Characteristics Of Ventricular Fibrillation Research Articles

Complexity analysis of electrical activity during endocardial and epicardial biventricular mapping of ventricular fibrillation.

Ventricular fibrillation (VF) is a lethal cardiac arrhythmia that is a significant cause of sudden cardiac death. Comprehensive studies of spatiotemporal characteristics of VF in situ are difficult to perform with current mapping systems and catheter technology. The goal of this study was to develop a computational approach to characterize VF using a commercially available technology in a large animal model. Prior data suggests that characterization of spatiotemporal organization of electrical activity during VF can be used to provide better mechanistic understanding and potential ablation targets to modify VF and its substrate. We therefore evaluated intracardiac electrograms during biventricular mapping of the endocardium (ENDO) and epicardium (EPI) in acute canine studies. To develop thresholds for organized and disorganized activity, a linear discriminant analysis (LDA)-based approach was performed to the known organized and disorganized activities recorded in ex vivo Langendorff-perfused rat and rabbit hearts using optical mapping experiments. Several frequency- and time-domain approaches were used as individual and paired features to identify the optimal thresholds for the LDA approach. Subsequently, VF was sequentially mapped in 4 canine hearts, using the CARTO mapping system with a multipolar mapping catheter in the ENDO left and right ventricles and EPI to capture the progression of VF at 3 discrete post-induction time intervals: VF period 1 (just after induction of VF to 15 min), VF period 2 (15 to 30 min), and VF period 3 (30 to 45 min). The developed LDA model, cycle lengths (CL), and regularity indices (RI) were applied to all recorded intracardiac electrograms to quantify the spatiotemporal organization of VF in canine hearts. We demonstrated the presence of organized activity in the EPI as VF progresses, in contrary to the ENDO, where the activity stays disorganized. The shortest CL always occurred in the ENDO, especially the RV, indicating a faster VF activity. The highest RI was found in the EPI in all hearts for all VF stages, indicating spatiotemporal consistency of RR intervals. We identified electrical organization and spatiotemporal differences throughout VF in canine hearts from induction to asystole. Notably, the RV ENDO is characterized by a high level of disorganization and faster VF frequency. In contrast, EPI has a high spatiotemporal organization of VF and consistently long RR intervals.

Regional and Temporal Variation of Ventricular and Conduction Tissue Activity During Ventricular Fibrillation in Canines.

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Computerized Analysis of the Ventricular Fibrillation Waveform Allows Identification of Myocardial Infarction: A Proof-of-Concept Study for Smart Defibrillator Applications in Cardiac Arrest.

BackgroundIn cardiac arrest, computerized analysis of the ventricular fibrillation (VF) waveform provides prognostic information, while its diagnostic potential is subject of study. Animal studies suggest that VF morphology is affected by prior myocardial infarction (MI), and even more by acute MI. This experimental in‐human study reports on the discriminative value of VF waveform analysis to identify a prior MI. Outcomes may provide support for in‐field studies on acute MI.Methods and ResultsWe conducted a prospective registry of implantable cardioverter defibrillator recipients with defibrillation testing (2010–2014). From 12‐lead surface ECG VF recordings, we calculated 10 VF waveform characteristics. First, we studied detection of prior MI with lead II, using one key VF characteristic (amplitude spectrum area [AMSA]). Subsequently, we constructed diagnostic machine learning models: model A, lead II, all VF characteristics; model B, 12‐lead, AMSA only; and model C, 12‐lead, all VF characteristics. Prior MI was present in 58% (119/206) of patients. The approach using the AMSA of lead II demonstrated a C‐statistic of 0.61 (95% CI, 0.54–0.68). Model A performance was not significantly better: 0.66 (95% CI, 0.59–0.73), P=0.09 versus AMSA lead II. Model B yielded a higher C‐statistic: 0.75 (95% CI, 0.68–0.81), P<0.001 versus AMSA lead II. Model C did not improve this further: 0.74 (95% CI, 0.67–0.80), P=0.66 versus model B.ConclusionsThis proof‐of‐concept study provides the first in‐human evidence that MI detection seems feasible using VF waveform analysis. Information from multiple ECG leads rather than from multiple VF characteristics may improve diagnostic accuracy. These results require additional experimental studies and may serve as pilot data for in‐field smart defibrillator studies, to try and identify acute MI in the earliest stages of cardiac arrest.

