sign often associated with severe heart failure. The mechanisms are incompletely understood, but theorised aetiologies include beat-to-beat changes in left ventricular loading conditions, variations in myocardial oxygen supply/demand, and alternations in myocardial contractility...
March 2018: Cardiology in the Young
Zhen Song, Michael B Liu, Zhilin Qu
RATIONALE: The major role of a transverse-tubular (TT) network in a cardiac cell is to facilitate effective excitation-contraction coupling and signaling. The TT network structures are heterogeneous within a single cell, and vary between different types of cells and species. They are also remodeled in cardiac diseases. However, how different TT network structures predispose cardiac cells to arrhythmogenesis remains to be revealed. OBJECTIVE: To systematically investigate the roles of TT network structure and the underlying mechanisms in the genesis of intracellular calcium (Ca2+ ) alternans and triggered activity (TA)...
January 2018: Journal of Molecular and Cellular Cardiology
Dan Wilson, Bard Ermentrout
Depressed heart rate variability is a well-established risk factor for sudden cardiac death in survivors of acute myocardial infarction and for those with congestive heart failure. Although measurements of heart rate variability provide a valuable prognostic tool, it is unclear whether reduced heart rate variability itself is proarrhythmic or if it simply correlates with the severity of autonomic nervous system dysfunction. In this work, we investigate a possible mechanism by which heart rate variability could protect against cardiac arrhythmia...
December 5, 2017: Biophysical Journal
Gulhan Tunca Sahin, Yakup Ergul
Timothy syndrome (TS) is a multisystemic disease that occurs because of a mutation in CACN1C gene and is characterized by prolonged QT interval. Mexiletine is a Class 1B antiarrhythmic drug that causes the disappearance of T-wave alternans by shortening QTc and peak-to-end of the T wave. It may block the development of torsades de pointes in a prolonged QT. This study presented the case of a patient diagnosed with TS and had a cardiac arrest history, prolonged QT, and T-wave alternans. After mexiletine treatment, the QTc interval shortened and T-wave alternans disappeared...
November 30, 2017: Annals of Noninvasive Electrocardiology
Xiaowei Zhong, Alexander Vallmitjana, Bo Sun, Zhichao Xiao, Wenting Guo, Jinhong Wei, Mingke Ni, Yongxiang Chen, Edward R O'Brien, Anne M Gillis, Masahiko Hoshijima, Hiroshi Takeshima, Leif Hove-Madsen, Raul Benitez, Darrell Belke, S R Wayne Chen
Reduced protein expression of the cardiac ryanodine receptor type 2 (RyR2) is thought to affect the susceptibility to stress-induced ventricular tachyarrhythmia (VT) and cardiac alternans, but direct evidence for the role of RyR2 protein expression in VT and cardiac alternans is lacking. Here, we used a mouse model ( crr m1 ) that expresses a reduced level of the RyR2 protein to determine the impact of reduced RyR2 protein expression on the susceptibility to VT, cardiac alternans, cardiac hypertrophy, and sudden death...
January 5, 2018: Biochemical Journal
Joseph S Piktel, Aurelia Cheng, Matthew McCauley, Zack Dale, Michelle Nassal, Danielle Maleski, Gary Pawlowski, Kenneth R Laurita, Lance D Wilson
BACKGROUND: We designed an innovative porcine model of ischemia-induced arrest to determine dynamic arrhythmia substrates during focal infarct, global ischemia from ventricular tachycardia or fibrillation (VT/VF) and then reperfusion to determine the effect of therapeutic hypothermia (TH) on dynamic arrhythmia substrates and resuscitation outcomes. METHODS AND RESULTS: Anesthetized adult pigs underwent thoracotomy and regional plunge electrode placement in the left ventricle...
November 17, 2017: Journal of the American Heart Association
Ikeotunye Royal Chinyere, Talal Moukabary, Steven Goldman, Elizabeth Juneman
A chronic heart failure (CHF) rat underwent epicardial programmed electrical stimulation (PES). Ventricular tachycardia (VT) developed during PES. Mechanical alternans was noted despite fixed tachycardia cycle length. Anti-tachycardia pacing attempts initiated a second VT that generated pulse intermittently and then degenerated into pulseless VT with electrical alternans.To our knowledge electrical and mechanical alternans have not been recorded in animal models of CHF during VT. The distinct events of mechanical alternans and electrical alternans may be indicative of progressively worsened calcium handling in the compromised cardiomyocytes...
