Ventricular Fibrillation In Patients Research Articles

Predictors of Polymorphic Ventricular Tachycardia and Ventricular Fibrillation in Patients with Takotsubo Syndrome

Polymorphic ventricular tachycardia (PVT) and ventricular fibrillation (VF) are life-threatening complications of Takotsubo syndrome (TTS). Data regarding risk factors for PVT/VF based on the TTS variant are lacking. This study aims to identify demographic and clinical factors associated with PVT and VF in patients with TTS. Patients meeting the InterTak criteria for TTS between 2010-2022 were retrospectively identified. The occurrence of PVT/VF with each risk factor was analyzed using logistic regression. Sensitivity analysis was performed to assess the interaction between risk factors. PVT/VF occurred in 27 of the 296 patients with TTS (9.1%). Patients with PVT/VF were younger (52 vs. 62 years, P=0.019) and more frequently used stimulants in the 4 weeks before admission (22.2% vs. 8.2%, OR 3.20, p =0.023). All PVT/VF occurred within 24 hours of hospitalization. An initial QTc threshold of 490 ms had the highest sensitivity and specificity for the occurrence of PVT/VF (AUC=0.687). Patients with PVT/VF were more likely to have a QTc >490 ms on admission (55.6% vs. 18.7%, OR=5.45, P< 0.01), apical variant TTS (78% vs. 56%, OR=2.69, p=0.038), and an admission EF < 30% (63% vs. 41.5%, OR=2.39, p=0.032); each factor was independently associated with PVT/VF irrespective of QTc duration on sensitivity analysis. In conclusion, nearly 1 in 10 of patients with TTS had PVT/VF. A QTc > 490 ms, recent stimulant use, apical variant TTS, and severe left ventricular systolic dysfunction on admission are associated with higher PVT/VF risk, with the first 24 hours being a high-risk period.

Using cardiac magnetic resonance feature tracking to discover novel abnormalities in patients with idiopathic ventricular fibrillation

Abstract Background Despite an extensive diagnostic work-up, the underlying diagnosis leading to ventricular fibrillation (VF) remains elusive in patients with idiopathic VF. Emerging diagnostic techniques can be used to discover previously unidentified abnormalities in these patients. Purpose The purpose of this study was to investigate the potential of cardiac magnetic resonance feature tracking (CMR-FT) to discover structural abnormalities in idiopathic VF patients. Methods Cine CMR images of idiopathic VF patients and age and sex matched controls were analyzed. Left ventricle global circumferential strain (GCS), global longitudinal strain (GLS) and global radial strain (GRS) were determined using Circle Cardiovascular Imaging. Student’s t-test was used to compare means. Results In total, 26 idiopathic VF patients (mean age 37 (±13) years, 62% male) and 26 controls (mean age 38 (±13) years) were included. CMR was performed in idiopathic VF patients at a median of 9 [IQR 3 – 15] days after the index event. Left ventricle ejection fraction was 55 ± 6% for idiopathic VF patients, 59 ± 6% for controls, p = 0.04. GCS and GRS were comparable for idiopathic VF patients and controls (-17.36 ± 1.78% vs. -18.04 ± 1.83%, p = 0.182 and 28.28 ± 4.63 vs. 29.29 ± 5.09, p = 0.438, respectively). GLS was lower for idiopathic VF patients compared with controls (-14.85 ± 3.21% vs. -18.44 ± 2.11%, p &amp;lt; 0.001). Conclusion CMR-FT GLS distinguished idiopathic VF patients from controls and could imply subclinical abnormalities in idiopathic VF patients. Future studies with a larger cohort should reveal if this finding can be correlated with an arrhythmic substrate.

Risk stratification for the occurrence of ventricular fibrillation in patients with early repolarization syndrome

BackgroundSeveral signs of malignant early repolarizations have been proposed in patients with early repolarization syndrome (ERS). However, reports have challenged the efficacy of these signs in predicting future ventricular fibrillation (VF) in patients with ERS. ObjectiveThis study aimed to assess the predictive value of various electrocardiogram (ECG) markers for future VF events in patients with ERS. MethodsWe retrospectively evaluated the clinical characteristics of 44 patients with ERS to identify risk factors for VF during follow-up. ResultsAfter the initial event, 16 patients experienced VF (VF group), whereas 28 did not (non-VF group). The VF group had a longer QRS interval, more fragmented QRS (fQRS), and a higher T/R voltage ratio than the non-VF group. Wide J waves were more prevalent in the VF group; however, other J-wave markers did not differ between the groups. Positive late potentials recorded on signal-averaged ECGs were more frequent in the VF group. Whereas none of the patients showed spontaneous Brugada syndrome on ECG, the VF group frequently exhibited pilsicainide-induced ST-segment elevation. These ECG markers were significantly associated with the occurrence of VF during follow-up. Patients with multiple ECG factors, including QRS abnormalities (wide QRS or fQRS), wide J waves, and a high T/R ratio, had a worse prognosis than patients without multiple factors, effectively stratifying patient risk. ConclusionThe occurrence of VF in patients with ERS may be associated with conduction abnormalities such as QRS widening, fQRS, high T/R ratio, positive late potentials, and pilsicainide test results. Therefore, ECG factors could be useful in identifying high-risk patients.