Effects of JTV-519 on stretch-induced manifestations of mechanoelectric feedback.

JTV-519 is a 1,4-benzothiazepine derivative with multichannel effects that inhibits Ca2+ release from the sarcoplasmic reticulum and stabilizes the closed state of the ryanodine receptor, preventing myocardial damage and the induction of arrhythmias during Ca2+ overload. Mechanical stretch increases cellular Na+ inflow, activates the reverse mode of the Na+ /Ca2+ exchanger, and modifies Ca2+ handling and myocardial electrophysiology, favoring arrhythmogenesis. This study aims to determine whether JTV-519 modifies the stretch-induced manifestations of mechanoelectric feedback. The ventricular fibrillation (VF) modifications induced by acute stretch were studied in Langendorff-perfused rabbit hearts using epicardial multiple electrodes under control conditions (n=9) or during JTV-519 perfusion: 0.1μmol/L (n=9) and 1μmol/L (n=9). Spectral and mapping techniques were used to establish the baseline, stretch and post-stretch VF characteristics. JTV-519 slowed baseline VF and decreased activation complexity. These effects were dose-dependent (baseline VF dominant frequency: control=13.9±2.2Hz; JTV 0.1μmol/L=11.1±1.1Hz, P<.01; JTV 1μmol/L=6.6±1.1Hz, P<.0001). The stretch-induced acceleration of VF (control=38.8%) was significantly reduced by JTV-519 0.1μmol/L (19.8%) and abolished by JTV 1μmol/L (-1.5%). During stretch, the VF activation complexity index was reduced in both JTV-519 series (control=1.60±0.15; JTV 0.1μmol/L=1.13±0.3, P<.0001; JTV 1μmol/L=0.57±0.21, P<.0001), and was independently related to VF dominant frequency (R=.82; P<.0001). The fifth percentile of the VF activation intervals, conduction velocity and wavelength entered the multiple linear regression model using dominant frequency as the dependent variable (R=-.84; P<.0001). In conclusion, JTV-519 slowed and simplified the baseline VF activation patterns and abolished the stretch-induced manifestations of mechanoelectric feedback.

Post-infarction ventricular fibrillation mechanisms: Insights from combined body surface potential mapping and late gadolinium-enhanced CMR

Background The mechanisms involved in the sustenance of scarrelated ventricular fibrillation (VF) are poorly understood. Recent developments in body surface potential mapping (BSM) now enable non-invasive, real-time and wholeheart assessment of cardiac activation during VF. We sought to analyze the relationships between focal/reentrant activities during VF and scar characteristics on late gadonlinium-enhanced (LGE) CMR in patients with ischemic VF. Methods 7 patients with history of prior myocardial infarction who presented a VF episode underwent CMR prior to ICD implantation. LGE imaging was performed on a 1.5T system (Avanto, Siemens Medical Solutions, Erlangen, Germany) 15 min after the injection of 0.2 mmol/Kg gadoterate meglumine, using an inversion recovery-prepared and respiratory navigated 3D Turbo FLASH sequence with fat saturation, in order to acquire a whole heart volume at high spatial resolution (pixel size 1.25 × 1.25

Temporal changes in morphological characteristics of ventricular fibrillation from out-of-hospital cardiac arrests in an Asian community

Introduction: Ventricular fibrillation (VF) is the most common arrhythmia causing out-of-hospital cardiac arrest (OOHCA) and defibrillation remains the mainstay of its treatment. Successful defibri...

Ventricular fibrillation waveform characteristics differ according to the presence of a previous myocardial infarction: A surface ECG study in ICD-patients

