Ventricular Fibrillation Research Articles

Amplitude spectrum area is dependent on the electrocardiogram magnitude: evaluation of different normalization approaches.

Amplitude Spectrum Area (AMSA) of the electrocardiogram (ECG) waveform during ventricular fibrillation (VF) has shown promise as a predictor of defibrillation success during cardiopulmonary resuscitation (CPR). However, AMSA relies on the magnitude of the ECG waveform, raising concerns about reproducibility across different settings that may introduce magnitude bias. This study aimed to evaluate different AMSA normalization approaches and their impact on removing bias while preserving predictive value. ECG were recorded in 118 piglets (1-2 months old) during a model of asphyxia-associated VF cardiac arrest and CPR. An initial subset (91/118) was recorded using one device (Device 1), and the remaining piglets were recorded in the second device (Device 2). Raw AMSA and three ECG magnitude metrics were estimated to assess magnitude-related bias between devices. Five AMSA normalization approaches were assessed for their ability to remove detected bias and to classify defibrillation success. Device 2 showed significantly lower ECG magnitude and raw AMSA compared to Device 1. CPR-based AMSA normalization approaches mitigated device-associated bias. Raw AMSA normalized by the average AMSA in the 1st minute of CPR (AMSA1m-cpr) exhibited the best sensitivity and specificity for classification of successful and unsuccessful defibrillation. While the optimal AMSA1m-cpr thresholds for balanced sensitivity and specificity were consistent across both devices, the optimal raw AMSA thresholds varied between the two devices. The area under the receiver operating characteristic curve for AMSA1m-cpr did not significantly differ from raw AMSA for both devices (Device 1: 0.74 vs. 0.88, P=0.14; Device 2: 0.56 vs. 0.59, P=0.81). Unlike raw AMSA, AMSA1m-cpr demonstrated consistent results across different devices while maintaining predictive value for defibrillation success. This consistency has important implications for the widespread use of AMSA and the development of future guidelines on optimal AMSA thresholds for successful defibrillation.&#xD.

Abstract Su306: Impact of Ventricular Fibrillation on Myocardial Infarct Size: A Clinical and Experimental Study

Background: Ventricular fibrillation (VF) - induced cardiac arrest is a frequent complication of ST-segment elevation myocardial infarction (STEMI). Although larger infarct sizes (IS) are associated with a higher risk of VF, there has been no investigation into the influence of VF itself on IS. To address this knowledge gap, we analyzed the impact of VF on IS in patients and 2 experimental models. Methods: From the prospective cohort HIBISCUS-STEMI, 30 STEMI patients with VF were matched on common determinants of IS in a 1:2 ratio with patients without VF. The primary endpoint was IS, assessed using the 48-hour area under the curve (AUC) for troponin. We compared IS in pigs with/without spontaneous VF during STEMI (n=15/group), and in an isolated rat heart model of acute myocardial infarction with/without electrically induced VF (n=7/group); IS was assessed using the ratio of the area of necrosis (AN) to the area at risk (AAR). Results: While patient characteristics were similar after matching (including AAR), IS was 33% lower in the VF group than in the control group (troponin AUC 1.6 [0.5-3.3] 10 6 vs. 2.4 [0.9-4.1] 10 6 arbitrary units; p=0.049). In pigs, IS was lower (p<0.01) in the VF group (24% [11-40]) than in controls (71% [48-75]). In the isolated heart model, IS was lower (p<0.05) in the VF group (9% [7-15]) than in controls (42% [38-44]). Conclusion: When common determinants of IS are comparable, the occurrence of VF prior to MI reperfusion is associated with significantly smaller IS.

Abstract 4145899: The Danger of Moderator Band Ectopy: A Case of Premature Ventricular Contraction induced Recurrent Ventricular Fibrillation

Introduction: Premature Ventricular Contractions (PVCs) are often a benign arrhythmia. However, those originating from the Purkinje system can result in fatal arrhythmias. One example is PVCs originating from the moderator band (MB) within the right ventricle (RV) of the heart. We present a case of PVCs originating from the MB triggering idiopathic ventricular fibrillation (VF) and electrical storm. Case: A previously healthy 49-year-old woman was admitted following a witnessed VF cardiac arrest. She had recurrent episodes of VF, initially treated with Amiodarone and Procainamide which failed to suppress the recurrent VF. She received 54 external defibrillations before a transvenous pacer (TVP) was placed to override the PVCs at a pacing rate of 110 bpm. Post-resuscitation ECGs revealed frequent PVCs originating from the RV free wall, potentially from the lateral part of MB (Figure 1). Quinidine was added to suppress the PVCs ultimately allowing removal of the TVP. Transthoracic Echocardiogram revealed normal cardiac function and a prominent MB. A cardiac MRI was performed showing no infiltrative disease or any other abnormalities. The patient underwent sympathectomy and defibrillator placement. Despite recurrent cardiac arrest, she had excellent neurologic recovery and was subsequently discharged on Quinidine. Discussion: MB extends from the septal wall to the base of the anterior papillary muscle in the RV, carrying Purkinje fibers(PF) from the right bundle branch as it exits the septum. Purkinje fibers have been shown to initiate arrhythmias by several mechanisms including enhanced automaticity, triggered activity and re-entry. In the genesis of PVCs, triggered activity is the likely mechanism. This can degenerate into VF in a structurally normal heart, hence the term “idiopathic VF”. Familiarity with this entity and ECG features of MB ectopy leads to timely management and may potentially prevent lethal arrhythmias in symptomatic patients with such PVCs. Further studies are required to fully understand the arrhythmogenic mechanisms and the optimal management approach for MB ectopy.

