Idiopathic ventricular outflow tract tachycardia

Can exercise test intensity and modality affect the prevalence of arrhythmic events in young athletes?

Pre-participation screening is performed to identify underlying cardiac conditions that may also lead to sudden cardiac death. Our aim is to compare submaximal Harvard Step Test (HST) with incremental Maximal Exercise Test (MET) on treadmill to induce and detect arrhythmias in younger athletes. A total of 1000 athletes (mean age 14.6 ± 4.7 years) were evaluated, 500 with MET and 500 with HST, all with continuous ECG monitoring until three minutes of recovery. Pre-test evaluation includes medical history, clinical evaluation and resting electrocardiogram. Ventricular and/or supraventricular arrhythmias were observed in 2.6% of athletes performing HST and in 8.4% during MET (p < 0.001). Incidence of arrhythmias remained higher for MET also considering separately exercise phase (0.8% vs. 5.2%; p < 0.001) and recovery phase (2.0% vs. 6.0%; p < 0.01). No gender differences were observed. Results suggest that MET induces more arrhythmias than submaximal HST, regardless of test phase. Higher test intensity and longer exercise duration might influence test outcomes, making MET more arrhythmogenic.

Calcium dysregulation increases right ventricular outflow tract arrhythmogenesis in rabbit model of chronic kidney disease

Chronic kidney disease (CKD) increases the risk of arrhythmia. The right ventricular outflow tract (RVOT) is a crucial site of ventricular tachycardia (VT) origination. We hypothesize that CKD increases RVOT arrhythmogenesis through its effects on calcium dysregulation. We analysed measurements obtained using conventional microelectrodes, patch clamp, confocal microscopy, western blotting, immunohistochemical examination and lipid peroxidation for both control and CKD (induced by 150 mg/kg neomycin and 500 mg/kg cefazolin daily) rabbit RVOT tissues or cardiomyocytes. The RVOT of CKD rabbits exhibited a short action potential duration, high incidence of tachypacing (20 Hz)‐induced sustained VT, and long duration of isoproterenol and tachypacing‐induced sustained and non‐sustained VT. Tachypacing‐induced sustained and non‐sustained VT in isoproterenol‐treated CKD RVOT tissues were attenuated by KB‐R7943 and partially inhibited by KN93 and H89. The CKD RVOT myocytes had high levels of phosphorylated CaMKII and PKA, and an increased expression of tyrosine hydroxylase‐positive neural density. The CKD RVOT myocytes exhibited large levels of I_to, I_Kr, NCX and L‐type calcium currents, calcium leak and malondialdehyde but low sodium current, SERCA2a activity and SR calcium content. The RVOT in CKD with oxidative stress and autonomic neuron hyperactivity exhibited calcium handling abnormalities, which contributed to the induction of VT.

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

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

Cardiac magnetic resonance imaging in right ventricular outflow tract arrhythmia: a retrospective analysis from a tertiary care centre in South India

INTRODUCTION

Arrhythmia arising from right ventricular outflow tract (RVOT) is the most common cause of idiopathic ventricular arrhythmia. Previous studies involving cardiac magnetic resonance imaging (MRI) in these patients are known to show abnormalities in up to 60% of patients.

METHODOLOGY

This was a retrospective descriptive analysis of patients having idiopathic RVOT arrhythmia who underwent cardiac MRI between January 2010 and December 2020. Clinical and demographic details were recorded from the electronic medical records and cardiac MRI of all patients were reviewed.

RESULTS

Among 214 patients with RVOT arrhythmia, 64 underwent cardiac MRI. A total of 41 patients, who did not have any abnormality on baseline echocardiogram were included in the study. There was male preponderance (56.1%), with median age of 43 years. About 43.9% had syncope. Twenty-four-hour Holter study revealed a premature ventricular complex (PVC) burden of 26.3 ± 11.7%. MRI showed structural abnormalities in 51.2% of patients, which commonly included RV sacculations and aneurysms. Late gadolinium enhancement (LGE) was seen in six patients, which was mostly seen in RV free wall. Right ventricular (RV) systolic dysfunction was evident in 29.3%. About 9.8% fulfilled the criteria for arrhythmogenic RV cardiomyopathy (ARVC). Out of 23 patients with baseline abnormalities on ECHO, 87% had structural abnormalities on MRI, and 43.5% fulfilled the criteria for ARVC.

CONCLUSIONS

Additional imaging by cardiac MRI helps to identify structural abnormalities in 51.2% of patients with RVOT arrhythmias, even with normal baseline echocardiogram and electrocardiogram (ECG). It is useful tool to rule out ARVC in this subset of patients, and can help in increasing the diagnostic yield in the early stages.

A case of successful ablation of ventricular tachycardia focus in the left ventricular summit through the left atrial appendage: a case report

Background

Although premature ventricular complexes and ventricular tachycardia (VT) from outflow tracts are easy to map and ablate, some foci create the greatest challenges for the electrophysiologist. One such example is the 'Bermuda triangle' of the heart.