Catheter Ablation for Channelopathies: When Is Less More?

Ventricular fibrillation (VF) is a common cause of sudden cardiac death in patients with channelopathies, particularly in the young population. Although pharmacological treatment, cardiac sympathectomy, and implantable cardioverter defibrillators (ICD) have been the mainstay in the management of VF in patients with channelopathies, they are associated with significant adverse effects and complications, leading to poor quality of life. Given these drawbacks, catheter ablation has been proposed as a therapeutic option for patients with channelopathies. Advances in imaging techniques and modern mapping technologies have enabled increased precision in identifying arrhythmia triggers and substrate modification. This has aided our understanding of the underlying pathophysiology of ventricular arrhythmias in channelopathies, highlighting the roles of the Purkinje network and the epicardial right ventricular outflow tract in arrhythmogenesis. This review explores the role of catheter ablation in managing the most common channelopathies (Brugada syndrome, congenital long QT syndrome, short QT syndrome, and catecholaminergic polymorphic ventricular tachycardia). While the initial results for ablation in Brugada syndrome are promising, the long-term efficacy and durability of ablation in different channelopathies require further investigation. Given the genetic and phenotypic heterogeneity of channelopathies, future studies are needed to show whether catheter ablation in patients with channelopathies is associated with a reduction in VF, and psychological distress stemming from recurrent ICD shocks, particularly relative to other available therapeutic options (e.g., quinidine in high-risk Brugada patients).

Distinct Electrogram Features and Ventricular Arrhythmia Induction Modes Between Repolarization and Conduction Heterogeneities

BackgroundRecent clinical studies have indicated the presence of localized electrical abnormalities in idiopathic ventricular fibrillation and J-wave syndrome patients. ObjectivesThis study aims to characterize the specific electrical signatures of localized repolarization and conduction heterogeneities and their respective role in vulnerability to arrhythmias. MethodsOptical mapping was performed in porcine right ventricles with local: 1) repolarization shortening; 2) conduction slowing; or 3) structural heterogeneity induced by locally perfusing: 1) pinacidil (20 μmol/L, n = 13); or 2) flecainide (2 μmol/L, n = 13) via an epicardial catheter; or 3) by local epicardial tissue destruction (9 radiofrequency lesions n = 12). Electrograms were recorded (n = 5 in each group) and spontaneous and induced arrhythmias were quantified and optically mapped. ResultsElectrograms were normal in (1) but showed local fragmentation in 40% of preparations in (2) with greater effects observed at high pacing frequencies dependent on the wavefront direction. In (3), the structural substrate alone increased the width and number of peaks in the electrograms, and addition of flecainide induced pronounced fragmentation (≥3 peaks and ≥70 ms) in all cases. Occurrence of spontaneous arrhythmias was significantly increased in (1) and (2) (P < 0.0001 and 0.05, respectively, vs baseline) and were triggered by ectopies. Vulnerability to arrhythmias at high pacing frequencies (≥2 Hz) was the lowest in (1) and greatest in (2). ConclusionsMicrostructural substrates have the most pronounced impact on electrograms, especially when combined with sodium channel blockers, whereas local action potential duration shortening does not lead to electrogram fragmentation even though it is associated with the highest prevalence of spontaneous arrhythmias.