Abstract Su503: Relationships Between Quantitative ECG Measures and Defibrillation Success in Early Ventricular Fibrillation

Introduction: Rapid termination of ventricular fibrillation (VF) has long been recognized as the cornerstone of effective cardiac arrest resuscitation. In recent years, amplitude spectral area (AMSA) has been shown to be highly associated with defibrillation success, and AMSA has been experimentally used to personalize defibrillation timing and strategy. However, questions remain about whether the interpretation of AMSA holds uniformly in varied conditions, such as ultra-early or prolonged cardiac arrest or after anti-arrhythmic administration. Hypothesis: AMSA is greater after 20 seconds of untreated VF compared to 50 seconds of untreated VF; a higher AMSA predicts greater first-defibrillation success. Methods: VF was induced in adult swine (n = 3) with a bipolar pacing catheter placed in the right ventricle. Animals were randomized to 20- or 50-second-long episodes of VF (n = 123), followed by standard 150 J biphasic defibrillation. In MATLAB, AMSA was calculated as the summed product of frequency and square root of power after Fast Fourier Transform for the four second period of VF immediately prior to defibrillation. Results were analyzed by a two-sided Chi-squared test or ANOVA with Tukey’s HSD in R; a p-value < 0.05 was considered significant. Results: First shock success was lower in the 20-second-VF group compared to the 50 second group (31/78 (39.7%) vs 31/45 (68.8%), p = 0.003). The AMSA at 20 seconds was significantly higher for successful compared to unsuccessful first defibrillation (8.20 vs. 7.31 mV-Hz, p = 0.034). The AMSA at 50 seconds was not statistically different between successful and unsuccessful defibrillations (6.32 vs. 5.67 mV-Hz, p = 0.470). Evaluating the AMSA after a duration of VF irrespective of shock success, AMSA was higher at 20 seconds compared to 50 seconds (7.66 vs 6.12 mV-Hz, p < 0.001). Conclusion(s): AMSA decreases from 20 to 50 seconds of untreated VF, and higher AMSA at a given time point is associated with greater first defibrillation success. However, first defibrillation success was higher after 50 seconds of untreated VF compared to 20 seconds, raising questions about special cases, such as edge effects, that may influence AMSA interpretation.

Abstract Su502: Is 80% a Reasonable Minimal Goal for Defibrillation Efficacy of Out-of-Hospital Cardiac Arrest ?

Introduction: There is no clear goal defined by standards or learned societies on clinical performance related to defibrillation efficacy. In literature, monophasic shocks defibrillation efficacy is mainly >70% whereas biphasic is >80%. Resuscitation guidelines define efficient defibrillation as cessation of shockable rhythm at 5s post-shock and proceed to state that beyond 5s, shock outcomes are biased by known confounders (call to AED connection time (CallAEDTime), bystander, cardio-pulmonary resuscitation (CPR), drugs…). Thus, it is consistent that automated external defibrillator (AED) performance should be assessed in terms of defibrillation efficacy right after the shock rather than in terms of restoration of a spontaneous circulation or survival to hospital discharge. This study aimed to define an acceptable goal for validation of defibrillation efficacy. Method: In this observational retrospective study, we included AED tracings of adult non-traumatic out-of-hospital cardiac arrest (OHCA) patients with initial ventricular fibrillation (VF) rescued by basic life support teams (Paris Fire Brigade) from 01/2017 to 02/2022. Cardiac rhythm was examined during the 10 first minutes of connection of the AED (DGT7, Schiller Médical, France). Shockable rhythm is defined as coarse-VF with at least 200µV peak-to-peak amplitude (ptpA). Efficient defibrillation was defined as cessation of shockable rhythm at 5s post-shock. We fitted a linear mixed model to predict defibrillation efficacy using the 4s ptpA of pre-shock VF. The model included the patient as random effect and a p-value <0.05 was considered statistically significant. Results: We analyzed 1333 shocks from 547 patients, with: median age of 59 (interquartile range, IQR[49-71]), 78% male, 36% in public places, 72% with bystander CPR and median[IQR] CallAEDTime of 13min [10-15]min. The effect of the pre-shock ptpA of VF on the defibrillation efficacy is statistically significant: OR=1.023, 95% Confidence Interval (CI) [1.010,1.036], p<0.001. That means that for each 100µv increment in VF amplitude pre-shock, the probability of success at 5s post-shock increases by 2.3%. Adjusting for age, sex, location, CPR and CallAEDTime does not change the results. The logistic regression of Figure1, shows a defibrillation efficacy at 200µV ptpA of 79%, CI [75,82]%. Conclusion: Based on 1333 OHCA biphasic shocks, this study suggests defining 80% as a reasonable minimal goal for validation of the AED defibrillation efficacy.

