Ventricular tachycardia and sudden cardiac death

Epidemiology, clinical characteristics and potential mechanism of ibrutinib-induced ventricular arrhythmias

The Bruton's Tyrosine Kinase Inhibitor, ibrutinib, has been widely employed due to its significant efficacy in B-cell lymphoma. However, the subsequent cardiac complications, notably atrial fibrillation (AF) and ventricular arrhythmias (VAs),associated with ibrutinib treatment have emerged as a major concern in cardio-oncology and hematology. Ibrutinib-induced AF has been well described, whereas mechanisms of ibrutinib-induced VAs are still under-investigation. The incidence of ibrutinib-induced VAs can vary vastly due to under-recognition and limitations of the retrospective studies. Recent investigations, including our previous work, have proposed several potential mechanisms contributing to this adverse event, necessitating further validation. The development of effective strategies for the prevention and treatment of ibrutinib-induced VAs still requires in-depth exploration. This review aims to establish a comprehensive framework encompassing the epidemiology, mechanistic insights, and clinical considerations related to ibrutinib-induced VAs. This article outlines potential strategies for the clinical management of patients undergoing ibrutinib therapy based on suggested mechanisms.

Epicardial Ablation as a Treatment of Recurrent Ventricular Tachycardia Originating From a Left Ventricular Aneurysm: A Case Report and Review of the Literature

Catheter ablation (CA) is an important therapeutic modality for the management of ventricular tachycardia (VT). In some patients, CA may be ineffective because of the inability to reach the effective target site from the endocardial surface. Partly, this is due to the effect of the transmural extent of the myocardial scars. The operator's ability to map and ablate the epicardial surface has enhanced our understanding of scar-related VT in various substrate states. A left ventricular aneurysm (LVA) that develops after myocardial infarction may increase the risk of VT. Endocardial ablation alone of LVA may be insufficient in preventing recurrent VT. Numerous studies have demonstrated greater freedom from recurrence with adjunctive epicardial mapping and ablation via a percutaneous subxiphoid technique. Currently, epicardial ablation is performed predominantly at high-volume tertiary referral centers via the percutaneous subxiphoid approach. In this review, we first report a case of a man in his 70s with ischemic cardiomyopathy, a large apical aneurysm, and recurrent VT status post-endocardial ablation who presented with incessant VT. The patient underwent successful epicardial ablation over the apical aneurysm. Second, our case showcases the percutaneous approach and underscores its clinical indications and potential complications.

The role of pulse timing in cardiac defibrillation

Life-threatening cardiac arrhythmias require immediate defibrillation. For state-of-the-art shock treatments, a high field strength is required to achieve a sufficient success rate for terminating the complex spiral wave (rotor) dynamics underlying cardiac fibrillation. However, such high energy shocks have many adverse side effects due to the large electric currents applied. In this study, we show, using 2D simulations based on the Fenton-Karma model, that also pulses of relatively low energy may terminate the chaotic activity if applied at the right moment in time. In our simplified model for defibrillation, complex spiral waves are terminated by local perturbations corresponding to conductance heterogeneities acting as virtual electrodes in the presence of an external electric field. We demonstrate that time series of the success rate for low energy shocks exhibit pronounced peaks which correspond to short intervals in time during which perturbations aiming at terminating the chaotic fibrillation state are (much) more successful. Thus, the low energy shock regime, although yielding very low temporal average success rates, exhibits moments in time for which success rates are significantly higher than the average value shown in dose-response curves. This feature might be exploited in future defibrillation protocols for achieving high termination success rates with low or medium pulse energies.

Severe Traumatic Brain Injury Presenting with Wide Complex Tachycardia: a Case Report

Background

Ventricular tachycardia (VT) is an abnormal heart rhythm that can lead to pump failure and hypoperfusion. Its causes, presentation, and treatment are well established in the literature. However, the VT treatment algorithm is based on non-traumatic patients. Due to different pathophysiology and presentation, treating VT in trauma patients should be different.

Objective

The main purpose is to emphasize the approach to treating VT in severe head trauma patients.

Case presentation

This case is a unique presentation of severe head trauma with a paucity of treatment approaches in the literature. In this article, we present a case of a middle-aged male patient presented to a level one trauma center with a history of falls from 2 stories height with a Glasgow Coma Scale (GCS) of 3/15. ATLS approach was followed in treating this patient, his rhythm strip showed a wide complex regular rhythm, likely representing a VT with a pulse. The patient was treated as unstable because of a decreased level of consciousness. A 100 J synchronized cardioversion was given without restoration of normal sinus rhythm, followed by Mannitol 1g/kg, treating the possibility of high intracranial pressure (ICP), after which his rhythm was restored to sinus.

Conclusion

The restoration of sinus rhythm after treating the possibility of high ICP suggests that the cause of VT in this severe TBI patient was the high ICP.

Racial disparities in ventricular tachycardia in young adults: analysis of national trends

BACKGROUND

In the last two decades, risk factors, prevalence, and mortality due to coronary artery disease in young adults are on the rise. We sought to assess the prevalence, trends, and economic burden of ventricular tachycardia (VT) hospitalizations in young adults (< 45 years), further stratified by race and gender.

METHODS

The Nationwide Inpatient Sample was explored for hospitalizations with VT in patients (< 45 years) between 2005 and 2018 and divided among 3 groups of the quadrennial period using validated International Classification of Diseases (ICD) 9^th and 10^th revision Clinical Modification (CM) codes. The Pearson chi-square test and Wilcoxon rank-sum were used for categorical and continuous variables, respectively. We assessed the temporal trends of mortality in VT hospitalizations and trends of VT hospitalization stratified by age, sex, and race by using Joinpoint regression analysis. The primary outcome was in-hospital mortality trends. Secondary outcomes were trends of hospital stay in days, cost of care in US dollars, cardiac arrest, and discharge disposition.

RESULTS

Out of 5,156,326 patients admitted with VT between 2005 and 2018, 309,636 were young adults. Among them, 102,433 were admitted between 2005 and 2009 (mean age 36.1 ± 6.99; 61% male, 58.5% White), 109,591 between 2010 and 2014 (mean age 35.5 ± 7.16; 59% male, 54.2% White), and 97,495 between 2015 and 2018 (mean age 35.4 ± 7.00; 60% male, 52.3% White) (p < 0.07). In the young adults with VT, all-cause mortality was 7.37% from 2005 to 2009, 7.85% from 2010 to 2014 (6.5% relative increase from 2005 to 2009), and 8.98% from 2015 to 2018 (relative increase of 14.4% from 2010 to 2014) (p < 0.0001). Similarly, risk of cardiac arrest was on the rise (6.15% from 2005 to 2009 to 7.77% in 2010-2014 and 9.97% in 2015-2018). Inflation-adjusted cost increased over the years [$12,177 in 2005-2009; $13,249 in 2010-2014; $15,807 in 2015-2018; p < 0.0001)].

CONCLUSIONS

VT hospitalizations and related all-cause mortality, and healthcare utilization costs in young adults are on the rise in the study period. Hospitalization burden related to VT and poor outcomes were more notable for Black adults. Further studies are required for targeted screening and preventative measures in young adults.