The Rate of Success of CPR in Patients Suffering from Cardiac Arrest in Patients Admitted in CCU in Cardiology Department Ayub Medical Teaching Institute

Cardiopulmonary resuscitation (CPR) is an essential procedure used to treat patients who are in cardiac arrest, particularly in the Critical Care Unit (CCU). Objective: To assess the success rate of CPR admitted to the CCU, revealing insight on the effectiveness of current resuscitation techniques. Methods: This retrospective study was conducted at Department of Cardiology Ayub Medical Teaching Institute, Abbottabad, between 13th April 2023 to 30th November 2023, 110 patients had cardiac arrest while in the intensive care unit. Data were gathered and examined on patient demographics, pre-existing comorbidities, time to start CPR, duration of CPR, and results. CPR success was defined as a sustained restoration of spontaneous circulation (ROSC) for at least 20 minutes. Results: This study included 110 cardiac patients. Most patients (68.18%) were male. Hypertension was the most common comorbidity at 72.7%. CPR started on average 4.8 minutes late, with a 1.2-minute standard deviation. The average CPR time was 18.2 minutes, with a 5.6-minute SD. After cardiac arrest, 60 (54.5%) patients began CPR within 5 minutes. Another subgroup found 96.0% CPR success in 25 (22.7%) ventricular fibrillation patients. Then occurred ventricular tachycardia (80.0%), pulseless electrical activity (76.0%), and asystole (68.9%). These data suggest that CPR works better in ventricular fibrillation patients. Conclusions: This research sheds light on cardiac arrest CCU patients' demographics, care, and outcomes. The data show that early CPR and ventricular fibrillation detection and treatment improve outcomes for these individuals.

Failure to defibrillate or cardiovert due to premature truncation of biphasic shocks from implantable defibrillators

BackgroundIn 2022 and 2023, Medtronic recalled implantable defibrillators because they may deliver less than full-energy shocks. The 2022 problem truncates the second phase of the waveform (SCP-T2), resulting in ∼32-J shocks, and is mitigated by downloadable software. The 2023 malfunction truncates the first phase of the waveform, resulting in 0- to 12-J shocks due to a glassed feedthrough problem (GFT-T1) that might be avoided by programming B>AX shock polarity. ObjectiveThe purpose of this study was to assess the consequences of GFT-T1 and SCP-T2 shocks in the Food and Drug Administration’s Manufacturers and User Facility Device Experience (MAUDE) database and to estimate the incidences of GFT-T1 and SCP-T2. MethodsWe analyzed MAUDE reports supplemented by Medtronic data; lead failures were excluded. The incidences of SCP-T2 and GFT-T1 were estimated using USA volumes for devices with glassed feedthroughs. ResultsOne hundred thirty-two devices delivered truncated shocks: 27 (20.5%) were GFT-T1; 103 (78.0%) were SCP-T2; and 2 (1.5%) truncated both phases (BOTH-T1&2). Of 54 ventricular fibrillation (VF) patients, 21 (38.9%) were not defibrillated by truncated shocks: 8 (38.1%) received GFT-T1 shocks, 12 (57.1%) received SCP-T2 shocks, and 1 received a BOTH-T1&2 shock; 2 patients suffered unrelated deaths; 1 was externally rescued; 1 outcome was unknown; the others were defibrillated by subsequent shocks or terminated spontaneously. The majority of patients (79.1%) shocked for ventricular tachycardia (VT) were converted, primarily (94.1%) by SCP-T2 shocks. Estimated incidences of GFT-T1 and SCP-T2 were 0.0078%–0.0088% and 0.1062%–0.1110%. ConclusionGFT-T1 and SCP-T2 shocks can result in failure to terminate VF/VT, but they may be preventable. Although the incidences of these truncated shocks are very low, heightened surveillance is warranted.

Immediate, early and late ventricular fibrillation complicating acute myocardial infarction: insights from a real life registry

