Review

Authors: Akihiko Nogami, Yuki Komatsu, Ahmed Karim Talib...

Of the monomorphic ventricular tachycardias, there are 4 specific tachycardias related to the Purkinje system: 1) idiopathic verapamil-sensitive fascicular ventricular tachycardia (FVT); 2) non-re-entrant FVT; 3) bundle branch re-entry and interfascicular re-entry; and 4) Purkinje-mediated VT in structural heart disease. Verapamil-sensitive FVT is classified into 4 types according to the location of the circuit: 1) left posterior type; 2) left anterior type; 3) left upper septal type;and 4) reverse type. And, in the left anterior and posterior types, there are septal and papillary muscle subtypes. Although macro-re-entry has been reported to be the mechanism underlying verapamil-sensitive FVT, recording the entire circuit is challenging. One possible reason is that the Purkinje-muscle junction may penetrate the myocardial layer as a part of the circuit. The Purkinje network may thus play an important role in the initiation and maintenance of ventricular fibrillation. Further, it has been reported that the development and the abnormalities of the Purkinje system are associated with the arrhythmogenesis of ventricular fibrillation. Furthermore, it has been reported that catheter ablation of trigger ventricular premature complexes, and/or "de-networking" of the Purkinje system, can be used as electrical bailout therapy. There is a hypothesis that the intramural Purkinje system is involved in the generation of J waves. Nevertheless, as there are still unresolved issues that must be debated and accurately analyzed, this review aims to discuss the solved and unsolved questions related to Purkinje-related arrhythmias.

Topics: Humans; Ventricular Fibrillation; Purkinje Fibers; Tachycardia, Ventricular; Verapamil; Ventricular Premature Complexes

PubMed: 37498247
DOI: 10.1016/j.jacep.2023.05.040

Meta-Analysis Review

Authors: Mohamed T Abuelazm, Ahmed Ghanem, Basant E Katamesh...

BACKGROUND AND OBJECTIVE

Double sequential external defibrillation (DSED) and vector-change defibrillation (VCD) have been suggested to enhance clinical outcomes for patients with ventricular fibrillation (VF) refractory of standard defibrillation (SD). Therefore, this network meta-analysis aims to evaluate the comparative efficacy of DSED, VCD, and SD for refractory VF.

METHODS

A systematic review and network meta-analysis synthesizing randomized controlled trials (RCTs) and comparative observational studies retrieved from PubMed, EMBASE, WOS, SCOPUS, and Cochrane through November 15th, 2022. R software netmeta and netrank package (R version 4.2.0) and meta-insight software were used to pool dichotomous outcomes using odds ratio (OR) presented with the corresponding confidence interval (CI). Our protocol was prospectively published in PROSPERO with ID: CRD42022378533.

RESULTS

We included seven studies with a total of 1632 participants. DSED was similar to SD in survival to hospital discharge (OR: 1.14 with 95% CI [0.55, 2.83]), favorable neurological outcome (modified Rankin scale ≤2 or cerebral performance category ≤2) (OR: 1.35 with 95% CI [0.46, 3.99]), and return of spontaneous circulation (ROSC) (OR: 0.81 with 95% CI [0.43; 1.5]). In addition, VCD was similar to SD in survival to hospital discharge (OR: 1.12 with 95% CI [0.27, 4.57]), favorable neurological outcome (OR: 1.01 with 95% CI [0.18, 5.75]), and ROSC (OR: 0.88 with 95% CI [0.24; 3.15]).

CONCLUSION

Double sequential external defibrillation and VCD were not associated with enhanced outcomes in patients with refractory VF out-of-hospital cardiac arrest, compared to SD. However, the current evidence is still inconclusive, warranting further large-scale RCTs.

Topics: Humans; Electric Countershock; Ventricular Fibrillation; Out-of-Hospital Cardiac Arrest; Network Meta-Analysis; Electrocardiography; Cardiopulmonary Resuscitation

PubMed: 37482919
DOI: 10.1111/anec.13075

Review

Authors: Eduard Guasch, Lluís Mont

The cardiovascular benefits of physical activity are indisputable. Nevertheless, growing evidence suggests that both atrial fibrillation and right ventricular arrhythmia can be caused by intense exercise in some individuals. Exercise-induced atrial fibrillation is most commonly diagnosed in middle-aged, otherwise healthy men who have been engaged in endurance training for >10 years, and is mediated by atrial dilatation, parasympathetic enhancement, and possibly atrial fibrosis. Cardiac ablation is evolving as a first-line tool for athletes with exercise-induced arrhythmia who are eager to remain active. The relationship between physical activity and right ventricular arrhythmia is complex and involves genetic and physical factors that, in a few athletes, eventually lead to right ventricular dilatation, followed by subsequent myocardial fibrosis and lethal ventricular arrhythmias. Sinus bradycardia and atrioventricular conduction blocks are common in athletes, most of whom remain asymptomatic, although incomplete reversibility has been shown after exercise cessation. In this Review, we summarize the evidence supporting the existence of exercise-induced arrhythmias and discuss the specific considerations for the clinical management of these patients.

