Mean Ventricular Rate Research Articles

Heart rate is an important predictor of pacing induced cardiomyopathy in a machine learning analysis

Abstract Background 10-20% of patients who have right ventricular pacing develop pacing induced cardiomyopathy (PICM). Home monitoring (HM) could identify patients developing PICM in real-time and facilitate echocardiographic confirmation, medication optimisation and if necessary cardiac resynchronisation therapy (CRT). Purpose To identify predictors of PICM using machine learning models. Methods Consecutive cases of patients who developed PICM (12) after dual chamber pacing were identified from our implant database and matched 4:1 with propensity matched controls who underwent pacing but did not develop PICM (48) (Table 1.) HM data from the 6 months prior to echocardiographic diagnosis of PICM was analysed. PICM was defined as (1) a deterioration in left ventricular (LV) ejection fraction (EF) of >10%, (2) to an EF of <45%, (3) with right ventricular (RV) pacing >20% and (4) the exclusion of alternative causes. Three types of ML models were generated (1) random forest, (2) extreme gradient boosted (XGBoost) (3) K-nearest neighbours algorithm (KNN), with 10-fold cross-validation. Results HM data were available for 12 PICM cases (75 ± 8 years, 72% male). PICM occurred at 2.0 ± 1.2 years. There was no difference between cases and controls in atrial pacing (8±15% vs 18±22% p=0.14), ventricular pacing (81±29% vs 85±24% p=0.62) or base rate (53±5bpm vs 53±5bpm p=0.80). Of the 34 RM features analysed, mean ventricular heart rate was identified as the most important predictor of PICM; area under curve with XG Boost 0.95, KNN 0.95, and random forest 0.86. Other RM features failed to add any more predictive power to the models. Mean ventricular rate was significantly higher in cases than controls (80±6 bpm vs 69±9 bpm p<0.001). Sensitivity analysis was performed to assess whether episodes of atrial fibrillation (AF) were responsible for the higher ventricular rates. After days of AF days were excluded, mean ventricular rate was still significantly higher in cases than controls (79± 6vs 69±9bpm p<0.001) (Figure 1). 10/12 patients had a subsequent CRT upgrade. No consistent pattern emerged in heart rate changes in the first 3 months after CRT upgrade. Conclusion In a group of patients with normal left ventricular function at implant, remotely monitored heart rate can predict early-onset PICM. Further work is required to understand when these heart rate differences emerge, and whether they improve with positive LV remodelling.Table 1.Figure 1.

Machine learning can predict implantable cardioverter defibrillator therapy: a development study

Abstract Introduction Remote monitoring (RM) data has been used to develop predictive algorithms that warn of decompensated heart failure before a heart failure episode. The same RM data could also be used to predict other adverse events in heart failure patients, such as ventricular arrhythmias. Machine learning (ML) models can be used to process complex multivariate time series RM data. Purpose The aim of this analysis was to generate a clinically useful model to predict defibrillator therapy (shock or anti-tachycardia pacing (ATP)). The output of the model is the likelihood of a shock in the next 24 hours. Methods RM data of all 292 implantable cardioverter defibrillators (ICDs) at our centre were collected (male 81%, 66±12 years). Electrograms of ICD therapies were manually verified. 63 time series variables were collated. Atrial lead-dependent RM parameters and ones with >30% missing data were excluded leaving 23 variables for analysis. After the exclusion of inappropriate therapies and patients with missing RM data, 218 patients were analysed. Of these, 41 (18.8%) had at least one ICD therapy. Three types of ML models were generated (1) random forest (RF), (2) extreme gradient boosted model (XGBoost), (3) one-dimensional convolutional neural network (1D-CNN) with three different intervals preceding ICD therapy: 30, 10, and 4 days. The model accuracy was measured utilising stratified grouped 5-fold cross-validation, with 20% of data used for testing in each fold. Results 4-day decision tree-based models (RF, XGBoost) demonstrated higher area under the curve (AUC) scores, compared with 10- and 30-day models. Percentage accuracy was similar across all three models and interval lengths. RF: The 4-day model had the highest AUC of 0.86 and an accuracy of 83.8%, compared to the 10-day (AUC 0.85, 83.0%) and 30-day (AUC 0.80, 82.2%) models. XGBoost: The 4-day model had an AUC of 0.85 and an accuracy of 83.4%, compared to the 10-day (AUC 0.84, 83.1%) and 30-day (AUC 0.81, 82.4%) models. 1D-CNN: The 4-day model had an AUC of 0.78 and an accuracy of 83.5%, compared to the 10-day (AUC 0.74, 83.1%) and 30-day (AUC 0.71, 82.2%) models. Episodes of prior ventricular tachycardia (VT) in the VT2 zone and prior ICD therapies contributed the most to model predictions, with their importance highest in the days immediately preceding ICD therapy (Figure 1). To better identify ‘first ICD therapy’, prior ICD therapies were excluded, and the models were re-run. AUC was lower at 0.70 with an accuracy of 72.9% in the highest-performing model (10-day XGBoost). The most important features were patient activity, RV pacing impedance, and mean ventricular heart rate (Figure 2). Conclusion We were able to predict ICD therapy with an AUC of 0.86. 4-day models were better than the 10-day and 30-day models. Model performance remained high (AUC 0.70), even after exclusion of prior ventricular arrhythmias from the predictors.1.Importance of top variables over time2.Top features without prior ICD therapy