Abstract 4140168: Association of left and right branch blocks with clinical outcomes in patients with heart failure with preserved ejection fraction (HFpEF)

Background: Although left (LBBB) and right (RBBB) bundle branch blocks play a critical role in cardiovascular pathogenesis, the associations of LBBB and RBBB with cardiovascular (CV) outcomes, especially in patients with HFpEF is understudied compared with normal QRS. Aim: We assessed clinical outcomes of LBBB and RBBB in patients with HFpEF who were admitted for acute decompensated heart failure compared with those without bundle branch blocks. Method: A cross-sectional study was conducted using the National Inpatient Sample (NIS) database from 2019. We only included adult hospitalizations with HFpEF admitted for acute decompensated heart failure in the study. Hospitalized records were categorized into three groups (LBBB, or RBBB, and those with normal QRS). Clinical outcomes included atrial fibrillation (AF), ventricular fibrillation (VF), complete heart block (CHB), sick sinus rhythm (SSR), cardiac arrest (CA), length of stay (LOS) and in-hospital mortality. Propensity score (PS) inverse probability of treatment weighting and matching were applied to determine the association between BBB types and CV outcomes and validated associations in sensitivity analyses. Results: A total of 334511 hospitalizations with HFpEF included LBBB (6818, 2%) and RBBB (7948, 2.4%) were analyzed. Compared to normal QRS, LBBB was associated with VF (odds ratio [OR]=2.47, p<0.001), SSR (OR=1.72, p<0.001), CHB (OR=2.77, p<0.001) and longer LOS (relative risk [RR]=1.15, p<0.001) after adjusting for covariates in PS analysis. Similarly, RBBB was associated with AF (OR=1.30, p<0.001), VF (OR=1.59, p=0.033), SSR (OR=1.72, p<0.001), CHB (OR=2.81, p<0.001), CA (OR=1.19, p<0.001), and longer LOS (RR=1.08, p<0.001) [Table 1]. These associations remained consistent in multiple validation analyses including after additionally adjusting for obesity, hypertension and diabetes. Conclusion: In hospitalized records with acute decompensated HFpEF, BBB was associated with increased risk of CV outcomes and longer hospital length of stay. The extent of association with multiple CV outcomes varied according to RBBB and LBBB.

Abstract Su304: The Effect of Time to DC Shock on Return of Spontaneous Circulation in Out-of-Hospital Cardiac Arrest with Recurrent Shockable Rhythm

Objective: The optimal timing for defibrillation attempts in out-of-hospital cardiac arrest (OHCA) patients with recurrent shockable rhythms [ventricular fibrillation (VF) or pulseless ventricular tachycardia (VT)] is uncertain. This study examined the association between "time to DC shock" and the return of spontaneous circulation (ROSC) in OHCA patients with recurrent shockable rhythms. Methods: This was a retrospective analysis of data from the Salt Lake City Fire Department (SLCFD) from 2012 to 2023. Rhythm-filtering technology, used since 2012, enabled real-time and accurate interpretation of cardiac rhythms during CPR, with local protocols allowing early defibrillation for recurrent VF/ pulseless VT cases. Patients who experienced four or five episodes of shockable rhythms and received defibrillation were included. Generalized estimating equation (GEE) analysis was used to evaluate the association between time to shock preceding recurrent defibrillation and ROSC. Results: A total of 142 patients were included, with a mean age of 59.7 ± 15 years; 105 (73.9%) were male, 63 (44.4%) arrested in public locations, and 101 (71.1%) had witnessed arrests. Adjusted GEE analysis revealed that longer time to shock was associated with lower odds of achieving ROSC (OR: 0.81, 95% CI: 0.72–0.93, p = 0.005). Every one-minute delay in defibrillation is predicted to decrease the likelihood of achieving ROSC by 19%. Conclusion: In patients with recurrent shockable rhythms, every one-minute delay in delivering a shock was associated with a statistically significant 19% reduction in the chance of achieving ROSC. This finding highlights the importance of reducing the time to defibrillation in managing recurrent shockable rhythms and suggests reevaluating the current recommendation of two-minute intervals for rhythm check and shock delivery.

Abstract 4123826: Very Short-Term Blood Pressure Variability Determined by Pulse Transit Time Predicts Major Adverse Cardiac and Cerebrovascular Event in Patients with Heart Failure

Introduction: It has been reported that day-to-day blood pressure (BP) variability (BPV) is associated with major adverse cardiac and cerebrovascular events (MACCE) in patients with heart failure (HF). However, the clinical significance of beat-to-beat BPV is unclear. Methods and Results: We recruited data on patients with HF who underwent nighttime pulse transit time (PTT)-based continuous beat-to-beat BP measurement (n = 379, median age 71, male sex 53.6%). Standard deviation (SD) of PTT-based BP was considered as BPV. The primary outcome was MACCE defined as coronary artery disease, stroke, or death due to HF, acute coronary syndrome or ventricular fibrillation. Median values (25th and 75th percentiles) of SD of PTT-based systolic, diastolic, and mean BP were 4.2 (3.5, 5.3), 3.3 (2.7, 4.1), and 3.4 (2.8, 4.1) mmHg, respectively. During the follow-up period of median 1,083 days after BPV evaluation, 43 patients experienced MACCE. When patients were divided into three tertiles based on the systolic, diastolic, and mean BPV, MACCE occurred more frequently in those with higher tertiles of BPV ( Figure ). In the Cox proportional hazard analysis, systolic, diastolic, and mean BPV as continuous variables were associated with MACCE (hazard ratio, 1.191, 1.228, and 1.243, respectively). Conclusion: Beat-to-beat BPV was associated with MACCE in patients with HF.