Identification of astroglia-like cardiac nexus glia that are critical regulators of cardiac development and function

Glial cells are essential for functionality of the nervous system. Growing evidence underscores the importance of astrocytes; however, analogous astroglia in peripheral organs are poorly understood. Using confocal time-lapse imaging, fate mapping, and mutant genesis in a zebrafish model, we identify a neural crest-derived glial cell, termed nexus glia, which utilizes Meteorin signaling via Jak/Stat3 to drive differentiation and regulate heart rate and rhythm. Nexus glia are labeled with gfap, glast, and glutamine synthetase, markers that typically denote astroglia cells. Further, analysis of single-cell sequencing datasets of human and murine hearts across ages reveals astrocyte-like cells, which we confirm through a multispecies approach. We show that cardiac nexus glia at the outflow tract are critical regulators of both the sympathetic and parasympathetic system. These data establish the crucial role of glia on cardiac homeostasis and provide a description of nexus glia in the PNS.

Cardiac radioablation in the treatment of ventricular tachycardia

Cardiac radioablation with SBRT is a very promising non-invasive modality for the treatment of refractory VT and potentially other cardiac arrhythmias. Initial reports indicate that it is relatively safe and associated with excellent responses, particularly in reduction of ICD-related events, need for anti-arrhythmic medications, and resulting in significantly improved quality of life for patients. Establishment of objective criteria for candidates for cardiac radioablation will accelerate the adoption of this important radiation therapy modality in the treatment of refractory VT and other cardiac arrhythmias in the coming years. In addition, in order to develop more prospective safety and efficacy data, treatment of patients should ideally be performed in the context of clinical trials or prospective registries at, or in collaboration with, experienced centers. Taken together, the future of cardiac radioablation is rich and worthy of further investigation to become a standard treatment in the armamentarium against refractory VT.

Unique clinical features and long term follow up of survivors of sudden cardiac death in an Asian multicenter study

There has been no long-term clinical follow-up data of survivors or victims of sudden cardiac death (SCD). The Taiwan multi-center sudden arrhythmia death syndrome follow-up and clinical study (TFS-SADS) is a collaborative multi-center study with median follow-up time 43 months. In this cohort, the clinical characteristics of these SADS patients were compared with those with ischemic heart disease (IHD). In this SCD cohort, around half (42%) were patients with IHD, which was different from Caucasian SCD cohorts. Among those with normal heart, most had Brugada syndrome (BrS). Compared to those with SADS, patients with IHD were older, more males and more comorbidities, more arrhythmic death, and lower left ventricular ejection fraction. In the long-term follow-up, patients with SADS had a better survival than those with IHD (p < 0.001). In the Cox regression analysis to identify the independent predictors of mortality, older age, lower LVEF, prior myocardial infarction and history of out-of-hospital cardiac arrest were associated with higher mortality and beta blocker use and idiopathic ventricular fibrillation or tachycardia (IVF/IVT) with a better survival during follow-up. History of prior MI was associated with more arrhythmic death. Several distinct features of SCD were found in the Asia-Pacific region, such as higher proportion of SADS, poorer prognosis of LQTS and better prognosis of IVF/IVT. Patients with SADS had a better survival than those with IHD. For those with SADS, patients with channelopathy had a better survival than those with cardiomyopathy.

Primary hyperparathyroidism associated with acquired long QT interval and ventricular tachycardia

SUMMARY

We present a 54-year-old patient admitted to the emergency department due to loss of consciousness. The initial ECG registered monomorphic ventricular extrasystoles and prolonged QT interval (QT corrected (QTc) >500 ms). Sustained ventricular tachycardia (VT) was registered on 24-h Holter ECG monitoring, which clinically was presented as a crisis of consciousness. Coronary angiography and other visualization methods were normal. Implantable cardioverter-defibrillator (ICD) implantation was planned for the purpose of secondary prevention of sudden cardiac death (SCD). Laboratory and hormonal analyzes revealed primary hyperparathyroidism (PHPT), chronic kidney disease, and hypokalemia. Neck ultrasound showed a 25 mm, sharply outlined homogenous tumor mass which was separated from thyroid gland (TG) and exerted a mild impression on lower parts of the left lobe. Dual wash technetium-99m sestamibi parathyroid scintigraphy with single-photon emission CT (SPECT)/CT also showed the uptake of tracer behind the lower half of the left lobe of the TG. Surgical treatment, lower left parathyroidectomy, was performed, and pathohistological analysis verified parathyroid adenoma. The patient was rhythmically and hemodynamically stable for 7 days after surgery, without additional complaints, and was discharged from the hospital. Timely diagnosis of PHPT, correct assessment and surgical treatment, did not lead our patient to unnecessary ICD implantation. Our case suggests an additional intertwining of electrolyte disorders and ventricular arrhythmias in PHPT and more importantly emphasizes the need for caution when indicating ICD, even in patients with the most serious life-threatening arrhythmias.

LEARNING POINTS

Electrolyte abnormalities in PHPT can have highly malignant consequences, and the occurrence of hypokalemia in the presence of hypercalcemia is underestimated in PHPT, and the consequences can be life-threatening. Although hypercalcemia causes shortened QT interval, concomitant severe hypokalemia may overcome hypercalcemia and prolong QT interval, even in the absence of structural heart disease or LQTS. Timely diagnosis of PHPT, correct assessment and surgical treatment, do not lead to unnecessary ICD implantation.

Genetically Determined Serum Calcium Levels and Markers of Ventricular Repolarization: A Mendelian Randomization Study in the UK Biobank

BACKGROUND

ECG markers of ventricular depolarization and repolarization are associated with an increased risk of arrhythmia and sudden cardiac death. Our prior work indicated lower serum calcium concentrations are associated with longer QT and JT intervals in the general population. Here, we investigate whether serum calcium is a causal risk factor for changes in ECG measures using Mendelian randomization (MR).

METHODS

Independent lead variants from a newly performed genome-wide association study for serum calcium in >300 000 European-ancestry participants from UK Biobank were used as instrumental variables. Two-sample MR analyses were performed to approximate the causal effect of serum calcium on QT, JT, and QRS intervals using an inverse-weighted method in 76 226 participants not contributing to the serum calcium genome-wide association study. Sensitivity analyses including MR-Egger, weighted-median estimator, and MR pleiotropy residual sum and outlier were performed to test for the presence of horizontal pleiotropy.

RESULTS

Two hundred five independent lead calcium-associated variants were used as instrumental variables for MR. A decrease of 0.1 mmol/L serum calcium was associated with longer QT (3.01 ms [95% CI, 2.03 to 3.99]) and JT (2.89 ms [1.91 to 3.87]) intervals. A weak association was observed for QRS duration (secondary analyses only). Results were concordant in all sensitivity analyses.

CONCLUSIONS

These analyses support a causal effect of serum calcium levels on ventricular repolarization, in a middle-aged population of European-ancestry where serum calcium concentrations are likely stable and chronic. Modulation of calcium concentration may, therefore, directly influence cardiovascular disease risk.