Abstract 14394: Complete Atrioventricular Block in a Young Patient With Alport Syndrome: A Case Report

Background: Atrioventricular block (AVB) in young adults is rare, and the etiologies and mechanisms in most cases remain uncertain. Alport syndrome is a heterogeneous, hereditary disorder characterized by nephropathy, hearing loss, and ocular abnormalities. Complete AVB has never been reported in Alport syndrome patients with normal kidney function. Case report: A 20-year-old male patient was admitted to hospital with “asymptomatic bradycardia for years”. On admission, the patient’s blood pressure was normal and electrocardiogram (ECG) showed third-degree AVB with atrial rate of 63 bpm and ventricular rate of 36 bpm. He was diagnosed with Alport syndrome at the age of 10. Genetic testing at that time showed single nucleotide variants (c.2372T>C, c.2072T>G) and deletion (c.1781-1949(Exon25)) in COL4A5 gene. During the subsequent 10-year follow-up, the patient was presented with consistent hematuria and proteinuria, but his renal function has never been found impaired. He denied other medical history as well as family history of arrhythmia. Laboratory tests indicated hypoproteinemia, hyperuricemia, hyperlipidemia, and hyperhomocysteinemia. The 24-hour ambulatory ECG revealed a heart rhythm consisting of sinus rhythm with second-degree AVB (2:1 downward transmission) and complete AVB with junctional escape. The mean ventricular rate was 36 bpm (ranged 25-60 bpm). Neither echocardiography nor cardiac magnetic imaging with delayed gadolinium enhancement found any significant abnormality. We then did whole exome sequencing (WES), which did not identify specific pathogenic variant (Table1). 3mg atropine was admitted to the patient for an atropine test to rule out the possibility of vagally mediated AVB and the pacemaker implantation was then performed. Conclusion: We report a case of complete AVB with unknown etiology in a young patient with Alport syndrome.

CLOSURE OF AN AGED OSTIUM SECUNDUM ATRIAL SEPTAL DEFECT: WHICH PROCEDURE TO CHOOSE? CASE REPORT AND REVIEW OF THE LITERATURE

Ostium secundum atrial septal defect (OS ASD) is the mostfrequentlydiagnosedcardiac malformation in adulthood. The presence of an ASD iscompletely compatible with a normal life and evenpregnancy. It issometimesdiagnosedduring a work-up for a stroke or at the onset of atrial fibrillation(1). Percutaneousclosureappears to be the preferredapproach for ostium secundum ASD with a favourableanatomicalshape, but surgicalclosureshouldbeconsidered in cases of contraindication, following a detailedpreoperativeassessment (2). The latestrecommendations are strict with regard to establishing the acceptable threshold of pulmonaryarterial pressure (PAP) and pulmonaryvascularresistance (PVR) for closure of the ASD in cases of pulmonaryarterial hypertension (PAH) (3). We report the case of a 61-year-old female patient diagnosedwith an atrial septal defectcomplicated by PAH during a work-up for exertionaldyspnoea. The somaticexaminationwasunremarkable. The ECG showed atrial fibrillation (AF) with a meanventricular rate of 77bpm and complete right bundle branch block. A diagnosis of large (26mm) ostium secondum ASDwas made on transthoracicultrasound (TTU), and transoesophagalultrasound (TOU) ruled out a venous return abnormality. Right heart catheterization revealed a mixed Pulmonary hypertension (PH) withpredominant flow and PVRs of 3-5 WU, allowingpercutaneousclosure. However, the presence of non-ablatable atrial fibrillation and moderatetricuspidinsufficiencycontraindicated the procedure, whichled to surgicalclosureusing an autologouspericardial patch combinedwith a DE VEGA-type tricuspidannuloplasty, with a simple postoperative course.