BackgroundCharacteristics of the ventricular fibrillation (VF) waveform reflect arrest duration and have been incorporated in studies on algorithms to guide resuscitative interventions. Findings in animals indicate that VF characteristics are also affected by the presence of a previous myocardial infarction (MI). As studies in humans are scarce, we assessed the impact of a previous MI on VF characteristics in ICD-patients. MethodsProspective cohort of ICD-patients (n=190) with defibrillation testing at the Radboudumc (2010–2013). VF characteristics of the 12-lead surface ECG were compared between three groups: patients without a history of MI (n=88), with a previous anterior (n=47) and a previous inferior MI (n=55). ResultsAs compared to each of the other groups, the mean amplitude and amplitude spectrum area were lower, for an anterior MI in lead V3 and for an inferior MI in leads II and aVF. Across the three groups, the bandwidth was broader in the leads corresponding with the infarct localisation. In contrast, the dominant and median frequencies only differed between previous anterior MI and no history of MI, being lower in the former. ConclusionsThe VF waveform is affected by the presence of a previous MI. Amplitude-related measures were lower and VF was less organised in the ECG-lead(s) adjacent to the area of infarction. Although VF characteristics of the surface ECG have so far primarily been considered a proxy for arrest duration and metabolic state, our findings question this paradigm and may provide additional insights into the future potential of VF-guided resuscitative interventions.

Abstract 188: Temporal Changes in Morphological Characteristics of Ventricular Fibrillation from Out-of-Hospital Cardiac Arrest in an Asian Community

Introduction: Ventricular fibrillation (VF) is the most common arrhythmia causing out-of-hospital cardiac arrest (OOHCA) and defibrillation remains the mainstay of its treatment. Successful defibrillation is linked to VF morphology characteristics, and is affected by VF duration, quality of cardiopulmonary resuscitation (CPR) and emergency medical service (EMS) responsiveness. This study aimed at comparing VF morphology characteristics and their relationships with patients and EMS characteristics, as well as outcomes, in an Asian community. Method: Electrocardiographic recordings of VF signals from automated external defibrillators (AEDs) in 2008 to 2012 were obtained from OOHCA subjects in Taipei city, a metropolitan with 2.65 million residents in 272km2. Amplitude spectrum analysis (AMSA) and DFAα2 were calculated and compared year by year in the study period. Results: A total of 612 OOHCA subjects with VF were included for analysis. Both DFA and AMSA changed significantly over time (χ 2 for trend: -0.128 for DFA, p&lt;0.01; 0.092 for AMSA, p=0.02). There was no change in gender, age, and bystander CPR rates; however, in later years there were more witnessed arrests, shortened EMS responses, and better sustained (&gt;2 hr) return of spontaneous circulation (ROSC) and neurological outcomes (CPC 1&amp;2). The time trend for DFAα2 (OR 0.98, CI 0.96-0.99, p=0.003), but not for AMSA (OR 1.07, CI 0.99-1.14), remained after adjustment for confounders. Both DFAα2 and AMSA were associated with sustained ROSC (DFA OR 0.08, CI 0.04-0.18, p&lt;0.001; AMSA OR 1.18, CI 1.01-1.38, p=0.03) and CPC 1&amp;2 (DFA OR 0.04, CI 0.01-0.16, p&lt;0.001; AMSA OR 1.30, CI 1.07-1.57, p=0.008) in multiple regression models. Conclusions: DFAα2 and AMSA, two important VF characteristics, changed significantly over time in an Asian community, and were associated with improved outcomes. This might reflect improvement in community chain of survival especially among EMS responses and community quality of CPR.

Characteristics of ventricular fibrillation in relation to cardiac aetiology and shock success: A waveform analysis study in ICD-patients

BackgroundVentricular fibrillation (VF) waveform characteristics are associated with cardiac arrest duration and defibrillation success. Recent animal studies found that VF characteristics and shock success also depend on the presence of myocardial infarction (MI). In patients, VF induction after implantable cardioverter defibrillator (ICD) implantation offers a unique setting to study early VF characteristics: we studied the relation with cardiac disease – either presence or absence of a previous MI – and with shock success. MethodsRetrospective cohort study of ICD-patients who underwent defibrillation testing, 117 (63%) with and 69 (37%) without a previous MI. Intracardiac recordings of induced VF were analysed using Fourier analysis. ResultsIn previous MI-patients, the fundamental frequency and organisation index of the VF signal were significantly lower as compared with patients without a previous MI: 4.9Hz±0.6 vs. 5.2Hz±0.6 (p=0.005) and 56%±10 vs. 60%±9 (p=0.001), respectively. The median frequency was not different (p=0.25). We found no association between VF characteristics and ICD shock success. ConclusionsIn analogy with observations in animals, we found that a history of a previous MI was associated with slower and less organised VF. In our cohort of ICD-patients, early VF waveform characteristics were not associated with shock outcomes. Further study is warranted to determine to what extent VF characteristics are influenced by the underlying aetiology on the one hand, and time delay on the other. These findings could improve insight into the potential value of VF analysis to guide shock delivery.