Abstract 4145802: Association between Glucagon-like peptide-1 receptor agonists and risk of Arrhythmias or Heart Failure among patients with Type 2 Diabetes: A Meta-Analysis of 29 Randomized Controlled Trials.

Background: Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) have shown a reduction in major adverse cardiovascular events (MACE) among patients with type 2 diabetes mellitus (T2DM). However, their effect on reducing the risk of incidence of arrhythmias and heart failure has not been established, and there is very limited literature to date. Objective: We evaluated the effect of GLP-1 RAs on the incidence of arrhythmias and heart failure among patients with T2DM. Methods: We performed a systematic review and meta-analysis of randomized controlled trials (RCTs) that enrolled patients with type 2 diabetes and compared GLP-1 RAs and control groups. PubMed and ClinicalTrials.gov were systematically searched from inspection till May 2024 without any language restrictions. Odds ratios (OR) and 95% confidence intervals (CI) were pooled using a random-effect model. Results: A total of 29 RCTs with 72,868 patients (35,631 in the GLP-1 RA group and 37,237 in the control group) were included in the analysis. Pooled analysis showed that there is no significant association between GLP-1 RAs and incidence of atrial fibrillation (OR, 0.94(95%CI: 0.75-1.18), P=0.60), atrial flutter (OR, 0.87(95%CI: 0.60-1.26), P=0.46), cardiac arrest (OR, 0.79(95%CI: 0.51-1.23), P=0.30), ventricular tachycardia (OR, 1.37(95%CI: 0.90-2.07), P=0.14), and ventricular fibrillation (OR, 0.91 (95%CI: 0.45-1.84), P=0.80) when compared with control group. However, GLP-RAs reduced the incidence of atrioventricular block complete (OR, 0.58 (95%CI: 0.35-0.97), P=0.04), and heart failure (OR, 0.795 (95%CI: 0.634-0.997), P=0.047). Conclusion: This study shows that GLP-1 RAs reduced the incidence of atrioventricular block complete and incidence of heart failure. However, no significant association has been observed for arrhythmias.

Abstract 4136459: Machine Learning in Time-to-Event Prediction of Ventricular Arrhythmias among Older Adults with Type 2 Diabetes and Coronary Artery Disease

Introduction: Patients with Type 2 diabetes mellitus (T2DM) have an increased risk for coronary artery disease (CAD) compared to patients without T2DM. Ventricular arrhythmias (VA), such as ventricular fibrillation and ventricular tachycardia, are the major causes of mortality among patients with CAD. Thus, T2DM patients with CAD, especially older adults, have a higher risk of VA compared to patients without T2DM. The time-to-event prediction can contribute to decreasing mortality due to VA in older adults with T2DM and CAD by providing an estimated time and probability of diagnosis at specific time points. However, the limited number of older T2DM patients with CAD, who are diagnosed with ventricular arrhythmias, lowers the performance of a traditional time-to-event analysis model. Hypothesis: We hypothesize that machine learning can improve performance in time-to-event prediction. Methods: This study includes 3975 participants aged >65 years, diagnosed with T2DM and CAD in the All of US database. The baseline time was the earliest date when the patients were older than 65 years and diagnosed with T2DM and CAD. Of all participants, 379 were diagnosed with VA within 5 years from baseline. We compared the machine learning–based time-to-event analysis models to the Cox Proportional Hazards model to explore the potential of machine learning in time-to-event analysis. Additionally, the Synthetic Minority Oversampling Technique was applied to resolve the imbalanced data issue. The model performance was evaluated based on the concordance index, which calculates the correlation between predicted risk scores and actual observations, after 5-fold cross-validation. Results: The average concordance index of the Gradient Boosting Machines model was the highest among the five models, including the Cox Proportional Hazards model, with balanced data (Table). Conclusion: We identified that machine learning could improve the performance of prediction models in time-to-event analysis. The Synthetic Minority Oversampling Technique could mitigate the issue of imbalanced data. In addition, machine learning-based survival models showed higher concordance index values compared to the Cox Proportional Hazards model.