C67 ATRIOVENTRICULAR BLOCK DUE TO CARDIAC CONDUCTION TISSUE INFILTRATION: A CLINICAL PRESENTATION OF TRANSTHYRETIN CARDIAC AMYLOIDOSIS

Abstract Background In cardiac amyloidosis, the deposition of insoluble amyloid fibrils can affect the cardiac conduction tissue, causing bradyarrhythmic clinical manifestations, often in the advanced stages of the disease. In this clinical case, atrioventricular block represented the clinical onset of transthyretin cardiac amyloidosis. Clinical case A 68–year–old man was admitted to our ward for recurrent syncopal episodes. He had in his medical history bilateral carpal tunnel syndrome. The electrocardiogram documented sinus rhythm with preserved QRS voltages, right bundle branch block, left anterior hemiblock, and first and second degree atrioventricular block with mean ventricular rate of 38 beats/min. A color–Doppler echocardiogram revealed increased left and right ventricular thickness (maximum thickness 16 and 10 mm, respectively), diastolic dysfunction, and preserved ejection fraction (60%). The patient underwent a coronary angiography, which was normal, and an endomyocardial biopsy of the left ventricle, which revealed the presence of hypotrophic and degenerated cardiomyocytes surrounded by large areas of amorphous substance that exhibited apple–green birefringence in polarized light after staining with Congo red, suggesting the diagnosis of cardiac amyloidosis. Sections of conduction tissue were included in the specimens, which appeared on histology as small myocytes positive by immunohistochemistry for HCN4, suggestive of conduction tissue cardiomyocytes. The conducting tissue was almost completely replaced by amyloid deposits positive by immunohistochemistry for transthyretin. The affected patient underwent a genetic test which revealed the mutation of the TTR gene (p.Thr79Lys). The patient subsequently underwent pacemaker implantation and started treatment with Tafamidis due to the absence of neurological involvement. Conclusion In patients presenting clinically with syncope and conduction abnormalities, the diagnosis of cardiac amyloidosis should always be considered, because they may represent the clinical onset of the disease.

P467 CHALLENGING MANAGEMENT OF ORAL ANTICOAGULANT THERAPY IN A OBESE PATIENT WITH DILATED CARDIOMYOPATHY, ATRIAL FIBRILLATION AND ICD LEAD THROMBUS

Abstract Obesity is a worldwide epidemic condition at high risk for AF development; nevertheless, obese patients are underrepresented in RCTs of anticoagulant agents. Robust evidence assessing efficacy of DOACs in these patients is lacking and, to date, major Associations do not recommend DOACs in patients > 120 Kg (BMI>40 Kg/m2). The use of implantable cardiac devices has substantially increased in recent years; among potential complications are sterile intracardiac clots on the leads, typically discovered as incidental echocardiographic findings. 46 ys old male patient, III degree obesity (160 Kg,BMI 51 Kg/m2), ex–smoker. In 2012, acute heart failure and diagnosis of non–ischemic dilated cardiomyopathy (EF 20%). During the follow–up by a tertiary Center, in 2021 he was implanted with single–chamber ICD in primary prevention. At presentation, HFrEF pharmacological therapy was optimal (ARNI,SLGT2i,MRA,B–blocker). He came to the ED complaining of weakness; ECG showed atrial fibrillation, mean ventricular rate 160 bpm. CHA2DS2–VASc was 1. Anticoagulation with subcutaneous enoxaparin 10000UI twice daily was started. He was admitted to the cardiology ward and remained hemodynamically stable, with persistence of AF. Transesophageal echocardiography excluded thrombus in the left atrial appendage; unexpectedly, a filamentous, floating formation of about 30mm on the atrial side of the ICD lead was observed, compatible with a thrombotic formation, since the patient, afebrile, didn’t show any suggestive sign of endocarditis nor past history of infection; blood cultures, CRP and Procalcitonin were negative. In the absence of any shunt at the level of interatrial septum, it was felt safe to proceed to electrical cardioversion, able to restore sinus rhythm with a single 250J biphasic synchronized shock. Oral anticoagulation with warfarin was started, since no DOAC was considered adequate for effective anticoagulation. The following in hospital course and post–discharge weeks were uneventful, despite unstable INR values. Follow–up is ongoing; the patient has not yet repeated imaging to check for mass resolution. Stroke prevention in severely obese patients with AF is challenging and points toward warfarin use, as the evidence of DOACs efficacy is sparse. In our case, anticoagulant choice was also motivated by concomitant presence of a lead thrombus, a scenario in which optimal management and anticoagulation regimen are not clearly established yet.

Amiodarone vs. metoprolol succinate in HFrEF complicated with persistent atrial fibrillation with rapid ventricular response: A prospective observational study.