Pathobiology and evolving therapies of coronary artery vasospasm

Coronary artery vasospasm is a known cause of chest pain and requires a high level of clinical suspicion for diagnosis. It also remains in the differential diagnosis for patients presenting with type 2 myocardial infarction. There are few randomized controlled trials for guideline-based prevention and treatment for coronary artery vasospasm. In this article, we review updated concepts in coronary artery vasospasm. Specifically, our aim is to provide current evidence of pathophysiology, identify the risk factors, propose a diagnostic algorithm, review available evidence of evolving therapies, and identify patients who would benefit from automatic implantable cardioverter defibrillators.

Three-dimensional mapping discovered arrhythmic substrate missed in the initial diagnosis of idiopathic ventricular fibrillation

During an initial diagnosis of IVF, an arrhythmic substrate may be missed for several reasons such as lack of information; thus, a careful follow-up is important. A three-dimensional mapping may identify a possible missed arrhythmic substrate in IVF.

The efficacy of catheter ablation versus ICD for prevention of ventricular tachycardia in patients with ischemic heart disease: a systematic review and meta-analysis

Purpose

Although implantable cardioverter defibrillator (ICD) could prevent the sudden death of ventricular tachycardia (VT) in patients with ischemic heart disease, it could not effectively prevent the recurrence of ventricular tachycardia. Several studies have suggested that catheter ablation may effectively decrease the incidence of ICD events, but relevant dates from randomized controlled trials were limited.

Methods

A systematic review and meta-analysis of randomized controlled trials were performed to evaluate the effect of catheter ablation for the prevention of VT in patients with ischemic heart disease. Random-effects model with inverse-variance weighting method was used to pool odds ratios. Egger method was performed to evaluate whether there was public bias in each outcome.

Results

Four studies enrolling a total of 605 patients were included in the present meta-analysis. Compared with the control group (ICD ± AAD), catheter ablation could significantly reduce the incidence of ICD therapy (OR, 0.49; 95% CI, 0.28 ~ 0.87), ICD shock (OR, 0.50; 95% CI, 0.28 ~ 0.87), VT storm (OR, 0.60; 95% CI, 0.40 ~ 0.90), and cardiovascular-related hospitalization (OR, 0.66; 95% CI, 0.45 ~ 0.9). But there was no significant difference among the risk of all-cause mortality (OR, 0.89; 95% CI, 0.59 ~ 1.34), cardiovascular mortality (OR, 0.76; 95% CI, 0.44 ~ 1.30), and complication (OR, 0.89; 95% CI, 0.30 ~ 2.67).

Conclusion

These results showed that catheter ablation combined with ICD could reduce ICD therapy, ICD shock, and VT storm in patients with ischemic heart disease, but there was no improvement in all-cause mortality. Meanwhile, it also provided a basic guidance for the design of larger clinical randomized trials with longer follow-up in the future.

Electronic supplementary material

The online version of this article (10.1007/s10840-020-00848-1) contains supplementary material, which is available to authorized users.

Feasibility study shows concordance between image-based virtual-heart ablation targets and predicted ECG-based arrhythmia exit-sites

INTRODUCTION

We recently developed two noninvasive methodologies to help guide VT ablation: population-derived automated VT exit localization (PAVEL) and virtual-heart arrhythmia ablation targeting (VAAT). We hypothesized that while very different in their nature, limitations, and type of ablation targets (substrate-based vs. clinical VT), the image-based VAAT and the ECG-based PAVEL technologies would be spatially concordant in their predictions.

OBJECTIVE

The objective is to test this hypothesis in ischemic cardiomyopathy patients in a retrospective feasibility study.

METHODS

Four post-infarct patients who underwent LV VT ablation and had pre-procedural LGE-CMRs were enrolled. Virtual hearts with patient-specific scar and border zone identified potential VTs and ablation targets. Patient-specific PAVEL based on a population-derived statistical method localized VT exit sites onto a patient-specific 238-triangle LV endocardial surface.

RESULTS

Ten induced VTs were analyzed and 9-exit sites were localized by PAVEL onto the patient-specific LV endocardial surface. All nine predicted VT exit sites were in the scar border zone defined by voltage mapping and spatially correlated with successful clinical lesions. There were 2.3 ± 1.9 VTs per patient in the models. All five VAAT lesions fell within regions ablated clinically. VAAT targets correlated well with 6 PAVEL-predicted VT exit sites. The distance between the center of the predicted VT-exit-site triangle and nearest corresponding VAAT ablation lesion was 10.7 ± 7.3 mm.

CONCLUSIONS

VAAT targets are concordant with the patient-specific PAVEL-predicted VT exit sites. These findings support investigation into combining these two complementary technologies as a noninvasive, clinical tool for targeting clinically induced VTs and regions likely to harbor potential VTs.

Progression of infarct-mediated arrhythmogenesis in a rodent model of heart failure

Heart failure (HF) post-myocardial infarction (MI) presents with increased vulnerability to monomorphic ventricular tachycardia (mmVT). To appropriately evaluate new therapies for infarct-mediated reentrant arrhythmia in the preclinical setting, chronologic characterization of the preclinical animal model pathophysiology is critical. This study aimed to evaluate the rigor and reproducibility of mmVT incidence in a rodent model of HF. We hypothesize a progressive increase in the incidence of mmVT as the duration of HF increases. Adult male Sprague-Dawley rats underwent permanent left coronary artery ligation or SHAM surgery and were maintained for either 6 or 10 wk. At end point, SHAM and HF rats underwent echocardiographic and invasive hemodynamic evaluation. Finally, rats underwent electrophysiologic (EP) assessment to assess susceptibility to mmVT and define ventricular effective refractory period (ERP). In 6-wk HF rats (n = 20), left ventricular (LV) ejection fraction (EF) decreased (P < 0.05) and LV end-diastolic pressure (EDP) increased (P < 0.05) compared with SHAM (n = 10). Ten-week HF (n = 12) revealed maintenance of LVEF and LVEDP (P > 0.05), (P > 0.05). Electrophysiology studies revealed an increase in incidence of mmVT between SHAM and 6-wk HF (P = 0.0016) and ERP prolongation (P = 0.0186). The incidence of mmVT and ventricular ERP did not differ between 6- and 10-wk HF (P = 1.0000), (P = 0.9831). Findings from this rodent model of HF suggest that once the ischemia-mediated infarct stabilizes, proarrhythmic deterioration ceases. Within the 6- and 10-wk period post-MI, no echocardiographic, invasive hemodynamic, or electrophysiologic changes were observed, suggesting stable HF. This is the necessary context for the evaluation of experimental therapies in rodent HF.NEW & NOTEWORTHY Rodent model of ischemic cardiomyopathy exhibits a plateau of inducible monomorphic ventricular tachycardia incidence between 6 and 10 wk postinfarction.

MAGNETO cardiography parameters to predict future Sudden Cardiac Death (MAGNETO-SCD) or ventricular events from implantable cardioverter defibrillators: study protocol, design and rationale

INTRODUCTION

Predicting sudden cardiac death (SCD) is challenging as current risk predictors have significant limitations. Evaluating magnetocardiogram (MCG) parameters could be of great value and we plan to assess the capability of a new mobile unshielded MCG device in predicting SCD and ventricular arrhythmias (VA) in patients undergoing implantable cardioverter defibrillator (ICD) implantation.

