Inducible Ventricular Arrhythmias Research Articles

ATRIAL STRETCH-DEPENDENT TUMOR NECROSIS FACTOR-MEDIATED ADVERSE ATRIAL REMODELING AND ATRIAL ARRHYTHMIA INDUCIBILITY IN A MOUSE MODEL OF AORTIC REGURGITATION

<h3>BACKGROUND</h3> Atrial fibrillation (AF) is the most common sustained supraventricular arrhythmia worldwide, with its incidence linked to cardiovascular (CV) disease and, paradoxically, endurance exercise. Most conditions linked to AF are associated with elevated atrial pressures and stretch, which are powerful stimuli for atrial hypertrophy, fibrosis, and inflammation. We previously established adverse atrial changes and arrhythmogenesis required the pro-inflammatory and mechanosensitive cytokine tumor necrosis factor (TNF) in intense swim exercised mice. Thus, we hypothesize that stretch-mediated TNF-dependent signaling may provide a unifying mechanism linking AF in exercise and disease. <h3>METHODS AND RESULTS</h3> We developed a clinically-relevant mouse model of aortic regurgitation (AR), which is characterized by diastolic volume overload and elevated left ventricular end-diastolic (LVEDPs) and atrial pressures, to study atrial stretch-dependent TNF-mediated AF pathogenesis. AR was induced by retrograde puncture of the aortic valve in 8-week-old CD1 wild-type and whole-body TNF knockout (TNF-/-) mice. Four weeks after regurgitation, AR resulted in volume overload-mediated progressive LV dilatation, functional impairment, hypertrophy, and elevated LVEDPs in the absence of ventricular arrhythmia inducibility in both groups. In wild-type mice, AR resulted in adverse atrial remodeling, characterized by atrial hypertrophy and fibrosis, decreased conduction velocity, reduced atrial effective refractory period and action potential duration, and increased in vivo and ex vivo AF susceptibility. By contrast, TNF-/- prevented AR-induced adverse atrial remodeling and arrhythmia inducibility, independent of ventricular changes. <h3>CONCLUSION</h3> Our results establish that adverse atrial remodeling and AF vulnerability with AR requires TNF, providing a mechanistic link between elevated atrial pressures, adverse remodeling, and AF susceptibility with CV disease and exercise.

DST-Tiso Interval, a Novel Electrocardiographic Marker of Ventricular Arrhythmia Inducibility in Individuals With Ajmaline-Induced Brugada Type I Pattern

The aim of this study was to investigate the reliability of a novel electrocardiographic (ECG) marker in predicting ventricular arrhythmia (VA) inducibility in individuals with drug-induced Brugada syndrome (BrS) type I pattern. Consecutive patients with drug-induced type I BrS pattern underwent programmed ventricular stimulation (PVS) and, according to their response, were divided into 2 groups. Clinical characteristics and 12-lead ECG intervals before and after ajmaline infusion were compared between the 2 groups. A novel ECG marker named dST-Tiso interval consisting in the interval between the onset of the coved ST-segment elevation and its termination at the isoelectric line was also evaluated. Our cohort included 76 individuals (median age 44 years, 75% male). Twenty-five (32.9%) had VA inducibility requiring defibrillation. As compared with not inducible subjects, those with VA inducibility were more frequently male (92% vs 65%, p=0.013), had longer PQ interval (basal: 172 vs 152 ms, p=0.033; after ajmaline: 216 vs 200 ms, p=0.040), higher J peak (0.6 vs 0.5 mV, p=0.006) and longer dST-Tiso (360 vs 240 ms, p < 0.001). The dST-Tiso showed a C-statistics of 0.90 (95% confidence interval: 0.82 to 0.99) and an adjusted odds ratio for VA of 1.03 (1.01 to 1.04, p < 0.001). A dST-Tiso interval >300 ms yielded a sensitivity of 92.0%, a specificity of 90.2%, positive and negative predictive values of 82.1% and 95.8%. In conclusion, the dST-Tiso interval is a powerful predictor of VA inducibility in drug-induced BrS type I pattern. External validation is needed, but this marker might be useful in the clinical counseling process of these individuals before invasive PVS.

Extracellular vesicles from immortalized cardiosphere-derived cells attenuate arrhythmogenic cardiomyopathy in desmoglein-2 mutant mice.

Arrhythmogenic cardiomyopathy (ACM) is characterized by progressive loss of cardiomyocytes, and fibrofatty tissue replacement. Extracellular vesicles (EVs) secreted by cardiosphere-derived cells, immortalized, and engineered to express high levels of β-catenin, exert anti-inflammatory, and anti-fibrotic effects. The aim of the current study was to assess efficacy of EVs in an ACM murine model. Four-week-old homozygous knock-in mutant desmoglein-2 (Dsg2mt/mt) were randomized to receive weekly EVs or vehicle for 4 weeks. After 4 weeks, DSG2mt/mt mice receiving EVs showed improved biventricular function (left, P < 0.0001; right, P = 0.0037) and less left ventricular dilation (P < 0.0179). Electrocardiography revealed abbreviated QRS duration (P = 0.0003) and QTc interval (P = 0.0006) in EV-treated DSG2mt/mt mice. Further electrophysiology testing in the EV group showed decreased burden (P = 0.0042) and inducibility of ventricular arrhythmias (P = 0.0037). Optical mapping demonstrated accelerated repolarization (P = 0.0290) and faster conduction (P = 0.0274) in Dsg2mt/mt mice receiving EVs. DSG2mt/mt hearts exhibited reduced fibrosis, less cell death, and preserved connexin 43 expression after EV treatment. Hearts of Dsg2mt/mt mice expressed markedly increased levels of inflammatory cytokines that were, in part, attenuated by EV therapy. The pan-inflammatory transcription factor nuclear factor-κB (NF-κB), the inflammasome sensor NLRP3, and the macrophage marker CD68 were all reduced in EV-treated animals. Blocking EV hsa-miR-4488 in vitro and in vivo reactivates NF-κB and blunts the beneficial effects of EVs. Extracellular vesicle treatment improved cardiac function, reduced cardiac inflammation, and suppressed arrhythmogenesis in ACM. Further studies are needed prior to translating the present findings to human forms of this heterogenous disease.