β-blockers have been recommended for patients with heart failure (HF) and atrial fibrillation (AF), but studies have shown that β-blockers do not reduce all-cause mortality or cardiovascular mortality in patients with HF and AF. To investigate the difference in efficacy between oral amiodarone and metoprolol succinate for patients with HF with reduced ejection fraction (HFrEF) and persistent atrial fibrillation (pAF) with rapid ventricular response (RVR). Patients with HFrEF complicated with pAF with RVR treated in the People's Hospital of Chongqing Hechuan between March 2018 and March 2019 were enrolled in this prospective observational study. The primary outcomes were cardiovascular mortality and the first hospitalization for HF rate. The secondary outcomes were type B pro-brain natriuretic peptide (NT-proBNP) before/after treatment, left ventricular ejection fraction (LVEF) before/after treatment, average heart rate (AhR), and the rate of sinus rhythm after 1 year of follow-up. A total of 242 patients with HFrEF complicated with pAF with RVR were enrolled and divided into amiodarone + perindopril + spironolactone+ routine drug (amiodarone group, n = 121) and metoprolol succinate + perindopril + spironolactone +routine drug (metoprolol succinate group, n = 121) according to their treatment strategy. Cardiovascular mortality (4.9 vs. 12.4%, HR: 2.500, 95%CI: 1.002-6.237, P = 0.040) and first hospitalization for HF (52.9 vs. 67.8%, HR: 1.281, 95%CI: 1.033-1.589, P = 0.024) were significantly lower in the amiodarone group than in the metoprolol group. The mean ventricular rate in the amiodarone group was significantly lower than in the metoprolol group (64.5 ± 3.2 vs. 72.4 ± 4.2, P < 0.001). After 1 year of follow-up, the sinus rhythm rate was significantly higher in the amiodarone group than in the metoprolol group (38.8 vs. 7.4%, HR: 0.191, 95%CI: 0.098-0.374, P < 0.001). The difference in proBNP (3,914.88 vs. 2,558.07, P < 0.001) and LVEF (-6.89 vs. -0.98, P < 0.001) before and after treatment was significantly higher in the amiodarone group than in the metoprolol group. In conclusion, in this prospective observational study, the amiodarone group had lower risk of cardiovascular death and the first hospitalization for HF than metoprolol in HFrEF and persistent atrial fibrillation (pAF) with RVR. The mechanism may be related to improved cardiac function, rhythm control and ventricular rate control. ChiCTR2200057816; Registered 7 March 2022-Retrospectively registered: http://www.medresman.org.cn/pub/cn/proj/projectshshow.aspx?proj=4222.

Alleviation of AF related symptoms following acute conversion of recent-onset, symptomatic atrial fibrillation to sinus rhythm with flecainide acetate oral inhalation solution

Abstract Introduction Pharmacological restoration of sinus rhythm (SR) in patients with symptomatic atrial fibrillation (AF) is expected to be accompanied by prompt alleviation of symptoms to avoid the need for electrical cardioversion (ECV) and/or hospitalization. The feasibility and safety of acute cardioversion of recent-onset (≤48 hours) symptomatic AF to SR with flecainide acetate oral inhalation (FlecIH) solution was shown in the Phase 2, open-label INSTANT trial. We examined symptoms, heart rate, time to discharge and need for ECV reported among patients in the INSTANT trial whose AF was successfully converted to SR (“conversion group”; N=25) versus those whose AF did not convert to SR (“no conversion group”; N=29). Methods Conversion success was determined using 12-lead Holter monitoring during a 90-minute observation period. Patients in the no conversion group were offered alternative treatment per the investigator discretion. Symptoms, vital signs, time to discharge, and the need for ECV were evaluated through Day 5. Results Data from 54 patients (33.3% female) with a mean age of 62.1 years and a mean BMI of 26.8 kg/m2 were analyzed. All patients reported at least one AF-related symptoms at baseline (palpitations=85%; dizziness=35%; shortness of breath=37%; chest discomfort=39%) and 83.3% presented with AF symptoms ≤24 hours in duration. At 90 minutes, 80.0% of the conversion group were asymptomatic compared to 37.9% of the no conversion group (p&amp;lt;0.001). Mean (SD) ventricular rate at 90 minutes was 70.6 (12.5) bpm in the conversion group compared to 100.4 (29.4) bpm in the no conversion group (p&amp;lt;0.001). Median time to discharge was 2.3 (IQR: 0.75) hours for the conversion group compared to 3.6 (IQR: 1.02) hours for the no conversion group (p=0.001). By Day 5, 23 (79.3%) patients in the no conversion group had undergone ECV; no patients in the conversion group experienced AF recurrence by Day 5 (0% required ECV; p&amp;lt;0.001). Conclusions Conversion of recent onset AF to SR with inhaled flecainide was associated with a reduction in symptoms, normalization of heart rate, rapid hospital discharge and avoidance of ECV during a 5-day follow-up period. Funding Acknowledgement Type of funding sources: Private company. Main funding source(s): InCarda Therapeutics