METHODS AND ANALYSIS

A prospective multicentre (University Hospitals Coventry and Warwickshire (UHCW) National Health Service (NHS) Trust/University Hospital North Midlands NHS Trust, UK) observational study evaluating the VitalScan MCG (Creavo Medical Technologies, UK) to predict future VA risk; 270 patients meeting criteria for primary or secondary prevention ICDs (ischaemic or non-ischaemic aetiology) are being recruited. The first patient was recruited September 2019 and the study will be completed at final participant follow-up. The primary endpoint is appropriate ICD therapy for VA, secondary endpoint is SCD. Previous trials using MCG identified late QRS signals/QRS fragmentation as potential indicators of SCD in small samples using large shielded expensive MCG devices that were difficult to use clinically. It is hoped the MAGNETO-SCD trial will show this new MCG device can provide real world risk stratification for SCD/VA risk. The trial has recruited 25 patients (13 with secondary prevention indication) from a single site (UHCW) with recruitment starting at the second site in March 2020.

ETHICS AND DISSEMINATION

Research Ethics Committee, Yorkshire and Humber Sheffield Research Ethics Committee UK (Ref: 19/YH/0143) and Health Research Authority (IRAS reference 254466, EDGE ID: 123146) approval received on 17/07/2019. The Medicines and Healthcare products Regulatory Agency approval received 11/07/2019. Results will be disseminated via a peer-reviewed publication and presentation at international conferences.

TRIAL REGISTRATION NUMBERS

ClinicalTrials.gov Registry (NCT04352816) and EU Clinical Trials Registry (EudraCT2019-002994-78).

A hybrid machine learning approach to localizing the origin of ventricular tachycardia using 12-lead electrocardiograms

BACKGROUND

Machine learning models may help localize the site of origin of ventricular tachycardia (VT) using 12-lead electrocardiograms. However, population-based models suffer from inter-subject anatomical variations within ECG data, while patient-specific models face the open challenge of what pacing data to collect for training.

METHODS

This study presents and validates the first hybrid model that combines population and patient-specific machine learning for rapid "computer-guided pace-mapping". A population-based deep learning model was first trained offline to disentangle inter-subject variations and regionalize the site of VT origin. Given a new patient with a target VT, an on-line patient-specific model -- after being initialized by the population-based prediction -- was then built in real time by actively suggesting where to pace next and improving the prediction with each added pacing data, progressively guiding pace-mapping towards the site of VT origin.

RESULTS

The population model was trained on pace-mapping data from 38 patients and the patient-specific model was subsequently tuned on one patient. The resulting hybrid model was tested on a separate cohort of eight patients in localizing 1) 193 LV endocardial pacing sites, and 2) nine VTs with clinically determined exit sites. The hybrid model achieved a localization error of 5.3 ± 2.6 mm using 5.4 ± 2.5 pacing sites in localizing LV pacing sites, achieving a significantly higher accuracy with a significantly smaller amount of training sites in comparison to models without active guidance.

CONCLUSION

The presented hybrid model has the potential to assist rapid pace-mapping of interventional targets in VT.

Real-world characteristics and readmissions among patients undergoing ablation for ventricular tachycardia: a retrospective database analysis of commercially insured patients in the USA

BACKGROUND

Radiofrequency catheter ablation is an effective treatment to alleviate symptoms and reduce recurrent implantable cardioverter-defibrillator (ICD/CRT-D) shocks in patients with ventricular tachycardia (VT).

OBJECTIVE

To assess the characteristics and outcomes (complications, inpatient readmissions) of commercially insured patients in the USA undergoing ablation for ischaemic or non-ischaemic VT.

METHODS

Patients aged 18-64 years with a primary diagnosis of VT who underwent ablation between 2006 and 2015 were identified using the IBM MarketScan Commercial Database. The rate of complications including vascular complications, pericarditis, pulmonary embolism and pericardial tamponade over a 30-day post-ablation period (including index admission) was examined. Inpatient readmissions (VT-related, heart failure (HF)-related and non-VT arrhythmia-related) over the 12-month post-ablation period were examined. A Cox regression model was used to determine factors associated with inpatient readmissions.

RESULTS

5242 patients (488 with ischaemic and 4754 with non-ischaemic VT) met the study criteria. The majority of VT ablations occurred in an outpatient setting (57% for ischaemic and 66% for non-ischaemic VT). Among complications, vascular complications were most frequent (2.05% among ischaemic and 1.6% among non-ischaemic VT patients) over the 30-day post-ablation period. Among ischaemic VT patients, 17%, 7.6% and 4.7% had VT-related, HF-related and non-VT arrhythmia-related inpatient readmissions, respectively in the 12-month post-ablation period. For non-ischaemic VT patients, these numbers were 7.5%, 1.7% and 3.1%, respectively. Inpatient setting (vs outpatient), baseline ICD/CRT-D implantation, HF comorbidity and ≥2 prior hospitalisations were associated with a higher risk of post-ablation VT-related inpatient readmissions among ischaemic VT patients. Similar factors also were associated with a higher risk of post-ablation VT-related inpatient readmission among non-ischaemic VT patients.

CONCLUSION

Setting of ablation and comorbidity status were found to influence readmission rates. Complication and readmission rates following VT ablation were low indicating towards the favourable safety profile of VT ablation.

Updating the Risk Stratification for Sudden Cardiac Death in Cardiomyopathies: The Evolving Role of Cardiac Magnetic Resonance Imaging. An Approach for the Electrophysiologist

The prevention of sudden cardiac death (SCD) in cardiomyopathies (CM) remains a challenge. The current guidelines still favor the implantation of devices for the primary prevention of SCD only in patients with severely reduced left ventricular ejection fraction (LVEF) and heart failure (HF) symptoms. The implantation of an implantable cardioverter-defibrillator (ICD) is a protective barrier against arrhythmic events in CMs, but the benefit does not outweigh the cost in low risk patients. The identification of high risk patients is the key to an individualized prevention strategy. Cardiac magnetic resonance (CMR) provides reliable and reproducible information about biventricular function and tissue characterization. Furthermore, late gadolinium enhancement (LGE) quantification and pattern of distribution, as well as abnormal T1 mapping and extracellular volume (ECV), representing indices of diffuse fibrosis, can enhance our ability to detect high risk patients. CMR can also complement electro-anatomical mapping (EAM), a technique already applied in the risk evaluation and in the ventricular arrhythmias ablation therapy of CM patients, providing a more accurate assessment of fibrosis and arrhythmic corridors. As a result, CMR provides a new insight into the pathological substrate of CM. CMR may help identify high risk CM patients and, combined with EAM, can provide an integrated evaluation of scar and arrhythmic corridors in the ablative therapy of ventricular arrhythmias.

The Associations of Diuretics and Laxatives Use with Cardiovascular Mortality. An Individual Patient-Data Meta-analysis of Two Large Cohort Studies

Purpose

To investigate the associations of diuretics overall, non-potassium-sparing diuretics in specific, and laxative use with cardiovascular mortality (CVM) in subjects with antihypertensive treatment.

