Premature Ventricular Contraction Coupling Interval Variability Destabilizes Cardiac Neuronal and Electrophysiological Control: Insights From Simultaneous Cardioneural Mapping

Antiarrhythmic Mechanisms of Epidural Blockade After Myocardial Infarction

BACKGROUND

Thoracic epidural anesthesia (TEA) has been shown to reduce the burden of ventricular tachycardia in small case series of patients with refractory ventricular tachyarrhythmias and cardiomyopathy. However, its electrophysiological and autonomic effects in diseased hearts remain unclear, and its use after myocardial infarction is limited by concerns for potential right ventricular dysfunction.

METHODS

Myocardial infarction was created in Yorkshire pigs (N=22) by left anterior descending coronary artery occlusion. Approximately, six weeks after myocardial infarction, an epidural catheter was placed at the C7-T1 vertebral level for injection of 2% lidocaine. Right and left ventricular hemodynamics were recorded using Millar pressure-conductance catheters, and ventricular activation recovery intervals (ARIs), a surrogate of action potential durations, by a 56-electrode sock and 64-electrode basket catheter. Hemodynamics and ARIs, baroreflex sensitivity and intrinsic cardiac neural activity, and ventricular effective refractory periods and slope of restitution (Smax) were assessed before and after TEA. Ventricular tachyarrhythmia inducibility was assessed by programmed electrical stimulation.

RESULTS

TEA reduced inducibility of ventricular tachyarrhythmias by 70%. TEA did not affect right ventricular-systolic pressure or contractility, although left ventricular-systolic pressure and contractility decreased modestly. Global and regional ventricular ARIs increased, including in scar and border zone regions post-TEA. TEA reduced ARI dispersion specifically in border zone regions. Ventricular effective refractory periods prolonged significantly at critical sites of arrhythmogenesis, and Smax was reduced. Interestingly, TEA significantly improved cardiac vagal function, as measured by both baroreflex sensitivity and intrinsic cardiac neural activity.

CONCLUSIONS

TEA does not compromise right ventricular function in infarcted hearts. Its antiarrhythmic mechanisms are mediated by increases in ventricular effective refractory period and ARIs, decreases in Smax, and reductions in border zone electrophysiological heterogeneities. TEA improves parasympathetic function, which may independently underlie some of its observed antiarrhythmic mechanisms. This study provides novel insights into the antiarrhythmic mechanisms of TEA while highlighting its applicability to the clinical setting.

Functional-Molecular Mechanisms of Sympathetic-Parasympathetic Dysfunction in PVC-Induced Cardiomyopathy Revealed by Dual Stressor PVC-Exercise Challenge

BACKGROUND

The significance of autonomic dysfunction in premature ventricular contraction-induced cardiomyopathy (PVC-CM) remain unknown.

OBJECTIVE

Utilizing a novel "dual stressor" provocative challenge combining exercise with premature ventricular contraction (PVCs), the authors characterized the functional and molecular mechanisms of cardiac autonomic (cardiac autonomic nervous system) remodeling in a PVC-CM animal model.

METHODS

In 15 canines (8 experimental, 7 sham), we implanted pacemakers and neurotelemetry devices and subjected animals to 12 weeks of bigeminal PVCs to induce PVC-CM. Sympathetic nerve activity (SNA), vagal nerve activity (VNA), and heart rate were continuously recorded before, during, and after treadmill exercise challenge with and without PVCs, at baseline and after development of PVC-CM. Western blot and enzyme-linked immunosorbent assay were used to evaluate molecular markers of neural remodeling.

RESULTS

Exercise triggered an increase in both SNA and VNA followed by late VNA withdrawal. With PVCs, the degree of exercise-induced SNA augmentation was magnified, whereas late VNA withdrawal became blunted. After PVC-CM development, SNA was increased at rest but failed to adequately augment during exercise, especially with PVCs, coupled with impaired VNA and heart rate recovery after exercise. In the remodeled cardiac autonomic nervous system, there was widespread sympathetic hyperinnervation and elevated transcardiac norepinephrine levels but unchanged parasympathetic innervation, indicating sympathetic overload. However, cardiac nerve growth factor was paradoxically downregulated, suggesting an antineurotrophic counteradaptive response to PVC-triggered sympathetic overload.

CONCLUSIONS

Sympathetic overload, sympathetic dysfunction, and parasympathetic dysfunction in PVC-CM are unmasked by combined exercise and PVC challenge. Reduced cardiac neurotrophic factor might underlie the mechanisms of this dysfunction. Neuromodulation therapies to restore autonomic function could constitute a novel therapeutic approach for PVC-CM.

Arrhythmia-Induced Cardiomyopathy: JACC State-of-the-Art Review

Arrhythmias frequently accompany heart failure and left ventricular dysfunction. Tachycardias, atrial fibrillation, and premature ventricular contractions can induce a reversible form of dilated cardiomyopathy (CM) known as arrhythmia-induced CM (AiCM). The intriguing question is why certain individuals are more susceptible to AiCM, despite similar arrhythmia burdens. The primary challenge is determining the extent of arrhythmias' contribution to left ventricular systolic dysfunction. AiCM should be considered in patients with a mean heart rate of >100 beats/min, atrial fibrillation, or a PVC burden of >10%. Confirmation of AiCM occurs when CM reverses upon eliminating the responsible arrhythmia. Therapy choice depends on the specific arrhythmia, patient comorbidities, and preferences. After left ventricular function is restored, ongoing follow-up is essential if an abnormal myocardial substrate persists. Accurate diagnosis and treatment of AiCM have the potential to enhance patients' quality of life, improve clinical outcomes, and reduce hospital admissions and overall health care costs.

Number of Premature Ventricular Complexes Predicts Long-Term Outcomes in Patients with Persistent Atrial Fibrillation

BACKGROUND

Premature ventricular complexes (PVCs) are common electrocardiographic abnormalities and may be a prognosticator in predicting mortality in patients with structurally normal hearts or chronic heart diseases. Whether PVC burden was associated with mortality in patients with chronic atrial fibrillation (AF) remained unknown. We investigated the prognostic value of PVC burden in patients with persistent AF.

METHODS

A retrospective analysis of 24 h Holter recordings of 1767 patients with persistent AF was conducted. Clinical characteristics, 24 h average heart rate (HR), and PVC measures, including 24 h PVC burden and the presence of consecutive PVCs (including any PVC couplet, triplet, or non-sustained ventricular tachycardia) were examined for the prediction of all-cause and cardiovascular mortality using the Cox proportional hazards model.