Amiodarone versus beta-blockers for the prevention of postoperative atrial fibrillation after cardiac surgery: An updated systematic review and meta-analysis of randomised controlled trials

Background: Amiodarone and beta-blockers are widely used as prophylaxis for postoperative atrial fibrillation (AF). The current recommendations from society guidelines are inconclusive, leading to differing practices among physicians. This meta-analysis aimed to compare the efficacy of both agents in preventing postoperative AF after cardiac surgery. Methods: We explored online medical databases, such as CINAHL, CENTRAL, MEDLINE, and EMBASE for randomised controlled trials (RCTs) comparing amiodarone and beta-blocker for prevention of AF after cardiac surgery. Outcomes analysed in this study were AF number of events and duration, hospital stay, and mean ventricular rate. Heterogeneity was assessed using the I² test, and publication bias was analysed using Egger’s test. Results: In total, eight RCTs comprising 1370 patients met the inclusion criteria. Pooled analysis showed that patients in both groups had no significant difference in both AF episodes (RR 0.83, 95% CI 0.66 to 1.04, p=0.10) and AF duration (SMD 0.46, 95% CI -1.14 to 2.05, p=0.57). Furthermore, secondary outcome analysis on mean ventricular rate and mean hospital length of stay in both groups showed no significant difference (MD -4.48, 95% CI -14.36 to 5.39, p=0.37 and MD 0.29, 95% CI -0.06 to 0.63, p=0.11, respectively). Conclusions: Amiodarone and beta-blockers are equally effective in preventing postoperative atrial fibrillation after cardiac surgery, with no difference in AF episode and duration, mean ventricular rate, and hospital length of stay.

A computational analysis of atrial fibrillation effects on coronary perfusion across the different myocardial layers

Patients with atrial fibrillation (AF) may present ischemic chest pain in the absence of classical obstructive coronary disease. Among the possible causes, the direct hemodynamic effect exerted by the irregular arrhythmia has not been studied in detail. We performed a computational fluid dynamics analysis by means of a 1D-0D multiscale model of the entire human cardiovascular system, enriched by a detailed mathematical modeling of the coronary arteries and their downstream distal microcirculatory districts (subepicardial, midwall and subendocardial layers). Three mean ventricular rates were simulated (75, 100, 125 bpm) in both sinus rhythm (SR) and atrial fibrillation, and an inter-layer and inter-frequency analysis was conducted focusing on the ratio between mean beat-to-beat blood flow in AF compared to SR. Our results show that AF exerts direct hemodynamic consequences on the coronary microcirculation, causing a reduction in microvascular coronary flow particularly at higher ventricular rates; the most prominent reduction was seen in the subendocardial layers perfused by left coronary arteries (left anterior descending and left circumflex arteries).

108 Atrial fibrillation effects on coronary perfusion across the different myocardial layers: a computational analysis

Abstract Aims Atrial fibrillation (AF) patients may present ischaemic chest pain in the absence of classical obstructive coronary disease. Among the possible causes, the direct haemodynamic effect exerted by the irregular arrhythmia has not been studied in detail. Methods and results A computational fluid dynamics analysis was performed by means of a 1D-0D multiscale model of the entire human cardiovascular system, characterized by a detailed mathematical modelling of the coronary arteries and their downstream distal microcirculatory districts (subepicardial, midwall, and subendocardial layers). Three mean ventricular rates were simulated in both sinus rhythm (SR) and AF: 75, 100, 125 b.p.m. We conducted inter-layer and inter-frequency analysis of the ratio between mean beat-to-beat blood flow in AF compared to SR (Q¯AP/Q¯SR Inter-layer analysis showed that, for each simulated ventricular rate, Q¯AP/Q¯SR progressively decreased from the epicardial to the endocardial layer in the distal left coronary artery districts (P-values &amp;lt; 0.001 for both left anterior descending artery—LAD, and left circumflex artery—LCx), while this was not the case for the distal right coronary artery (RCA) district. Inter-frequency analysis showed that, focusing on each myocardial layer, Q¯AP/Q¯SR progressively worsened as the ventricular rates increased in all investigated microcirculatory districts (LAD, LCx, and RCA) (P-values &amp;lt; 0.001 for all layer-specific comparisons). Conclusions AF exerts direct haemodynamic consequences on the coronary microcirculation, causing a reduction in microvascular coronary flow particularly at higher ventricular rates; the most prominent reduction was seen in the subendocardial layers perfused by left coronary arteries (LAD and LCx).

2021 PACES Expert Consensus Statement on the Indications and Management of Cardiovascular Implantable Electronic Devices in Pediatric Patients: Executive Summary.