Long-term outcome of ventricular tachycardia ablation in patients who did not undergo programmed electrical stimulation after ablation.

Ventricular arrhythmia inducibility is one of the ideal endpoints of ventricular tachycardia (VT) ablation. However, it may be challenging to implement programmed electrical stimulation (PES) at the end of the procedure under several circumstances. The long-term outcome of patients who did not undergo PES after VT ablation remains largely unknown. To investigate the details and long-term outcome of VT ablation in patients who did not undergo PES at the end of the ablation procedure. Among 183 VT ablation procedures in patients with structural heart disease who underwent VT ablation using an irrigated catheter, we enrolled those who did not undergo PES after VT ablation. VT ablation strategy involved targeting clinical VT plus pacemap-guided substrate ablation if inducible. When VT was not inducible, substrate-based ablation was performed. The primary endpoint was VT recurrence. In 58 procedures, post-ablation VT inducibility was not assessed. The causes were non-inducibility of sustained VT before ablation (27/58, 46.6%), long procedure time (27.6%, mean 392min), complications (10.3%), intolerant hemodynamic state (10.3%), and inaccessible or unsafe target (6.9%). With regard to the primary endpoint, 23 recurrences (39.7%) were observed during a mean follow-up period of 2.5years. Patients with non-inducibility before ablation showed less VT recurrences (4/27, 14.8%) during follow-up than patients with other causes of untested PES after ablation (19/31, 61.2%) (Log-rank < 0.001). VT recurrence was not observed in approximately 60% of the patients who did not undergo PES at the end of the ablation procedure. PES after VT ablation may be not needed among patients with pre-ablation non-inducibility.

B-PO02-215 MONOMORPHIC PREMATURE VENTRICULAR CONTRACTION TRIGGERING VENTRICULAR FIBRILLATION IN SICKLE CELL CARDIOMYOPATHY

The life expectancy of those with sickle cell (SC) continues to rise with treatment but so do the chronic complications including arrhythmias. Report a case of monomorphic PVCs triggering incessant VF in sickle cell cardiomyopathy. N/A A 49-year-old male with SC presented with acute back pain. Hemoglobin (Hb) was 7.2gm/dL and potassium was 6.9mmol/L. ECG revealed sinus rhythm, peaked T waves, and QTc of 460 msec. T waves normalized after hyperkalemia correction. On the 6th day, Hb trickled to 4.7gm/dL. He had frequent monomorphic PVCs triggering/terminating SVT (figure A and B). The following day, he developed abrupt VF triggered by a PVC (figure C) requiring cardiac compression. Echocardiography showed LVEF 35-40% and dilated LA. The patient was commenced on metoprolol tartrate but continued to have monomorphic PVCs and SVT. On the 13th day, the patient underwent EPS, which showed similar PVCs frequently trigger/terminate SVT mediated by a right posterior concealed accessory pathway, which was successfully ablated. No further SVT was induced and the PVC burden decreased with no inducible ventricular arrhythmia. Due to low Hb, LV access for PVC ablation was not pursued. He was implanted an ICD and discharged. Three months later, the ICD interrogation showed 6% PVC burden and no sustained arrhythmia. A week later, the patient collapsed at home and was brought to the ED where he was declared dead. The ICD interrogation showed incessant episodes of VF and the device exhausted all 6 shocks (figure D). Monomorphic PVCs may trigger VF in sickle cell patients that may become incessant and lead to sudden cardiac death despite having a defibrillator.

Mechanism of angiotensin receptor-neprilysin inhibitor in suppression of ventricular arrhythmia

BackgroundThe mechanisms underlying angiotensin receptor-neprilysin inhibitor (ARNi) suppression of ventricular arrhythmia (VA) are unclear. This study aimed to investigate the mechanism of ARNi-related suppression of VA in a heart failure (HF) model. MethodsNew Zealand white rabbits (n = 6 per group) were assigned to normal, HF [4 weeks of left ascending artery (LAD) ligation], angiotensin receptor blocker (ARB, valsartan at 27 mg/kg/day for 3 weeks after 1 week of LAD ligation), and ARNi (sacubitril at 34 mg/kg/day and valsartan at 27 mg/kg/day for 3 weeks after 1 week of LAD ligation) groups. Experiments involving echocardiogram, optical mapping, histological of trichrome stain and immunostain, and flow cytometry were performed. ResultsHF group had larger left ventricular (LV) internal dimensions in diastole and systole, and lower LV ejection fraction and fractional shortening than normal, ARB, and ARNi groups. HF group had a prolonged action potential duration (APD) and decreased conduction velocity (CV), which was mitigated in ARB and ARNi groups. HF group had a prolonged QRS duration, QT and QTc intervals, which was reversed in ARB and ARNi groups. HF group had a steeper maximum slope of APD restitutions, which was attenuated in normal, ARB, and ARNi groups. HF group had increased number of phase singularities (PSs) and VA inducibility than normal, ARB, and ARNi groups. A higher content of fibrosis was found in HF group than that in normal, ARB, and ARNi groups. Compared to ARB group, ARNi had a lower context of fibrosis. HF group had more peripheral blood CD4+ and CD8+ cells count than normal, ARB, and ARNi group. ConclusionsIn a rabbit model of ischemic HF, ventricular arrhythmogenesis could be suppressed by ARNi treatment. This appears to be mediated by reversing changes in the APD, CV, maximum slope of the APDR, PSs, fibrosis, and inflammation.