Topics: Arrhythmias, Cardiac; Athletes; Atrial Fibrillation; Exercise; Humans; Risk Factors; Ventricular Fibrillation

PubMed: 27830772
DOI: 10.1038/nrcardio.2016.173

Review

Authors: Bastiaan J Boukens, Sarah R Gutbrod, Igor R Efimov...

Ventricular fibrillation is the major underlying cause of sudden cardiac death. Understanding the complex activation patterns that give rise to ventricular fibrillation requires high resolution mapping of localized activation. The use of multi-electrode mapping unraveled re-entrant activation patterns that underlie ventricular fibrillation. However, optical mapping contributed critically to understanding the mechanism of defibrillation, where multi-electrode recordings could not measure activation patterns during and immediately after a shock. In addition, optical mapping visualizes the virtual electrodes that are generated during stimulation and defibrillation pulses, which contributed to the formulation of the virtual electrode hypothesis. The generation of virtual electrode induced phase singularities during defibrillation is arrhythmogenic and may lead to the induction of fibrillation subsequent to defibrillation. Defibrillating with low energy may circumvent this problem. Therefore, the current challenge is to use the knowledge provided by optical mapping to develop a low energy approach of defibrillation, which may lead to more successful defibrillation.

Topics: Animals; Electric Countershock; Electrodes; Fluorescent Dyes; Heart; Humans; Optical Imaging; User-Computer Interface; Ventricular Fibrillation; Voltage-Sensitive Dye Imaging

PubMed: 26238060
DOI: 10.1007/978-3-319-17641-3_14

Authors: Zhilin Qu

Topics: Arrhythmias, Cardiac; Humans; Ventricular Fibrillation

PubMed: 34757188
DOI: 10.1016/j.hrthm.2021.10.021

Meta-Analysis

Authors: Jinzhou Yu, Yanwu Yu, Huoyan Liang...

AIM

The aim of this study was to summarize the existing evidence about the effectiveness of double defibrillation (DD) in comparison to standard defibrillation for patients with refractory ventricular fibrillation (RVF). DD encompasses double "sequential" external defibrillation (DSeq-D) and double "simultaneous" defibrillation (DSim-D), with the study also shedding light on the respective effects of DSeq-D and DSim-D.

METHODS

Investigators systematically searched PubMed, EMBASE and Cochrane Central databases for randomized controlled trials (RCTs) and cohort studies from their inception until June 06, 2024. The rate of survival to hospital discharge was the primary outcome, while the incidence of return of spontaneous circulation (ROSC), termination of ventricular fibrillation (VF), survival to hospital admission and good neurologic outcome were secondary outcomes. Relative ratios (RR) and 95% confidence intervals (CIs) were calculated for each outcome. Heterogeneity was assessed using I square value.

RESULTS

A total of 6 trials, comprising 1360 patients, were included. One was an RCT, and five were observational cohort studies. The RCT showed that, compared to standard defibrillation, DSeq-D was associated with higher incidences of survival to hospital discharge, termination of VF, ROSC and good neurologic outcome. However, the pooled results of cohort studies found no benefit of DD over standard defibrillation in survival to hospital discharge (RR, 0.91; 95% CI, 0.46-1.78), nor in secondary outcomes. Furthermore, subgroup analysis suggested DSim-D was linked with lower ROSC rate compared to standard defibrillation (RR, 0.65; 95% CI, 0.49-0.86), while there was no significance between DSeq-D and standard defibrillation (RR, 1.00; 95% CI, 0.70-1.42).

CONCLUSIONS

The benefit of DSeq-D in survival to hospital discharge for RVF patients was found in the RCT, but not in cohort studies. Additionally, DSim-D should be applied with greater caution for RVF patients. Further validation is needed through larger-scale and higher-quality trials.

TRIAL REGISTRY

INPLASY; Registration number: INPLASY202340015; URL: https://inplasy.com/.

Topics: Humans; Electric Countershock; Ventricular Fibrillation

PubMed: 39127020
DOI: 10.1016/j.ajem.2024.07.059

Review

Authors: Reza Jabbari

In this PhD thesis, we report that VF is still a common complication of STEMI, with an incidence of 11.6% in the population of Danish STEMI patients who survive to reach the hospital. In this STEMI population, we identified several risk factors associated with VF independent of MI. We identified and confirmed findings from several previous studies and found several risk factors, such as younger age, a family history of sudden death, a TIMI flow grade of 0, the absence of angina, anterior infarction (i.e., VF before PPCI), and inferior infarction (i.e., VF during PPCI) that were associated with VF in a Danish cohort. Furthermore, a history of atrial fibrillation and alcohol intake were identified as novel risk factors for VF. To the best of our knowledge, this study contains data on the largest VF cohort with the longest reported follow-up published; we found that VF mortality is significantly higher within the first 30 days for patients who experience VF before and during PPCI compared with STEMI patients without VF. However, the long-term mortality rates of the three groups are the same. Importantly, our results contradict the previous understanding that VF during PPCI is "benign"; the mortality rate within the first 30 days was as high for patients with VF during PPCI as the mortality rate of patients with VF before PPCI. Finally, although it is difficult to draw clinical implications from a descriptive study, due to the comprehensiveness of Danish death certificates, we reported a high incidence of cardiac symptoms and contact with healthcare professionals based on cardiac symptoms in young SCD patients who died due to CAD, although death was not avoided.