Effect of chronic exercise and ATP-sensitive potassium channel blockade on the spectral characteristics evolution of ventricular fibrillation in acute regional ischemia

Purpose: It has been proposed that chronic exercise produces a KATP channel blockade in ischemic myocardium. We have also reported that channel blockade and training exert very similar effects on energy required to defibrillate. In fact it is postulated that one mechanism by which exercise exerts an antiarrhythmic effect, is by blocking KATP channel. We have analyzed the evolution of spectrum characteristics of ventricular fibrillation (VF), in normoxic conditions and after acute myocardial ischemia, in isolated hearts from trained rabbits, and in hearts submitted to KATP channel blockade. Our hypothesis is that the spectrum characteristics of VF evolve similarly in trained hearts and in hearts undergoing KATP channel blockade. Material and method: 12 NZW rabbits were submitted to a six-week endurance exercise training program, and 14 rabbits (glibenclamide group) and 17 rabbits (control group) were not trained. After exercise program, rabbits were anaesthetized (ketamine, 10 mg/kg i.v.), euthanized and the hearts excised, isolated and perfused in a Langendorff system. A pacing electrode and a plaque with 256 recording electrodes were positioned on the left ventricle. The blockade of KATP channels was performed by glibenclamide (10 μM). VF was induced at increasing frequencies. Five minutes after VF triggering, the circumflex coronary artery was occluded. Dominant frequency (DF) of VF was determined by a spectral analysis. Determinations were analyzed 5min after the onset of VF and 60 and 180 s after coronary occlusion. An ANOVA test (two factors) repeated on one factor was used to comparisons. Differences were significant when p<0.05. Results: See Table. View this table: Dominant frequency of VF Conclusions: Unlike what occurs with other parameters, the effect of training on the evolution of VF characteristics in the ischemic myocardium does not appear to be mediated by the blockade of KATP channel.

Ventricular Fibrillation Characteristics: What Measurements are Best?

Ventricular Fibrillation Characteristics: What Measurements are Best?

Abstract 9290: Clinical, Electrocardiographic, and Genetic Characteristics of Patients with Idiopathic Ventricular Fibrillation Associated with Early Repolarization

Background: Early repolarization or J-wave has generally been considered benign for decades. However, we and others recently reported that early repolarization is associated with idiopathic ventricular fibrillation (VF). This study aimed to investigate its clinical and genetic characteristics and to identify risk factors for arrhythmia events. Methods and results: This study included 38 patients (32 men; age, 42±17 years) with idiopathic VF associated with early repolarization. All of the patients had arrhythmia events. The events occurred during sleeping (n=12) or at rest (n=9) in more than half of the patients. An electrical storm defined as ≥3 episodes of VF during 24 hours was observed in 8 patients (21%). A family history of sudden cardiac death was reported in 7 patients (18%). In 12-lead electrocardiograms, early repolarization was present in the inferior leads in 9 patients, in the lateral/precordial leads in 12 patients, and in both of the inferior and lateral/precordial leads in the remaining 17 patients. Conduction disease, mostly prolongation of PR interval, was present in 13 patients (34%). The heart rate was slower, and the PR interval and QRS duration were longer in patients with idiopathic VF compared to 190 age- and sex-matched healthy controls. VF was inducible by programmed electrical stimulation in 15 of 27 patients (55%). We identified loss-of-function mutations in SCN5A in 3 unrelated patients, and interestingly, His-ventricular interval was prolonged in all of them. During a follow-up of 6.0±5.7 years, VF recurred in 9 patients. Multivariate analyses revealed that a family history of sudden cardiac death and a history of electrical storm were associated with increased risk of arrhythmia recurrences. The age of arrhythmia onset, gender, lead location of early repolarization, activity at the initial event, conduction disease, or inducibility of VF were not associated with the risk of recurrences. Conclusions: This study showed the clinical and genetic characteristics of idiopathic VF associated with early repolarization, suggesting the underlying mechanism for arrhythmia susceptibility. Our data may be useful for risk stratification for arrhythmia events.