Sudden cardiac death risk stratification in patients with a preserved or mildly reduced ejection fraction: role of cardiac magnetic resonance and electrophysiological study

Abstract Funding Acknowledgements Type of funding sources: None. BACKGROUND Patients presenting with syncope of suspected arrhythmogenic origin or symptomatic documented non sustained ventricular tachycardia (NSVT) may represent a population with higher risk for sudden cardiac death (SCD). However today there are still no defined criteria to stratify the risk of SCD in this population. PURPOSE To assess the prognostic value of magnetic resonance (MRI) and electrophysiological study (EPS) in the risk stratification for SCD of patients with a preserved or mildly-reduced ejection fraction (EF) that may benefit from implantable cardiac defibrillator (ICD) therapy. METHODS We selected ischemic and non-ischemic patients with a preserved or mildly-reduced ejection fraction who came to our attention either after a probably arrhythmogenic syncopal event or a documented NSVT between 12/2018 and 09/2020. Patients with other ICD indications following current guideline-criteria were excluded (id est Brugada syndrome, Long QT and hypertrophic cardiomyopathy). All patients underwent an echocardiography, a coronary angiography, and an MRI with gadolinium, those among them with a positive LGE also underwent an induction EPS. Non inducible patients were followed-up clinically or with an implantable event-recorder, while inducible patients received an ICD. RESULTS In our observational study seventeen patients with preserved or only mildly-reduced EF were enrolled (13 males and 5 females; mean age 68 years). Among these patients, nine were identified with an underlying myocardial scar with positive Late-Gadolinium-Enhancement (LGE) in MRI. Based on the clinical orientation and the MRI LGE pattern patients were divided in ischemic group (5 patients) and non-ischemic group (4 patients). All 9 patients underwent an induction EPS. Three of them, 2 with non-ischemic and 1 with an ischemic pattern, demonstrated a reproducible inducibility of a sustained ventricular tachycardia or ventricular fibrillation and were implanted with an ICD. During our follow-up two of the three patients had an adequate shock within a year from the ICD implantation. Among the 6 patients with negative induction EPS there were no clinical events in the follow up, except one death for unknown causes. CONCLUSION Our preliminary results demonstrated that in patients with ischemic or non ischemic cardiopathy with preserved or mildly reduced EF, a positive MRI LGE pattern and the inducibility of ventricular arrhythmias during induction EPS identify a population at higher risk for clinical recurrence of ventricular arryhthmic events. Further investigation is needed to validate this combined diagnostic strategy as new SCD prevention tool.

Renal denervation prevents myocardial structural remodeling and arrhythmogenicity in a chronic kidney disease rabbit model.

The electrophysiological (EP) effects and safety of renal artery denervation (RDN) in chronic kidney disease (CKD) are unclear. The purpose of this study was to investigate the arrhythmogenicity of RDN in a rabbit model of CKD. Eighteen New Zealand white rabbits were randomized to control (n = 6), CKD (n = 6), and CKD-RDN (n = 6) groups. A 5/6 nephrectomy was selected for the CKD model. RDN was applied in the CKD-RDN group. All rabbits underwent cardiac EP studies for evaluation. Immunohistochemistry, myocardial fibrosis, and renal catecholamine levels were evaluated. The CKD group (34.8% ± 9.2%) had a significantly higher ventricular arrhythmia (VA) inducibility than the control (8.6% ± 3.8%; P <.01) and CKD-RDN (19.5% ± 6.3%; P = .01) groups. In the CKD-RDN group, ventricular fibrosis was significantly decreased compared to the CKD group (7.4% ± 2.0 % vs 10.4% ± 3.7%; P=.02). Sympathetic innervation in the CKD group was significantly increased compared to the control and CKD-RDN groups [left ventricle: 4.1 ± 1.8 vs 0.8 ± 0.5 (102 μm2/mm2), P <.01; 4.1 ± 1.8 vs 0.9± 0.6 (102 μm2/mm2), P <.01; right ventricle: 3.6 ± 1.0 vs 1.0 ± 0.4 (102 μm2/mm2), P <.01; 3.6 ± 1.0 vs 1.0± 0.5 (102 μm2/mm2), P <.01]. Neuromodulation by RDN demonstrated protective effects with less structural and electrical remodeling, leading to attenuated VAs. In a rabbit model of CKD, RDN plays a therapeutic role by lowering the risk of VA caused by autonomic dysfunction.