Topics: Age Factors; Death, Sudden, Cardiac; Denmark; Female; Humans; Incidence; Male; Registries; Risk Factors; ST Elevation Myocardial Infarction; Severity of Illness Index; Survival Rate; Ventricular Fibrillation

PubMed: 27127021
DOI: No ID Found

Review

Authors: Michel Haïssaguerre, Wee Nademanee, Mélèze Hocini...

Idiopathic ventricular fibrillation and J-wave syndromes are causes of sudden cardiac death (SCD) without any identified structural cardiac disease after extensive investigations. Recent data show that high-density electrophysiological mapping may ultimately offer diagnoses of subclinical diseases in most patients including those termed "unexplained" SCD. Three major conditions can underlie the occurrence of SCD: (1) localized depolarization abnormalities (due to microstructural myocardial alteration), (2) Purkinje abnormalities manifesting as triggering ectopy and inducible reentry; or (3) repolarization heterogeneities. Each condition may result from a spectrum of pathophysiologic processes with implications for individual therapy.

Topics: Brugada Syndrome; Death, Sudden, Cardiac; Electrocardiography; Electrophysiologic Techniques, Cardiac; Heart Conduction System; Humans; Ventricular Fibrillation

PubMed: 31706476
DOI: 10.1016/j.ccep.2019.08.011

Review

Authors: P Sanders, L F Hsu, M Hocini...

Sudden cardiac death frequently results from ventricular fibrillation (VF). While VF is frequently the eventual mode of death in patients with abnormal ventricular substrates, it has also been described in patients with structurally normally hearts. Until recently, the management of patients who have survived sudden cardiac death has focused on treating the consequences by implantation of a defibrillator. However, such therapy remains restricted in many countries, is associated with a prohibitive cost to the community, and may be a cause of significant morbidity in patients with frequent episodes or storms of arrhythmia. Evidence emerging from the study of fibrillation both in the atria and the ventricle suggests an important role for triggers arising from the Purkinje network or the right ventricular outflow tract in the initiation of VF. Initial experience in patients with idiopathic VF and even those with VF associated with abnormal repolarization syndromes (LQT or Brugada syndrome) or myocardial infarction suggests that long term suppression of recurrent VF may be feasible by the elimination of these triggers. With the development of new mapping and ablation technologies, and greater physician experience, catheter ablation of VF, with the ultimate aim of curing such patients at risks of sudden cardiac death, may not be an unrealistic goal in the future.

Topics: Electrocardiography; Humans; Long QT Syndrome; Myocardial Infarction; Patient Selection; Ventricular Fibrillation

PubMed: 15194978
DOI: No ID Found

Review

Authors: Sami F Noujaim, David S Auerbach, José Jalife...

Ventricular fibrillation (VF) is the leading cause of sudden cardiac death. This brief review addresses issues relevant to the dynamics of the rotors responsible for functional reentry and VF. It also makes an attempt to summarize present-day knowledge of the manner in which the dynamic interplay between inward and outward transmembrane currents and the heterogeneous cardiac structure establish a substrate for the initiation and maintenance of rotors and VF. The fragmentary nature of our current understanding of ionic VF mechanisms does not even allow an approach toward a "Theory of VF". Yet some hope is provided by recently obtained insight into the roles played in VF by some of the sarcolemmal ion channels that control the excitation-recovery process. For example, strong evidence supports the idea that the interplay between the rapid-inward sodium current and the inward-rectifier potassium current controls rotor formation, as well as rotor stability and frequency. Solid evidence also exists for an involvement of L-type calcium current in the control of rotor frequency and in determining VF-to-ventricular tachycardia conversion. Less clear, however, is whether or not time dependent outward currents through voltage-gated potassium channels affect the fibrillatory process. Hopefully, taking advantage of currently available approaches of structural, molecular and cellular biology, together with computational and imaging techniques, will afford us the opportunity to further advance knowledge on VF mechanisms.

Topics: Action Potentials; Animals; Anti-Arrhythmia Agents; Excitation Contraction Coupling; Heart Conduction System; Heart Rate; Humans; Ion Channels; Kinetics; Ventricular Fibrillation

PubMed: 17587732
DOI: 10.1253/circj.71.a1