Abstract 4136788: Lipoprotein(a) Levels and the Risk of Ventricular Arrhythmia: Insights from a Comprehensive Retrospective Cohort Study

Background: Sustained ventricular arrhythmias (VAs) are associated with an elevated risk of sudden cardiac death (SCD). Lipoprotein(a) (Lp[a]) is a recognized risk factor for atherosclerotic cardiovascular disease (ASCVD), which in turn associated with increased risk of VAs. However, whether Lp(a) is linked with VAs independent of ASCVD remains unknown. Objective: To examine the association of Lp(a) with VAs in a population-based, retrospective cohort study utilizing data from the TriNetX Research Network. Methods: We conducted a retrospective analysis of the data from 89 healthcare organizations within the TriNetX Research Network. Patients over 18 years old with available serum Lp(a) measurement were included. Participants were divided into two cohorts based on their Lp(a) levels: cohort 1 (Lp(a) ≤75 nmol/L), and cohort 2 (Lp(a) ≥76 nmol/L). Follow-up time to VA occurrence was calculated from the time of Lp(a) level measurement within each cohort. The composite endpoint was the incidence of VAs to include ventricular tachycardia, ventricular fibrillation, ventricular flutter, or cardiac arrest due to underlying cardiac conditions. We compared the two cohorts using Kaplan-Meier survival analysis along with cox proportional hazard regression analysis after propensity score matching. Results: 50,752 patients were included in cohort 1 and 24,474 in cohort 2. After propensity score matching, both cohorts had 23,668 patients. In cohort 1, 307 patients experienced VAs, compared to 303 in cohort 2 (Table 1). The mean age was 53.3 ± 15.7 years, with 53.35% of participants being female, 10.75% being Black, and 69.89% being White. The Kaplan-Meier survival analysis showed a higher survival probability at the end of the study period for the Lp(a) ≤75 compared to the Lp(a) ≥76 cohort (95.11% vs 85.35%, p=0.002). The hazard ratio (HR) for VA was 0.768 (95% CI: 0.652-0.904, p = 0.002), indicating that lower Lp(a) levels are associated with reduced VA risk. Conclusion: This study shows that increased Lp(a) levels are independently associated with a higher incidence of VA. Future research should focus on the mechanisms underlying the relationship between Lp(a) levels and VA, and whether Lp(a) reduction can reduce the risk of VA and other cardiovascular outcomes.

Abstract 4139144: "Comparative Analysis of Inpatient Outcomes: Decompensated Systolic Heart Failure (HFrEF) with and without Iron Deficiency Anemia, Propensity-Matched Nationwide Study (2017-2021)."

Background: Iron deficiency anemia (IDA) affects approximately one-third of patients with systolic heart failure, yet comprehensive population-based analyses of its impact on in-hospital outcomes remain limited. This study seeks to examine how IDA influences in-hospital outcomes among individuals with decompensated systolic congestive heart failure (HFrEF). Methods: Using data from the National Inpatient Sample (NIS) database spanning from 2017 to 2021, this study identified patients hospitalized for decompensated systolic congestive heart failure (HFrEF) with a secondary diagnosis of IDA using ICD-10 codes such as I5020-23 and D500, D501, D508, D509. Propensity score matching (PSM) was then employed to create cohorts without and with IDA at a 1:3 ratio. Multivariate regression analyses were conducted to evaluate various outcomes, including in-hospital mortality, cardiogenic shock (CS), acute myocardial injury (AMI), cardiac arrest, ventricular tachycardia (VT), ventricular fibrillation (VF), length of stay (LOS), and total hospitalization charges. Furthermore, the utilization rate of mechanical ventilation and circulatory support, including intra-aortic balloon pump and extracorporeal membrane oxygenation, was evaluated in both cohorts. Results: Among 253,034 HFrEF hospitalizations, 16,200 (6.4%) had a secondary diagnosis of IDA. After PSM, multivariate regression analyses revealed no significant differences in the odds of cardiogenic shock (10% vs. 10%, p=0.86), in-hospital mortality (2.6% vs. 2.8%, p=0.71), and LOS (7.19 vs. 7.27 days) between the two groups. Additionally, the likelihood of cardiac arrest, ventricular arrhythmias, AMI, and utilization of mechanical ventilation and circulatory support did not reach statistical significance. However, patients with IDA and HFrEF had higher hospitalization charges ($85,516 vs. $93,000). Conclusion: HFrEF patients, with or without IDA, had similar odds of cardiogenic shock, in-hospital mortality, mechanical circulatory support utilization, as well as LOS. However, IDA with HFrEF correlated with higher hospitalization charges.

Abstract 4122247: Impact of serum chloride levels for ventricular arrhythmias in patients with heart failure undergoing cardiac resynchronization therapy