Hydrogen peroxide accelerates ventricular arrhythmogenesis by inactivating N‐type calcium channels in cardiac vagal postganglionic neurons in type 2 diabetic rats

Withdrawal of cardiac vagal activity is a common complication in patients with type 2 diabetes mellitus (T2DM), and is associated with arrhythmia-related sudden cardiac death and high mortality in T2DM patients. Although our recent study has demonstrated that reduction of N-type calcium (Cav2.2) currents and cell excitability of cardiac vagal postganglionic (CVP) neurons exacerbates myocardial infarction-evoked ventricular arrhythmias and mortality in T2DM rats, the mechanisms responsible for T2DM-reduced Cav2.2 channel activity in CVP neurons remain unclear. Since reactive oxygen species (ROS) has been reported to modulate calcium channel activity in peripheral postganglionic neurons, here we tested if hydrogen peroxide (H2O2, a type of ROS) overproduction inactivates Cav2.2 channels and further contributes to ventricular vagal dysfunction and ventricular arrhythmogenesis in T2DM. Rat T2DM was induced by a high-fat diet plus streptozotocin injection. Adenoviral catalase gene (Ad.CAT, 2 µl, 1 x 1010 pfu/ml) was microinjected into CVP neurons to scavenge local H2O2 production. Reduced catalase expression accompanied by overproduction of H2O2 was detected in the CVP neurons in T2DM rats. In vivo transfection of Ad.CAT not only increased protein expression of catalase but also attenuated H2O2 production in CVP neurons in T2DM rats. Data from reverse-phase protein array also demonstrated that overexpression of catalase by transfection of Ad.CAT into CVP neurons markedly increased T2DM-reduced protein expression of Cav2.2 in CVP neurons. Local microinjection of Ad.CAT into CVP neurons also significantly restored T2DM-blunted ventricular vagal activity, as demonstrated by an improvement in the response of left ventricular systolic pressure to left vagal efferent nerve stimulation. Additionally, in the power spectral analysis of heart rate variability (HRV), transfection of Ad.CAT into CVP neurons increased the T2DM-attenuated high frequency power (an index of vagal activity), leading to further restoration of the low frequency to high frequency ratio. Moreover, the inducibility of ventricular arrhythmia measured in anesthetized condition was significantly reduced in T2DM rats transfected with Ad.CAT, compared with T2DM rats (0.75±0.48 in T2DM+Ad.CAT group vs. 3.0±1.38 in T2DM group). Transfection of Ad. vector into CVP neurons had no effects on protein expression of catalase and Cav2.2, ventricular vagal activity, HRV, as well as susceptibility to ventricular arrhythmias in T2DM. Based on above data, we conclude that H2O2 overproduction inactivates Cav2.2 channels and further contributes to ventricular vagal dysfunction and ventricular arrhythmogenesis in T2DM, suggesting that H2O2 signaling pathway might be an effective therapeutic target to suppress ventricular arrhythmias in patients with T2DM.

Atrial Stretch‐Dependent Tumor Necrosis Factor (TNF)‐Mediated Adverse Atrial Remodeling and Atrial Arrhythmia Inducibility in a Mouse Model of Aortic Regurgitation

Atrial fibrillation (AF) is the most common sustained supraventricular arrhythmia worldwide, with its incidence linked to cardiovascular (CV) disease and, paradoxically, endurance exercise. Most conditions linked to AF are associated with elevated atrial pressures and stretch, which are powerful stimuli for atrial hypertrophy, fibrosis, and inflammation. We previously established adverse atrial changes and arrhythmogenesis required the pro-inflammatory and mechanosensitive cytokine tumor necrosis factor (TNF) in intense swim exercised mice. Thus, we hypothesize that stretch-mediated TNF-dependent signaling may provide a unifying mechanism linking AF in exercise and disease. We developed a clinically-relevant mouse model of aortic regurgitation (AR), which is characterized by chronic diastolic volume overload and elevated left ventricular end-diastolic (LVEDPs) and atrial pressures, to study atrial stretch-dependent TNF-mediated AF pathogenesis. AR was induced by retrograde puncture of the aortic valve in 8-week-old CD1 wild-type and whole-body TNF knockout (TNF-/-) mice and cardiac and electrophysiological changes were assessed using echocardiography, invasive hemodynamics, histology, in vivo intracardiacs, and ex vivo optical mapping in isolated atria. Four weeks after regurgitation, AR resulted in volume overload-mediated progressive LV dilatation, functional impairment, hypertrophy, and elevated LVEDPs in the absence of ventricular arrhythmia inducibility in both groups. In wild-type mice, AR resulted in adverse atrial remodeling, characterized by atrial hypertrophy and fibrosis, decreased conduction velocity, reduced atrial effective refractory period and action potential duration, and increased in vivo and ex vivo AF susceptibility. By contrast, TNF-/- prevented AR-induced adverse atrial remodeling and arrhythmia inducibility, independent of ventricular changes. Our results establish that adverse atrial remodeling and AF vulnerability with AR requires TNF, providing a mechanistic link between elevated atrial pressures, adverse atrial remodeling, and AF susceptibility with CV disease and exercise.

Deterministic and Stochastic Cellular Mechanisms Contributing to Carbon Monoxide Induced Ventricular Arrhythmias.

Chronic exposure to low levels of Carbon Monoxide is associated with an increased risk of cardiac arrhythmia. Microelectrode recordings from rat and guinea pig single isolated ventricular myocytes exposed to CO releasing molecule CORM-2 and excited at 0.2/s show repolarisation changes that develop over hundreds of seconds: action potential prolongation by delayed repolarisation, EADs, multiple EADs and oscillations around the plateau, leading to irreversible repolarisation failure. The measured direct effects of CO on currents in these cells, and ion channels expressed in mammalian systems showed an increase in prolonged late Na+, and a decrease in the maximal T- and L-type Ca++. peak and late Na+, ultra-rapid delayed, delayed rectifier, and the inward rectifier K+ currents. Incorporation of these CO induced changes in maximal currents in ventricular cell models; (Gattoni et al., J. Physiol., 2016, 594, 4193–4224) (rat) and (Luo and Rudy, Circ. Res., 1994, 74, 1071–1096) (guinea-pig) and human endo-, mid-myo- and epi-cardial (O’Hara et al., PLoS Comput. Biol., 2011, 7, e1002061) models, by changes in maximal ionic conductance reproduces these repolarisation abnormalities. Simulations of cell populations with Gaussian distributions of maximal conductance parameters predict a CO induced increase in APD and its variability. Incorporation of these predicted CO induced conductance changes in human ventricular cell electrophysiology into ventricular tissue and wall models give changes in indices for the probability of the initiation of re-entrant arrhythmia.