RESULTS

After a median follow-up time of 30 months, 286 (16%) patients died and 1481 (84%) patients survived. Multivariate analysis revealed that age, heart failure, stroke, angiotensin-converting enzyme inhibitor/angiotensin receptor blocker, beta-blocker, digoxin, oral anticoagulant use, and estimated glomerular filtration rate were significant baseline predictors of all-cause mortality and cardiovascular mortality. Twenty-four-hour PVC burden and the presence of consecutive PVCs were significantly associated with all-cause and cardiovascular mortality after adjusting for significant clinical factors. When compared to the first quartile of PVC burden (<0.003%/day), the highest quartile (>0.3%/day) was significantly associated with an increased risk of all-cause mortality (hazard ratio, 2.46; 95% CI, 1.77-3.42) and cardiovascular mortality (hazard ratio: 2.67; 95% CI, 1.76-4.06).

CONCLUSIONS

Twenty-four-hour PVC burden is independently associated with all-cause and cardiovascular mortality in patients with persistent AF.

Propensity-score matched comparison of renal and neurohormonal effects of catheter ablation for frequent premature ventricular contractions in patients with and without systolic dysfunction

Background

Catheter ablation (CA) for premature ventricular contractions (PVCs) restores cardiac and renal functions in patients with reduced left ventricular ejection fraction (LVEF); however, its effects on preserved EF remain unelucidated.

Methods

The study cohort comprised 246 patients with a PVC burden of >10% on Holter electrocardiography. Using propensity matching, we compared the changes in B-type natriuretic peptide (BNP) levels and estimated glomerular filtration rate (eGFR) in patients who underwent CA or did not.

Results

Postoperative BNP levels were decreased significantly in the CA group, regardless of the degree of LVEF, whereas there was no change in those of the non-CA group. Among patients who underwent CA, BNP levels decreased from 44.1 to 33.0 pg/mL in those with LVEF ≥50% (p = .002) and from 141.0 to 87.9 pg/mL in those with LVEF <50% (p < .001). Regarding eGFR, postoperative eGFR was significantly improved in the CA group of patients with LVEF ≥50% (from 71.4 to 74.7 mL/min/1.73 m2, p = .006), whereas it decreased in the non-CA group. A similar trend was observed in the group with a reduced LVEF. Adjusted for propensity score matching, there was a significant decrease in the BNP level and recovery of eGFR after CA in patients with LVEF >50%.

Conclusions

This study showed that CA for frequent PVCs decreases BNP levels and increases eGFR even in patients with preserved LVEF.

Thoracic epidural blockade after myocardial infarction benefits from anti-arrhythmic pathways mediated in part by parasympathetic modulation

Background

Thoracic epidural anesthesia (TEA) has been shown to reduce the burden of ventricular tachyarrhythmias (VT) in small case-series of patients with refractory VT and cardiomyopathy. However, its electrophysiological and autonomic effects in diseased hearts remain unclear and its use after myocardial infarction (MI) is limited by concerns for potential RV dysfunction.

Methods

MI was created in Yorkshire pigs ( N =22) by LAD occlusion. Six weeks post-MI, an epidural catheter was placed at the C7-T1 vertebral level for injection of 2% lidocaine. RV and LV hemodynamics were recorded using Millar pressure-conductance catheters, and ventricular activation-recovery intervals (ARIs), a surrogate of action potential durations, by a 56-electrode sock and 64-electrode basket catheter. Hemodynamics and ARIs, baroreflex sensitivity (BRS) and intrinsic cardiac neural activity, and ventricular effective refractory periods (ERP) and slope of restitution (S max ) were assessed before and after TEA. VT/VF inducibility was assessed by programmed electrical stimulation.

Results

TEA reduced inducibility of VT/VF by 70%. TEA did not affect RV-systolic pressure or contractility, although LV-systolic pressure and contractility decreased modestly. Global and regional ventricular ARIs increased, including in scar and border zone regions post-TEA. TEA reduced ARI dispersion specifically in border zone regions. Ventricular ERPs prolonged significantly at critical sites of arrhythmogenesis, and S max was reduced. Interestingly, TEA significantly improved cardiac vagal function, as measured by both BRS and intrinsic cardiac neural activity.

Conclusion

TEA does not compromise RV function in infarcted hearts. Its anti-arrhythmic mechanisms are mediated by increases in ventricular ERP and ARIs, decreases in S max , and reductions in border zone heterogeneity. TEA improves parasympathetic function, which may independently underlie some of its observed anti-arrhythmic mechanisms. This study provides novel insights into the anti-arrhythmic mechanisms of TEA, while highlighting its applicability to the clinical setting.

Abstract Illustration

Myocardial infarction is known to cause cardiac autonomic dysfunction characterized by sympathoexcitation coupled with reduced vagal tone. This pathological remodeling collectively predisposes to ventricular arrhythmia. Thoracic epidural anesthesia not only blocks central efferent sympathetic outflow, but by also blocking ascending projections of sympathetic afferents, relieving central inhibition of vagal function. These complementary autonomic effects of thoracic epidural anesthesia may thus restore autonomic balance, thereby improving ventricular electrical stability and suppressing arrhythmogenesis. DRG=dorsal root ganglion, SG=stellate ganglion.

The inverse problem for cardiac arrhythmias

A cardiac arrhythmia is an abnormality in the rate or rhythm of the heart beat. We study a type of arrhythmia called a premature ventricular complex (PVC), which is typically benign, but in rare cases can lead to more serious arrhythmias or heart failure. There are three known mechanisms for PVCs: reentry, an ectopic focus, and triggered activity. We develop minimal models for each mechanism and attempt the inverse problem of determining which model (and therefore which mechanism) best describes the beat dynamics observed in an ambulatory electrocardiogram. We demonstrate our approach on a patient who exhibits frequent PVCs and find that their PVC dynamics are best described by a model of triggered activity. Better identification of the PVC mechanism from wearable device data could improve risk stratification for the development of more serious arrhythmias.