Background: As previous reports of ventricular arrhythmia (VA) as a prognostic marker of mortality in heart failure (HF) patients included those with implantable cardioverter defibrillator (ICD) and cardiac resynchronization therapy (CRT) devices, little is known about the risk factors of VA among patients undergoing cardiac resynchronization therapy (CRT), especially those without previous VA. The prognostic role of electrolyte abnormalities has been highlighted in HF patients. This study evaluated the impact of serum chloride levels for VA and all-cause death in patients with HF who underwent CRT without VA before CRT implantation. Methods: From the retrospective cohort of 397 HF patients (age 63+/-13, male 74%) who undergoing CRT implantation between 2010 and 2020, this study enrolled 175 patients (82% implanted CRT with a defibrillator) without a previous history of VA (sustained ventricular tachycardia (VT) of ventricular fibrillation (VF)). We studied the impact of serum chloride levels before CRT implantation. The primary endpoint was defined as VA, VA with ICD therapy and sudden cardiac death. The secondary endpoint was all-cause mortality. Results: During median follow-up of 35 months, 53 patients (30%) experienced VA. Patients with VA had a tendency toward high LVESV (172ml vs. 150ml, p<0.09) and low left ventricular ejection fraction (26 vs. 29, p<0.09), and significantly reduced rate of angiotensin converting enzyme inhibitors or angiotensin receptor blockers (30% vs. 70%, p<0.05) at the time of CRT implantation. The rate of CRT responders was significantly higher in patients without VA than with VA (59% vs. 40%, p<0.05). The cut-off value of chloride for VA was determined to be 102mEq/l using receiver operating characteristic analysis. The patients with chloride ≤102mEq/l had significantly higher rates of VA (41% vs. 25%, log-rank p<0.05) and mortality (33% vs. 18%, log-rank p<0.05) (Figure). By multivariate cox analysis, the level of chloride had an independent predictive value of VA in patients with CRT (hazard ratio [HR] 1.08 per 1mEq/l decrease, 95% confidence interval [CI] 1.00-1.16, p<0.05) (Table). Conclusions: The chloride level had a predictive value for VA after CRT implantation in HF patients without previous VA. The management of electrolytes, including chloride, might be important for preventing fatal arrhythmia in patients with HF undergoing CRT implantation.

Abstract 4118415: Device Dislodgement and Embolization associated with a New Leadless Pacemaker

Background: Leadless pacemakers (LP) avoid the pocket and lead-related complications of transvenous pacing. A potential complication of LPs is dislodgement and/or embolization (D/E) during or after implant. No D/E occurred in the original 725-patient Micra™ VR clinical trial. However, in the 526-patient LEADLESS II-phase 2 trial, the rate of dislodgement for 200 Aveir™ VR LPs was 1.5%. Thus, there appears to be a significant difference in D/E rates between these LPs that have different fixation mechanisms and insertion tools. Aims: We aimed to determine if the Aveir VR LP has continued to exhibit D/E since it was approved by the Food and Drug Administration (FDA) in April 2022. Methods: We queried the FDA's Manufacturers and User Facility Device Experience (MAUDE) database for Aveir D/E that occurred in the U.S. and were reported by the manufacturer from April 2022-December 2023. The number of Aveir VR implants in the U. S. was obtained from the manufacturer's publicly available product performance report. D/E outside the U.S. were excluded. Results: During the 21 months, 55 of 3,139 (1.75%) Aveir VR implants exhibited D/E. More D/E (34;61.8%) occurred during implant, with 18 (52.9%) of these happening after release of the device from the tether mode. Fourteen (41.2%) of the intra-procedural D/E occurred when the device prematurely released from the delivery catheter, and two dislodged during cardiopulmonary resuscitation (CPR). D/E occurred in 21 patients (38.2%) after implant and were signified by loss of pacing or inability to interrogate the device. Four (19%) out of those 21 patients presented with symptomatic bradycardia. The dislodged devices commonly embolized to the pulmonary artery and right atrium/vena cava. LP retrieval was successful in 49 (89%) cases. Thirty-two patients (58.1%) received a new LP, 5 patients were transitioned to a transvenous system, and a replacement device was not specified for 17 (31%) patients. One patient died during implantation due to ventricular fibrillation (VF) not related to D/E. Conclusions: Fixation issues and premature separation of the device from the delivery catheter appear to be responsible for most of these D/E. Studies are needed to determine if impedance or another metric is associated with adequate Aveir fixation. The manufacturer should address the premature separation problem with Aveir. Success of D/E retrieval may be related to tools specific for Aveir. Further studies are needed to compare between the two LPs.

Abstract 4137267: A novel reproducible low-cost model of acute myocardial infarction in swine

Background: Traditional open- and closed-chest methods for inducing acute myocardial infarction (AMI) in pigs typically require extensive and expensive instrumentation, including ventilators and inhalation anesthesia. This study aims to evaluate a reproducible and low-cost model for AMI in pigs using lower hemisternotomy. Methods: Twenty Yorkshire swine (15-20 kg, 45-50 days of age) underwent permanent ligation of the roots of the first and second diagonal branches of the left anterior descending coronary artery. The procedure was performed under intramuscular anesthesia (1ml 0.5mg/kg Zoletil™ and 2ml 10mg/kg xylazine hydrochloride) with spontaneous respiration. Cardiac function was assessed via echocardiography and cardiac PET/MRI scans at 1 and 4 weeks post-MI. Heart tissue was collected for pathological analysis to evaluate the establishment of the AMI model. Results: All animals exhibited ECG changes, including premature ventricular complexes and ST-segment elevation immediately after ligation. No ventricular tachycardia and fibrillation was observed during the operation. No animals (0%) died during infarct creation. The "Skin-to-Skin" procedure time was 18±3.3 minutes. this procedure produced an infarction that occupies ~10% of the left ventricular mass accompanied with the decrease of LV heart function and LV anterior wall thickness 4 weeks post-MI. Conclusions: This novel low-cost technique provides reproducible acute coronary artery occlusion at a selected location with subsequent AMI. It avoids ventilation, inhalation anesthesia, major surgery and does not require expensive instrumentation for intracoronary intervention.