Kv1.1 potassium channel subunit deficiency alters ventricular arrhythmia susceptibility, contractility, and repolarization.

Epilepsy‐associated Kv1.1 voltage‐gated potassium channel subunits encoded by the Kcna1 gene have traditionally been considered absent in heart, but recent studies reveal they are expressed in cardiomyocytes where they could regulate intrinsic cardiac electrophysiology. Although Kv1.1 now has a demonstrated functional role in atria, its role in the ventricles has never been investigated. In this work, electrophysiological, histological, and gene expression approaches were used to explore the consequences of Kv1.1 deficiency in the ventricles of Kcna1 knockout (KO) mice at the organ, cellular, and molecular levels to determine whether the absence of Kv1.1 leads to ventricular dysfunction that increases the risk of premature or sudden death. When subjected to intracardiac pacing, KO mice showed normal baseline susceptibility to inducible ventricular arrhythmias (VA) but resistance to VA under conditions of sympathetic challenge with isoproterenol. Echocardiography revealed cardiac contractile dysfunction manifesting as decreased ejection fraction and fractional shortening. In whole‐cell patch‐clamp recordings, KO ventricular cardiomyocytes exhibited action potential prolongation indicative of impaired repolarization. Imaging, histological, and transcript analyses showed no evidence of structural or channel gene expression remodeling, suggesting that the observed deficits are likely electrogenic due to Kv1.1 deficiency. Immunoblots of patient heart samples detected the presence of Kv1.1 at relatively high levels, implying that Kv1.1 contributes to human cardiac electrophysiology. Taken together, this work describes an important functional role for Kv1.1 in ventricles where its absence causes repolarization and contractility deficits but reduced susceptibility to arrhythmia under conditions of sympathetic drive.

In vitro and in vivo cardiac toxicity of flavored electronic nicotine delivery systems.

The usage of flavored electronic nicotine delivery systems (ENDS) is popular, specifically in the teen and young adult age-groups. The possible cardiac toxicity of the flavoring aspect of ENDS is largely unknown. Vaping, a form of electronic nicotine delivery, uses "e-liquid" to generate "e-vapor," an aerosolized mixture of nicotine and/or flavors. We report our investigation into the cardiotoxic effects of flavored e-liquids. E-vapors containing flavoring aldehydes such as vanillin and cinnamaldehyde, as indicated by mass spectrometry, were more toxic in HL-1 cardiomyocytes than fruit-flavored e-vapor. Exposure of human induced pluripotent stem cell-derived cardiomyocytes to cinnamaldehyde or vanillin-flavored e-vapor affected the beating frequency and prolonged the field potential duration of these cells more than fruit-flavored e-vapor. In addition, vanillin aldehyde-flavored e-vapor reduced the human ether-à-go-go-related gene (hERG)-encoded potassium current in transfected human embryonic kidney cells. In mice, inhalation exposure to vanillin aldehyde-flavored e-vapor for 10 wk caused increased sympathetic predominance in heart rate variability measurements. In vivo inducible ventricular tachycardia was significantly longer, and in optical mapping, the magnitude of ventricular action potential duration alternans was significantly larger in the vanillin aldehyde-flavored e-vapor-exposed mice than in controls. We conclude that the widely popular flavored ENDS are not harm free, and they have a potential for cardiac harm. More studies are needed to further assess their cardiac safety profile and long-term health effects.NEW & NOTEWORTHY The use of electronic nicotine delivery systems (ENDS) is not harm free. It is not known whether ENDS negatively affect cardiac electrophysiological function. Our study in cell lines and in mice shows that ENDS can compromise cardiac electrophysiology, leading to action potential instability and inducible ventricular arrhythmias. Further investigations are necessary to assess the long-term cardiac safety profile of ENDS products in humans and to better understand how individual components of ENDS affect cardiac toxicity.

Abstract 12947: Development of Molecular Targeted Therapy Against Right Ventricular Failure: Involvement in A Network of Immunocompetent Cells