Diversity of cells and signals in the cardiovascular system

This white paper is the outcome of the seventh UC Davis Cardiovascular Research Symposium on Systems Approach to Understanding Cardiovascular Disease and Arrhythmia. This biannual meeting aims to bring together leading experts in subfields of cardiovascular biomedicine to focus on topics of importance to the field. The theme of the 2022 Symposium was 'Cell Diversity in the Cardiovascular System, cell-autonomous and cell-cell signalling'. Experts in the field contributed their experimental and mathematical modelling perspectives and discussed emerging questions, controversies, and challenges in examining cell and signal diversity, co-ordination and interrelationships involved in cardiovascular function. This paper originates from the topics of formal presentations and informal discussions from the Symposium, which aimed to develop a holistic view of how the multiple cell types in the cardiovascular system integrate to influence cardiovascular function, disease progression and therapeutic strategies. The first section describes the major cell types (e.g. cardiomyocytes, vascular smooth muscle and endothelial cells, fibroblasts, neurons, immune cells, etc.) and the signals involved in cardiovascular function. The second section emphasizes the complexity at the subcellular, cellular and system levels in the context of cardiovascular development, ageing and disease. Finally, the third section surveys the technological innovations that allow the interrogation of this diversity and advancing our understanding of the integrated cardiovascular function and dysfunction.

Temporal and Spatial Changes of Proarrhythmic Substrate in Premature Ventricular Contraction-Induced Cardiomyopathy

BACKGROUND

The changes in proarrhythmic substrates and malignant ventricular arrhythmia mechanisms caused by premature ventricular contraction-induced cardiomyopathy (PVCCM) remain unclear.

OBJECTIVES

The goal of this study was to establish the electrophysiological mechanism of how high-load PVC causes malignant arrhythmia.

METHODS

Thirteen swine were exposed to 50% paced PVC from the right ventricular apex for 12 weeks (PVCCM, n = 6) and no pacing for 12 weeks (control, n = 7). Cardiac function was quantified biweekly with echocardiography. Computed tomography scans and electrophysiological examinations were performed monthly to dynamically evaluate the changes in the cardiac structure and the arrhythmogenic substrate.

RESULTS

The decreases in the cardiac function and ventricular enlargement in the PVCCM group were significant after 12 weeks of PVC stimulation compared with the control group (P < 0.001). Electrophysiological examination found that the ventricular effective refractory period dispersion (0.071 ± 0.008), area of the low-voltage zone (9.41 ± 1.55 cm2), and malignant ventricular arrhythmia inducibility (33.3%) of the PVCCM group increased significantly at week 8 after pacing (P < 0.001 vs the control group); these changes slowed down after 8 weeks. Moreover, the distribution of the low-voltage zone presented obvious spatial heterogeneity, especially in the anterior wall of the right ventricle, accompanied by delayed activation in the sinus rhythm (67 ± 13 milliseconds). Consistently, the proportion of ventricular fibrosis- and expression-related proteins were significantly increased in the PVCCM group (P < 0.001), especially in the right ventricle. Moreover, proteomic analysis confirmed the spatial profile of these fibrotic changes in the PVCCM group.

CONCLUSIONS

High-burden PVC can cause significant temporal and spatial heterogeneity changes in proarrhythmic substrates, which are potentially related to the upregulation of calcium signaling caused by asynchronous activation.

Clinical predictors and implications of cardiac inflammation detected on positron emission tomography (PET) in patients referred for premature ventricular complex (PVC) ablation

BACKGROUND

Positron emission tomography computed tomography (PET-CT) is not routinely used for premature ventricular complexes (PVCs). Whether specific clinical factors are associated with abnormal PET-CT results is not clear.

METHODS

The treatment courses and baseline characteristics of consecutive patients in a single center between 2012 and 2021, age > 18 years old, and who received ¹⁸F-fluorodeoxyglucose (FDG) PET-CT imaging for evaluation of PVCs were retrospectively analyzed.

RESULTS

A total of 102 patients was included. Of these, 27 patients (26.4%) had abnormal PET-CT and 61 (59.8%) had normal imaging. Abnormal PET-CT findings were associated with non-sustained ventricular tachycardia (NSVT) (95.2% vs. 52.6%, p = 0.001), higher number of PVC morphologies (2.29 ± 0.7 vs. 1.31 ± 0.6, p < 0.001), greater PVC coupling interval dispersion (72.47 ± 66.4 ms vs. 13.42 ± 17.9 ms, p < 0.001), and greater likelihood of fast heart rate dependent PVCs (78.5% vs. 38.2%, p = 0.017). Fourteen (51.8%) patients had an abnormal PET-CT and abnormal late gadolinium enhancement (LGE). Patients with abnormal PET-CT were more frequently treated with immunosuppression (81.4% vs. 3.2%, p < .0001) than with catheter ablation (11.1% vs. 45.9%, p = 0.002) compared to the normal PET-CT group. Over a median follow-up of 862 days (IQR 134, 1407), PVC burden decreased in both groups [from 23 ± 16% to 9 ± 10% (p < 0.001) in abnormal PET-CT group and from 21 ± 15% to 7 ± 10% (p < 0.001) in normal PET-CT group].

CONCLUSIONS

Abnormal PET-CT findings were more commonly associated with NSVT, multiform PVCs, greater PVC coupling interval dispersion, and fast heart rate dependent PVCs. LGE was not sensitive for detecting inflammation. Immunosuppression was effective in managing PVCs with abnormal PET-CT.

Mechanisms, time course and predictability of premature ventricular contractions cardiomyopathy-an update on its development and resolution

Frequent premature ventricular contractions (PVCs) associated left ventricular systolic dysfunction (LVSD) is a well-known clinical scenario and numerous predictors for cardiomyopathy (CMP) development have been already thoroughly described. It may present as a "pure" form of dissynchrony-induced cardiomyopathy or it may be an aggravating component of a multifactorial structural heart disease. However, the precise risk to develop PVC-induced CMP (which would allow for tailored-patient monitoring and/or early treatment) and the degree of CMP reversibility after PVC suppression/elimination (which may permit appropriate candidate selection for therapy) are unclear. Moreover, there is limited data regarding the time course of CMP development and resolution after arrhythmia suppression. Even less known are the other components of PVC-induced CMP, such as right ventricular (RV) and atrial myopathies. This review targets to synthetize the most recent information in this regard and bring a deeper understanding of this heart failure scenario. The mechanisms, time course (both in experimental models and clinical experiences) and predictors of reverse-remodelling after arrhythmia suppression are described. The novel experience hereby presented may aid everyday clinical practice, promoting a new paradigm involving more complex, multi-level and multi-modality evaluation and possible earlier intervention at least in some patient subsets.

Premature Ventricular Contractions Are Presaged by a Mechanically Abnormal Sinus Beat

BACKGROUND

Frequent premature ventricular contractions (PVCs) can lead to cardiomyopathy; it is unclear if there are abnormal myocardial mechanics operative in the PVC and non-PVC beats.

OBJECTIVES

The aim of this study was to investigate regional and global myocardial mechanics, including dyssynchrony, in patients with frequent PVCs.

