Unilateral cervicothoracic sympathetic ganglionectomy for the treatment of long QT interval syndrome

Cardiac Neuromodulation and Neurocardiology

Neurocardiology has mostly been a specialty of medicine led by anatomists and physiologists. The characterization of the cardiac autonomic nervous system has resulted in a new understanding and appreciation of neurocardiology, leading to potential novel neuromodulation therapies in clinical cardiology and cardiac electrophysiology. Sympathectomy or spinal cord stimulation for the treatment of angina pectoris, as well as cardiac sympathetic denervation for the treatment of long QT syndrome associated with malignant ventricular arrhythmias, have been available and performed for more than half a century. However, a new neuromodulation has emerged, based on contemporary research findings, assisted by state-of-the art imaging and ablation techniques. Patients with structural heart disease and malignant ventricular arrhythmias, as well as symptomatic ventricular ectopy, can potentially benefit from techniques to reduce autonomic tone, such as stellate ganglionic block, epidural anesthesia and cardiac sympathetic denervation. Renal sympathetic denervation not only has been shown to ameliorate the treatment of patients with hypertension, but may also reduce atrial and ventricular arrhythmias. Patients with heart failure may be improved clinically by potentiating parasympathetic tone. Cardiac mapping of ganglia and nerves can be performed to delineate regions of ablation that can suppress atrial fibrillation, and potentially treat symptomatic bradyarrhythmias and cardio-inhibitory syncope.

The role of cardiac sympathetic denervation for ventricular arrhythmias: an updated systematic review and meta-analysis

INTRODUCTION

The role of the sympathetic nervous system in the initiation and continuation of ventricular tachyarrhythmias (VTA) is well established. However, whether CSD reduces implantable cardioverter-defibrillator (ICD) shocks and recurrent VTA is still uncertain.

METHODS

A comprehensive literature search was performed at Medline and Embase until March 2023. The primary outcome was the rate of ICD shocks and VTA per patient-year in our pooled analysis of all included articles. Analyses were conducted using Comprehensive Meta-Analysis software.

RESULTS

Initial search yielded 1324 scientific studies with a total of 15 studies fitting our inclusion criteria. ICD shocks at 1 year post-CSD revealed an event rate of 69.8% (95% CI, 56.4-80.4% with 50% heterogeneity) (I2 statistic). ICD shocks at 6 months had an event rate of 59.1% (95% CI, 46.9-70.4%; 47 I2). Analysis of our pooled studies showed that 64.3% of individuals achieved freedom from VTA at 1 year post-CSD (95% CI, 42.3-81.5%; 26% I2), while 62.3% were free from recurrent VTA 6 months post-CSD (95% CI, 51.2-72.2%; 40% I2). Time to mortality directly caused by recurrent VTA post-CSD was subdivided into short-term (0-30 days), intermediate-term (31-364 days), and long-term (≥ 365). Mortality for the short-term tertile was 8.9% (95% CI, 5.0-15.4%; 0% I2), medium-term was 5.3% (95% CI, 2.4-11.3%; 0% I2), and long-term 5.2% (95% CI, 2.4-10.9%; 0% I2).

CONCLUSION

CSD seems to be promising as an acceptable treatment strategy for recurrent VTA refractory to traditional pharmacological or ablation therapy.

Clinical neurocardiology: defining the value of neuroscience-based cardiovascular therapeutics - 2024 update

The intricate role of the autonomic nervous system (ANS) in regulating cardiac physiology has long been recognized. Aberrant function of the ANS is central to the pathophysiology of cardiovascular diseases. It stands to reason, therefore, that neuroscience-based cardiovascular therapeutics hold great promise in the treatment of cardiovascular diseases in humans. A decade after the inaugural edition, this White Paper reviews the current state of understanding of human cardiac neuroanatomy, neurophysiology and pathophysiology in specific disease conditions, autonomic testing, risk stratification, and neuromodulatory strategies to mitigate the progression of cardiovascular diseases.

Cardiac sympathetic denervation for untreatable ventricular tachycardia in structural heart disease. Strengths and pitfalls of evolving surgical techniques

Cardiac sympathetic denervation (CSD) is a valuable option in the setting of refractory ventricular arrhythmias in patient with structural heart disease. Since the procedure was introduced for non structural heart disease patients the techniques evolved and were modified to be adopted in several settings. In this state-of-the-art article we revised different techniques, their rationale, strengths, and pitfalls.

Artificial intelligence-driven intelligent learning models for identification and prediction of cardioneurological disorders: A comprehensive study

The integration of Artificial Intelligence (AI) and Intelligent Learning Models (ILMs) in healthcare has transformed the field, offering precise diagnostics, remote monitoring, personalized treatment, and more. Cardioneurological disorders (CD), affecting the cardiovascular and neurological systems, present significant diagnostic and management challenges. Traditional testing methods often lack sensitivity and specificity, leading to delayed or inaccurate diagnoses. AI-driven ILMs trained on large datasets offer promise for accurate identification and prediction of CD by analyzing complex data patterns. However, there is a lack of comprehensive studies reviewing AI applications for the diagnosis of CD and inter related disorders. This paper comprehensively reviews existing integrated solutions involving AI and ILMs in CD, examining their clinical manifestations, epidemiology, diagnostic challenges, and therapeutic considerations. The study examines recent research on CD, reviews AI-driven models' landscape, evaluates existing models, addresses practical considerations, and outlines future research directions. Through this work, we aim to provide insights into the transformative potential of AI-driven ILMs in improving clinical practice and patient outcomes for CD.

Case Report: The unrelenting journey-successful resolution of catecholaminergic polymorphic ventricular tachycardia (CPVT) through right cardiac sympathetic denervation in a teenager after left cardiac sympathetic denervation

Background

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a rare inherited arrhythmia disorder characterized by ventricular arrhythmia triggered by adrenergic stimulation.

Case presentation

A 9-year-old boy presented with convulsions following physical exertion. Bidirectional ventricular tachycardia (VT) during a treadmill test led to the diagnosis of catecholaminergic polymorphic ventricular tachycardia (CPVT). Genetic testing revealed a pathogenic variant of RYR2:c.720G>A (p.ArG2401His). Nadolol was initially started. However, he experienced aborted VT arrest three years later. Flecainide was thus added as dual therapy and he underwent left cardiac sympathetic denervation (LCSD). Subsequently, a transvenous implantable cardioverter-defibrillator (ICD) was implanted because he still had several episodes of bidirectional VT. Despite a good compliance to medication, the patient still had exercise induced VT episodes with new onset of atrial fibrillation. High dose nadolol was required and amiodarone was added. Despite maximizing the dosage of these three antiarrhythmics, the patient continued to experience multiple episodes of ventricular fibrillation with appropriate ICD shocks and persistent atrial arrhythmias. Right cardiac sympathetic denervation (RCSD) was performed as the last modality of treatment. Patient had a total elimination of VT post bilateral sympathectomy. He remained asymptomatic on follow up. A follow-up treadmill test showed no recurrence of exercise-induced PVCs and VT.