Methods

Analyses included 4253 participants, aged 50 to 75 years, from the German ESTHER cohort and 105,359 participants, aged 50 to 69 years, from the UK Biobank. Cox proportional hazard regression models were applied in both studies, and then results were pooled using random-effects model meta-analyses.

Results

During 14 and 7 years of follow-up, 476 and 1616 CVM cases were observed in the ESTHER study and the UK Biobank, respectively. Compared to non-users, a 1.6-fold (hazard ratio [95% confidence interval] 1.57 [1.29; 1.90]), a 1.4-fold (1.39 [1.26; 1.53]), and no statistically significantly increased (1.13 [0.94; 1.36]) CVM were observed in users of diuretics overall, non-potassium-sparing diuretics in specific, and laxatives, respectively. Concurrent use of non-potassium-sparing diuretics and laxatives was associated with a 2-fold increased CVM (2.05 [1.55; 2.71]) when compared to users of neither diuretics nor laxatives. However, a test for interaction slightly missed statistical significance (p = 0.075).

Conclusions

These consistent results from two large cohort studies imply that more research is needed on the safety of diuretics in routine care. Although not statistically significant in this study, a drug-drug interaction of non-potassium-sparing diuretics and laxatives appears plausible. Physicians and pharmacists are advised to clarify additional laxative use in users of non-potassium-sparing diuretics and inform about the risk of concurrent use. Moreover, closer potassium monitoring intervals (e.g., every 3 months) might be indicated in concurrent users to prevent fatal cardiovascular events.

Electronic supplementary material

The online version of this article (10.1007/s10557-019-06894-w) contains supplementary material, which is available to authorized users.

Factors Promoting Conduction Slowing as Substrates for Block and Reentry in Infarcted Hearts

The development of effective and safe therapies for scar-related ventricular tachycardias requires a detailed understanding of the mechanisms underlying the conduction block that initiates electrical re-entries associated with these arrhythmias. Conduction block has been often associated with electrophysiological changes that prolong action potential duration (APD) within the border zone (BZ) of chronically infarcted hearts. However, experimental evidence suggests that remodeling processes promoting conduction slowing as opposed to APD prolongation mark the chronic phase. In this context, the substrate for the initial block at the mouth of an isthmus/diastolic channel leading to ventricular tachycardia is unclear. The goal of this study was to determine whether electrophysiological parameters associated with conduction slowing can cause block and re-entry in the BZ. In silico experiments were conducted on two-dimensional idealized infarct tissue as well as on a cohort of postinfarction porcine left ventricular models constructed from ex vivo magnetic resonance imaging scans. Functional conduction slowing in the BZ was modeled by reducing sodium current density, whereas structural conduction slowing was represented by decreasing tissue conductivity and including fibrosis. The arrhythmogenic potential of APD prolongation was also tested as a basis for comparison. Within all models, the combination of reduced sodium current with structural remodeling more often degenerated into re-entry and, if so, was more likely to be sustained for more cycles. Although re-entries were also detected in experiments with prolonged APD, they were often not sustained because of the subsequent block caused by long-lasting repolarization. Functional and structural conditions associated with slow conduction rather than APD prolongation form a potent substrate for arrhythmogenesis at the isthmus/BZ of chronically infarcted hearts. Reduced excitability led to block while slow conduction shortened the wavelength of propagation, facilitating the sustenance of re-entries. These findings provide important insights for models of patient-specific risk stratification and therapy planning.

Resting Heart Rate Variability Predicts Vulnerability to Pharmacologically-Induced Ventricular Arrhythmias in Male Rats

The electrical stability of the myocardium is dependent on the dynamic balance between sympathetic and parasympathetic influences on the heart, which is reflected by heart rate variability (HRV). Reduced HRV is a proposed predictor of sudden death caused by ventricular tachyarrhythmias in cardiac patients. However, the link between individual differences in HRV and ventricular tachyarrhythmic risk in populations without known pre-existing cardiac conditions is less well explored. In this study we investigated the extent to which individual differences in resting state HRV predict susceptibility to spontaneous and pharmacologically-induced ventricular arrhythmias in healthy rats. Radiotelemetric transmitters were implanted in 42 adult male Wild-type Groningen rats. ECG signals were recorded during 24-h resting conditions and under β-adrenoceptor pharmacological stimulation with isoproterenol and analyzed by means of time- and frequency-domain indexes of HRV. No significant association was found between individual differences in resting measures of HRV and spontaneous incidence of ventricular arrhythmias. However, lower resting values of HRV predicted a higher number of ventricular ectopic beats following β-adrenergic pharmacological stimulation with isoproterenol (0.02 mg/kg). Moreover, after isoproterenol administration, one rat with low resting HRV developed sustained ventricular tachycardia that led to death. The present results might be indicative of the potential utility of HRV measures of resting cardiac autonomic function for the prediction of ventricular arrhythmias, particularly during conditions of strong sympathetic activation, in populations without known cardiac disease.

An Efficient Cardiac Arrhythmia Onset Detection Technique Using a Novel Feature Rank Score Algorithm

The interpretation of various cardiovascular blood flow abnormalities can be identified using Electrocardiogram (ECG). The predominant anomaly due to the blood flow dynamics leads to the occurrence of cardiac arrhythmias in the cardiac system. In this work, estimation of cardiac output (CO) parameter using blood flow rate analysis is carried out, which is a vital parameter to identify the subjects with left- ventricular arrhythmias (LVA). In particular, LVA is a resultant component of characteristic changes in blood rheology (blood flow rate). The CO is an intrinsic parameter derived from the stroke volume (SV) characterized by end-diastolic/systolic volumes (EDV/ESV) and heart rate. The pumping of blood from left ventricle (LV) reconciles in to R-R intervals depicted on ECG, which are used for heart rate estimation. The deviation from the nominal values of CO implies that, the subject is more prone to LVA. Further, the identification of subjects with LVA is accomplished by computing the features from the ECG signals. The proposed Feature Ranking Score (FRS) algorithm employs different statistical parameters to label the score of the extracted features. The feature score enables the selection optimal features for classification. The optimal features are further given to the Least Square- Support Vector Machine (LS-SVM) classifier for training and testing phases. The signals are acquired from public domain MIT-BIH arrhythmia database, used for validating the proposed technique for identifying the LVA using blood flow.

Environmental Tobacco Smoke and Cardiovascular Disease

Environmental tobacco smoke (ETS) and its sequelae are among the largest economic and healthcare burdens in the United States and worldwide. The relationship between active smoking and atherosclerosis is well-described in the literature. However, the specific mechanisms by which ETS influences atherosclerosis are incompletely understood. In this paper, we highlight the definition and chemical constituents of ETS, review the existing literature outlining the effects of ETS on atherogenesis and thrombosis in both animal and human models, and briefly outline the public health implications of ETS based on these data.