Abstract Background Conflicting data exist on the prognosis of ventricular fibrillation (VF) based on its timing in relation to coronary occlusion in acute myocardial infarction (AMI). Purpose To describe the patient profile and prognostic impact of VF during AMI according to its time of occurrence. Methods Data from three nationwide French cohorts carried out 5 years apart from 2005 to 2015 were analysed (FAST-MI program). All consecutive patients with AMI (STEMI and Non-STEMI) over a 1-month period were enrolled and followed 5 years. The present analysis focused on patients who presented with VF according to its time of occurrence defined as: immediate (out-of-hospital cardiac arrest), early (&amp;lt;48h at admission) and late (≥48h after admission). Results Out of 13 125 patients admitted for AMI (66±14 years, 71% men, 52% ST-elevation myocardial infarction-STEMI), 406 (3.1%) presented with VF including 205 immediate (50.5%), 147 early (36.2%) and 54 late (13.3%) VF episodes. Immediate and early VF were most frequent during STEMI (respectively 2.3% and 1.8% vs. 0.8% and 0.4% in non-STEMI, p&amp;lt;0.001), while late VF incidence was as frequent in ST-elevation and non-STEMI (0.5% vs 0.4%, p value). The proportion of immediate, early and late VF in AMI were similar in 2005, 2010 and 2015. Patients with immediate (61.6±13.2 yo) or early (62.4±14.2 yo) VF were younger than those with no VF (66.1±14.1 yo, p&amp;lt;0.001) while patients with late VF patients were the oldest (70.5±13.6 yo). LVEF was lower in patients with early (48±10%) or late (48±13%), compared with patients without VF (52±11%) or those with immediate VF (51±12%) (p&amp;lt;0.001). In-hospital mortality was particularly high in patients who developed immediate (24.9%) and late (37.0%) VF, intermediate in early VF patients (10.9%) and lowest in non-VF patients (3.0%) (p&amp;lt;0.001). Among patients alived at hospital discharge, and compared with patients with no VF (4.2%), the six-month mortality was considerably increased in the late VF subgroup (17.6%, adjusted HR: 6.04 [2.69-13.58], P&amp;lt;0.001), moderately increased in immediate VF (5.2%, HR:2.15 [1.06-4.34, P=0.03) ) and did not differ in early VF (1.5%, HR: 0.52 [0.13-2.11 P=0.36). At five years, mortality was also significantly higher in patients with late VF (38.2%, adjusted HR 1.72 [1.01-2.91]), with no significant difference between immediate, early, and non VF patients (14.2%, 11.5% and 19.3% respectively). Conclusions Patients with immediate, early and late VF during AMI do present with significantly different profiles. Still, only late VF (≥48h after admission) was associated with poorer outcome after the index hospitalisation, especially within the initial 6 months. By contrast with current guidelines based on relatively old data from the 2000s in secondary prevention in ischemic or non-ischemic settings, the extent to which patients with late VF would benefit from rapid cardioverter defibrillator implantation is questionable.3 months survival after VF in AMI5 year survival after VF in AMI

Impact of the number of citizens officially certified for government-organized civilian cardiopulmonary resuscitation courses on the prognosis for patients with out-of-hospital cardiac arrest in Japan

Abstract Background To improve the prognosis of patients with out-of-hospital cardiac arrest (OHCA), the rate of high-quality cardiopulmonary resuscitation (CPR) and immediate use of automated external defibrillators (AEDs) by citizens must be further increased. Japanese government launched certified CPR courses for citizens throughout Japan in 1994 and the number of citizens certified on the course is increasing. However, the impact of the number of citizens officially certified for the courses on the rate of CPR implementation by citizens and the outcomes in patients with OHCA is unclear. Methods From a prospective, nationwide, population-based registry of patients with OHCA in Japan, we identified 350,444 patients from 2005 through 2020 with bystander-witnessed OHCA with 72,069 ventricular-fibrillation (VF) and the other non-VF cardiac arrests. The association between the number of citizens certified for the CPR courses and the rate of CPR implementation by citizens throughout Japan was analyzed by Poisson distribution and Cochran–Armitage test for trend. The primary outcome was survival at 1 month. The secondary outcomes were favorable neurologic outcome at 1 month. The associations between the CPR attempted by citizens [categorized into three (chest-compression-only CPR, chest compression with rescue breathing, and use of AEDs with chest compression and rescue breathing)] and outcomes were determined by multivariable mixed logistic regression analyses. Results Cumulative number of citizens certified for the CPR courses increased from 717,808 in 2005 to 34,938,322 in 2020, which reached to 27.8% of total Japanese population. Annual course receivers were also linearly increased during the period (Incidence Rate Ratios 1.03, p&amp;lt;0.001). Similarly, the rate of patients receiving CPR by citizens increased linearly from 40.6% in 2005 to 56.8% in 2020 (P for trend&amp;lt;0.001). In the multivariable mixed logistic regression analyses, higher CPR activity by citizens were significantly associated with better 1-year survival in both VF and non-VF patients even after adjusted for covariates [VF = chest compression: odds ratio (OR) 1.17; 95% confidence interval (CI) 0.98–1.39; P =0.078; chest compression with rescue breathing: OR 1.22; 95% CI 1.02–1.49; P =0.030; use of AEDs with chest compression and rescue breathing: OR 1.54; 95% CI 1.54–1.92; P &amp;lt;0.001 vs no CPR, non-VF= chest compression: OR 1.19; 95% CI 0.76–1.87; P =0.45; chest compression with rescue breathing: OR 2.26; 95% CI 1.34–3.82; P =0.020 vs non-CPR]. Similar results were also found in neurological outcomes in 1 month. Conclusions The rate of CPR implementation by citizens throughout Japan has continuously and linearly increased in these 15 years in proportion to the increase in the number of citizens certified for the government-organized CPR courses. Higher CPR activity by citizens were significantly associated with better 1-year survival and favorable functional status in both VF and non-VF patients.