Conclusion

We illustrated the challenges and the complex decision-making process encountered in managing refractory CPVT. In patients unresponsive to conventional therapies, RCSD in additional to LCSD is a safe and effective alternative treatment. A history of LCSD should not preclude physicians from considering RCSD in children with refractory CPVT.

Efficacy of stellate ganglion block in treatment of electrical storm: a systematic review and meta-analysis

Electrical storm (ES) is a life-threatening condition of recurrent ventricular arrhythmias (VA) in a short period of time. Percutaneous stellate ganglion blockade (SGB) is frequently used - however the efficacy is undefined. The objective of our systematic review was to determine the efficacy of SGB in reducing VA events and mortality among patients with ES. A search of Medline, EMBASE, Scopus, CINAHL and CENTRAL was performed on February 29, 2024 to include studies with adult patients (≥ 18 years) with ES treated with SGB. Our outcomes of interest were VA burden pre- and post-SGB, and in-hospital/30-day mortality. A total of 553 ES episodes in 542 patients from 15 observational studies were included. Treated VAs pre- and post-SGB were pooled from eight studies including 383 patients and demonstrated a decrease from 3.5 (IQR 2.25-7.25) to 0 (IQR 0-0) events (p = 0.008). Complete resolution after SGB occurred in 190 of 294 patients (64.6%). Despite this, in-hospital or 30-day mortality remained high occurring in 140 of 527 patients (random effects prevalence 22%). Repeat SGB for recurrent VAs was performed in 132 of 490 patients (random effects prevalence 21%). In conclusion, observational data suggests SGB may be effective in reducing VAs in ES. Definitive studies for SGB in VA management are needed. Study protocol: PROSPERO - registration number CRD42023430031.

Frequency of and outcomes associated with nonadherence to guideline-based recommendations for an implantable cardioverter-defibrillator in patients with congenital long QT syndrome

BACKGROUND

Guideline-directed device therapy for long QT syndrome (LQTS) has evolved during the years, and indications for an implantable cardioverter-defibrillator (ICD) vary between professional cardiac societies.

OBJECTIVE

We aimed to identify the subset of patients with LQTS who satisfied a class I or class II 2022 European Society of Cardiology guideline-based recommendation for an ICD and to determine the outcomes of those patients who received an ICD compared with those treated without an ICD.

METHODS

Retrospective analysis was conducted of 2861 patients with LQT1, LQT2, or LQT3 to identify patients meeting contemporary recommendations for guideline-directed device therapy. Basic demographics, clinical characteristics, and frequency/type of breakthrough cardiac events (BCEs) were extracted, and outcomes/complications were compared between patients treated with an ICD and those treated without one.

RESULTS

Of the 290 patients (approximately 10%) who met a guideline-based recommendation, 53 (18%) satisfied a class I/level B indication for an ICD; 56 (19%), a class I/level C indication; 19 (7%), a class IIa/level C indication; and 162 (56%), a class IIb/level B indication. However, most patients (156/290 [54%]) did not receive an ICD. Of those who received an ICD, 55 of 134 (41%) experienced ≥1 appropriate ventricular fibrillation-terminating ICD therapy, whereas ICD-related complications occurred in 13 patients (10%). Of those who were treated without an ICD, only 6 of 156 patients (4%) had nonlethal BCEs, which was significantly lower compared with the ICD group (P < .001).

CONCLUSION

With >1200 years of combined follow-up, the experience and evidence from our 2 LQTS specialty centers suggest that many patients who satisfy a recommendation for an ICD based on the latest 2022 European Society of Cardiology guidelines may not need one. This is particularly true when the indication stemmed from a BCE while receiving beta blocker therapy or in asymptomatic patients with an increased 1-2-3-LQTS-Risk score.

Does IV fentanyl, frequently used in emergency departments, change QTC value? A prospective observational study

BACKGROUND

Fentanyl is an opioid analgesic frequently used in the emergency department (ED) and is usually administered without knowing the QTC values of the patients or being monitored. However, the effect of fentanyl on QTC, prolongation or shortening, has not been elucidated. This study aimed to determine the effect of fentanyl on QTC.

METHODS

This is a prospective observational study in the ED of a tertiary hospital on patients who received intravenous fentanyl for procedures other than intubation. ECG was performed before and at 1, 5, 15, 30, and 60 min after the initiation of fentanyl administration, and QTC value was calculated. Primary outcomes were QTC prolongation, defined as an increase in the QTC to ≥ 500 ms or any increase in QTC by ≥ 60 ms.

RESULTS

The study included 109 patients. Of these, 60 patients were male, and the median age was 40. Compared with the baseline QTC value, statistically significant prolongation was detected at the 5th, 15th, 30th, and 60th minutes, with the maximum prolongation at 30 min, and the median was 13.08 ms. Most patients with QTC prolongation were female and over 40 years of age. Clinically, none of these patients developed malignant arrhythmias during the 60-minute monitored observation period.

CONCLUSION

Fentanyl prolonged the QTC value statistically significantly. Although no patient developed malignant arrhythmia clinically, our results suggest that this QTC-prolonging effect should be considered when using fentanyl in patients at risk of torsades.

Historical Perspective of the Cardiac Autonomic Nervous System

The contemporary history of the cardiac autonomic nervous system includes early descriptions of neuroanatomy in the 19th century, followed by an understanding of the physiologic determinants of neurocardiology in the 20th century. Neurology and cardiology preceded the arrival of clinical cardiac electrophysiology, a specialized field in medicine devoted to the diagnosis and treatment of cardiac arrhythmias. The rapid growth in pharmacology, ablation, pacing and defibrillation, associated with significant technological breakthroughs, have resulted in new opportunities for neuromodulation in the 21st century. Small changes in autonomic tone can potentially provide important therapeutic benefits for patients with cardiac and arrhythmia disorders.

Cardiac Neuroanatomy and Fundamentals of Neurocardiology

Cardiac control is mediated via nested-feedback reflex control networks involving the intrinsic cardiac ganglia, intra-thoracic extra-cardiac ganglia, spinal cord, brainstem, and higher centers. This control system is optimized to respond to normal physiologic stressors; however, it can be catastrophically disrupted by pathologic events such as myocardial ischemia. In fact, it is now recognized that cardiac disease progression reflects the dynamic interplay between adverse remodeling of the cardiac substrate coupled with autonomic dysregulation. With advances in understanding of this network dynamic in normal and pathologic states, neuroscience-based neuromodulation therapies can be devised for the management of acute and chronic cardiac pathologies.