Ventricular Tachycardia: A Treatment Comparison Study of the CyberKnife with Conventional Linear Accelerators

The work described here compared the available technical solutions for the treatment of ventricular tachycardia with stereotactic body radiation therapy. Due to the complexity of target motion during cardiac and pulmonary motion as well as the several proximate radio-sensitive structures of the tracheobronchial tree and esophagogastrointestinal tract, four potential candidates for this treatment were identified: Accuray CyberKnife (Accuray Incorporated, Sunnyvale, California, United States), Varian TrueBeam (Varian Medical Systems, Palo Alto, California, USA), Elekta Infinity (Elekta, Stockholm, Sweden), and Varian Edge (Varian Medical Systems, Palo Alto, California, USA). All four treatment modalities were evaluated for their ability to deliver a conformal, homogeneous dose to most of the target volume, to spare nearby and distant critical and sensitive anatomical structures as well as for treatment efficiency. It was found that conventional linear accelerator technology was superior in their ability to spare distant critical structures and deliver treatments efficiently while the CyberKnife showed superiority in sparing nearby critical structures more aggressively by creating larger dose gradients at the periphery of the target volume. Both treatment modalities were similar in their ability to cover the entire target with the prescription dose, conform that dose to the target volume, and deliver a homogeneous dose.

Prospects of using cardiovascular magnetic resonance in the identification of arrhythmogenic substrate in autoimmune rheumatic diseases

Sudden cardiac death (SCD) is due to ventricular tachycardia/fibrillation (VT/VF) and may occur with or without any structural or functional heart disease. The presence of myocardial edema, ischemia and/or fibrosis plays a crucial role in the pathogenesis of VT/VF, irrespective of the pathophysiologic background of the disease. Specifically, in autoimmune rheumatic diseases (ARDs), various entities such as myocardial/vascular inflammation, ischemia and fibrosis may lead to VT/VF. Furthermore, autonomic dysfunction, commonly found in ARDs, may also contribute to SCD in these patients. The only non-invasive, radiation-free imaging modality that can perform functional assessment and tissue characterization is cardiovascular magnetic resonance (CMR). Due to its capability to detect and quantify edema, ischemia and fibrosis in parallel with ventricular function assessment, CMR has the great potential to identify ARD patients at high risk for VT/VF, thus influencing both cardiac and anti-rheumatic treatment and modifying perhaps the criteria for implantation of cardioverter defibrillators.

Prophylactic catheter ablation of ventricular tachycardia in ischemic cardiomyopathy: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Catheter ablation is proven to be an effective strategy for drug refractory ventricular tachycardia (VT) in ischemic cardiomyopathy. However, the appropriate timing of VT ablation and identifying the group of patients that may receive the greatest benefit remains uncertain. There is limited data on the effect on prophylactic catheter ablation (PCA) in the prevention of implantable cardioverter defibrillator (ICD) therapy, electrical storm, and mortality.

METHODS

We performed a comprehensive literature search through November 1, 2017, for all eligible studies comparing PCA + ICD versus ICD only in eligible patients with ischemic cardiomyopathy. Clinical outcomes included all ICD therapies including ICD shocks and electrical storm. Additional outcomes included all-cause mortality, cardiovascular mortality, and complications.

RESULTS

Three randomized controlled trials (RCTs) (N = 346) met inclusion criteria. PCA was associated with a significantly lower ICD therapies (OR 0.49; CI 0.28 to 0.87; p = 0.01) including ICD shocks [OR 0.38; CI 0.22 to 0.64; p = 0.0003) and electrical storm (OR 0.55; CI 0.30 to 1.01; p = 0.05) when compared with ICD only. There was no significant difference in all-cause mortality (OR 0.77; CI 0.41 to 1.46; p = 0.42), cardiovascular mortality (OR 0.49; CI 0.16 to 1.50; p = 0.21), and major adverse events (OR 1.45; CI 0.52 to 4.01; p = 0.47) between two groups.

CONCLUSION

These results suggest prophylactic catheter ablation decreases ICD therapies, including shocks and electrical storm with no improvement in overall mortality. There is a need for future carefully designed randomized clinical trials.

Angiotensin II Overstimulation Leads to an Increased Susceptibility to Dilated Cardiomyopathy and Higher Mortality in Female Mice

Heart failure (HF) is associated with high mortality and affects men and women differently. The underlying mechanisms for these sex-related differences remain largely unexplored. Accordingly, using mice with cardiac-specific overexpression of the angiotensin II (ANGII) type 1 receptor (AT1R), we explored male-female differences in the manifestations of hypertrophy and HF. AT1R mice of both sexes feature electrical and Ca²⁺ handling alterations, systolic dysfunction, hypertrophy and develop HF. However, females had much higher mortality (21.0%) rate than males (5.5%). In females, AT1R stimulation leads to more pronounced eccentric hypertrophy (larger increase in LV mass/body weight ratio [+31%], in cell length [+27%], in LV internal end-diastolic [LVIDd, +34%] and systolic [LVIDs, +67%] diameter) and dilation (larger decrease in LV posterior wall thickness, +17%) than males. In addition, in female AT1R mice the cytosolic Ca²⁺ extrusion mechanisms were more severely compromised and were associated with a specific increased in Ca²⁺ sparks (by 187%) and evidence of SR Ca²⁺ leak. Altogether, these results suggest that female AT1R mice have more severe eccentric hypertrophy, dysfunction and compromised Ca²⁺ dynamics. These findings indicate that females are more susceptible to the adverse effects of AT1R stimulation than males favouring the development of HF and increased mortality.

Sufentanil-medetomidine anaesthesia compared with fentanyl/fluanisone-midazolam is associated with fewer ventricular arrhythmias and death during experimental myocardial infarction in rats and limits infarct size following reperfusion

To improve infarct healing following myocardial infarction in humans, therapeutic interventions can be applied during the inflammatory response. Animal models are widely used to study this process. However, induction of MI in rodents is associated with high mortality due to ventricular fibrillation (VF) during coronary artery ligation. The anaesthetic agent used during the procedure appears to influence the frequency of this complication. In this retrospective study, the effect on ventricular arrhythmia incidence during ligation and infarct size following in vivo reperfusion of two anaesthetic regimens, sufentanil–medetomidine (SM) and fentanyl/fluanisone–midazolam (FFM) was evaluated in rats. Anaesthetics were administered subcutaneously using fentanyl/fluanisone (0.5 mL/kg) with midazolam (5 mg/kg) (FFM group, n = 48) or sufentanil (0.05 mg/kg) with medetomidine (0.15 mg/kg) (SM group, n = 47). The coronary artery was ligated for 40 min to induce MI. Heart rate and ventricular arrhythmias were recorded during ligation, and infarct size was measured via histochemistry after three days of reperfusion. In the SM group, heart rate and VF incidence were lower throughout the experiment compared with the FFM group (6% versus 30%) (P < 0.01). Fatal VF did not occur in the SM group whereas this occurred in 25% of the animals in the FFM group. Additionally, after three days of reperfusion, the infarcted area following SM anaesthesia was less than half as large as that following FFM anaesthesia (8.5 ± 6.4% versus 20.7 ± 5.6%) (P < 0.01). Therefore, to minimize the possibility of complications related to VF and acute death arising during ligation, SM anaesthesia is recommended for experimental MI in rats.

