Role of Substrate and Triggers in the Genesis of Cardiac Alternans, From the Myocyte to the Whole Heart

Merchant, Faisal M.; Armoundas, Antonis A.

doi:10.1161/circulationaha.111.033563

Cited by 48 publications

(52 citation statements)

References 140 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…3 However, irrespective of the underlying subcellular mechanism of alternans, it is likely that alternans of APD begins in a localized area in the heart and gives rise to microvolt level alternans on the surface ECG. In this regard, we believe that alternans induced by using R-wave triggered pacing during the absolute refractory period does bear similarities to spontaneously occurring alternans: it originates from a localized area in the heart; it results from a group of myocytes exhibiting longer/shorter APD, depending on the R-wave triggered pacing pulse characteristics, such as the amplitude and width (Figure 2), and it is likely to propagate similarly to spontaneously occurring alternans, as manifested by the progressively reduced alternans amplitude away from the source ( Figure 5).…”

Section: Discussionmentioning

confidence: 99%

“…The presence of RA has been associated with an increased risk of ventricular tachycardia/ventricular fibrillation (VT/VF) and sudden cardiac death during medium-and long-term follow-up across various disease states including both ischemic and nonischemic congestive heart failure with impaired left ventricular ejection fraction and recent myocardial infarction. [1][2][3] Numerous experimental 4,5 and computational [6][7][8] studies have demonstrated that spatially heterogeneous action potential duration (APD) alternans can provide the substrate for reentry and VT/VF, thus providing a plausible mechanism for the association between RA and arrhythmogenesis. 4,9,10 Clinical evidence also supports the presence of a state of heightened RA magnitude immediately prior to the onset of spontaneous ventricular arrhythmias, [11][12][13][14][15] further supporting the notion that the heart either passes through a state of heightened RA en route to VT/VF or RA occurs in close conjunction with developing VT/VF.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A novel pacing method to suppress repolarization alternans in vivo: Implications for arrhythmia prevention

et al. 2013

Self Cite

View full text Add to dashboard Cite

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A novel pacing method to suppress repolarization alternans in vivo: Implications for arrhythmia prevention

et al. 2013

Self Cite

View full text Add to dashboard Cite

“…However, the mechanistic basis of MTWA preceding lethal ventricular arrhythmias has been under debate since MTWA is most successful in stratifying risk in patients at heart rates < 110 bpm, where APD restitution is flat [86]. Computational models of the left ventricular (LV) wall in combination with clinical data revealed that abnormal intracellular calcium handling underlies alternans in action potential voltage, which result in MTWA at heart rates < 110 bpm [17,85]; abnormalities in intracellular calcium have long been linked to ventricular fibrillation [80,129]. Computational modeling studies have also shown that under conditions of abnormal calcium dynamics, the T-wave alternans magnitude is enhanced by structural heterogeneities in the myocardium [47].…”

Section: Modeling To Identify Individuals With a High Risk Of Developmentioning

confidence: 99%

Cardiac Arrhythmias: Mechanistic Knowledge and Innovation from Computer Models

Trayanova

Boyle

2015

MS&A

View full text Add to dashboard Cite

Computational simulation is increasingly recognized as an integral aspect of modern cardiovascular research. Realistic and biophysically detailed models of the cardio-circulatory system can help interpret complex experimental observations, dissect underlying mechanisms, and explain emerging organ-scale phenomena resulting from subtle changes at the tissue, cellular, and/or sub-cellular scales. This chapter provides an overview of recent advances in the simulation of cardiac electrical behavior, focusing specifically on detailed models of the initiation, perpetuation, and termination of ventricular arrhythmias, including fibrillation. The development and validation of such models has opened several noteworthy avenues of research, including close scrutiny of arrhythmia dynamics in healthy and diseased hearts, dissection of arrhythmogenic and cardioprotective properties of specialized cardiac tissue regions such as the Purkinje system, and exploration of emerging paradigms for anti-arrhythmia treatment, such as optogenetics. Excitingly, the clinical community is currently taking the first steps towards using patient-specific ventricular models to stratify arrhythmia risk, personalize treatment planning, and optimize device placement for difficult or unusual procedures.

show abstract

“…One model for understanding rare behaviour comes from the study of the electrical basis of arrhythmias, the Trigger-Substrate model [10]. Triggers are proximate causes that are short-lived, unpredictable, and idiosyncratic events, while substrates are permissive states that are medium-term, more predictable and measurable.…”

Section: Introductionmentioning

confidence: 99%

A trigger-substrate model for smiling during an automated formative quiz

Witchel

Claxton

Holmes

et al. 2018

Proceedings of the 36th European Conference on Cognitive Ergonomics

View full text Add to dashboard Cite

Introduction: Automated tutoring systems aim to respond to the learner's cognitive state in order to maintain engagement. The end-user's state might be inferred by interactive timings, bodily movements or facial expressions. Problematic computerized stimuli are known to cause smiling during periods of frustration. Methods: Forty-four seated, healthy participants (age range 18-35, 18 male) used a handheld trackball to answer a computer-presented, formative, 3-way multiple choice geography quiz, with 9 questions, lasting a total of 175 seconds. Frontal facial videos (10 Hz) were collected with a webcam and processed for facial expressions by CrowdEmotion using a pattern recognition algorithm. Interactivity was recorded by a keystroke logger (Inputlog 5.2). Subjective responses were collected immediately after each quiz using a panel of visual analogue scales (VAS). Results: Smiling was five-fold enriched during the instantaneous feedback segments of the quiz, and this was correlated with VAS ratings for engagement but not with happiness or frustration. Nevertheless, smiling rate was significantly higher after wrong answers compared to correct ones, and frustration was correlated with the number of questions answered incorrectly. Conclusion: The apparent disconnect between the increased smiling during incorrect answers but the lack of correlation between VAS frustration and smiles suggests a trigger-substrate model where engagement is the permissive substrate, while the noises made by the quiz after wrong answers may be the trigger. CCS CONCEPTS• HCI design and evaluation methods; * Correspondence: h.witchel@bsms.ac.uk † Current address: IMS, Goldsmiths, University of London, UK Permission to make digital or hard copies of part or all of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. Copyrights for third-party components of this work must be honored. For all other uses, contact the owner/author(s

show abstract

Role of Substrate and Triggers in the Genesis of Cardiac Alternans, From the Myocyte to the Whole Heart

Cited by 48 publications

References 140 publications

A novel pacing method to suppress repolarization alternans in vivo: Implications for arrhythmia prevention

A novel pacing method to suppress repolarization alternans in vivo: Implications for arrhythmia prevention

Cardiac Arrhythmias: Mechanistic Knowledge and Innovation from Computer Models

A trigger-substrate model for smiling during an automated formative quiz

Contact Info

Product

Resources

About