Cardiac sympathetic denervation prevents sudden cardiac arrest and improves cardiac function by enhancing mitochondrial-antioxidant capacity

RATIONALE

Sudden cardiac arrest (SCA) and heart failure (HF) are leading causes of death. The underlying mechanisms are incompletely understood, limiting the design of new therapies. Whereas most autonomic modulation therapies have not shown clear benefit in HF patients, growing evidence indicates cardiac sympathetic denervation (CSD) exerts cardioprotective effects. The underlying molecular and cellular mechanisms remain unexplored.

OBJECTIVE

Based on the hypothesis that mitochondrial reactive oxygen species (mROS) drive the pathogenesis of HF and SCA, we investigated whether CSD prevents SCA and HF by improving mitochondrial antioxidant capacity and redox balance, to correct impaired Ca2+ handling and repolarization reserve.

METHODS AND RESULTS

We interrogated CSD-specific responses in pressure-overload HF models with spontaneous SCA using in vivo echocardiographic and electrocardiographic studies and in vitro biochemical and functional studies including ratiometric measures of mROS, Ca2+ and sarcomere dynamics in left ventricular myocytes. Pressure-overloaded HF reduced mitochondrial antioxidant capacity and increased mROS, which impaired β-adrenergic signaling and caused SR Ca2+ leak, reducing SR Ca2+ and increasing diastolic Ca2+, impaired myofilament contraction and further increased the sympathetic stress response. CSD improved contractile function and mitigated mROS-mediated diastolic Ca2+ overload, dispersion of repolarization, triggered activity and SCA by upregulating mitochondrial antioxidant and NADPH-producing enzymes.

CONCLUSIONS

Our findings support a fundamental role of sympathetic stress-induced downregulation of mROS scavenging enzymes and RyR-leak mediated diastolic Ca2+ overload in HF and SCA pathogenesis that are mitigated by CSD. This first report on the molecular and cellular mechanisms of CSD supports its evaluation in additional high-risk patient groups.

Left cardiac sympathetic denervation in children with Jervell Lange-Nielsen syndrome and drug refractory torsades - A case series

INTRODUCTION

Long QT syndrome is an inherited malignant channelopathy which leads to life-threatening arrhythmia, with multiple genotypes. Jervell and Lange-Nielsen syndrome (JLNS) is an autosomal recessive subtype of this disease, characterized by congenital sensorineural deafness and a high incidence of sudden cardiac death (SCD).

METHODOLOGY

We prospectively followed up six children who underwent left cardiac sympathetic denervation (LCSD) for JLNS in view of high-risk features despite being on maximally tolerated doses of oral propranolol.

RESULTS

Mean age at diagnosis was 2.75 ± 0.39 years, with a significant delay between onset of symptoms and diagnosis (mean 7.2 ± 3.5 months). All had sensorineural hearing loss, conforming to the JLNS phenotype. Mean QTc interval was 603 ± 93 ms, with T wave alternans (TWA) seen in all cases. All were started on propranolol and subsequently subjected to LCSD, and 3 underwent AAI permanent pacemaker implantation. Over a mean follow-up of 20 months, there was a significant reduction in QTc (603 ± 93 ms to 501 ± 33 ms, p = .04), which was persistent on follow-up (525 ± 41 ms) and only two out of six had persistent T wave alternans on ECG (p < .01). None of these children had presyncope, syncope, seizures, torsades de pointes, cardiac arrest or death on follow up following LCSD.

CONCLUSION

Jervell Lange-Nielsen syndrome is a subtype of LQTS with high-risk features. LCSD, an effective therapeutic option for those having symptoms despite being on propranolol, results in significant reduction of QTc interval and amelioration of symptoms.

Pharmacological Screening of Kv7.1 and Kv7.1/KCNE1 Activators as Potential Antiarrhythmic Drugs in the Zebrafish Heart

Long QT syndrome (LQTS) can lead to ventricular arrhythmia and sudden cardiac death. The most common congenital cause of LQTS is mutations in the channel subunits generating the cardiac potassium current IKs. Zebrafish (Danio rerio) have been proposed as a powerful system to model human cardiac diseases due to the similar electrical properties of the zebrafish heart and the human heart. We used high-resolution all-optical electrophysiology on ex vivo zebrafish hearts to assess the effects of IKs analogues on the cardiac action potential. We found that chromanol 293B (an IKs inhibitor) prolonged the action potential duration (APD) in the presence of E4031 (an IKr inhibitor applied to drug-induced LQT2), and to a lesser extent, in the absence of E4031. Moreover, we showed that PUFA analogues slightly shortened the APD of the zebrafish heart. However, PUFA analogues failed to reverse the APD prolongation in drug-induced LQT2. However, a more potent IKs activator, ML-277, partially reversed the APD prolongation in drug-induced LQT2 zebrafish hearts. Our results suggest that IKs plays a limited role in ventricular repolarizations in the zebrafish heart under resting conditions, although it plays a more important role when the IKr is compromised, as if the IKs in zebrafish serves as a repolarization reserve as in human hearts. This study shows that potent IKs activators can restore the action potential duration in drug-induced LQT2 in the zebrafish heart.

Bilateral cardiac sympathetic denervation in patients with congenital long QT syndrome

BACKGROUND

Long QT syndrome (LQTS) is a potentially lethal yet treatable genetic heart disease for which left cardiac sympathetic denervation (LCSD) is a class I recommendation. Recent reports have suggested bilateral cardiac sympathetic denervation (BiCSD) as the initial surgical denervation therapy in LQTS.

OBJECTIVE

The purpose of this study was to determine the frequency and settings in which BiCSD was used in a tertiary referral center with expertise in LCSD.

METHODS

We performed a retrospective review of 234 out of 1638 patients with LQTS who underwent sympathetic denervation (14%) at our institution to identify the subset of patients who underwent BiCSD. Cardiac events (CEs) before LCSD, after LCSD, and after the completion of BiCSD were recorded and defined as being an appropriate implantable cardioverter-defibrillator shock, arrhythmic syncope, or sudden cardiac arrest.

RESULTS

Only 11 patients (4.7%; 6 females [55%]) had BiCSD at our institution. Patients who received BiCSD trended toward being younger at diagnosis (6 ± 15 years vs 14 ± 13 years; P = .06) and being more likely to be symptomatic (73% vs 53%; P = .07) than the larger LCSD-only cohort. Continued CEs post-LCSD (3.8 CEs per patient on average) was the predominant determinant to return for BiCSD. Over 60 combined years of follow-up, 4 patients have not had a CE post-BiCSD while the other 7 patients average 3.6 nonlethal CEs.

CONCLUSION

Less than 5% of all patients receiving denervation therapy underwent BiCSD. When BiCSD was chosen, it was almost always done in a staged sequential manner beginning with LCSD first and when driven by the arrhythmogenicity of the LQTS substrate, despite otherwise optimized guideline-directed therapies.