METHODS

Fifty-six consecutive patients referred for PVC ablation were prospectively studied. During sinus rhythm (SR) and PVC beats, left ventricular (LV) global longitudinal strain (GLS), LV dyssynchrony (measured as the SD of time to peak GLS), and dyssynergy (measured as maximum regional strain minus minimum regional strain at aortic valve closure) were quantified using 2-dimensional strain echocardiography. GLS, dyssynchrony, and dyssynergy were compared in remote SR, pre-PVC SR, PVC, and post-PVC SR beats.

RESULTS

In SR beats remote from the PVC, GLS was -17.3% ± 4%, dyssynchrony was 49 ± 14 ms, and dyssynergy was 22% ± 9%. Myocardial mechanics were significantly abnormal during PVCs compared with remote SR beats (GLS -7.7% ± 3% [P < 0.001], dyssynchrony 115 ± 37 milliseconds [P < 0.001], and dyssynergy 26% ± 10% [P < 0.001]). There were significant mechanical abnormalities in the SR beat preceding the PVC, which demonstrated significantly lower LV strain (pre-PVC SR, -13% ± 4%; P < 0.001) and more dyssynchrony (pre-PVC SR, 63 ± 19 milliseconds; P < 0.001) compared with remote SR beats. Dyssynergy was significantly higher for pre-PVC SR and PVC beats compared with remote SR (pre-PVC SR, 25% ± 8% [P < 0.001]; PVC, 26% ± 10% [P < 0.001]).

CONCLUSIONS

In patients with frequent PVCs, the SR beat preceding the PVC demonstrates significant mechanical abnormalities. This finding suggests that perturbations in cellular physiological processes such as excitation-contraction coupling may underlie the generation of frequent PVCs.

Risk Factors and Heart Rate Variability Associated with Left Ventricular Enlargement in Patients with Frequent Premature Ventricular Contractions

INTRODUCTION

Premature ventricular contractions (PVCs) were now well recognized to carry the risk of inducing left ventricular (LV) enlargement and were closely related to the cardiac autonomic nervous activity quantified by heart rate variability (HRV) analysis. However, the relationship between LV enlargement and HRV in patients with frequent PVCs is still unclear. This study aimed to investigate the risk factors and HRV for LV enlargement in patients with frequent PVCs.

METHODS

Patients with frequent PVCs (n = 571), whose PVC burden counts >10,000/24 h or PVC burden >10%, were recruited. Patients were divided into LV enlargement group (n = 161), defined as female left ventricular end-diastolic diameter (LVEDD) >49.8 mm or male LVEDD >54.2 mm, and LV normal group (n = 410). Two groups were compared on their clinical, electrocardiographic, and HRV parameters. Logistic regression analysis was used to predict the risk factors of LV enlargement in patients with frequent PVCs. The parameters of echocardiography, Holter monitoring, and HRV were collected after ablation.

RESULTS

There were significant differences between the patients with left enlargement and with normal LV structure, in terms of sex, left ventricular ejection fraction (LVEF), level of N-terminal pro-brain natriuretic peptide (NT-proBNP), 24-h PVC burden, with nonsustained ventricular tachycardia, multifocal PVCs, QRS duration of PVC, and values of very low-frequency power of HRV parameter (all p < 0.05). Multivariate analysis showed that female gender (odds ratio [OR] = 2.753, p < 0.001), increased NT-proBNP (OR = 1.011, p = 0.022), increased LVEF (OR = 0.292, p < 0.001), increased 24-h PVC burden (OR = 1.594, p < 0.001), increased standard deviation of all NN intervals (SDNN) (OR = 1.100, p = 0.003), increased the proportion of consecutive NN intervals that differ by more than 50 ms (pNN50) (OR = 0.844, p = 0.026) were predictors for LV enlargement in patients with frequent PVCs. 84.4% (54/64) of patients with LV enlargement at baseline had normalized their LV structure after ablation. The values of SDNN, standard deviation of the averages of NN intervals in all 5-min segments, the square root of the mean of the sum of the squares of differences between adjacent NN intervals, pNN50, low-frequency power (LF), LF/high-frequency power ratio of patients were significantly decreased after ablation (all p < 0.05).

CONCLUSION

Female gender, increased level of NT-proBNP, lower LVEF, higher PVC burden, increased sympathetic parameters SDNN, and reduced parasympathetic parameters pNN50 were the independent risk factors of LV enlargement in patients with frequent PVCs. LV enlargement induced by PVCs can be reversible after PVC elimination by ablation. The activities of sympathetic and parasympathetic were reduced after ablation.

The Burden of Ventricular Premature Complex Is Associated With Cardiovascular Mortality

Background

Ventricular premature complex (VPC) is one of the most common ventricular arrhythmias. The presence of VPC is associated with an increased risk of heart failure (HF).

Method

We designed a single-center, retrospective, and large population-based cohort to clarify the role of VPC burden in long-term prognosis in Taiwan. We analyzed the database from the National Cheng Kung University Hospital-Electronic Medical Record (NCKUH-EMR) and NCKUH-Holter (NCKUH-Holter). A total of 19,527 patients who underwent 24-h Holter ECG monitoring due to palpitation, syncope, and clinical suspicion of arrhythmias were enrolled in this study.

Results

The clinical outcome of interests involved 5.65% noncardiovascular death and 1.53% cardiovascular-specific deaths between 2011 and 2018. Multivariate Cox regression analysis, Fine and Gray's competing risk model, and propensity score matching demonstrated that both moderate (1,000–10,000/day) and high (>10,000/day) VPC burdens contributed to cardiovascular death in comparison with a low VPC burden (<1,000/day).

Conclusion

A higher VPC burden via Holter ECG is an independent risk factor of cardiovascular mortality.

Premature ventricular complexes and development of heart failure in a community-based population

OBJECTIVE

A higher premature ventricular complex (PVC) frequency is associated with incident congestive heart failure (CHF) and death. While certain PVC characteristics may contribute to that risk, the current literature stems from patients in medical settings and is therefore prone to referral bias. This study aims to identify PVC characteristics associated with incident CHF in a community-based setting.

METHODS

The Cardiovascular Health Study is a cohort of community-dwelling individuals who underwent prospective evaluation and follow-up. We analysed 24-hour Holter data to assess PVC characteristics and used multivariable logistic and Cox proportional hazards models to identify predictors of a left ventricular ejection fraction (LVEF) decline and incident CHF, respectively.