Remote ischemic preconditioning differentially attenuates post-ischemic cardiac arrhythmia in streptozotocin-induced diabetic versus nondiabetic rats

Background

Sudden cardiac death (SCD), a leading cause of global mortality, most commonly arises from a substrate of cardiac ischemia, but requires an additional trigger. Diabetes mellitus (DM) predisposes to SCD even after adjusting for other DM-linked cardiovascular pathology such as coronary artery disease. We previously showed that remote liver ischemia preconditioning (RLIPC) is highly protective against cardiac ischemia reperfusion injury (IRI) linked ventricular arrhythmias and myocardial infarction, via induction of the cardioprotective RISK pathway, and specifically, inhibitory phosphorylation of GSK-3β (Ser 9).

Methods

We evaluated the impact of acute streptozotocin-induced DM on coronary artery ligation IRI-linked ventricular arrhythmogenesis and RLIPC therapy in rats.

Results

Post-IRI arrhythmia induction was similar in nondiabetic and DM rats, but, unexpectedly, DM rats exhibited lower incidence of SCD during reperfusion (41 vs. 100%), suggesting uncontrolled hyperglycemia does not acutely predispose to SCD. RLIPC was highly effective in both nondiabetic and DM rats at reducing incidence and duration of, and increasing latency to, all classes of ventricular tachyarrhythmias. In contrast, atrioventricular block (AVB) was highly responsive to RLIPC in nondiabetic rats (incidence reduced from 72 to 18%) but unresponsive in DM rats. RISK pathway induction was similar in nondiabetic and DM rats, thus not explaining the DM-specific resistance of AVB to therapy.

Conclusions

Our findings uncover important acute DM-specific differences in responsiveness to remote preconditioning for ventricular tachyarrhythmias versus AVB, which may have clinical significance given that AVB is a malignant arrhythmia twofold more common in human diabetics than nondiabetics, and correlated to plasma glucose levels >10 mmol/L.

Phellinus linteus Mycelium Alleviates Myocardial Ischemia-Reperfusion Injury through Autophagic Regulation

The incidence of myocardial ischemia-reperfusion (IR) injury is rapidly increasing around the world and this disease is a major contributor to global morbidity and mortality. It is known that regulation of programmed cell death including apoptosis and autophagy reduces the impact of myocardial IR injury. In this study, the cardioprotective effects and underlying mechanisms of Phellinus linteus (Berk. and Curt.) Teng, Hymenochaetaceae (PL), a type of medicinal mushroom, were examined in rats subjected to myocardial IR injury. The left main coronary artery of rats was ligated for 1 h and reperfused for 3 h. The arrhythmia levels were monitored during the entire process and the infarct size was evaluated after myocardial IR injury. Furthermore, the expression levels of proteins in apoptotic and autophagic pathways were observed. Pretreatment with PL mycelium (PLM) significantly reduced ventricular arrhythmia and mortality due to myocardial IR injury. PLM also significantly decreased myocardial infarct size and plasma lactate dehydrogenase level after myocardial IR injury. Moreover, PLM administration resulted in decreased caspase 3 and caspase 9 activation and increased Bcl-2/Bax ratio. Phosphorylation level of AMPK was elevated while mTOR level was reduced. Becline-1 and p62 levels decreased. These findings suggest that PLM is effective in protecting the myocardium against IR injury. The mechanism involves mediation through suppressed pro-apoptotic signaling and regulation of autophagic signaling, including stimulation of AMPK-dependent pathway and inhibition of beclin-1-dependent pathway, resulting in enhancement of protective autophagy and inhibition of excessive autophagy.

Allopurinol and the risk of ventricular arrhythmias in the elderly: a study using US Medicare data

BACKGROUND

There are no published human studies investigating whether the use of allopurinol, the most commonly used medication for the treatment of hyperuricemia in gout, the most common type of inflammatory arthritis in adults, has any beneficial effects on ventricular electrophysiology. The objective of our study was to assess whether allopurinol use is associated with a reduction in the risk of ventricular arrhythmias (VA).

METHODS

We used the 5% random sample of Medicare beneficiaries from 2006-2012 to examine new allopurinol use and the risk of incident VA. Multivariable Cox regression analyses were adjusted for demographics (age, race, sex), comorbidity, cardiac medications, and conditions associated with VA. We calculated hazard ratios (HR) and 95% confidence intervals (CI).

RESULTS

Of the 28,755 episodes of new allopurinol use, 2538 were associated with incident VA (8.8%). Among patients with incident VA, 54% were male, 78% were White, 75% had gout as the underlying diagnosis, and the mean Charlson-Romano comorbidity score was 4.8. The crude incidence of VA per 1,000,000 person-days declined as the duration of allopurinol use increased: 1-180 days, 151; 181 days to 2 years, 105; and > 2 years, 85. In multivariable-adjusted analyses, compared to non-use, allopurinol use was associated with lower HR of VA of 0.82 (95% CI, 0.76-0.90). Compared to allopurinol non-use, longer allopurinol use durations were significantly associated with lower multivariable-adjusted HR for VA: 1-180 days, 0.96 (95% CI, 0.85-1.08); 181 days to 2 years, 0.76 (95% CI, 0.68-0.85); and > 2 years, 0.72 (95% CI, 0.60-0.87). Multiple sensitivity analyses adjusting for cardiac conditions, anti-arrhythmic drugs and alternate definitions confirmed our findings with minimal/no attenuation of estimates.

CONCLUSION

Allopurinol use and use duration of more than 6 months were independently associated with a lower risk of VA. Future studies need to assess the pathophysiology of this potential benefit.

Alterations in the carnitine cycle in a mouse model of Rett syndrome

Rett syndrome (RTT) is a neurodevelopmental disease that leads to intellectual deficit, motor disability, epilepsy and increased risk of sudden death. Although in up to 95% of cases this disease is caused by de novo loss-of-function mutations in the X-linked methyl-CpG binding protein 2 gene, it is a multisystem disease associated also with mitochondrial metabolic imbalance. In addition, the presence of long QT intervals (LQT) on the patients’ electrocardiograms has been associated with the development of ventricular tachyarrhythmias and sudden death. In the attempt to shed light on the mechanism underlying heart failure in RTT, we investigated the contribution of the carnitine cycle to the onset of mitochondrial dysfunction in the cardiac tissues of two subgroups of RTT mice, namely Mecp2^+/− NQTc and Mecp2^+/− LQTc mice, that have a normal and an LQT interval, respectively. We found that carnitine palmitoyltransferase 1 A/B and carnitine acylcarnitine translocase were significantly upregulated at mRNA and protein level in the heart of Mecp2^+/− mice. Moreover, the carnitine system was imbalanced in Mecp2^+/− LQTc mice due to decreased carnitine acylcarnitine transferase expression. By causing accumulation of intramitochondrial acylcarnitines, this imbalance exacerbated incomplete fatty acid oxidation, which, in turn, could contribute to mitochondrial overload and sudden death.