Neuromodulation for the Treatment of Refractory Ventricular Arrhythmias

BACKGROUND

Neuromodulation is increasingly recognized as a therapeutic strategy for patients with refractory ventricular arrhythmias (VAs). Percutaneous stellate ganglion blockade (SGB), transcutaneous magnetic stimulation (TcMS), and surgical cardiac sympathetic denervation (CSD) have all been utilized in this setting.

OBJECTIVES

This study sought to characterize contemporary use and outcomes of these neuromodulation techniques for patients with refractory VA.

METHODS

This retrospective cohort study included all patients at the Hospital of the University of Pennsylvania with antiarrhythmic drug (AAD)-refractory VA from 2019 to 2021 who were treated with SGB, TcMS, or CSD.

RESULTS

A total of 34 patients (age 61 ± 14 years, 15 polymorphic VAs [44%], refractory to 1.8 ± 0.8 AADs) met inclusion criteria. SGB was performed on 11 patients (32%), TcMS on 19 (56%), and CSD on 7 (21%). Neuromodulation was associated with a reduction in the number of episodes of sustained VAs from 7 [IQR: 4-12] episodes in the 24 hours before the initial neuromodulation strategy to 0 [IQR: 0-1] episodes in the subsequent 24 hours (P < 0.001). During 1.2 ± 1.1 years of follow-up, 21 (62%) experienced recurrent VAs, and among those patients, the median time to recurrence was 3 [IQR: 1-25] days. Outcomes were similar among patients with monomorphic and polymorphic VAs. Among patients who had an acute myocardial infarction within 30 days before neuromodulation, the burden of VAs decreased from 11 [IQR: 7-12] episodes to 0 episodes in the 24 hours after treatment.

CONCLUSIONS

Autonomic neuromodulation with SGB, TcMS, or CSD in patients with AAD-refractory VAs is safe and results in substantial acute reduction of VA although recurrent arrhythmias are common, and not all patients experience a reduction in arrhythmia burden.

Blocking nerves and saving lives: Left stellate ganglion block for electrical storms

Patients who present with electrical storms (ES) due to rapid recurrence of ventricular tachycardia/ventricular fibrillation represent major medical emergencies without easy solutions. Antiarrhythmic drugs have limited value, and ES need to be stopped quickly to prevent irreversible patient deterioration and death. Since the mid-1970s, we have provided the rationale for interrupting cardiac sympathetic nerves and evidence of its antifibrillatory action in different clinical settings. Slowly but progressively, from isolated clinical reports to small case series, increasing evidence has indicated that pharmacologic stellate ganglion block (SGB) is highly effective in interrupting ES. However, medical guidelines have largely ignored SGB, and few centers are prepared to perform SGB in actual emergencies. Our own experience shows that a direct anatomic approach that does not require echocardiographic assistance can be performed rapidly, thus saving time in highly critical patients. In this review, we retrace the evolution in our understanding of the mechanism of action of SGB, discuss the current approaches and their limitations, and review the correct indications that overcome still existing biases. Furthermore, we propose a practical solution to increase the availability of SGB to more patients by extending the number of centers where this approach can be rapidly implemented.

Cardiac Sympathetic Denervation for the Management of Ventricular Arrhythmias

BACKGROUND

The autonomic nervous system contributes to the pathogenesis of ventricular arrhythmias (VA). Though anti-arrhythmic drug therapy and catheter ablation are the mainstay of management of VAs, success may be limited in patients with more refractory arrhythmias. Sympathetic modulation is increasingly recognized as a valuable adjunct tool for managing VAs in patients with structural heart disease and inherited arrhythmias.

RESULTS

In this review, we explore the role of the sympathetic nervous system and rationale for cardiac sympathetic denervation (CSD) in VAs and provide a disease-focused review of the utility of CSD for patients both with and without structural heart disease.

CONCLUSIONS

We conclude that CSD is a reasonable therapeutic option for patients with VA, both with and without structural heart disease. Though not curative, many studies have demonstrated a significant reduction in the burden of VAs for the majority of patients undergoing the procedure. However, in patients with unilateral CSD and subsequent VA recurrence, complete bilateral CSD may provide long-lasting reprieve from VA.

Implantable defibrillators in primary prevention of genetic arrhythmias. A shocking choice?

Many previously unexplained life-threatening ventricular arrhythmias and sudden cardiac deaths (SCDs) in young individuals are now recognized to be genetic in nature and are ascribed to a growing number of distinct inherited arrhythmogenic diseases. These include hypertrophic cardiomyopathy, arrhythmogenic cardiomyopathy, long QT syndrome, Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia (VT), and short QT syndrome. Because of their lower frequency compared to coronary disease, risk factors for SCD are not very precise in patients with inherited arrhythmogenic diseases. As randomized studies are generally non-feasible and may even be ethically unjustifiable, especially in the presence of effective therapies, the risk assessment of malignant arrhythmic events such as SCD, cardiac arrest due to ventricular fibrillation (VF), appropriate implantable cardioverter defibrillator (ICD) interventions, or ICD therapy on fast VT/VF to guide ICD implantation is based on observational data and expert consensus. In this document, we review risk factors for SCD and indications for ICD implantation and additional therapies. What emerges is that, allowing for some important differences between cardiomyopathies and channelopathies, there is a growing and disquieting trend to create, and then use, semi-automated systems (risk scores, risk calculators, and, to some extent, even guidelines) which then dictate therapeutic choices. Their common denominator is a tendency to favour ICD implantation, sometime with reason, sometime without it. This contrasts with the time-honoured approach of selecting, among the available therapies, the best option (ICDs included) based on the clinical judgement for the specific patient and after having assessed the protection provided by optimal medical treatment.

Long-term outcome after thoracoscopic cardiac sympathectomy for refractory ventricular tachyarrhythmia storm

A man in his 40s presented with an acute anterior wall myocardial infarction (MI) 6 hours after symptom onset to a non-percutaneous intervention enabled hospital and underwent thrombolysis with tenecteplase. His chest pain resolved post-thrombolysis although ST segment resolution was less than 50%. He had an episode of sustained ventricular tachycardia (VT) 48 hours after MI which was successfully cardioverted with 150 J biphasic shock. A month later he presented with a ventricular tachycardia storm that was refractory to pharmacological management. He underwent radiofrequency ablation of the VT using three-dimensional mapping. Although the patient remained free of VT/ventricular fibrillation (VF) for 48 hours, he had an episode of VF subsequently. A decision for bilateral surgical video assisted thoracoscopic cardiac sympathetic denervation was taken and the patient remained free of ventricular tachyarrhythmias after the procedure until.

Left Cardiac Sympathetic Denervation for Long QT Syndrome: 50 Years' Experience Provides Guidance for Management

OBJECTIVES

This study sought to report our single-center experience with left cardiac sympathetic denervation (LCSD) for long QT syndrome (LQTS) since 1973.