Abstract Su202: Physiological response to vasopressor administration during hemodynamic-directed CPR

Background: The hemodynamic response to successive vasopressor doses during CPR and its association with survival is poorly defined. Understanding these relationships can facilitate identification of alternative vasopressor strategies. Hypothesis: Non-survival is associated with lower responsivity to successive vasopressors. Methods: We performed retrospective analysis of hemodynamic data acquired in pediatric swine models (sus scrofa, 9-12kg) of asphyxia-associated ventricular fibrillation cardiac arrest with use of hemodynamic-directed CPR (n=175). Starting 2m into CPR, if hemodynamic targets were not met, vasopressors were given in cycles comprising two doses of 0.02mg/kg epinephrine (Epi) followed by vasopressin (Vaso, 0.4U/kg), separated by a minimum of 1m. After a minimum of 2m, the cycle was repeated. Hemodynamic response was evaluated using the peak diastolic blood pressure (DBP) within 1m for Epi, 2m for Vaso administration and the difference between the initial and peak DBP (delta DBP). Subjects were classified as “responder” if either a delta DBP > 5 mmHg or a peak DBP > 25 mmHg was achieved, and a “non-responder” otherwise. Animals were deemed “survivors” if ROSC was achieved following initial defibrillation. The change in delta DBP for successive vasopressors was compared in survivors versus non-survivors using two-sided Wilcoxon rank-sum tests. Continuous variables are summarized using the median with interquartile ranges. The burden of “non-response” was used to a construct confusion matrix and calculate performance. Results: Non-survivors (n=30) had lower delta DBP than survivors (n=145) following successive vasopressor administration at the first cycle (first Epi dose: 7.8 [2.4, 14] vs 16 [7.5, 24], p< 0.01; second Epi: 2.0 [0, 4.7] vs 7.1 [2.0, 12], p< 0.01; Vaso : 1.1 [0, 2.3] vs 7.1 [2.0, 12], p< 0.01). Classification as a “non-responder” at the first cycle (Epi-Epi-Vaso) was significantly predictive of non-survival (Sensitivity 32%, Specificity 92%). Animals that failed to respond to all vasopressors at the first cycle had a significantly increased rate of mortality (86%; 6 non-survivors, 1 survivors) compared to animals that responded to all 3 vasopressors (13%; 16 non-survivors, 111 survivors). Conclusion: Mortality was significantly associated with lower DBP response to successive vasopressors during hemodynamic-directed CPR in pediatric swine models of cardiac arrest, which may suggest a critical timepoint to activate ECPR.

Abstract Su501: Feasibility and Implications of Electrocardiogram-based Prediction of Incessant Refractory Ventricular Fibrillation

Background: Refractory ventricular fibrillation (R-VF) patients, defined as requiring ≥ 3 shocks during resuscitation of OHCA, have relatively poor outcomes. Prior studies have predicted R-VF using the ECG, suggesting potential to guide early patient-specific treatment for R-VF. However, R-VF comprises multiple phenotypes with distinct defibrillation response profiles: Incessant VF (no shocks terminate VF), recurrent VF (all shocks terminate VF but VF recurs), or mixed VF (shocks variably terminate VF). These phenotypes may have distinct prognoses, and may also respond differently to R-VF treatments such as early antiarrhythmics, modified vasopressor dosing, alternative defibrillation strategies, or expedited invasive interventions. Early prediction of specific R-VF phenotype could potentially improve outcome through preemptive targeting of treatment to individual phenotype. Aim: We sought to predict incessant R-VF using machine learning analysis of the defibrillator ECG. Methods: We performed a retrospective study of adult VF OHCA treated by EMS from 2006–2019 in King County WA. We linked a clinical OHCA registry with defibrillator recordings to evaluate ROSC and survival to hospital discharge by VF type (non-refractory; or incessant, recurrent, or mixed R-VF prior to the third shock). To predict incessant R-VF specifically, we used a series of four 2-s ECG segments from each patient within 60s surrounding the first shock. Patients were randomized 65%/35% for training/test. A support vector machine classifier was trained to predict subsequent incessant R-VF using ECG scalograms. Algorithm performance was assessed by area under the receiver operating characteristic curve (AUC) and by sensitivity at >75% specificity. Results: Of 1111 included VF patients, median age was 62, 241 (22%) were female, 658 (59%) were refractory (≥ 3 shocks), 800 (72%) achieved ROSC, and 520 (47%) survived. The incessant R-VF phenotype accounted for 10% (N=116) and had worse ROSC and survival compared to recurrent R-VF and non-refractory patients (Table). Training and test AUCs to predict incessant R-VF were 0.77 (95% CI: 0.72–0.82, N=723) and 0.76 (95% CI: 0.66–0.82, N=388) respectively. Test sensitivity and specificity were 64% and 76%. Conclusion: Refractory VF comprises distinct phenotypes with disparate outcomes. Incessant R-VF has notably poor prognosis. Machine learning may be able to predict incessant R-VF, potentially guiding preemptive, patient-specific treatments to improve outcome.