2021 PACES Expert Consensus Statement on the Indications and Management of Cardiovascular Implantable Electronic Devices in Pediatric Patients: Executive Summary.

B-PO05-159 CLINICAL PROFILE OF YOUNG PATIENTS WITH ATRIOVENTRICULAR CONDUCTION BLOCKS REQUIRING PERMANENT PACING

Atrioventricular (AV) conduction blocks are uncommon at a young age, most common causes being congenital or genetic. Other causes include inflammatory cardiomyopathies (IC) which can infiltrate the His-Purkinje system leading to AV blocks. The clinical profile of this group of patients has not been described previously. To describe the clinical and imaging profile of young patients with AV blocks and IC. We included young (<60 years) patients presenting with AV blocks (requiring permanent pacing) between August 2019 and December 2020. All patients underwent clinical evaluation, transthoracic echocardiography, and positron emission tomography computed tomography (PET-CT) of the chest to look for associated IC. Patients with mediastinal lymphadenopathy underwent transbronchial lymph node biopsy for histopathological confirmation of IC. Patients were categorized into clinical cardiac sarcoidosis (CS), isolated CS, or nonspecific IC based on the 2016 Japanese Circulation Society guidelines (JCS). A total of 21 patients were included in the study with a mean age of 40.4±12.4 years with a male predominance (M:F=2:1). Complete AV block was the commonest type of AV block (85.7%), with a mean ventricular escape rate of 39.7±11 bpm and a wide QRS morphology in 66% of the patients. Five of the patients (23.8%) had left ventricular systolic dysfunction. The mean left ventricular ejection fraction was 53.1±10.9%. Ten (47.6%) patients showed a combination of metabolic and perfusion defect on PET CT whereas seven (33.3%) patients had mediastinal lymphadenopathy. Four patients (19.1%) underwent transbronchial lymph node biopsy, of which only one (4.8%) had granulomatous lymphadenitis. After complete evaluation, the most common classification was nonspecific inflammatory cardiomyopathy in 13 (61.9%) patients, followed by isolated cardiac sarcoidosis in seven (33.3%) patients, and one patient (4.8%) had clinical cardiac sarcoidosis. Patients presenting with AV blocks at a young age (<60 years) should be evaluated for inflammatory cardiomyopathy, even with normal LVEF. They can be considered for appropriate anti-inflammatory medications for the underlying cardiomyopathy.

Association between electrocardiographic features and mortality in COVID-19 patients.

BackgroundCardiovascular events have been reported in the setting of coronavirus disease‐19 (COVID‐19). It has been hypothesized that systemic inflammation may aggravate arrhythmias or trigger new‐onset conduction abnormalities. However, the specific type and distribution of electrocardiographic disturbances in COVID‐19 as well as their influence on mortality remain to be fully characterized.MethodsElectrocardiograms (ECGs) were obtained from 186 COVID‐19‐positive patients at a large tertiary care hospital in Northern Nevada. The following arrhythmias were identified by cardiologists: sinus bradycardia, sinus tachycardia, atrial fibrillation (A‐Fib), atrial flutter, multifocal atrial tachycardia (MAT), premature atrial contraction (PAC), premature ventricular contraction (PVC), atrioventricular block (AVB), and right bundle branch block (RBBB). The mean PR interval, QRS duration, and corrected QT interval were documented. Fisher's exact test was used to compare the ECG features of patients who died during the hospitalization with those who survived. The influence of ECG features on mortality was assessed with multivariable logistic regression analysis.ResultsA‐Fib, atrial flutter, and ST‐segment depression were predictive of mortality. In addition, the mean ventricular rate was higher among patients who died as compared to those who survived. The use of therapeutic anticoagulation was associated with reduced odds of death; however, this association did not reach statistical significance.ConclusionThe underlying pathogenesis of COVID‐19‐associated arrhythmias remains to be established, but we postulate that systemic inflammation and/or hypoxia may induce potentially lethal conduction abnormalities in affected individuals. Longitudinal studies are warranted to evaluate the risk factors, pathogenesis, and management of COVID‐19‐associated cardiac arrhythmias.

Routine Measurement of Thyroid Stimulating Hormone in Patients Presenting With Third-Degree Atrioventricular Block: Do We Really Need It?