BACKGROUND

LCSD is still underutilized because clinicians are often uncertain whether to use it versus an implantable cardioverter-defibrillator (ICD).

METHODS

We performed LCSD in 125 patients with LQTS (58% women, mean QT interval corrected for frequency [QTc] 527 ± 60 ms, 90% on beta blockers) with a follow-up of 12.9 ± 10.3 years. They were retrospectively divided into 4 groups according to the clinical/genetic status: very high risk (n = 18, symptomatic in the first year of life or with highly malignant genetics), with aborted cardiac arrest (ACA) (n = 31), with syncope and/or ICD shocks on beta blockers (n = 45), in primary prevention (n = 31).

RESULTS

After LCSD, 17% in the very high risk group remained asymptomatic, compared with 52%, 47%, and 97% in the other 3 groups (P < 0.0001), with an overall 86% decrease in the mean yearly cardiac event rate (P < 0.0001). Among 45 patients with only syncope/ICD shocks before LCSD, none had ACA/sudden death as first symptom after LCSD and a 6-month post-LCSD QTc <500 ms predicted excellent outcome. Patients with a QTc ≥500 ms have a 50% chance of shortening it by an average of 60 ms. LCSD results are not affected by common genotypes.

CONCLUSIONS

We provide definitive evidence for the long-term efficacy of LCSD in LQTS. The degree of antiarrhythmic protection is influenced by patient's specificity and amount of QTc shortening. This novel approach to the analysis of the outcome allows cardiologists to rationally decide and tailor their management strategies to the individual features of their patients.

Diagnosis, management and therapeutic strategies for congenital long QT syndrome

Congenital long QT syndrome (LQTS) is characterised by heart rate corrected QT interval prolongation and life-threatening arrhythmias, leading to syncope and sudden death. Variations in genes encoding for cardiac ion channels, accessory ion channel subunits or proteins modulating the function of the ion channel have been identified as disease-causing mutations in up to 75% of all LQTS cases. Based on the underlying genetic defect, LQTS has been subdivided into different subtypes. Growing insights into the genetic background and pathophysiology of LQTS has led to the identification of genotype-phenotype relationships for the most common genetic subtypes, the recognition of genetic and non-genetic modifiers of phenotype, optimisation of risk stratification algorithms and the discovery of gene-specific therapies in LQTS. Nevertheless, despite these great advancements in the LQTS field, large gaps in knowledge still exist. For example, up to 25% of LQTS cases still remain genotype elusive, which hampers proper identification of family members at risk, and it is still largely unknown what determines the large variability in disease severity, where even within one family an identical mutation causes malignant arrhythmias in some carriers, while in other carriers, the disease is clinically silent. In this review, we summarise the current evidence available on the diagnosis, clinical management and therapeutic strategies in LQTS. We also discuss new scientific developments and areas of research, which are expected to increase our understanding of the complex genetic architecture in genotype-negative patients, lead to improved risk stratification in asymptomatic mutation carriers and more targeted (gene-specific and even mutation-specific) therapies.

Bilateral cardiac sympathetic denervation for refractory arrhythmia in an individual with catecholaminergic polymorphic ventricular tachycardia associated with T-cell-mediated ganglionitis

The individual in our case was troubled with difficult to control arrhythmia in the context of RYR2-mutation positive catecholaminergic polymorphic ventricular tachycardia (CPVT) despite medication. Recurrent implantable cardioverter defibrillator (ICD) shocks occurred for ventricular tachycardia (VT) and ventricular fibrillation (VF) as well as inappropriate shocks as a result of rapidly conducted atrial fibrillation (AF). Catheter ablation was effective in controlling these episodes of AF. Despite left cardiac sympathetic denervation, episodes of ventricular arrhythmia and subsequent ICD shocks persisted. Contralateral sympathetic cardiac denervation was subsequently undertaken, with histology suggesting T-cell mediated ganglionitis. 18 months on, there have been no further episodes of ventricular arrhythmia.

Respiratory-cardiovascular interactions

Much of biology is rhythmical and comprises oscillators that can couple. These have optimized energy efficiency and have been preserved during evolution. The respiratory and cardiovascular systems contain numerous oscillators, and importantly, they couple. This coupling is dynamic but essential for an efficient transmission of neural information critical for the precise linking of breathing and oxygen delivery while permitting adaptive responses to changes in state. The respiratory pattern generator and the neural network responsible for sympathetic and cardiovagal (parasympathetic) tone generation interact at many levels ensuring that cardiac output and regional blood flow match oxygen delivery to the lungs and tissues efficiently. The most classic manifestations of these interactions are respiratory sinus arrhythmia and the respiratory modulation of sympathetic nerve activity. These interactions derive from shared somatic and cardiopulmonary afferent inputs, reciprocal interactions between brainstem networks and inputs from supra-pontine regions. Disrupted respiratory-cardiovascular coupling can result in disease, where it may further the pathophysiological sequelae and be a harbinger of poor outcomes. This has been well documented by diminished respiratory sinus arrhythmia and altered respiratory sympathetic coupling in animal models and/or patients with myocardial infarction, heart failure, diabetes mellitus, and neurological disorders as stroke, brain trauma, Parkinson disease, or epilepsy. Future research needs to assess the therapeutic potential for ameliorating respiratory-cardiovascular coupling in disease.

OUP accepted manuscript

Proper management of patients affected by genetic disorders causing life-threatening arrhythmias is important for several reasons, including even societal ones, given the predominantly young age of those affected. Incorrect management often has dire consequences, ranging from unnecessary psychologic damage for the patients whose life becomes too limited by the fear of sudden death to equally avoidable tragedies when the entire armamentarium of effective therapies is not fully utilized. In this review, we focus primarily on long QT syndrome (LQTS) and catecholaminergic polymorphic ventricular tachycardia (CPVT) and deal specifically with the clinical impact of the most commonly used cardiac sympathetic denervation (CSD), namely left cardiac sympathetic denervation (LCSD). The two of us have used LCSD in the management of our patients with either LQTS or CPVT for a very long time and have been involved in ∼500 such interventions. It is on the basis of this personal and direct experience that we wish to share our views with clinical cardiologists and electrophysiologists, adult and paediatric, and with genetic cardiologists. We will begin by reviewing the history and rationale underlying sympathetic denervation therapy and will continue with a disease-specific intensification of therapy, and then with a discussion on how the impressive efficacy of LCSD should translate into guideline-directed therapy in both current and future guidelines, in order to upgrade the quality of care in the era of precision medicine.