Abstract 15511: Predictors of Polymorphic Ventricular Tachycardia and Ventricular Fibrillation in Patients With Stress Cardiomyopathy

Introduction: Polymorphic ventricular tachycardia (PVT) and ventricular fibrillation (VF) are life-threatening complications of stress cardiomyopathy (SCM) that occur in 2-10% of patients with SCM. Hypothesis: To identify which social and medical factors are associated with an increased risk of PVT and VF in patients with SCM. Methods: All consecutive patients meeting the InterTAK (international takotsubo) diagnostic criteria for stress cardiomyopathy at the Hennepin County Medical Center between January 1 st , 2010, and December 31 st , 2022, were identified from electronic medical records. Logistic regression was used to estimate the odds ratios (OR). The receiver operating characteristic curve (ROC) was plotted to identify the best QTc cutoff at admission to predict ventricular arrhythmia. Results: A total of 296 patients were included in the study, of which 27 (9.1%) experienced PVT/VF. Baseline demographics, including gender, race, and age at diagnosis, were similar to patients without PVT/VF (median age 61 years, and 66.7% were females). Patients with PVT/VF were more likely to have a history of stimulant use (22.2% vs. 8.2%, OR =3.20 p =0.023), apical (Takotsubo) variant stress cardiomyopathy (78% vs.56%, OR=2.69 p=0.038), and an ejection fraction (EF) of less than 30% on admission (63% vs. 41.5%, OR=2.39 p=0.032) ( Table 1 ). Admission QTc interval cut-off value of 490 msec had the highest sensitivity and specificity in predicting the risk of ventricular arrhythmia (AUC=0.687). Notably, all PVT/VF events occurred within 17 hours of hospital admission. Conclusion: Nealy 1 in 10 patients with SCM had life-threatening ventricular arrhythmia. The presence of severe LV systolic dysfunction, recent stimulant use, apical variant SCM, or prolonged QTc &gt; 490 msec is associated with the occurrence of PVT/VF, with the first day of hospital admission being an especially high-risk period.

Abstract 219: Prediction of Shock-Refractory Ventricular Fibrillation Amidst Continuous Chest Compressions During Out-of-Hospital Cardiac Arrest Resuscitation

Background: Shock-refractory (SR) ventricular fibrillation (VF) patients (requiring ≥ 3 shocks) have relatively poor outcomes. Prediction of SR-VF may enable preemptive interventions targeted to improve SR-VF outcomes, such as earlier antiarrhythmics, alternative shock delivery strategies, or early transport for hospital-based interventions. We recently demonstrated prediction of SR-VF in the context of current practice whereby chest compressions (CCs) are interrupted for electrocardiogram (ECG) analysis prior to the initial shock. However, since pausing CCs is detrimental to outcome, ideally next-generation defibrillator algorithms will analyze during uninterrupted CCs, precluding CC interruption for SR-VF prediction. Aim: We designed a machine learning algorithm to predict SR-VF based on ECGs surrounding the first shock during CCs. Methods: We performed a retrospective study of adult out-of-hospital VF cardiac arrests treated by paramedics from 2008-2020 in King County WA. From each patient we collected a pair of 3-s VF ECG segments during uninterrupted CCs prior to and 1 minute following the first shock. Patients were randomized into 80%/20% groups for training/test. A random forest classifier was trained to predict SR-VF using dimensionally-reduced ECG scalograms. Performance was assessed by area under the receiver operating characteristic curve (AUC) and sensitivity for &gt;90% specificity. Results: Of 940 included patients, 584 (62%) had SR-VF, median age was 62, 206 (22%) were female, and 429 (46%) survived to hospital discharge. AUC for predicting SR-VF was 0.80 (95% CI: 0.72-0.85) in 188 test patients (Figure), with specificity of 92% and sensitivity of 52%. Conclusion: Automated SR-VF prediction during ongoing CCs is possible using the ECG surrounding the initial shock. Early identification of SR-VF during CCs could prompt preemptive, patient-specific treatments without compromising CPR, potentially improving resuscitation outcome.

A Contemporary Study of Pre-hospital Traumatic Cardiac Arrest: Distinguishing Exsanguination From Non-exsanguination Arrest With a Review of Current Literature.