BackgroundHypothyroidism can be a cause of sinus bradycardia. However, thyroid laboratory evaluation is often performed routinely in patients with complete heart block (CHB) though there is little data to support this practice. This study aimed to assess the frequency of thyroid dysfunction in patients presenting with CHB without clinical features of hypothyroidism.MethodologyAll patients referred for permanent pacemaker implantation for CHB were included in this cross-sectional study. Patients with known thyroid disorder or clinical features of thyroid disorder were excluded. Demographic, electrocardiography (EKG), and routine thyroid stimulating hormone (TSH) screening results were recorded.ResultsA total of 102 patients with complete atrioventricular (AV) block were enrolled in the study of which 50.0% (51) were male. The mean age was 61.09 ± 11.74. Co-morbidities included diabetes mellitus 44.1% (45), smoking 36.3% (37), and hypertension 55.9% (57). Mean EKG atrial rate was 82.97 ± 31.31 mmHg with a mean ventricular escape rate of 36.17 ± 5.93. Permanent pacemakers were implanted in all of the patients. Only one patient had an abnormal TSH.ConclusionsWe found a very low prevalence of thyroid dysfunction among patients without clinical features of thyroid dysfunction presenting with third-degree AV block. This calls for cautious prescription of thyroid testing in clinically euthyroid patients.

Abstract 13908: Prevalence and Implications of Junctional Rhythm During Transcatheter Aortic Valve Replacement

Introduction: Cardiac conduction abnormalities are among the most frequent complications of transcatheter aortic valve replacement (TAVR). A small case series has raised the possibility that junctional rhythm (JR) following TAVR may be associated with poor outcomes. However, the prevalence and implications of JR during TAVR have not been systematically studied. Methods: We retrospectively reviewed intra-procedural continuous 6-lead telemetry of 300 consecutive patients undergoing TAVR between April 2015 and April 2019 to identify JR that occurred after deploying the valve . Forty-two patients with pre-existing permanent pacemaker (PPM) were excluded. JR was defined as regular rhythm without P waves but with QRS morphology that was identical to baseline. Results: A total of 258 patients fulfilled the inclusion criteria (mean age of 77.5±8.5 years and 99% men). During TAVR, 79 (30.6%) patients developed new JR. The mean ventricular rate was 74.6±31.0 bpm. Patients who developed JR had similar baseline characteristics compared to those without JR (Table). After TAVR, 57 (22.1%) patients required PPM for complete atrioventricular block. There was a trend for a higher rate of PPM implantation in patients with rapid JR (39%) vs. slow JR (26%) vs. no JR (19.0%, p=0.10). In logistic regression analysis, patients who had a rapid JR (rate &gt;100 bpm) were 2.71 times (95% CI 0.98-7.52, p=0.055) more likely to require PPM than those without JR. Conclusions: Junctional rhythm after deploying the valve is common in TAVR. There was a trend for higher PPM implantation risk among patients who developed rapid JR. Further investigation of these observations in larger cohorts is needed.

Subcutaneous nerve stimulation for rate control in ambulatory dogs with persistent atrial fibrillation

Subcutaneous nerve stimulation (ScNS) damages the stellate ganglion and improves rhythm control of atrial fibrillation (AF) in ambulatory dogs. The purpose of this study was to test the hypothesis that thoracic ScNS can improve rate control in persistent AF. We created persistent AF in 13 dogs and randomly assigned them to ScNS (n = 6) and sham control (n = 7) groups. 18F-2-Fluoro-2-deoxyglucose positron emission tomography/magnetic resonance imaging of the brain stem was performed at baseline and at the end of the study. The average stellate ganglion nerve activity reduced from 4.00 ± 1.68 μV after the induction of persistent AF to 1.72 ± 0.42 μV (P = .032) after ScNS. In contrast, the average stellate ganglion nerve activity increased from 3.01 ± 1.26 μV during AF to 5.52 ± 2.69 μV after sham stimulation (P = .023). The mean ventricular rate during persistent AF reduced from 149 ± 36 to 84 ± 16 beats/min (P = .011) in the ScNS group, but no changes were observed in the sham control group. The left ventricular ejection fraction remained unchanged in the ScNS group but reduced significantly in the sham control group. Immunostaining showed damaged ganglion cells in bilateral stellate ganglia and increased brain stem glial cell reaction in the ScNS group but not in the control group. The 18F-2-fluoro-2-deoxyglucose uptake in the pons and medulla was significantly (P = .011) higher in the ScNS group than the sham control group at the end of the study. Thoracic ScNS causes neural remodeling in the brain stem and stellate ganglia, controls the ventricular rate, and preserves the left ventricular ejection fraction in ambulatory dogs with persistent AF.

Myocardial strain assessment using velocity vector imaging in normally grown fetuses at term.