Induced Pluripotent Stem Cell-Derived Cardiomyocytes with SCN5A R1623Q Mutation Associated with Severe Long QT Syndrome in Fetuses and Neonates Recapitulates Pathophysiological Phenotypes

The SCN5A R1623Q mutation is one of the most common genetic variants associated with severe congenital long QT syndrome 3 (LQT3) in fetal and neonatal patients. To investigate the properties of the R1623Q mutation, we established an induced pluripotent stem cell (iPSC) cardiomyocyte (CM) model from a patient with LQTS harboring a heterozygous R1623Q mutation. The properties and pharmacological responses of iPSC-CMs were characterized using a multi-electrode array system. The biophysical characteristic analysis revealed that R1623Q increased open probability and persistent currents of sodium channel, indicating a gain-of-function mutation. In the pharmacological study, mexiletine shortened FPDcF in R1623Q-iPSC-CMs, which exhibited prolonged field potential duration corrected by Fridericia's formula (FPDcF, analogous to QTcF). Meanwhile, E4031, a specific inhibitor of human ether-a-go-go-related gene (hERG) channel, significantly increased the frequency of arrhythmia-like early after depolarization (EAD) events. These characteristics partly reflect the patient phenotypes. To further analyze the effect of neonatal isoform, which is predominantly expressed in the fetal period, on the R1623Q mutant properties, we transfected adult form and neonatal isoform SCN5A of control and R1623Q mutant SCN5A genes to 293T cells. Whole-cell automated patch-clamp recordings revealed that R1623Q increased persistent Na+ currents, indicating a gain-of-function mutation. Our findings demonstrate the utility of LQT3-associated R1623Q mutation-harboring iPSC-CMs for assessing pharmacological responses to therapeutic drugs and improving treatment efficacy. Furthermore, developmental switching of neonatal/adult Nav1.5 isoforms may be involved in the pathological mechanisms underlying severe long QT syndrome in fetuses and neonates.

1970-2020: 50 years of research on the long QT syndrome-from almost zero knowledge to precision medicine

To those of us involved in clinical research it seldom happens to begin working on a rather obscure disease, still largely unexplored, and to follow its ripening into a medical entity of large interest to clinicians and basic scientists alike, and moreover to do so for exactly 50 years. This is what has been my privilege in the relentless pursuit of the intriguing disease known as the long QT syndrome (LQTS). This essay begins with the encounter with my first patient affected by LQTS when just a handful of cardiologists had seen similar cases and continues with the series of efforts, some sound some amateurish, which eventually led-together with many brilliant partners and associates-to describe and understand the natural history of the disease and the most effective therapies. It then touches on how our International Registry for LQTS, with its well-documented family trees, constituted the necessary springboard for the major genetic discoveries of the 1990s. From the explosion of genetic data, my own interest focused first on the intriguing genotype-phenotype correlation and then on 'modifier genes', in the attempt of understanding why family members with the same disease-causing mutation could have an opposite clinical history. And from there on to iPS-derived cardiomyocytes, used to unravelling the specific mechanisms of action of modifier genes and to exploring novel therapeutic strategies. This long, and highly rewarding, journey continues because the fascination and the attraction of the unknown are irresistible.

Bilateral thoracoscopic sympathectomy for cardiac denervation in pediatric population: Does Kuntz nerve cauterization have an impact on success?

INTRODUCTION

Cardiac sympathetic denervation (CSD) is an effective procedure for the treatment of inherited channelopathies. Left CSD has traditionally been recommended as neuromodulation to prevent arrhythmia episodes; however, it is thought that bilateral sympathectomy in combination with Kuntz ablation may have additional effects effective due to the anatomical variability of preganglionic sympathetic fibers. The aim of the study was to share our single-center clinical experience with bilateral thoracoscopic sympathectomy for cardiac denervation in different groups of pediatric patients with malignant arrhythmias.

METHODS

Fourteen patients (seven with CPVT, five with LQTS, one with resistant ventricular tachycardia as a sequela of myocarditis, and one with cardiomyopathy and atrial tachycardia) underwent bilateral thoracoscopic sympathectomy for cardiac denervation.

RESULTS

In all patients, arrhythmia episodes persisted despite medical therapy, and patients with implantable cardioverter-defibrillator received appropriate therapies. The rate of appropriate therapies was 3.25 per year (1-5 per year) in the year before sympathectomy. No major complications related to the procedure were observed in any of the patients. The QTc interval of LQTS patients decreased from 506.2 ± 16.9 ms before the procedure to 476 ± 28.8 ms after the procedure. The mean duration of follow-up after the procedure was 23.3 months (11-47 months). Only two patients received single episodes of therapy 12 and 22 months after CSD, and one patient had arrhythmic events due to noncompliance to medical therapy.

CONCLUSION

Due to the anatomical variability of preganglionic fibers bilateral CSD with Kuntz nerve ablation effective treatment and is a safe option.

A case of successful percutaneous ethanol stellate ganglion block on ventricular tachycardia storm

Stellate ganglion block is useful as emergency therapy in patients with ventricular tachycardia storm but is limited due to low availability of experienced teams in the condition of intensive care units. This method used urgently reduced life-threatening ventricular tachycardia when conservative and interventional methods were ineffective. <Learning objective: 1 Percutaneous stellate ganglion block should be considered in patients who suffered from ventricular tachycardia storm. 2 The ultrasound-guided technique is safer and more effective than other techniques. 3 Using ethanol as injection volume had a stronger beneficial effect than lidocaine.>.

Video-thoracoscopic left cardiac sympathetic denervation for long-QT syndrome

BACKGROUND

Congenital long-QT syndrome represents the most common cardiac channelopathy and manifests as potentially lethal ventricular arrhythmias. Prevention strategies include beta-blockade pharmacotherapy, implantable cardioverter-defibrillators, and left cardiac sympathetic denervation, which can increase the threshold for ventricular fibrillation. Herein, we report our experience with video-assisted thoracoscopic left cardiac sympathetic denervation.

METHODS

We performed a retrospective review of the electronic medical records of all patients with congenital long-QT syndrome who underwent video-assisted thoracoscopic left cardiac sympathetic denervation at our institution.

RESULTS

From September 2009 to May 2016, 6 patients with a mean age of 30.5 years (range 20-47 years) underwent video-assisted thoracoscopic left cardiac sympathetic denervation for medically refractory long-QT syndrome. All patients had an uneventful recovery and were discharged 1-3 days after the operation. At a median follow-up of 14 months (range 12-60 months), 4 patients had no cardiac events while 2 experienced 1 episode of arrhythmic syncope and 1 episode of appropriate implantable cardioverter-defibrillator shock. Following surgery, the mean annual cardiac events in the study cohort decreased from 2.13 to 0.33 (p = 0.004) and the mean corrected QT interval reduced from 560 ms to 491 ms (p = 0.006).

CONCLUSIONS

Video-assisted thoracoscopic left cardiac sympathetic denervation is a safe and effective therapy in patients with congenital long-QT syndrome who continue to suffer from recurrent life-threatening arrhythmias or frequent implantable cardioverter-defibrillator discharges despite maximum tolerated doses of beta blockers.