Remote Liver Ischemic Preconditioning Protects against Sudden Cardiac Death via an ERK/GSK-3β-Dependent Mechanism

BACKGROUND

Preconditioning stimuli conducted in remote organs can protect the heart against subsequent ischemic injury, but effects on arrhythmogenesis and sudden cardiac death (SCD) are unclear. Here, we investigated the effect of remote liver ischemia preconditioning (RLIPC) on ischemia/reperfusion (I/R)-induced cardiac arrhythmia and sudden cardiac death (SCD) in vivo, and determined the potential role of ERK/GSK-3βsignaling.

METHODS/RESULTS

Male Sprague Dawley rats were randomized to sham-operated, control, or RLIPC groups. RLIPC was induced by alternating four 5-minute cycles of liver ischemia with 5-minute intermittent reperfusions. To investigate I/R-induced arrhythmogenesis, hearts in each group were subsequently subjected to 5-minute left main coronary artery ligation followed by 20-minute reperfusion. RLIPC reduced post-I/R ventricular arrhythmias, and decreased the incidence of SCD >threefold. RLIPC increased phosphorylation of cardiac ERK1/2, and GSK-3β Ser9 but not Tyr216 post-I/R injury. Inhibition of either GSK-3β (with SB216763) or ERK1/2 (with U0126) abolished RLIPC-induced antiarrhythmic activity and GSK-3β Ser9 and ERK1/2 phosphorylation, leaving GSK-3β Tyr216 phosphorylation unchanged.

CONCLUSIONS

RLIPC exerts a powerful antiarrhythmic effect and reduces predisposition to post-IR SCD. The underlying mechanism of RLIPC cardioprotection against I/R-induced early arrhythmogenesis may involve ERK1/2/GSK-3β Ser9-dependent pathways.

Successful treatment of cardiac electrical storm in dilated cardiomyopathy using esmolol: A case report

The present study reports a case of electrical storm occurring in a 43-year-old woman with dilated cardiomyopathy. The patient suffered from a cardiac electrical storm, with 98 episodes of ventricular tachycardia rapidly degenerating to ventricular fibrillation in hospital. The patient was converted with a total of 120 defibrillations. Recurrent ventricular tachycardia/fibrillation was initiated by premature ventricular beats. The patient did not respond to the use of amiodaronum. However, the administration of esmolol stabilized the patient's heart rhythm. A moderate dose of the β-blocker esmolol, administered as an 0.5-mg intravenous bolus injection followed by an infusion at a rate of 0.15 mg/kg/min, inhibited the recurrence of ventricular fibrillation and normalized the electrocardiographic pattern. The results suggest that esmolol may be able to improve the survival rate of patients with electrical storm in dilated cardiomyopathy and should be considered as a primary therapy in the management of cardiac electrical storms.

An unusual case of sustained ventricular tachycardia following a wasp bite

Sustained ventricular tachycardia (VT) is a life-threatening condition which requires immediate intervention. We report a case of unusual etiology of sustained VT in a 42-year-old male after a wasp bite in the absence of anaphylaxis. The patient was treated with amiodarone and improved within 48 h. Thus, wasp stings can lead to serious tachyarrhythmias which can be life-threatening. Emergency care physicians should be aware of such arrhythmias in the setting of wasp bites which can be fatal.

A novel high throughput approach to screen for cardiac arrhythmic events following stem cell treatment

Although stem cell therapy is promising for repairing damaged cardiac tissue and improving heart function, there are safety concerns, especially regarding the risk of arrhythmias, which can be life threatening. To address this issue, we propose to develop a novel screening system to evaluate arrhythmic risk associated with stem cell therapy using a high-throughput multielectrode array system that can measure conduction velocity and action potential duration in cardiomyocytes co-cultured with different types of stem cells, such as mesenchymal stem cells, skeletal myoblasts, and resident cardiac stem cells. We will assess the arrhythmic potential of each of these types of stem cells under normoxic and hypoxic conditions, with/without application of oxidative stress or catecholamines. We hypothesize that these methods will prove to be an effective way to screen for arrhythmic risk of cardiac stem cell therapy. Ultimately, our approach can potentially be personalized to develop a robust screening protocol in order to identify which stem cell type carries the least amount of risk for arrhythmia. This system will have great clinical benefit to improve the risk/benefit ratio of human stem cell therapy for heart disease.

A systematic review of the association between obstructive sleep apnea and ventricular arrhythmias

INTRODUCTION

Obstructive sleep apnea (OSA) is an independent risk factor for sudden cardiac death. The aim of this review was to study the relationship between OSA and ventricular arrhythmias.

METHODS

PubMed, Medline, and Cochrane databases were searched with MESH headings to find studies linking OSA and ventricular arrhythmias including ventricular ectopy, ventricular tachycardia (VT), and ventricular fibrillation (VF). Studies were graded by a scoring system, and an attempt was made to pool data.

RESULTS

There were no matched cohort or case control studies to study the association between OSA and ventricular arrhythmias. Given data heterogeneity, pooling and meta-analysis of data were not possible. An attempt was made to judge the quality of evidence and present a systematic review. Patients with OSA were noted to have higher odds of ventricular ectopy, and were at a higher risk for ventricular arrhythmias. Associations included higher QTc dispersion and HR variability. We did not, however, find any clear evidence for a direct correlation between increased apnea hypopnea index and increased VT or VF.

CONCLUSIONS

Pooling and meta-analysis of studies linking OSA and ventricular arrhythmias were not possible due to heterogeneity of data. In a systemic review of studies, patients with OSA were noted to have higher odds of ventricular ectopy and arrhythmias. A single study showed that CPAP may help lower arrhythmogenicity; however, it was unclear if CPAP lowered the risk of VT. Further research should focus on studying the association of OSA and causes of sudden cardiac death, including ventricular arrhythmias.

Characteristics of patients that experience cardiopulmonary arrest following aortic dissection and aneurysm

Aim:

The aim of this study is to investigate the characteristics of patients experience cardiopulmonary arrest (CPA) in the acute phase following aortic dissection and aneurysm (AD).

Materials and Methods:

Patients who were transported to this department from January 2005 to December 2010 and subsequently diagnosed with AD were included in this study. Patients with asymptomatic AD or those with AD that did not develop CPA were excluded. The AD was classified into four categories: Stanford A (SA), Stanford B (SB), thoracic aortic aneurysm (TAA) and abdominal aortic aneurysm (AAA). The frequency of witnessed collapse, gender, average age, past history including hypertension, vascular complications and diabetes mellitus, the initial complaint at the timed of dissection, initial electrocardiogram at scene, classification of CPA and survival ratio were compared among the patient groups.

Results:

There were 24 cases of SA, 1 case of the SB, 8 cases of ruptured TAA and 9 cases of ruptured AAA. The frequency of males among all subjects was 69%, the average age was 72.3 years old and the frequency of hypertension was 47.6%. There was no ventricular fibrillation (VF) when the patients with AD collapsed. A loss of consciousness was the most common complaint. The outcome of the subjects was poor; however, three patients with SA achieved social rehabilitation. Two out of the three had cardiac tamponade and underwent open heart massage.

Conclusion:

The current study revealed that mortality of cardiac arrest caused by the AD remains very high, even when return of spontaneous circulation was obtained. VF was rare when the patients with AD collapsed. While some cases with CPA of SA may achieve a favorable outcome following immediate appropriate treatment.