Backgrounds: Right ventricular (RV) failure plays a critical role in right heart failure and left heart failure. However, there is no specific therapy developed for RV failure. To elucidate a novel therapeutic target against RV failure, we focus on differentially expressed genes in RV to develop novel therapeutics for RV failure. Methods: Microarray analysis using several parts of adult murine heart was conducted and differentially expressed genes (DEGs) were applied to pathway analysis by Ingenuity Pathway Analysis R . Molecular mechanism was examined by using neonatal rat ventricular cardiomyocyte (NRVM) in vitro . To understand the function of target molecule in vivo , we induced RV failure by pulmonary artery constriction (PAC) in mice and inhibition experiments were performed using these RV failure model mice. Results: In microarray analysis for RV, left ventricle and ventricular septum, 995 genes were extracted as DEGs in RV. Pathway analysis revealed that alternative complement pathway-related genes were significantly up-regulated in RV. Moreover, complement factor D (Cfd) and C3a was a potential upstream factor attributable to unique feature of RV. Administration of C3a recombinant protein to NRVM phosphorylated several MAP kinases. Moreover, in C3KO PAC mice, RV dysfunction was significantly suppressed, and histological study suggested that RV fibrosis was significantly suppressed by comparing to wild type PAC mice. Furthermore, administration of C3a receptor antagonist to wild type PAC mice dramatically improved RV dysfunction and reduced RV fibrosis. Additionally, in vivo electrophysiological study revealed that the inducibility of ventricular arrhythmia was increased in wild type PAC mice, but ventricular arrhythmia was significantly attenuated in C3KO PAC mice. Conclusion: We revealed that complement C3a was highly produced in RV, and genetic or chemical blockade of C3a ameliorates RV dysfunction and RV fibrosis in RV failure model mice. C3a was to be a potent bioactive protein for immunocompetent cells that played an important role in modulating RV function. Accordingly, we demonstrated that the blockade of C3a had a potential role for novel therapeutic target of RV failure.

Suppression of ventricular arrhythmia by mitochondrial calcium uptake via mitochondrial calcium uniporter in the ischemic heart failure mice

Abstract Background In heart failure (HF), diastolic calcium (Ca) leak from sarcoplasmic reticulum (SR) via ryanodine receptor (RyR) causes delayed after depolarization (DAD), leading ventricular arrhythmias (VAs). Recent study reported that Ca uptake into mitochondria via mitochondrial calcium uniporter (MCU) suppress Ca waves (CaWs) and DAD in catecholaminergic polymorphic ventricular tachycardia, in which diastolic Ca leak is thought to be a major cause of VAs as in HF. However, such anti-arrhythmic effect of mitochondrial Ca uptake via MCU remains unclear in HF. Purpose We sought to investigate whether mitochondrial Ca uptake via MCU decreases CAWs and VAs incidence in ischemic HF mice. Methods Ten-week-old male C57BL/6J mice were divided into 2 groups; sham operation mice (Sham) or HF mice (HF) in which myocardial infarction was induced by left coronary artery ligation. After 4–6 weeks, cardiomyocyte or mitochondria was isolated respectively from the myocardium of Sham and the non-infarct myocardium of HF. Influence of MCU activation on Ca dynamics, VA inducibility and left ventricular hemodynamics were evaluated using Kaemenpferol, a MCU activator. Intracellular Ca dynamics and mitochondrial Ca uptake were measured in isolated cardiomyocytes loaded with Fluo-4 AM on an epifluorescence microscopy and by estimating the extra-mitochondrial Ca reduction with Fluo-5N on a spectrofluoro-photometer, respectively. VAs was induced by programmed stimulation in the Langendorff perfused hearts. Left ventricular (LV) pressure was measured using a microtip transducer catheter. Finally, the effect of intravenous administration of Kaempferol (5mg/kg) on hemodynamic parameters was examined 30 minutes after administration in Sham and HF. Results HF mice showed left ventricular dysfunction, as well as the increased heart and lung weights compared to Sham. MCU protein expression in cardiomyocytes did not differ between Sham and HF. Kaempferol increased mitochondrial Ca uptake in the isolated mitochondria both in Sham and HF. The number of the diastolic CaWs was higher in HF compared to Sham. Such increased number of CaWs in HF was attenuated by 10 μM Kaempferol, which was, however, abolished by a MCU blocker Ruthenium Red. The incidence of induced VA was significantly higher in HF than Sham, which was suppressed by Kaempferol. In vivo measurements, intravenous administration of Kaempferol did not show significant changes in hemodynamic parameters in Sham and HF mice. Conclusions Mitochondrial Ca uptake via MCU suppresses CaWs and VAs, but did not change LV hemodynamics in HF. Whereas traditional antiarrhythmic drugs have limited use in heart failure patients, a novel strategy that promotes Ca uptake into mitochondria might be a new and safer option for treating VAs in HF. Funding Acknowledgement Type of funding source: None

Long-term efficacy and safety of hydroquinidine in patients with Brugada syndrome