Resuscitating Resuscitation: Advanced Therapies for Resistant Ventricular Dysrhythmias

BACKGROUND

More than 640,000 combined in-hospital and out-of-hospital cardiac arrests occur annually in the United States. However, survival rates and meaningful neurologic recovery remain poor. Although "shockable" rhythms (i.e., ventricular fibrillation (VF) and pulseless ventricular tachycardia (VT)) have the best outcomes, many of these ventricular dysrhythmias fail to return to a perfusing rhythm (resistant VF/VT), or recur shortly after they are resolved (recurrent VF/VT).

OBJECTIVE

This review discusses 4 emerging therapies in the emergency department for treating these resistant or recurrent ventricular dysrhythmias: beta-blocker therapy, dual simultaneous external defibrillation, stellate ganglion blockade, and extracorporeal cardiopulmonary resuscitation. We discuss the underlying physiology of each therapy, review relevant literature, describe when these approaches should be considered, and provide evidence-based recommendations for these techniques.

DISCUSSION

Esmolol may mitigate some of epinephrine's negative effects when used during resuscitation, improving both postresuscitation cardiac function and long-term survival. Dual simultaneous external defibrillation targets the region of the heart where ventricular fibrillation typically resumes and may apply a more efficient defibrillation across the heart, leading to higher rates of successful defibrillation. Stellate ganglion blocks, recently described in the emergency medicine literature, have been used to treat patients with recurrent VF/VT, resulting in significant dysrhythmia suppression. Finally, extracorporeal cardiopulmonary resuscitation is used to provide cardiopulmonary support while clinicians correct reversible causes of arrest, potentially resulting in improved survival and good neurologic functional outcomes.

CONCLUSION

These emerging therapies do not represent standard practice; however, they may be considered in the appropriate clinical scenario when standard therapies are exhausted without success.

Insights into Cardiac IKs (KCNQ1/KCNE1) Channels Regulation

The delayed rectifier potassium IKs channel is an important regulator of the duration of the ventricular action potential. Hundreds of mutations in the genes (KCNQ1 and KCNE1) encoding the IKs channel cause long QT syndrome (LQTS). LQTS is a heart disorder that can lead to severe cardiac arrhythmias and sudden cardiac death. A better understanding of the IKs channel (here called the KCNQ1/KCNE1 channel) properties and activities is of great importance to find the causes of LQTS and thus potentially treat LQTS. The KCNQ1/KCNE1 channel belongs to the superfamily of voltage-gated potassium channels. The KCNQ1/KCNE1 channel consists of both the pore-forming subunit KCNQ1 and the modulatory subunit KCNE1. KCNE1 regulates the function of the KCNQ1 channel in several ways. This review aims to describe the current structural and functional knowledge about the cardiac KCNQ1/KCNE1 channel. In addition, we focus on the modulation of the KCNQ1/KCNE1 channel and its potential as a target therapeutic of LQTS.

2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias

Ventricular arrhythmias are an important cause of morbidity and mortality and come in a variety of forms, from single premature ventricular complexes to sustained ventricular tachycardia and fibrillation. Rapid developments have taken place over the past decade in our understanding of these arrhythmias and in our ability to diagnose and treat them. The field of catheter ablation has progressed with the development of new methods and tools, and with the publication of large clinical trials. Therefore, global cardiac electrophysiology professional societies undertook to outline recommendations and best practices for these procedures in a document that will update and replace the 2009 EHRA/HRS Expert Consensus on Catheter Ablation of Ventricular Arrhythmias. An expert writing group, after reviewing and discussing the literature, including a systematic review and meta-analysis published in conjunction with this document, and drawing on their own experience, drafted and voted on recommendations and summarized current knowledge and practice in the field. Each recommendation is presented in knowledge byte format and is accompanied by supportive text and references. Further sections provide a practical synopsis of the various techniques and of the specific ventricular arrhythmia sites and substrates encountered in the electrophysiology lab. The purpose of this document is to help electrophysiologists around the world to appropriately select patients for catheter ablation, to perform procedures in a safe and efficacious manner, and to provide follow-up and adjunctive care in order to obtain the best possible outcomes for patients with ventricular arrhythmias.

Outcome of a Modified Sympathicotomy for Cardiac Neuromodulation of Untreatable Ventricular Tachycardia

OBJECTIVES

This study aimed to describe the preliminary results of a modified sympathicotomy for cardiac sympathetic denervation (CSD), which may reduce the predictive risk and intraoperative surgical time of the procedure.

BACKGROUND

CSD, in patients with refractory ventricular tachycardia (VT), is comprehensively recognized as an important treatment option for patients with structural heart disease as well as congenital inherited arrhythmia syndrome.

METHODS

We consecutively enrolled 5 patients with refractory VT. Baseline demographic, medical, and surgical data as well as arrhythmia outcomes and procedural complications were evaluated.

RESULTS

A total of 5 patients (mean age: 67.4 years) were enrolled for the treatment of refractory VT with a modified CSD technique. In 3 of 5 patients, an overall reduction in VT burden (ranging from 75% to 100%) and VT number was observed after the CSD despite an in-hospital early recurrence.

CONCLUSIONS

A modified CSD (sympathicotomy T2-T5) with stellate ganglion sparing and the use of unipolar radiofrequency is feasible, effective, and safe in the setting of untreatable VT.

2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias

Ventricular arrhythmias are an important cause of morbidity and mortality and come in a variety of forms, from single premature ventricular complexes to sustained ventricular tachycardia and fibrillation. Rapid developments have taken place over the past decade in our understanding of these arrhythmias and in our ability to diagnose and treat them. The field of catheter ablation has progressed with the development of new methods and tools, and with the publication of large clinical trials. Therefore, global cardiac electrophysiology professional societies undertook to outline recommendations and best practices for these procedures in a document that will update and replace the 2009 EHRA/HRS Expert Consensus on Catheter Ablation of Ventricular Arrhythmias. An expert writing group, after reviewing and discussing the literature, including a systematic review and meta-analysis published in conjunction with this document, and drawing on their own experience, drafted and voted on recommendations and summarized current knowledge and practice in the field. Each recommendation is presented in knowledge byte format and is accompanied by supportive text and references. Further sections provide a practical synopsis of the various techniques and of the specific ventricular arrhythmia sites and substrates encountered in the electrophysiology lab. The purpose of this document is to help electrophysiologists around the world to appropriately select patients for catheter ablation, to perform procedures in a safe and efficacious manner, and to provide follow-up and adjunctive care in order to obtain the best possible outcomes for patients with ventricular arrhythmias.

Autonomic and Cardiac Repolarization Lability in Long QT Syndrome Patients

OBJECTIVE

Long QT-Syndrome (LQTS) patients are at risk of arrhythmias and seizures. We investigated whether autonomic and cardiac repolarization measures differed based on LQTS genotypes, and in LQTS patients with vs. without arrhythmias and seizures.