Abstract 275: VF Characteristics and ICD Shock Success: Differences Between Ischemic and Nonischemic Heart Disease

Introduction: From animal studies we know that signal characteristics of ventricular fibrillation (VF) are affected by the presence of myocardial scarring. The impact of the underlying etiology of scar formation, ischemic or nonischemic, is unknown. Whether the origin of scar formation is correlated to shock success has not been thoroughly studied either. Therefore, our aim is to compare signal characteristics of VF and shock success in ICD-patients, with either ischemic or nonischemic heart disease. Methods: Consecutive patients undergoing Medtronic ICD implantation between 2005 and 2011 were studied. After ICD implantation VF was induced to test the device. A first ICD shock of 15J was delivered to terminate VF. Signal analysis was performed on the first 4 seconds of the induced VF. The frequency content of the signal was determined using the Fourier Analysis. In addition, the success rate of the first ICD shock was scored. Results: A total of 229 patients were studied of whom 149 (65%) had ischemic heart disease. The dominant, fundamental and median frequency were significantly lower in patients with ischemic heart disease (Table). Also the organization index was lower. In the ischemic heart disease group 83% (124/149) had a successful first ICD shock compared to 89% (71/80) in patients with nonischemic heart disease (p=0.26). Conclusion: Signal characteristics of induced VF are markedly different between patients with ischemic and nonischemic heart disease. VF in ischemic heart disease is slower, less regular and less organized. Shock success was not affected by the underlying etiology, but in 10-20% of cases a first shock was not sufficient. Identification of patients with a lower shock success is subject to further study.

Real-time electrogram analysis for monitoring coronary blood flow during human ventricular fibrillation: Implications for CPR

Effective chest compressions during prolonged ventricular fibrillation (VF) have been shown to increase the chances of successful defibrillation to a rhythm associated with a sustainable cardiac output. There is currently no effective method of recording the degree of antegrade coronary artery flow during chest compression in VF. This study sought to quantify the relationship between the antegrade coronary flow and the characteristics of human VF using near real-time wavelet-based electrocardiographic markers. VF experiments were conducted in 8 isolated human hearts. The Langendorff perfusion enabled different flow rates (perfusion) during VF, which allowed for the simulation of chest compression with different efficacies. After the initiation of VF, the hearts were maintained in ischemia (no flow) for 3 minutes, followed by a 2-minute reperfusion and defibrillation. The experiments were repeated at flows of 0%, 30%, and 100% of baseline perfusion, and volume-conducted surface electrograms were recorded and analyzed using continuous wavelet transform in 5-second frames. Near real-time wavelet features were derived that demonstrated significant differences in the multicomponent nature of VF signals and predicted perfusion rate characteristics for different flow rates (i.e., 0%, 30%, and 100%; P < .0006). A pattern classifier was trained using the feature values from 5 hearts, and the flow rates for 3 additional hearts were predicted with an accuracy of 90%. VF electrogram characteristics as measured by wavelet analysis relate to antegrade coronary flow rate during VF. These findings suggest that chest compression efficacy of physiological importance could be monitored using near real-time wavelet analysis.

Spectral Analysis of Sustained and Non-Sustained Ventricular Fibrillation in Patients With an Implantable Cardioverter-Defibrillator

The mechanisms responsible for the maintenance and termination of ventricular fibrillation (VF) are poorly understood. The aim of this study was to compare the spectral characteristics of the electrical signal during sustained and non-sustained VF in patients with an implantable cardioverter-defibrillator. The study included 51 patients who had had at least one episode of sustained VF (i.e., duration >5 s and requiring shock administration) and non-sustained VF (i.e., duration >3 s and spontaneously terminated) that were recorded by the device set in a unipolar configuration. Spectral analysis of the first 3 s of each episode was performed. The dominant frequency was higher in sustained VF (4.6+/-0.7 Hz) than in non-sustained VF (4.3+/-0.6 Hz; P=.01), while the other parameters were similar. Although the spectral characteristics of sustained and non-sustained VF were similar, differences were observed during the first 3 s that could be used in algorithms for the early detection of non-sustained VF.