Background Traumatic cardiac arrest (TCA) remains a challenging problem in terms of diagnosis and management. This is due to difficulty distinguishing the TCA cause and therefore understanding the pathophysiology. The goal of this study was to analyze a contemporary series of TCA patients and classify the causes of TCA into exsanguination (EX) arrest and non-exsanguination (non-EX) arrest. Methods This was a retrospective review of patients suffering TCA during 2019 at a level I trauma center. We excluded patients whose arrests were from medical causes such as ventricular fibrillation, ventricular tachycardia, pulmonary embolus, etc., hanging, drowning, thermal injury, outside transfer, and pediatric patients (age <13 as this is our institutional definition for pediatric trauma patients). We reviewed pre-hospital run-sheets, hospital charts including autopsy findings, and classified patients into EX and non-EX TCA. We defined a witnessed arrest (WA) using the traditional outside hospital cardiac (non-trauma) arrestdefinition. Outcomes included the incidence of EX arrest, survival to discharge, and hospital costs. Descriptive statistics were used.Significancewas set atp< 0.05. Results After exclusion, 54 patients suffered TCA with a mean age of 45.9 (±19.8) years.Eighty-three percent of patients were male. The average cost per TCA was ~$16,000. Of the 54 TCAs, 26 (48%) were WA, with one (1.85%) survivor (no non-WA TCA patients survived). Twenty-two (41%) patients died from EX-arrest; 59% penetrating vs. 28% blunt (p= 0.03). The one EX-arrest survivor was a 19-year-old gunshot wound to the leg whose arrest was witnessed, with a short downtime, and the cause of arrest (bleeding leg wound) was quickly reversible. Conclusion We classified 41% of TCAs to have died from EX-arrest with only a 1.85% survival rate. This study calls for a TCA pre-hospital registry with accurate and consistent data definitions and collection. The registry should capture the cause of arrest for future research, management decision-making, and prognostication.

Out-of-hospital cardiac arrest treated with prehospital double sequential external defibrillation during eCPR in refractory VF — a case report

BackgroundDouble sequential external defibrillation (DSED) has demonstrated increased survival with good neurological outcome in a recent randomized controlled trial. DSED has not been studied in patients with extracorporeal cardiopulmonary resuscitation (eCPR).CaseWe present the first case of prehospital eCPR with ongoing refractory ventricular fibrillation (VF), terminated by DSED. After six shocks, return of spontaneous circulation was initially achieved; however, the patient went into recurrent VF. ECPR was performed prehospital, with VF still refractory after three more shocks. DSED successfully terminated VF and showed a further increase in etCO2 and near-infrared spectroscopy cerebral oximetry values.ConclusionDSED can be a sufficient strategy for patients in refractory VF while on eCPR and should be evaluated in further studies.

Information theory-based direct causality measure to assess cardiac fibrillation dynamics.

Understanding the mechanism sustaining cardiac fibrillation can facilitate the personalization of treatment. Granger causality analysis can be used to determine the existence of a hierarchical fibrillation mechanism that is more amenable to ablation treatment in cardiac time-series data. Conventional Granger causality based on linear predictability may fail if the assumption is not met or given sparsely sampled, high-dimensional data. More recently developed information theory-based causality measures could potentially provide a more accurate estimate of the nonlinear coupling. However, despite their successful application to linear and nonlinear physical systems, their use is not known in the clinical field. Partial mutual information from mixed embedding (PMIME) was implemented to identify the direct coupling of cardiac electrophysiology signals. We show that PMIME requires less data and is more robust to extrinsic confounding factors. The algorithms were then extended for efficient characterization of fibrillation organization and hierarchy using clinical high-dimensional data. We show that PMIME network measures correlate well with the spatio-temporal organization of fibrillation and demonstrated that hierarchical type of fibrillation and drivers could be identified in a subset of ventricular fibrillation patients, such that regions of high hierarchy are associated with high dominant frequency.

Stable Ventricular Fibrillation: A Paradigm Rather Than Septal Shift?

Awake patients in ventricular fibrillation is a phenomenon limited to patients who are mechanically supported. We describe a cohort of patients supported by left ventricular assist devices (LVADs) presenting to the emergency department (ED) at a high-volume LVAD center while in awake ventricular fibrillation (VF)/ventricular tachycardia (VT). Among 175 patients reviewed, a total of 19 LVAD patients presented to the ED in awake VF/VT between December 2015 and July 2021. On ED presentation, patients maintained a median mean arterial blood pressure (MAP) of 70 mm Hg with a mean LVAD flow of 3.77 L/minute. ED management included cardioversion in the majority of cases: 58% were defibrillated once, 21% were defibrillated multiple times, 68% received amiodarone, and 21% received lidocaine. Inpatient management included defibrillation, ablation, and antiarrhythmic initiation in 37%, 11%, and 84% of cases, respectively. In total, five patients (26%) died with one death attributed to recurrent VT. Our findings support the short-term tolerability of sustained ventricular arrhythmias in LVAD patients, as evidenced by the maintained MAPs and mental status. Clinical teams, however, should be aware of the potential harbinger for in-hospital mortality heralded by an awake VF/VT presentation.