RESULTS

Of 871 analysed participants, 316 participants exhibited at least 10 PVCs during the 24-hour recording. For participants with PVCs, the average age was 72±5 years, 41% were women and 93% were white. Over a median follow-up of 11 years, 34% developed CHF. After adjusting for demographics, cardiovascular comorbidities, antiarrhythmic drug use and PVC frequency, a greater heterogeneity of the PVC coupling interval was associated with an increased risk of LVEF decline and incident CHF. Of note, neither PVC duration nor coupling interval duration exhibited a statistically significant relationship with either outcome.

CONCLUSIONS

In this first community-based study to identify Holter-based features of PVCs that are associated with LVEF reduction and incident CHF, the fact that coupling interval heterogeneity was an independent risk factor suggests that the mechanism of PVC generation may influence the risk of heart failure.

Hourly variability in outflow tract ectopy as a predictor of its site of origin

INTRODUCTION

Before ablation, predicting the site of origin (SOO) of outflow tract ventricular arrhythmia (OTVA), can inform patient consent and facilitate appropriate procedural planning. We set out to determine if OTVA variability can accurately predict SOO.

METHODS

Consecutive patients with a clear SOO identified at OTVA ablation had their prior 24-h ambulatory ECGs retrospectively analysed (derivation cohort). Percentage ventricular ectopic (VE) burden, hourly VE values, episodes of trigeminy/bigeminy, and the variability in these parameters were evaluated for their ability to distinguish right from left-sided SOO. Effective parameters were then prospectively tested on a validation cohort of consecutive patients undergoing their first OTVA ablation.

RESULTS

High VE variability (coefficient of variation ≥0.7) and the presence of any hour with <50 VE, were found to accurately predict RVOT SOO in a derivation cohort of 40 patients. In a validation cohort of 29 patients, the correct SOO was prospectively identified in 23/29 patients (79.3%) using CoV, and 26/29 patients (89.7%) using VE < 50. Including current ECG algorithms, VE < 50 had the highest Youden Index (78), the highest positive predictive value (95.0%) and the highest negative predictive value (77.8%).

CONCLUSION

VE variability and the presence of a single hour where VE < 50 can be used to accurately predict SOO in patients with OTVA. Accuracy of these parameters compares favorably to existing ECG algorithms.

A single cell transcriptomics map of paracrine networks in the intrinsic cardiac nervous system

We developed a spatially-tracked single neuron transcriptomics map of an intrinsic cardiac ganglion, the right atrial ganglionic plexus (RAGP) that is a critical mediator of sinoatrial node (SAN) activity. This 3D representation of RAGP used neuronal tracing to extensively map the spatial distribution of the subset of neurons that project to the SAN. RNA-seq of laser capture microdissected neurons revealed a distinct composition of RAGP neurons compared to the central nervous system and a surprising finding that cholinergic and catecholaminergic markers are coexpressed, suggesting multipotential phenotypes that can drive neuroplasticity within RAGP. High-throughput qPCR of hundreds of laser capture microdissected single neurons confirmed these findings and revealed a high dimensionality of neuromodulatory factors that contribute to dynamic control of the heart. Neuropeptide-receptor coexpression analysis revealed a combinatorial paracrine neuromodulatory network within RAGP informing follow-on studies on the vagal control of RAGP to regulate cardiac function in health and disease.

Cardiac afferent signaling partially underlies premature ventricular contraction-induced cardiomyopathy

BACKGROUND

The mechanisms underlying premature ventricular contraction (PVC)-induced cardiomyopathy (PIC) remain unknown. Transient receptor potential vanilloid-1 (TRPV1) afferent fibers are implicated in the reflex processing of cardiac stress.

OBJECTIVE

The purpose of this study was to determine whether cardiac TRPV1 afferent signaling promote PIC.

METHODS

A PIC swine model (50% PVC burden) was created via an implanted pacemaker. We selectively depleted cardiac TRPV1 afferent fibers using percutaneous epicardial application of resiniferatoxin (RTX). Animals were randomized to PVC only (n = 11), PVC+RTX (n = 11), or control (n = 6). We examined early-stage (4 weeks after implantation; n = 5) and late-stage PIC (8 weeks after implantation; n = 6). At terminal experimentation, animals underwent echocardiography, serum sampling, and physiological and autonomic reflex testing.

RESULTS

Depletion of cardiac TRPV1 afferents by RTX treatment was confirmed by absent sensory fibers and absent functional responses to TRPV1 activators. Left ventricular ejection fraction was worse in late-stage than early-stage PIC (P <.01). At 4 weeks (early stage), left ventricular ejection fraction was higher in PVC+RTX vs PVC animals (51.7% ± 1.6% vs 45.0% ± 2.1%; P = .030), whereas no significant difference between PVC and PVC+RTX was observed at 8 weeks (late stage). Histologic studies demonstrated reduced fibrosis in PVC+RTX vs PVC alone at 4 weeks (2.27% ± 0.14% vs 3.01% ± 0.21%; P = .020), suggesting that RTX mitigated profibrotic pathways induced by persistent PVCs.

CONCLUSION

TRPV1 afferent depletion alleviates left ventricular dysfunction in early- but not late-stage PIC. This temporal effect suggests that multiple pathways promote PIC, of which TRPV1 afferents are a part.

Interpretable morphological features for efficient single-lead automatic ventricular ectopy detection

OBJECTIVE

We designed an automatic, computationally efficient, and interpretable algorithm for detecting ventricular ectopic beats in long-term, single-lead electrocardiogram recordings.

METHODS

We built five simple, interpretable, and computationally efficient features from each cardiac cycle, including a novel morphological feature which described the distance to the median beat in the recording. After an unsupervised subject-specific normalization procedure, we trained an ensemble binary classifier using the AdaBoost algorithm RESULTS: After our classifier was trained on subset DS1 of the Massachusetts Institute of Technology-Beth Israel Hospital (MIT-BIH) Arrhythmia database, our classifier obtained an F1 score of 94.35% on subset DS2 of the same database. The same classifier achieved F1 scores of 92.06% on the St. Petersburg Institute of Cardiological Technics (INCART) 12-lead Arrhythmia database and 91.40% on the MIT-BIH Long-term database. A phenotype-specific analysis of model performance was afforded by the annotations included in the St. Petersburg INCART Arrhythmia database CONCLUSION: The five features this novel algorithm employed allowed our ventricular ectopy detector to obtain high precision on previously unseen subjects and databases SIGNIFICANCE: Our ventricular ectopy detector will be used to study the relationship between premature ventricular contractions and adverse patient outcomes such as congestive heart failure and death.