Abstract 4113864: Hyperkalemia In Patients With Heart Failure Correlates to Worse Inpatient Outcomes

Background: Heart failure (HF) is one of the leading causes of hospitalizations in the States. Hyperkalemia is not an infrequent comorbidity in patients with HF, limiting the maximum benefits of guideline-directed medical therapy. This study evaluates the outcomes in patients admitted for HF with and without hyperkalemia. Methods: We used the Nationwide Readmissions Database (NRD) from 2016-2019, extracting adult patients with a primary diagnosis of HF who were admitted between January and November of each year. Survey procedures were applied using SAS 9.4. Results: We included 4,454,273 weighted hospitalizations due to HF for which 380,446 patients (8.5%) had a concurrent diagnosis of hyperkalemia. Overall, patients with hyperkalemia, compared to HF cases with hyperkalemia, were slightly younger (mean age 70 years vs. 72 years, p <0.01) with fewer women (47% vs.48%) respectively. Patients with hyperkalemia had a higher frequency of diabetes mellitus, hypertension, chronic liver disease, acute kidney injury, chronic kidney disease, end-stage renal disease, and acute encephalopathy (p<0.001). They had more inpatient complications including ventricular fibrillation and cardiac arrest (p <0.001) with longer mean lengths of stay (7 days vs. 5 days, p <0.001) and 30-day readmissions (28% vs. 22%, p<0.001). In-hospital mortality during index admission was significantly higher in the hyperkalemic group (6.4% vs. 2.5%, p < 0.001). Inpatient outcomes including mortality were also worse during first readmission (7% vs. 6%, p<0.01). Even after adjustment for the above-mentioned comorbidities, multivariable analysis reveals that hyperkalemia is an independent factor for inpatient mortality (adjusted OR 1.9 [1.8-2], p<0.001). Conclusion: Hyperkalemia in patients admitted with HF is associated with increased inpatient mortality and readmission. Further studies can investigate whether novel potassium binders may improve outcomes.

Abstract 4129273: Severe Mitral Regurgitation from Impella-associated Mitral Chordae Rupture with Successful Transcatheter Edge-to-edge Repair

Background: Limited data exists describing Impella-related mechanical mitral valve complications. Diagnosis and management can be challenging due to potential underestimation of mitral regurgitation severity from Impella and acute clinical deterioration upon removal. We present a case of successful mitral transcatheter edge-to-edge repair (TEER) for acute severe MR secondary to Impella-related mitral chordae rupture resulting in acute pulmonary edema post-Impella removal. Case Summary: A 37-year-old male smoker presented with chest pain complicated by cardiac arrest due to ventricular fibrillation. Spontaneous circulation could not be restored, requiring veno-arterial extracorporeal membrane oxygenation (VA-ECMO). Coronary angiography revealed total occlusion of the proximal left anterior descending artery, which was successfully stented. Transfemoral Impella CP was placed for left ventricular venting under fluoroscopy (Panel A) with TTE showing no complications. In the intensive care unit, the Impella was advanced under TTE guidance; its tip was found to be positioned deep at the base of the posteromedial pupillary muscle without suction alarms or ventricular arrhythmias on the following day (Panel B). Several days later, TTE revealed new eccentric MR with hyperdynamic left ventricular motion (Panel C). The patient remained hemodynamically stable after VA-ECMO decannulation with Impella at P4. Following Impella removal, he developed repeated flash pulmonary edema despite aggressive fluid removal attributed to acute severe MR secondary to a flail P3 leaflet with ruptured chordae tendineae confirmed by transesophageal echocardiography (Panel D). Given the patient's poor surgical candidacy with a STS score of 13.2%, the team proceeded with mitral TEER, successfully reducing MR severity from severe to mild with a single NT Mitraclip ® across the medial commissure (Panel E). His post-operative cardiac course was uneventful without recurrence of pulmonary edema. Discussion: Irreversible mechanical damage to the mitral valve apparatus caused by Impella placement and repositioning is a rare, potentially fatal complication requiring emergent intervention. Mitral TEER can be a viable salvage option for poor surgical candidates.

Abstract Su404: Time difference between pad placement in double versus single external defibrillation: a live patient simulation model

Background: Out-of-hospital cardiac arrest (OHCA) cause significant patient morbidity and mortality. Double sequential external defibrillation (DSED) represents an alternative treatment for OHCA patients, but the use is currently reserved for patients in refractory ventricular fibrillation. However, OHCA patients may achieve return of spontaneous circulation earlier with the use of DSED as the initial treatment. Aims: To compare the necessary times needed to establish pad placement in DSED compared to standard pad placement in a live patient simulation model. Methods: This study was an observational cohort study with ambulance personnel and live patient models. Two-member teams established two defibrillators ready for rhythm analysis. Time spent for standard pad placement and DSED was registered in the same procedure. The procedure was performed on two patient categories, with BMI 20,9 (patient A) and BMI 32,8 (patient B). All team members performed the procedure on both patient categories. Results: In total, 108 procedures were performed on both patient categories. Mean difference in time needed for DSED versus standard pad placement was 13.7 ± 4.8 seconds for patient A, and 13.9 ± 4.6 seconds for patient B. There was no significant difference in time spent between the two patient categories (p=0.725). Conclusion: The necessary time to establish DSED versus standard defibrillation pad placement was short. This may support clinical studies on DSED as initial treatment for OHCA patients without risk of significant increase in time to first defibrillation.