September 23, 2017: Journal of Electrocardiology
Ilija Uzelac, Yanyan C Ji, Daniel Hornung, Johannes Schröder-Scheteling, Stefan Luther, Richard A Gray, Elizabeth M Cherry, Flavio H Fenton
Rationale: Discordant alternans, a phenomenon in which the action potential duration (APDs) and/or intracellular calcium transient durations (CaDs) in different spatial regions of cardiac tissue are out of phase, present a dynamical instability for complex spatial dispersion that can be associated with long-QT syndrome (LQTS) and the initiation of reentrant arrhythmias. Because the use of numerical simulations to investigate arrhythmic effects, such as acquired LQTS by drugs is beginning to be studied by the FDA, it is crucial to validate mathematical models that may be used during this process...
2017: Frontiers in Physiology
Chunlin Yin, Ping Zhang, Jing Yang, Li Zhang
A 26-year-old woman, 12 days in postpartum, developed recurrent syncope and cardiac arrest. Her ECG revealed QT-prolongation associated with LQT2-specific T-U wave patterns, T wave alternans, long QT-dependent torsade de pointes (TdP) and ventricular fibrillation (VF). She also had intermittent LBBB (80bpm) on alternate beats and RBBB at sinus tachycardia (113bpm). Family genotyping revealed a novel de novo missense mutation G604C of KCNH2. Propranolol slowed heart rate and further prolonged QT interval (610ms) that caused TdP recurrence...
August 17, 2017: Journal of Electrocardiology
Julia Ramírez, Michele Orini, Ana Mincholé, Violeta Monasterio, Iwona Cygankiewicz, Antonio Bayés de Luna, Juan Pablo Martínez, Pablo Laguna, Esther Pueyo
BACKGROUND: Sudden cardiac death (SCD) and pump failure death (PFD) are common endpoints in chronic heart failure (CHF) patients, but prevention strategies are different. Currently used tools to specifically predict these endpoints are limited. We developed risk models to specifically assess SCD and PFD risk in CHF by combining ECG markers and clinical variables. METHODS: The relation of clinical and ECG markers with SCD and PFD risk was assessed in 597 patients enrolled in the MUSIC (MUerte Súbita en Insuficiencia Cardiaca) study...
2017: PloS One
Andreas Mayer, Philip Bittihn, Stefan Luther
Spatiotemporal dynamics in cardiac tissue emerging from the coupling of individual cardiomyocytes underlie the heart's normal rhythm as well as undesired and possibly life-threatening arrhythmias. While single cells and their transmembrane currents have been studied extensively, systematically investigating spatiotemporal dynamics is complicated by the nontrivial relationship between single-cell and emergent tissue properties. Mathematical models have been employed to bridge this gap and contribute to a deepened understanding of the onset, development, and termination of arrhythmias...
October 2017: Physiological Reports
Changrong Ye, Xiaoping Zeng, Guojun Li, Chenyuan Shi, Xin Jian, Xichuan Zhou
Sudden cardiac death (SCD) is one of the most prominent causes of death among patients with cardiac diseases. Since ventricular arrhythmia is the main cause of SCD and it can be predicted by T wave alternans (TWA), the detection of TWA in the body-surface electrocardiograph (ECG) plays an important role in the prevention of SCD. But due to the multi-source nature of TWA, the nonlinear propagation through thorax, and the effects of the strong noises, the information from different channels is uncertain and competitive with each other...
September 2017: Review of Scientific Instruments
A Collet, J Bragard, P C Dauby
This article characterizes the cardiac autonomous electrical activity induced by the mechanical deformations in the cardiac tissue through the mechano-electric feedback. A simplified and qualitative model is used to describe the system and we also account for temperature effects. The analysis emphasizes a very rich dynamics for the system, with periodic solutions, alternans, chaotic behaviors, etc. The possibility of self-sustained oscillations is analyzed in detail, particularly in terms of the values of important parameters such as the dimension of the system and the importance of the stretch-activated currents...
September 2017: Chaos
Nicholas S LaVigne, Nathan Holt, Matthew J Hoffman, Elizabeth M Cherry
Reentrant electrical scroll waves have been shown to underlie many cardiac arrhythmias, but the inability to observe locations away from the heart surfaces and the restriction of observations to only one or two state variables have made understanding arrhythmia mechanisms challenging. Recently, we showed that data assimilation from spatiotemporally sparse surrogate observations could be used to reconstruct a reliable time series of state estimates of reentrant cardiac electrical waves including unobserved variables in one and three spatial dimensions...
September 2017: Chaos
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