Eccentric hypertrophy in an animal model of mid- and long-term premature ventricular contraction-induced cardiomyopathy

BACKGROUND

Tachycardia and heart rate irregularity are proposed triggers of premature ventricular contraction-induced cardiomyopathy (PVC-cardiomyopathy). Bigeminal premature atrial and ventricular contractions (PACs and PVCs) increase heart rate and result in rhythm irregularities but differ in their effects on ventricular synchrony. Comparing chronic bigeminal PACs with PVCs would provide insights into mechanisms of PVC-cardiomyopathy.

OBJECTIVE

To compare the impact of chronic PACs and PVCs on ventricular hemodynamics, structure, and function.

METHODS

Pacemakers were implanted in 27 canines to reproduce atrial (PACs, n = 7) or ventricular bigeminy (PVCs, n = 11) for 12 weeks, and compared to sham-operated animals (n = 9). Four additional animals were exposed to long-term bigeminal PVCs (48 weeks). Hemodynamic changes were assessed using a pressure-transducing catheter at baseline and 12 weeks. Cardiac remodeling was monitored by transthoracic echocardiography throughout the 12- and 48-week protocols in the respective groups.

RESULTS

PVC group demonstrated a significant decrease in left ventricular (LV) ejection fraction and contractility (max dP/dt), impaired LV lusitropy (min dP/dt), and increase in LV dimensions and LV mass at 12 weeks without further deterioration beyond 16 weeks. Despite increased LV mass, relative wall thickness decreased, consistent with eccentric hypertrophy. No significant cardiac remodeling was noted in either sham or PAC groups at 12 weeks.

CONCLUSION

In contrast to bigeminal PACs, PVCs result in a cardiomyopathy characterized by reduced LV ejection fraction, LV dilation, and eccentric hypertrophy that plateaus between 12 and 16 weeks. The lack of remodeling in chronic PACs suggests that tachycardia and heart rate irregularity do not play a significant role on the development of PVC-cardiomyopathy.

Causal Link between Ventricular Ectopy and Concussion

We present a unique case study report of a male individual with a history of mild nonischaemic cardiomyopathy, with no ventricular ectopy, that at the age of 76 years sustained multiple concussions (i.e., mild traumatic brain injury) within a week of each other. Concussion symptoms included cognitive difficulties, "not feeling well," lethargy, fatigue, and signs of depression. He was later medically diagnosed with postconcussion syndrome. The patient, WJT, was referred for cardiac and neurological assessment. Structural neuroimaging of the brain (MRI) was unremarkable, but electrocardiography (ECG) assessments using a 24-hour Holter monitor revealed significant incidence of ventricular ectopy (9.4%; 9,350/99,836 beats) over a period of 5-6 months after injury and then a further increase in ventricular ectopy to 18% (15,968/88,189 beats) during the subsequent 3 months. The patient was then prescribed Amiodarone 200 mg, and his ventricular ectopy and concussion symptoms completely resolved simultaneously within days. To the authors' knowledge, our study is the first to show a direct link between observable and documented cardiac dysregulation and concussion symptomology. Our study has important implications for both cardiac patients and the patients that sustain a concussion, and if medically managed with appropriate pharmacological intervention, it can reverse ventricular ectopy and concussion symptomology. More research is warranted to investigate the mechanisms for this dramatic and remarkable change in cardiac and cerebral functions and to further explore the brain-heart interaction and the intricate autonomic interaction that exists between the extrinsic and intracardiac nervous systems.

Combining tissue engineering and optical imaging approaches to explore interactions along the neuro-cardiac axis

Interactions along the neuro-cardiac axis are being explored with regard to their involvement in cardiac diseases, including catecholaminergic polymorphic ventricular tachycardia, hypertension, atrial fibrillation, long QT syndrome and sudden death in epilepsy. Interrogation of the pathophysiology and pathogenesis of neuro-cardiac diseases in animal models present challenges resulting from species differences, phenotypic variation, developmental effects and limited availability of data relevant at both the tissue and cellular level. By contrast, tissue-engineered models containing cardiomyocytes and peripheral sympathetic and parasympathetic neurons afford characterization of cellular- and tissue-level behaviours while maintaining precise control over developmental conditions, cellular genotype and phenotype. Such approaches are uniquely suited to long-term, high-throughput characterization using optical recording techniques with the potential for increased translational benefit compared to more established techniques. Furthermore, tissue-engineered constructs provide an intermediary between whole animal/tissue experiments and in silico models. This paper reviews the advantages of tissue engineering methods of multiple cell types and optical imaging techniques for the characterization of neuro-cardiac diseases.

Arrhythmia-Induced Cardiomyopathy: JACC State-of-the-Art Review

Arrhythmias coexist in patients with heart failure (HF) and left ventricular (LV) dysfunction. Tachycardias, atrial fibrillation, and premature ventricular contractions are known to trigger a reversible dilated cardiomyopathy referred as arrhythmia-induced cardiomyopathy (AiCM). It remains unclear why some patients are more prone to develop AiCM despite similar arrhythmia burdens. The challenge is to determine whether arrhythmias are fully, partially, or at all responsible for an observed LV dysfunction. AiCM should be suspected in patients with mean heart rate >100 beats/min, atrial fibrillation, and/or premature ventricular contractions burden ≥10%. Reversal of cardiomyopathy by elimination of the arrhythmia confirms AiCM. Therapeutic choice depends on the culprit arrhythmia, patient comorbidities, and preferences. Following recovery of LV function, patients require continued follow-up if an abnormal myocardial substrate is present. Appropriate diagnosis and treatment of AiCM is likely to improve quality of life and clinical outcomes and to reduce hospital admission and health care spending.

Persistent Proarrhythmic Neural Remodeling Despite Recovery From Premature Ventricular Contraction-Induced Cardiomyopathy

BACKGROUND

The presence and significance of neural remodeling in premature ventricular contraction-induced cardiomyopathy (PVC-CM) remain unknown.

OBJECTIVES

This study aimed to characterize cardiac sympathovagal balance and proarrhythmia in a canine model of PVC-CM.

METHODS

In 12 canines, the investigators implanted epicardial pacemakers and radiotelemetry units to record cardiac rhythm and nerve activity (NA) from the left stellate ganglion (SNA), left cardiac vagus (VNA), and arterial blood pressure. Bigeminal PVCs (200 ms coupling) were applied for 12 weeks to induce PVC-CM in 7 animals then disabled for 4 weeks to allow complete recovery of left ventricular ejection fraction (LVEF), versus 5 sham controls.