Early prediction of ventricular fibrillation using electrocardiographic characteristics in prehospital suspected ST-segment elevation myocardial infarction: a case-control study.

Our objective was to determine characteristics of electrocardiograms (ECG) that predict ventricular fibrillation (VF) among prehospital patients with suspected ST-segment elevation myocardial infarction (STEMI) in Québec. We performed a matched case-control study of prehospital adult suspected with STEMI. Patients in case group (STEMI/VF+) were matched with controls (STEMI/VF-) for age and sex and then compared for ECG characteristics, including ST-segment elevations (STE) and depressions (STD), duration of interval complexes, general characteristics, and several calculated variables. Logistic regression was used to measure the association between ECG characteristics and VF development. Overall, 310 prehospital patients with suspected STEMI were included in the analysis (case group, n = 155; control group, n = 155). We confirmed that the presence of TW-pattern complex (OR 7.0, 95% CI 1.55-31.58), premature ventricular contraction (PVC) (OR 5.5, 95% CI 2.04-14.82), and STE in V2-V6 (OR 3.8, 95% CI 1.21-11.74) were electrocardiographic predictors of VF. We also observed that STD in V3-V5 (OR 6.5, 95% CI 1.42-29.39), atrial fibrillation (AF) ≥ 100 beats per minute (bpm) (OR 6.3, 95% CI 1.80-21.90), the combination of STE in V4 and V5, and STD in II, III and aVF (OR 4.8, 95% CI 1.01-22.35), and the presence of STD in ≥ 6 leads (OR 4.2, 95% CI 1.33-13.13) were also associated with VF development. Finally, simultaneous association of 2 (OR 2.3, 95% CI 1.13-4.06) and 3 (OR 11.6, 95% CI 3.22-41.66) predictors showed significant association with VF. In addition to some already known predictors, we have identified several ECG findings associated with the development of VF in patients with suspected STEMI. Early identification of patients with STEMI at increased risk of VF should help EMS providers anticipate adverse events and encourage use of defibrillation pads.

History, ECG, Risk Factors (HER) Scoring for Cardiac Risk Stratification in Patients

Background Chest pain is a common chief complaint of patients presenting to the emergency department. Acute coronary syndrome (ACS) is found to be the etiology of this symptom in a minority of these patient encounters. This study aimed to determine the utility of using the History, ECG, Risk Factors (HER) components of theHistory, ECG, Age, Risk Factors, Troponin (HEART) score in ruling out 30-day Major Adverse Cardiac Event (MACE), ACS, ventricular tachycardia, and ventricular fibrillation in patients aged less than 45. Additionally, the utility of this score in ruling out a positive troponin was investigated as well. Methodology This is a retrospective chart review study that examined a consecutive cohort of 7,724 patients presenting with chest pain to the 11 emergency departments of a single healthcare system over a two-year period (January 2019 to December 2020). HER scores of 0 to 1 were categorized as negative (-) and scores of two or greater were categorized as positive (+). Sensitivity, specificity, and predictive values were calculated for the relationship between HER score positivity and primary cardiac disease and troponin results. Results Test characteristics of HER scoring for significant primary cardiac disease in patients between 18 and 45 years of age presenting with undifferentiated chest pain were sensitivity of 88.0 (CI = 80.0-94.0), specificity of 72.6 (CI = 71.8-73.8), positive predictive value of 3.1 (CI = 2.4-3.9), and negative predictive value of 99.8 (CI = 99.7-99.9). Furthermore, an HER score >1 was neither sensitive nor specific in predicting a positive troponin (sensitivity = 80, CI = 71.9-86; specificity = 71.3, CI = 70.3-72.3). However, the negative predictive value of an HER score of 0-1 was 99.5 (CI = 99.3-99.7) and the positive predictive value was 4.7 (CI = 3.9-5.7). Conclusions According to this study, when evaluating young patients who are deemed to have a subjectively non-highly suspicious history, who have minimal risk factors, and who have an ECG without significant ST deviation, troponin testing is low yield in the risk stratification of patients under the age of 45 for serious primary cardiac disease.

Real-time amplitude spectrum area estimation during chest compression from the ECG waveform using a 1D convolutional neural network.