METHODS

We used 24-h ECGs from LQTS1 (n = 87), LQTS2 (n = 50), and LQTS genotype negative patients (LQTS^(-), n = 16). Patients were stratified by LQTS genotype, and arrhythmias/seizures. Heart rate variability (HRV) and QT variability index (QTVI) measures were compared between groups during specific physiological states (minimum, middle, & maximum sympathovagal balance, LF/HF). Results were further tested using logistic regression for each ECG measure, and all HRV measures in a single multivariate model.

RESULTS

Across multiple physiological states, total autonomic (SDNN) and vagal (RMSSD, pNN50) function were lower and repolarization dynamics (QTVI) were elevated in LQTS⁽⁺⁾, LQTS1, and LQTS2, compared to LQTS^(-). Many measures remained significant in the regression models. Multivariate modeling demonstrated that SDNN, RMSSD, and pNN50 were independent markers of LQTS⁽⁺⁾ vs. LQTS^(-), and SDNN and pNN50 were markers for LQTS1 vs. LQTS^(-). During sympathovagal balance (middle LF/HF), RMSSD and pNN50 distinguished LQTS1 vs. LQTS2. LQTS1 patients with arrhythmias had lower total (SDNN) and vagal (RMSSD and pNN50) autonomic function, and SDNN remained significant in the models. In contrast, ECG measures did not differ in LQTS2 patients with vs. without arrhythmias, and LQTS1 and LQTS2 with vs. without seizures.

CONCLUSION

Autonomic (HRV) and cardiac repolarization (QTVI) ECG measures differ based on LQTS genotype and history of arrhythmias in LQTS1. SDNN, RMSSD, and pNN50 were each independent markers for LQTS genotype.

Inherited cardiac arrhythmias

The main inherited cardiac arrhythmias are long QT syndrome, short QT syndrome, catecholaminergic polymorphic ventricular tachycardia and Brugada syndrome. These rare diseases are often the underlying cause of sudden cardiac death in young individuals and result from mutations in several genes encoding ion channels or proteins involved in their regulation. The genetic defects lead to alterations in the ionic currents that determine the morphology and duration of the cardiac action potential, and individuals with these disorders often present with syncope or a life-threatening arrhythmic episode. The diagnosis is based on clinical presentation and history, the characteristics of the electrocardiographic recording at rest and during exercise and genetic analyses. Management relies on pharmacological therapy, mostly β-adrenergic receptor blockers (specifically, propranolol and nadolol) and sodium and transient outward current blockers (such as quinidine), or surgical interventions, including left cardiac sympathetic denervation and implantation of a cardioverter-defibrillator. All these arrhythmias are potentially life-threatening and have substantial negative effects on the quality of life of patients. Future research should focus on the identification of genes associated with the diseases and other risk factors, improved risk stratification and, in particular for Brugada syndrome, effective therapies.

Ablation of Neuroaxial in Patients with Ventricular Tachycardia

Ventricular tachycardia (VT) remains a common cause of sudden cardiac death. It is widely accepted that VTs are strongly associated with autonomic imbalance with reduced vagal and increased sympathetic activities. Pharmacologic therapy remains the first-line therapy, but antiarrhythmic agents may not be effective or carry significant side effects. Sympathetic denervation is an emerging therapy to prevent or treat VTs by rebalancing the sympathetic and parasympathetic activity. This article focuses on the role of sympathetic activation in VT, and the mapping and ablation of sympathetic nervous system in patients with VT.

The Brain-Heart Connection in Sympathetically Triggered Inherited Arrhythmia Syndromes

Sympathetically triggered inherited arrhythmia syndromes, including the long QT syndrome (LQTS) and catecholaminergic polymorphic ventricular tachycardia (CPVT), can cause sudden cardiac death in young individuals with structurally normal hearts. With cardiac events typically triggered by physical or emotional stress, not surprisingly, two of the most common treatments are neuromodulators, including mainstay beta blocker pharmacotherapy, and surgical sympathetic cardiac denervation. This review updates the clinician on the relevant anatomy and physiology of the cardiac autonomic nervous system, outlines neurocardiac arrhythmia mechanisms, and discusses the latest rationale for a neurocardiac therapeutic approach to manage sympathetic-induced arrhythmia in patients with inherited cardiac disease.

Stellate ganglion block and cardiac sympathetic denervation in patients with inappropriate sinus tachycardia

Background

Inappropriate sinus tachycardia (IST) remains a clinical challenge because patients often are highly symptomatic and not responsive to medical therapy.

Objective

To study the safety and efficacy of stellate ganglion (SG) block and cardiac sympathetic denervation (CSD) in patients with IST.

Methods

Twelve consecutive patients who had drug‐refractory IST (10 women) were studied. According to a prospectively initiated protocol, five patients underwent an electrophysiologic study before and after SG block (electrophysiology study group). The subsequent seven patients had ambulatory Holter monitoring before and after SG block (ambulatory group). All patients underwent SG block on the right side first, and then on the left side. Selected patients who had heart rate reduction ≥15 beats per minute (bpm) were recommended to consider CSD.

Results

The mean (SD) baseline heart rate (HR) was 106 (21) bpm. The HR significantly decreased to 93 (20) bpm (P = .02) at 10 minutes after right SG block and remained significantly slower at 97(19) bpm at 60 minutes. Left SG block reduced HR from 99 (21) to 87(16) bpm (P = .02) at 60 minutes. SG block had no significant effect on blood pressure or HR response to isoproterenol or exercise (all P > .05). Five patients underwent right (n = 4) or bilateral (n = 1) CSD. The clinical outcomes were heterogeneous: one patient had complete and two had partial symptomatic relief, and two did not have improvement.

Conclusion

SG blockade modestly reduces resting HR but has no significant effect on HR during exercise. Permanent CSD may have a modest role in alleviating symptoms in selected patients with IST.

Neuromodulation for Ventricular Tachycardia and Atrial Fibrillation: A Clinical Scenario-Based Review

Autonomic dysregulation in cardiovascular disease plays a major role in the pathogenesis of arrhythmias. Cardiac neural control relies on complex feedback loops consisting of efferent and afferent limbs, which carry sympathetic and parasympathetic signals from the brain to the heart and sensory signals from the heart to the brain. Cardiac disease leads to neural remodeling and sympathovagal imbalances with arrhythmogenic effects. Preclinical studies of modulation at central and peripheral levels of the cardiac autonomic nervous system have yielded promising results, leading to early stage clinical studies of these techniques in atrial fibrillation and refractory ventricular arrhythmias, particularly in patients with inherited primary arrhythmia syndromes and structural heart disease. However, significant knowledge gaps in basic cardiac neurophysiology limit the success of these neuromodulatory therapies. This review discusses the recent advances in neuromodulation for cardiac arrhythmia management, with a clinical scenario-based approach aimed at bringing neurocardiology closer to the realm of the clinical electrophysiologist.