Effects of verapamil on anterior ST segment and ventricular fibrillation cycle length in patients with Brugada syndrome

Purpose This study examined the effects of verapamil (5-10 mg intravenous) on the cardiac electrical activity of 10 Brugada syndrome (BS) patients having vasospastic angina, atrial fibrillation, and/or hypertension. Results Verapamil showed no significant change in the ST-segment elevation. Likewise, there was no significant change in the lengths of QRS complex, HV and corrected QT intervals, or effective refractory period at the right ventricle. The conduction time between right ventricular apex and outflow tract, measured at 400-millisecond pacing, was mildly prolonged by verapamil. At baseline, induced ventricular fibrillation (VF) was terminated by a 200-J shock in all patients. After verapamil, VF was reinduced in 7, was noninducible in 2, and self-terminated in 1 patient. Mean F-F interval was shorter after than before verapamil, and a 360-J shock was required in 2 of the 7 patients. Conclusion In some BS patients, calcium channel blockade may modify the electrical characteristics of VF.

Are Failed ICD Shocks Due to Changing Ventricular Fibrillation Characteristics?

Are Failed ICD Shocks Due to Changing Ventricular Fibrillation Characteristics?

Ventricular fibrillation characteristics are different in patients with coronary heart disease compared to patients with a primary arrhythmia

Ventricular fibrillation characteristics are different in patients with coronary heart disease compared to patients with a primary arrhythmia

Clinical Significance of Macroscopic T‐Wave Alternans After Sodium Channel Blocker Administration in Patients with Brugada Syndrome

Macroscopic T-wave alternans (TWA) is sometimes observed after sodium channel blocker administration in patients with Brugada syndrome (BS), but little is known about the association between occurrence of TWA and clinical characteristics in BS patients. We investigated the association between spontaneous ventricular fibrillation (VF) occurrence and TWA after pilsicainide, a sodium channel blocker administration in BS patients. We administered pilsicainide at a dose of 1 mg/kg to 77 BS patients (76 males and one female; mean age, 48.4 years) and examined the association between TWA after pilsicainide administration and clinical characteristics, including age, spontaneous VF, syncope, family history of sudden death, spontaneous coved ST elevation, late potentials (LP), induction of VF by programmed electrical stimulation, and SCN5A mutation. None of the patients had TWA before pilsicainide administration, but TWA became apparent in 17 (22.1%) of the patients after pilsicainide administration. Patients with TWA had a significantly higher incidence of spontaneous VF (52.9% vs 8.3%, P < 0.001) and syncope (58.8% vs 26.7%, P < 0.05) than did patients without TWA. Then, we focused on the association between spontaneous VF and clinical characteristics. Patients with spontaneous VF had a significantly higher incidence of TWA (64.3% vs 12.7%, P < 0.001) and LP positive (92.9% vs 56.5%, P < 0.01) than did patients without spontaneous VF. In multivariate analysis, TWA (P = 0.001) and LP (P = 0.047) appeared as the independent predictor for spontaneous VF. TWA after pilsicainide administration is associated with a high risk of clinical VF in patients with BS.

Incidence and Characteristics of Ventricular Fibrillation in Bystander-witnessed Out-of-hospital Cardiac Arrest with Cardiac Etiology in the City of Sendai, Japan

Ventricular fibrillation (VF) in out‐of‐hospital cardiac arrest (OHCA) is a main target for resuscitation.Methods and results: We analyzed Utstein‐style data in Sendai City (population 1,020,000), Japan from January 2002 to March 2004. The incidence of OHCA overall was 62.3/100,000/year. The incidence of the bystander‐witnessed VF was 2.5/100,000/year. In younger patients (20–65 years of age), the percentage of VF was 52% when cardiac origin was presumed by bystander witness, and ECG was recorded within 10 minutes from the collapse. In older patients (over 65 years of age), however, the percentage of VF was 21% when they were bystander‐witnessed, and ECG was recorded within 10 minutes from the collapse. No VF was reported when the ECG was recorded more than 15 minutes after the collapse. The thirty‐day survival rate was 21% in the bystander‐witnessed VF cases with cardiac etiology, but 0% in the non‐VF cases. The bystander CPR was significantly associated with improved 30‐day survival rate. Conclusion: Younger age, male gender, and shorter collapse‐to‐ECG time are significantly associated with the appearance of VF in bystander‐witnessed OHCA with cardiac etiology. Bystander CPR was significantly associated with the improvement in prognosis of those VF patients.