To assess prospectively fetal myocardial deformation at term in normally grown fetuses using the velocity vector imaging (VVI) two-dimensional speckle-tracking technique, and to explore myocardial deformation changes over the last 4 weeks of pregnancy. This was a prospective, observational cohort study of 276 women with an uncomplicated singleton pregnancy who underwent fortnightly ultrasound from 36 weeks' gestation until delivery at the Mater Mother's Hospital, Brisbane, Australia. Fetal myocardial deformation (assessed by global and segmental longitudinal systolic myocardial strain and strain rate of both right and left ventricles) was measured using VVI software. Mean global longitudinal left and right ventricular strain and strain rate values decreased between each time point. At 36, 38 and 40 weeks' gestation, left ventricular global strain (%) and strain rate (/s) decreased, respectively, as follows: -14.6 ± 3.8% and -1.2 ± 0.3/s at 36 weeks; -13.6 ± 3.3% and -1.1 ± 0.3/s at 38 weeks; and -12.3 ± 3.1% and -1.0 ± 0.3/s at 40 weeks. At 36, 38 and 40 weeks, mean right ventricular global strain (%) and mean strain rate (/s) decreased, respectively, as follows: -14.2 ± 3.4% and -1.2 ± 0.2/s at 36 weeks; -13.4 ± 3.0% and -1.1 ± 0.2/s at 38 weeks; and -12.8 ± 2.8% and -1.1 ± 0.2/s at 40 weeks. Global ventricular strain values diminish with advancing gestational age. Myocardial deformation imaging is feasible in late gestation and may be useful as an adjunct for the assessment of fetal cardiac function close to birth. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Predictors of Elevated Defibrillation Threshold with the Subcutaneous Implantable Cardioverter-defibrillator.

There are limited data regarding defibrillation thresholds (DFTs) for the subcutaneous implantable cardioverter-defibrillator (S-ICD), and factors associated with elevated DFTs remain incompletely understood. The objective of this study was to determine the factors associated with elevated DFTs in patients undergoing S-ICD implantation. A retrospective cross-sectional analysis of all patients undergoing S-ICD implantation at our institution between 2013 and 2016 who underwent step-down DFT testing was performed. Factors associated with a higher DFT were analyzed. In total, 56 patients (mean age: 49.3 ± 13.1 years, mean left ventricular ejection rate: 31.1% ± 13.7%) underwent S-ICD implantation in the study period. Full DFT testing was performed in 31 of the 56 patients (55%), with an average DFT of 46.4 joules (J) ± 25.9 J found among this cohort. The DFT was > 65 J in five of the 31 patients (16%). A high DFT was associated with increased body mass index (BMI) (37.7 kg/m2 versus 29.4 kg/m2; p = 0.02) and either increased septal or posterior wall thickness (1.5 cm versus 1.0 cm; p = 0.0003 and 1.4 cm versus 1.1 cm; p= 0.003, respectively). Patients with high DFTs also had higher failed shock impedance values (138 Ω versus 71 Ω; p = 0.005). Renal failure did not appear to affect DFT (51.4 J versus 51.7 J; p = 0.99). BMI, body surface area (BSA), and septal and posterior left ventricular wall thickness predicted elevated DFT on univariate analysis, although findings were not significant with multivariate analysis due to the small sample size. Thus, elevated S-ICD DFT appears to be associated with increased BMI, BSA, and septal or posterior wall thickness. In contrast, dialysis-dependent renal failure is not associated with elevated DFT. Further investigation is necessary in order to better characterize and predict which patients are at-risk for high DFTs.

Ivabradine reduced ventricular rate in patients with non-paroxysmal atrial fibrillation

BackgroundIt has been shown that If channels can be found in AV node, apart from the sinus node. Previous animal studies showed that If inhibitor resulted in the rate-dependent reduction in AV node conduction during atrial fibrillation (AF). Therefore, we aimed to examine the effect of ivabradine on ventricular rate in patients with non-paroxysmal AF. MethodThis study was a prospective randomized, double blind, placebo-controlled study. Ivabradine, 5mg twice a day (n=21), or placebo (n=11) was administered for 1month to adult patients with non-paroxysmal AF, in addition to standard therapy. The primary end point was the change in mean ventricular rate between baseline and 1month, as assessed by 24-hour Holter. ResultsThe baseline characteristics did not differ between ivabradine and placebo groups (mean age was 59.7±13.3years, male 62.5%). Mean 24-hour ventricular rate at baseline was comparable between 2 groups. We found that ivabradine significantly decreased mean ventricular rate from 86.0±10.9beats/min to 79.2±9.6beats/min (p<0.001). In contrast, no significant change in ventricular rate was observed in placebo group (84.3±11.2 vs. 82.9±9.9beats/min, p=0.469). The effect of ivabradine on rate reduction was significantly greater than placebo (6.9±6.3 vs. 1.4±6.0beats/min, p=0.024). No drug-related adverse effects were observed in both groups. ConclusionWe demonstrated that ivabradine significantly decreased ventricular rate during AF compared to placebo. Therefore, ivabradine can be a potential treatment to improve ventricular control in patients with non-paroxysmal AF. Due to the small sample size, larger studies are needed to confirm this effect of ivabradine.