Abstract Background Brugada syndrome (BrS) is an inherited channelopathy with an increased risk of supraventricular, ventricular arrhythmias (VAs) and sudden cardiac death (SCD). Implantable cardioverter-defibrillator (ICD) is a cornerstone of SCD prevention, but it does not reduce the incidence of life-threatening VAs and it can carry substantial complications. Hydroquinidine (HQ) is a class IA antiarrhythmic drug used for electrical storms, to reduce ICD's appropriate discharges and as an alternative to ICD in children with BrS or in patients with a contraindication to ICD. Nevertheless, HQ's side effects may undermine treatment compliance. Purpose The aim of this study was to evaluate the efficacy and safety of HQ in reducing VAs (ventricular fibrillation, sustained and non-sustained ventricular tachycardia) inducibility at electrophysiology study (EPS) and atrial fibrillation/flutter (AF/AFL) or VAs recurrence in patients with BrS. Methods From the prospective Piedmont Brugada Registry, patients treated with HQ were selected and divided into three groups according to the indication for HQ initiation: index EPS positive for VAs induction (group 1), secondary prevention of AF/AFl (group 2), secondary prevention of VAs (group 3). In group 3 recurrence of VAs was monitored by implantable devices or by periodic 24-hour ECG Holter monitoring. In 5 patients HQ was started for reasons different from the above mentioned, so they were considered only for safety outcomes. Safety was assessed considering the occurrence of HQ side effects and their impact on treatment discontinuation. Results A total of 98 patients (79 males, 80,6%) were included. Median follow-up was 61 months (IQR 31–89 months). None of the baseline clinical characteristics was associated with arrhythmic recurrences. Among 46 patients in group 1 HQ was effective in reducing EPS inducibility in 91.9% of patients (p&amp;lt;0.0001); in group 2 (31 patients) HQ reduced palpitations [before HQ 83,8%, with HQ 27,6%, RRR 67.1%, NNT 1.8; p&amp;lt;0.0001] and no AF/AFL recurrence was recorded during follow-up (p&amp;lt;0.0001); in group 3 (17 patients; 70.6% with ICD/LR implanted) VAs recurrences were significantly reduced in patients with HQ (5.9% recurrence rate, p&amp;lt;0.0001). Overall, no cardiac arrest occurred during follow-up. At ECG, HQ determined a significant increase in QTc duration (V5-lead mean QTc duration pre-HQ 406 ms vs with HQ 428 ms; p=0.001). Overall, 28.6% of patients presented HQ-related side effects, mainly due to gastrointestinal intolerance (18.3%). Treatment discontinuation rate was 25% but only about half of these patients discontinued HQ for adverse events (29.2% for GI intolerance, 16.7% for drug-induced QTc prolongation, 8.3% for elevated liver enzymes; 45.8% self-discontinuation). Conclusions In patients with BrS, HQ was effective in reducing VAs inducibility at EPS, AF/AFL and VAs recurrences; moreover, it was effective in reducing symptoms. Overall, HQ proved to be safe and well-tolerated. Funding Acknowledgement Type of funding source: None

Dexmedetomidine reduces ventricular arrhythmias in a model of drug-induced QT-prolongation

Abstract Background Dexmedetomidine is increasingly employed for conscious sedation during electrophysiological procedures. Recent experimental data have suggested direct effects of dexmedetomidine on cardiac electrophysiology. The aim of the present study was to assess the effects of dexmedetomidin on drug-induced QT-prolongation. Methods and results In 12 isolated rabbit hearts the macrolide antibiotic erythromycin (300μM) was infused as a potent Ikr blocker after obtaining baseline data. Eight endo- and epicardial monophasic action potentials and a simultaneously recorded 12-lead ECG showed a significant prolongation of QT-interval (+25ms, p&amp;lt;0.05) accompanied by a moderate increase of action potential duration (APD, +5ms, p=ns) after infusion of erythromycin as compared with baseline. Effective refractory period (ERP) was also elevated (+33ms, p&amp;lt;0.05). Erythromycin (+26ms, p&amp;lt;0.05) also significantly increased spatial dispersion of repolarisation. Additional infusion of dexmedetomidine (3μM) resulted in a rather stable QT-interval (+7ms, p=ns) and APD (+7ms, p=ns) as compared with sole erythromycin treatment. Of note, a significant decrease of spatial dispersion (−24ms, p&amp;lt;0.05) was observed while ERP was moderately increased (+13ms, p=ns). Lowering of potassium concentration in bradycardic AV-blocked hearts resulted in the occurrence of early afterdepolarizations (EAD) and drug induced proarrhythmia with torsade de pointes in 6 of 12 erythromycin-treated hearts (40 episodes). Additional infusion of dexmedetomidine reduced the occurrence of torsade de pointes (4 of 12 hearts, 9 episodes). Conclusion Infusion of dexmedetomidine resulted in a reduction of spatial dispersion of repolarization in the presence of a prolonged repolarization period. This resulted in a reduction of torsade de pointes with dexmedetomidine. Furthermore, an increase of ventricular refractory periods reduced inducibility of ventricular arrhythmias. Thus, in an experimental setting dexmedetomidine shows significant antiarrhythmic effects, which may influence electrophysiologic findings during clinical electrophysiologic studies. This needs to be studied in the clinical setting. Funding Acknowledgement Type of funding source: None

Predictors of success for Brugada syndrome epicardial ablation

Abstract Epicardial right ventricular outflow tract (RVOT) ablation has been described for the treatement of Brugada syndrome (BrS) high risk patients. Purpose Success evaluation of epicardial ablation for BrS. Methods Type 1 ECG was defined as spontaneous if recorded in absence of drugs and/or specific conditions. BrS patients were scheduled for ablation if presented at least one of: spontaneous type 1 ECG, syncope, ventricular arrhythmias (VA). Programmed electrical stimulation (PES) was performed (2 extrastimuli, 2 sites) in basal conditions and after ajmaline infusion. Epicardial subxifoid access and electroanatomical endo-epicardial maps were obtained during sinus rhythm. Delayed fragmented/low-frequency, low-voltage electrograms (EGM) were targeted: substrate area measured in basal conditions and after ajmaline. Epicardial ablation Radiofrequency (RF) was delivered (50 W power control mode) till complete elimination of targeted EGM and BrS-ECG pattern after ajmaline. Eventually PES repeated: if positive a repeated PES scheduled at follow-up (fu). Success was defined as absence of type 1 ECG either spontaneous or with ajmaline challenge at 3 month. Recurrences were scheduled to redo ablation. Results 55 patients were submitted to 58 ablation procedures. 38 spontaneous type 1 ECG: 18 symptomatic for syncope/polimorphic VT/VF or appropriate ICD shock; 13 had VA induction at PES. 4 patients with ajmaline-type 1 ECG had VA induction. 36% of the symptomatic patients and 26% of asymptomatic had PES-VA induction. In all patients abnormal EGM area (cm2) was detected in epicardial RVOT (table 1). Acute success: No patient had ECG type 1 with ajmaline. 5 patients had PES induction of VA. Complications: 1 cardiac tamponade, 16 mild pericarditis. At FU of 1,1±0,6 yrs no patient had spontaneous ECG type 1 nor arrhythmic events. 50 had negative ajmaline challenge (90% success rate after single procedure), 3 underwent redo: 2 had negative ajmaline challenge at FU, 1 had persistence type 1-ajmaline induction; 2 are scheduled for redo. No patient had VT induction at PES. Multivariate analysis: Single procedure success was not related either to history (symptoms, VA, type 1 ECG) or to procedural findings (PES results, substrate area). Conclusion Epicardial substrate ablation was safe end effective in BrS. No clinical or procedural findings were related to success Funding Acknowledgement Type of funding source: None