Introduction: Amplitude spectrum area (AMSA) is a well-established measure than can predict defibrillation outcome and guiding individualized resuscitation of ventricular fibrillation (VF) patients. However, accurate AMSA can only be calculated during cardiopulmonary resuscitation (CPR) pause due to artifacts produced by chest compression (CC). In this study, we developed a real-time AMSA estimation algorithm using a convolutional neural network (CNN). Methods: Data were collected from 698 patients, and the AMSA calculated from the uncorrupted signals served as the true value for both uncorrupted and the adjacent corrupted signals. An architecture consisting of a 6-layer 1D CNN and 3 fully connected layers was developed for AMSA estimation. A 5-fold cross-validation procedure was used to train, validate and optimize the algorithm. An independent testing set comprised of simulated data, real-life CC corrupted data, and preshock data was used to evaluate the performance. Results: The mean absolute error, root mean square error, percentage root mean square difference and correlation coefficient were 2.182/1.951mVHz, 2.957/2.574mVHz, 22.887/28.649% and 0.804/0.888 for simulated and real-life testing data, respectively. The area under the receiver operating characteristic curve regarding predicting defibrillation success was 0.835, which was comparable to that of 0.849 using the true value of the AMSA. Conclusions: AMSA can be accurately estimated during uninterrupted CPR using the proposed method.

Vagal response is involved in the occurrence of ventricular fibrillation in patients with early repolarization syndrome

Patients with early repolarization syndrome (ERS) and Brugada syndrome (BruS) have comparable clinical symptoms. In both conditions, ventricular fibrillation (VF) is experienced often near midnight or in the early morning hours when the parasympathetic tone is augmented. However, differences between ERS and BruS regarding the risk of VF occurrence have recently been reported. The role of vagal activity remains especially unclear. The study's goal was to determine the relationship between VF occurrence and autonomic nervous activity in patients with ERS and BruS. We enrolled 50 patients with ERS (n = 16) and BruS (n = 34) who received implantable cardioverter-defibrillators. Of these, 20 patients (5 ERS and 15 BruS) experienced VF recurrence (recurrent-VF group). We investigated baroreflex sensitivity (BaReS) with the phenylephrine method and heart rate variability (HRV) using a Holter ECG in all patients to estimate autonomic nervous function. In both patients with ERS and BruS, there was no significant difference in HRV between the recurrent-VF and the non-recurrent-VF groups. However, in patients with ERS, BaReS was significantly higher in the recurrent-VF group than in the non-recurrent-VF group (p = 0.03); this difference was not evident in BruS patients. High BaReS was independently associated with VF recurrence in patients with ERS, according to Cox proportional hazards regression analyses (HR: 1.52; 95% CI: 1.031-3.061; p = 0.032). Our findings suggest that in patients with ERS, an exaggerated vagal response, as represented by increased BaReS indices, may be involved in the risk of VF occurrence.

Ventricular Parasystole in Cardiomyopathy Patients: A Link Between His-Purkinje System Damage and Ventricular Fibrillation

BackgroundThe clinical relevance and prognostic implications of ventricular parasystole are unknown. ObjectivesThis study sought to assess the prevalence of ventricular parasystole in patients with implantable cardioverter-defibrillators (ICDs) and ventricular parasystole’s association with ventricular arrhythmias and conduction system abnormalities. MethodsThis study retrospectively evaluated patients who underwent ICD interrogation at a single center between June 1, 2019, and August 31, 2020, and reviewed all available ICD and electrocardiogram data. This study identified patients with ventricular parasystole and compared the prevalence of ventricular fibrillation (VF), ventricular tachycardia (VT), and new conduction system abnormalities in those with ≥5 years of intrinsic QRS-complex electrocardiograms to those without parasystole. ResultsThis study included 374 patients (age 57 ± 21 years, 72% male, 45% nonischemic, 32% ischemic cardiomyopathy), of which, 104 (28%) had VT only, 39 (10%) VF only, and 10 (3%) both VT/VF. Ventricular parasystole was identified in 33 patients (9%); parasystolic foci were predominantly from the His-Purkinje system. Compared with those without parasystole, patients with parasystole had a significantly higher rate of VF (36% vs 11%; P < 0.01), but not VT (42% vs 29%; P = 0.12). Patients with parasystole, compared with those without parasystole, had a higher prevalence of new conduction abnormalities, particularly progressive intraventricular conduction delay (11 of 18 [61%] vs 12 of 83 [14%]; P < 0.01) and new right bundle branch block (4 of 18 [22%] vs 1 of 83 [1%]; P < 0.01). ConclusionsVentricular parasystole was strongly associated with new conduction system abnormalities and VF in patients who have cardiomyopathy with ICDs, suggesting a potential link between VF and His-Purkinje damage in this patient population.