RESULTS

After 12 weeks of PVCs, LVEF (p = 0.006) and dP/dT (p = 0.007) decreased. Resting SNA (p = 0.002) and VNA (p = 0.04), exercise SNA (p = 0.01), SNA response to evoked PVCs (p = 0.005), heart rate (HR) at rest (p = 0.003), and exercise (p < 0.04) increased, whereas HR variability (HRV) decreased (p = 0.009). There was increased spontaneous atrial (p = 0.02) and ventricular arrhythmias (p = 0.03) in PVC-CM. Increased SNA preceded both atrial (p = 0.0003) and ventricular (p = 0.009) arrhythmia onset. Clonidine suppressed SNA and abolished all arrhythmias. After disabling PVC for 4 weeks, LVEF (p = 0.01), dP/dT (p = 0.047), and resting VNA (p = 0.03) recovered to baseline levels. However, SNA, resting HR, HRV, and atrial (p = 0.03) and ventricular (p = 0.03) proarrhythmia persisted. There was sympathetic hyperinnervation in stellate ganglia (p = 0.02) but not ventricles (p = 0.2) of PVC-CM and recovered animals versus sham controls.

CONCLUSIONS

Neural remodeling in PVC-CM is characterized by extracardiac sympathetic hyperinnervation and sympathetic neural hyperactivity that persists despite normalization of LVEF. The altered cardiac sympathovagal balance is an important trigger and substrate for atrial and ventricular proarrhythmia.

Non-invasive electrocardiographic imaging in patients with idiopathic premature ventricular contractions from the right ventricular outflow tract: New insights into arrhythmia substrate

AIMS

The aim of this study was to use non-invasive electrocardiographic imaging (ECGI) to study the electrophysiological properties of right ventricular outflow tract (RVOT) in patients with frequent premature ventricular contractions (PVCs) from the RVOT and in controls.

METHODS

ECGI is a combined application of body surface electrocardiograms and computed tomography or magnetic resonance imaging data. Unipolar electrograms are reconstructed on the epicardial and endocardial surfaces. Activation time (AT) was defined as the time of maximal negative slope of the electrogram (EGM) during QRS, recovery time (RT) as the time of maximal positive slope of the EGM during T wave, Activation recovery interval (ARI) was defined as the difference between RT and AT. ARI dispersion (Δ ARI) and RT dispersion (Δ RT) were calculated as the difference between maximal and minimal ARI and RT respectively. We evaluated those parameters in patients with frequent PVCs from the RVOT, defined as >10.000 per 24 h, and in a control group.

RESULTS

We studied 7 patients with frequent RVOT PVCs and 17 controls. Patients with PVCs from the RVOT had shorter median RT than controls, in the endocardium and in the epicardium, respectively 380 (239-397) vs 414 (372-448) ms, p = 0.047 and 275 (236-301) vs 330 (263-418) ms, p = 0.047. The dispersion of ARI and of RT in the epicardium was higher than in controls, Δ ARI of 145 (68-216) vs 17 (3-48) ms, p = 0.001 and Δ RT of 201 (160-235) vs 115 (65-177), p = 0.019.

CONCLUSION

In this group of patients we found a shorter median RT in the endocardium and in the epicardium of the RVOT and a higher dispersion of the ARI and RT across the epicardium in patients with PVCs from the RVOT when comparing to controls.

Consequences of chronic frequent premature atrial contractions: Association with cardiac arrhythmias and cardiac structural changes

INTRODUCTION

Frequent premature ventricular contractions (PVCs) can cause cardiomyopathy (CM). Postextrasystolic potentiation (PESP) and irregularity have been in implicated as triggers of PVC-CM. Because both phenomena can also be found in premature atrial contractions (PACs), it is speculated that frequent PACs have similar consequences.

METHODS AND RESULTS

A single-center, retrospective study included all consecutive patients undergoing a 14-day Holter monitors (November 2014 to October 2016). Patients were divided into four groups by ectopy burden group 1 (<1%) and remaining by tertiles (group 2-4). Echocardiographic and arrhythmic data were compared between PAC and PVC burdens. In addition, a translational PAC animal model was used to assess the chronic effects of frequent PACs. A total 846 patients were reviewed. In contrast to PVCs, we found no difference in left ventricular ejection fraction (LVEF), end-systolic and end-diastolic dimensions and presence of CM (LVEF <50%) between different PAC groups. Multivariate regression analysis demonstrated that only PVC burden predicted low EF (odds ratio, 1.1; confidence interval, 1.03-1.13; P = .001). While there was a weak correlation between PAC burden and supraventricular tachycardia (SVT) episodes and atrial fibrillation (AF) burden (r = 0.19; P < .001), there was no correlation between PAC burden and LVEF or CM. Finally, atrial bigeminy in our animal model did not significantly decrease LVEF after 3 months.

CONCLUSION

PAC burden is associated with increased AF and SVT episodes. In contrast to a high PVC burden, a high PAC burden is not associated with CM. Our findings suggest that heart rate irregularity and/or PESP may play a minimal role in the pathophysiology of PVC-CM.

Premature ventricular contractions activate vagal afferents and alter autonomic tone: implications for premature ventricular contraction-induced cardiomyopathy

Mechanisms behind development of premature ventricular contraction (PVC)-induced cardiomyopathy remain unclear. PVCs may adversely modulate the autonomic nervous system to promote development of heart failure. Afferent neurons in the inferior vagal (nodose) ganglia transduce cardiac activity and modulate parasympathetic output. Effects of PVCs on cardiac parasympathetic efferent and vagal afferent neurotransmission are unknown. The purpose of this study was to evaluate effects of PVCs on vagal afferent neurotransmission and compare these effects with a known powerful autonomic modulator, myocardial ischemia. In 16 pigs, effects of variably coupled PVCs on heart rate variability (HRV) and vagal afferent neurotransmission were evaluated. Direct nodose neuronal recordings were obtained in vivo, and cardiac-related afferent neurons were identified based on their response to cardiovascular interventions, including ventricular chemical and mechanical stimuli, left anterior descending (LAD) coronary artery occlusion, and variably coupled PVCs. On HRV analysis before versus after PVCs, parasympathetic tone decreased (normalized high frequency: 83.6 ± 2.8 to 72.5 ± 5.3; P < 0.05). PVCs had a powerful impact on activity of cardiac-related afferent neurons, altering activity of 51% of neurons versus 31% for LAD occlusion (P < 0.05 vs. LAD occlusion and all other cardiac interventions). Both chemosensitive and mechanosensitive neurons were activated by PVCs, and their activity remained elevated even after cessation of PVCs. Cardiac afferent neural responses to PVCs were greater than any other intervention, including ischemia of similar duration. These data suggest that even brief periods of PVCs powerfully modulate vagal afferent neurotransmission, reflexly decreasing parasympathetic efferent tone.NEW & NOTEWORTHY Premature ventricular contractions (PVCs) are common in many patients and, at an increased burden, are known to cause heart failure. This study determined that PVCs powerfully modulate cardiac vagal afferent neurotransmission (exerting even greater effects than ventricular ischemia) and reduce parasympathetic efferent outflow to the heart. PVCs activated both mechano- and chemosensory neurons in the nodose ganglia. These peripheral neurons demonstrated adaptation in response to PVCs. This study provides additional data on the potential role of the autonomic nervous system in PVC-induced cardiomyopathy.