Reverse electromechanical modelling of diastolic dysfunction in spontaneous hypertensive rat after sacubitril/valsartan therapy.

AimsHypertension is a significant risk for the development of left ventricular hypertrophy, diastolic dysfunction, followed by heart failure and sudden cardiac death. While therapy with sacubitril/valsartan (SV) reduces the risk of sudden cardiac death in patients with heart failure and systolic dysfunction, the effect on those with diastolic dysfunction remains unclear. We hypothesized that, in the animal model of hypertensive heart disease, treatment with SV reduces the susceptibility to ventricular arrhythmia.Methods and resultsYoung adult female spontaneous hypertensive rats (SHRs) were randomly separated into three groups, which were SHRs, SHRs treated with valsartan, and SHRs treated with SV. In addition, the age‐matched and weight‐matched Wistar Kyoto rats were considered as controls, and there were 12 rats in each group. In vivo ventricular tachyarrhythmia induction and in vitro optical mapping were used to measure the inducibility of ventricular arrhythmias and to characterize the dynamic properties of electrical propagation. The level of small‐conductance Ca2+‐activated potassium channel type 2 (KCNN2) was analysed in cardiac tissue. Compared with SHR with left ventricular hypertrophy, treatment with SV significantly improved cardiac geometry (relative wall thickness, 0.68 ± 0.11 vs. 0.76 ± 0.13, P < 0.05) and diastolic dysfunction (isovolumetric relaxation time, 59.4 ± 3.2 vs. 70.5 ± 4.2 ms, P < 0.05; deceleration time of mitral E wave, 46 ± 4.8 vs. 42 ± 3.8, P < 0.05). The incidence of induced ventricular arrhythmia was significantly reduced in SHR treated with SV compared with SHR (ventricular tachycardia, 1.14 ± 0.32 vs. 2.91 ± 0.5 episodes per 10 stimuli, P < 0.001; ventricular fibrillation, 1.72 ± 0.31 vs. 5.81 ± 0.42 episodes per 10 stimuli, P < 0.001). The prolonged action potential duration (APD) and increase of the maximum slope of APD restitution were observed in SHR, while the treatment of SV improved the arrhythmogeneity (APD, 37.12 ± 6.18 vs. 92.41 ± 10.71 ms at 250 ms pacing cycle length, P < 0.001; max slope 0.29 ± 0.01 vs. 1.48 ± 0.04, P < 0.001). These effects were strongly associated with down‐regulation of KCNN2 (0.38 ± 0.07 vs. 0.74 ± 0.12 ng/ml, P < 0.001). The treatment of SV also decreased the level of N‐terminal pro‐B‐type natriuretic peptide, cardiac bridging integrator‐1, and intramyocardial fibrosis of SHR.ConclusionsIn conclusion, synergistic blockade of the neprilysin and the renin–angiotensin system by SV in SHRs results in KCNN2‐associated electrical remodelling in ventricle, which stabilizes electrical dynamics and attenuates arrhythmogenesis.

Rhodiola crenulata reduces ventricular arrhythmia through mitigating the activation of IL-17 and inhibiting the MAPK signaling pathway.

Ventricular arrhythmia (VA) is related to inflammatory activity. Rhodiola crenulate (RC) and its main active component, salidroside, have been reported as anti-inflammatory agents. The aim of this study was to demonstrate the effect of RC and salidroside in preventing VA via the inhibition of IL-17 in an ischemic heart failure (HF) model. Rabbit HF models were established by coronary artery ligation for 4weeks. These rabbits were treated with RC (125, 250, 500mg/kg) and salidroside (9.5mg/kg) once every 2days for 4weeks. WBC, serum biochemistry, ECG, and the expression of CD4+ T cells were measured every 2weeks. The mRNA and protein expressions of IL-17 were measured by real time-PCR, ELISA, and Western blotting after RC and salidroside treatment for 4weeks. Open-chest epicardial catheter stimulation was performed for VA provocation. After RC and salidroside treatment in HF left ventricle, (1) the levels of WBC and CD4+ T cells decreased, (2) the expression of IL-17 and its downstream target genes, IL-6, TNF-α, IL-1β, IL-8, and CCL20, reduced, (3) the level of NLRP3 inflammasome was decreased, (4) fibrosis and collagen production were significantly downregulated, (5) p38 MAPK and ERK1/2 phosphorylation were attenuated, (6) the inducibility of VA was decreased, and (7) the levels of Kir2.1, Nav1.5, NCX, PLB, SERCA2a and RyR were up-regulated. RC inhibited the expression of IL-17 and its downstream target genes that were mediated by activation of several MAPKs, which decreased the levels of fibrosis and apoptosis and suppressed VA.