Neuromodulation Approaches for Cardiac Arrhythmias: Recent Advances

PURPOSE OF REVIEW

This review aims to describe the latest advances in autonomic neuromodulation approaches to treating cardiac arrhythmias, with a focus on ventricular arrhythmias.

RECENT FINDINGS

The increasing understanding of neuronal remodeling in cardiac diseases has led to the development and improvement of novel neuromodulation therapies targeting multiple levels of the autonomic nervous system. Thoracic epidural anesthesia, spinal cord stimulation, stellate ganglion modulatory therapies, vagal stimulation, renal denervation, and interventions on the intracardiac nervous system have all been studied in preclinical models, with encouraging preliminary clinical data. The autonomic nervous system regulates all the electrical processes of the heart and plays an important role in the pathophysiology of cardiac arrhythmias. Despite recent advances in the clinical application of cardiac neuromodulation, our comprehension of the anatomy and function of the cardiac autonomic nervous system is still limited. Hopefully in the near future, more preclinical data combined with larger clinical trials will lead to further improvements in neuromodulatory treatment for heart rhythm disorders.

Mechanisms and management of refractory ventricular arrhythmias in the age of autonomic modulation

Ventricular arrhythmias are responsible for hundreds of thousands of deaths every year. Catheter ablation of ventricular tachycardia (VT) is an essential component of the management of these life-threatening arrhythmias. However, in many patients, despite medical and interventional therapy, VT recurs. Furthermore, some VT substrates (mid-myocardial, left ventricular summit, and intraseptal) are not easily targeted because of limitations of currently available technology. In certain clinical settings, ventricular fibrillation (VF) episodes that have premature ventricular contraction triggers can also be targeted with catheter ablation. However, in most patients there is no clear VF trigger to target, and therefore polymorphic VT or VF cannot be adequately treated with catheter ablation. The autonomic nervous system plays a crucial role in all aspects of ventricular arrhythmias, yet interventions specific to the cardiac neuronal axis have been largely underutilized. This underutilization has been most pronounced in patients with structural heart disease. However, there is a growing body of literature on the physiology and pathophysiology of cardiac neural control and the benefits of neuromodulation to treat refractory ventricular arrhythmias in these patients. We present case-based examples of neuromodulatory interventions currently available and a review of the literature supporting their use.

Cardiac vanilloid receptor-1 afferent depletion enhances stellate ganglion neuronal activity and efferent sympathetic response to cardiac stress

Afferent fibers expressing the vanilloid receptor 1 (VR1) channel have been implicated in cardiac nociception; however, their role in modulating reflex responses to cardiac stress is not well understood. We evaluated this role in Yorkshire pigs by percutaneous epicardial application of resiniferatoxin (RTX), a toxic activator of the VR1 channel, resulting in the depletion of cardiac VR1-expressing afferents. Hemodynamics, epicardial activation recovery intervals, and in vivo activity of stellate ganglion neurons (SGNs) were recorded in control and RTX-treated animals. Stressors included inferior vena cava or aortic occlusion and rapid right ventricular pacing (RVP) to induce dyssynchrony and ischemia. In the epicardium, stellate ganglia, and dorsal root ganglia, immunostaining for the VR1 channel, calcitonin gene-related peptide, and substance P was significantly diminished by RTX. RTX-treated animals exhibited higher basal systolic blood pressures and contractility than control animals. Reflex responses to epicardial bradykinin and capsaicin were mitigated by RTX. Cardiovascular reflex function, as assessed by inferior vena cava or aortic occlusion, was similar in RTX-treated versus control animals. RTX-treated animals exhibited resistance to hemodynamic collapse induced by RVP. Activation recovery interval shortening during RVP, a marker of cardiac sympathetic outflow, was greater in RTX-treated animals and exhibited significant delay in returning to baseline values after cessation of RVP. The basal firing rate of SGNs and firing rates in response to RVP were also greater in RTX-treated animals, as was the SGN network activity in response to cardiac stressors. These data suggest that elimination of cardiac nociceptive afferents reorganizes the central-peripheral nervous system interaction to enhance cardiac sympathetic outflow. NEW & NOTEWORTHY Our work demonstrates a role for cardiac vanilloid receptor-1-expressing afferents in reflex processing of cardiovascular stress. Current understanding suggests that elimination of vanilloid receptor-1 afferents would decrease reflex cardiac sympathetic outflow. We found, paradoxically, that sympathetic outflow to the heart is instead enhanced at baseline and during cardiac stress.

Cardiac sympathectomy for the management of ventricular arrhythmias refractory to catheter ablation

BACKGROUND

Catheter ablation is now a mainstay of therapy for ventricular arrhythmias (VAs). However, there are scenarios where either physiological or anatomical factors make ablation less likely to be successful.

OBJECTIVE

The purpose of this study was to demonstrate that cardiac sympathetic denervation (CSD) may be an alternate therapy for patients with difficult-to-ablate VAs.

METHODS

We identified all patients referred for CSD at a single center for indications other than long QT syndrome and catecholaminergic polymorphic ventricular tachycardia who had failed catheter ablation. Medical records were reviewed for medical history, procedural details, and follow-up.

RESULTS

Seven cases of CSD were identified in patients who had failed prior catheter ablation or had disease not amenable to ablation. All patients had VAs refractory to antiarrhythmic drugs, with a median arrhythmia burden of 1 episode of sustained VA per month. There were no acute complications of sympathectomy. One of 7 patients (14%) underwent heart transplant. No patient had sustained VA after sympathectomy at a median follow-up of 7 months.

CONCLUSION

Because of anatomical and physiological constraints, many VAs remain refractory to catheter ablation and remain a significant challenge for the electrophysiologist. While CSD has been described as a therapy for long QT syndrome and catecholaminergic polymorphic ventricular tachycardia, data regarding its use in other cardiac conditions are sparse. This series illustrates that CSD may be a viable treatment option for patients with a variety of etiologies of VAs.