Case summary

In this article, we describe the rarely used but acceptable approach to the 'Bermudian' focus. We present a case of a 38-year-old male patient with sustained monomorphic VT, who underwent radiofrequency ablation of arrhythmogenic myocardium. After unsuccessful ablation through the posterior right ventricular outflow tract (RVOT), left coronary cusp (LCC), and distal coronary sinus, tachycardia was eliminated from the left atrial appendage (LAA). Complaints such as palpitations and weakness disappeared after the procedure.

Discussion

Radiofrequency ablation of VT might be performed using LAA. This approach is used when the epicardial location of arrhythmia-causing tissue is suspected and ablation through the RVOT, LCC, and great cardiac vein fails.

Effect of burden and origin sites of premature ventricular contractions on left ventricular function by 7-day Holter monitor

Recent studies have shown that premature ventricular contractions (PVCs) could enlarge the heart, but its risk factors are incompletely understood as a single 24-hour recording cannot reflect the true PVC burden due to day-to-day variability. Our purpose was to investigate the effect of burden and origin sites on left ventricular (LV) function in patients with PVCs by 7-day Holter electrocardiography (ECG). From May 2012 to August 2013, 112 consecutive patients with PVCs were recruited from the authors' affiliated hospital. All patients received 2-dimensional transthoracic echocardiography, 12-lead routing ECG and 7-days Holter ECG. Serum N-terminal pro-brain natriuretic peptide (NT-proBNP) levels were measured. A total of 102 participants with PVCs were included in the final analysis. Origin of PVCs from the tricuspid annulus had the highest burden and NT-proBNP level. LV papillary muscle had a higher LV ejection fraction (EF) level and a lower LV end-systolic dimension (ESD) than other PVC foci (P<0.05). The high burden group had a higher LV end-diastolic dimension (EDD) and LVESD but lower LVEF than the other two groups (P<0.05). Female, older age, physical work, and history of PVCs had a significantly positive correlation with symptoms. Male, older age, physical work, and high burden were positive predictors of enlarged LVEDD, LVESD and higher serum NT-proBNP level, but lower LVEF. Seven-day dynamic ECG Holter monitor showed the true PVC burden on patients with PVCs. PVCs with a lower burden or origin from the LV papillary muscle and the fascicle were relatively benign, while PVCs with a higher burden or origin from the tricuspid annulus may lead to cardiac dysfunction.

Which Is The Appropriate Arrhythmia Burden To Offer RF Ablation For RVOT Tachycardias?

Premature ventricular complexes (PVCs) and ventricular tachycardia (VT) in patients with structurally normal hearts originate from the right ventricular outflow tract (RVOT) in the majority of cases. In the last few decades catheter ablation of these arrhythmias has been proven to be effective. RVOT VT/PVCs may cause disabling symptoms or arrhythmia induced cardiomyopathy. However, the PVC burden at which catheter ablation should be recommended is still controversial. What adds to the controversy is why some patients with only a low number of PVCs can be highly symptomatic and may even develop arrhythmia induced cardiomyopathy, whilst others may have a higher PVC/VT burden and remain asymptomatic and do not develop cardiomyopathy for a long period of time. Therefore, although catheter ablation of RVOT PVCs has high success and low complication rates, the time point of when ablation should be recommended is currently still under debate. This review discusses the treatment strategies and prognosis for RVOT tachycardias and focuses on the question of which arrhythmia burden is appropriate to offer RF ablation.

β1-Adrenoceptor blocker aggravated ventricular arrhythmia

OBJECTIVES

To assess the impact of β1 -adrenoceptor blockers (β1 -blocker) and isoprenaline on the incidence of idiopathic repetitive ventricular arrhythmia that apparently decreases with preprocedural anxiety.

METHODS

From January 2010 to July 2012, six patients were identified who had idiopathic ventricular arrhythmias that apparently decreased (by greater than 90%) with preprocedural anxiety. The number of ectopic ventricular beats per hour (VPH) was calculated from Holter or telemetry monitoring to assess the ectopic burden. The mean VPH of 24 hours from Holter before admission (VPH-m) was used as baseline (100%) for normalization. β1 -Blockers, isoprenaline, and/or aminophylline were administrated successively on the ward and catheter lab to evaluate their effects on the ventricular arrhythmias.

RESULTS

Among 97 consecutive patients with idiopathic ventricular arrhythmias, six had reduction in normalized VPHs in the hour before the scheduled procedure time from (104.6 ± 4.6%) to (2.8 ± 1.6%) possibly due to preprocedural anxiety (P < 0.05), then increased to (97.9 ± 9.7%) during β1 -blocker administration (P < 0.05), then quickly reduced to (1.6 ± 1.0%) during subsequent isoprenaline infusion. Repeated β1 -blocker quickly counteracted the inhibitory effect of isoprenaline, and VPHs increased to (120.9 ± 2.4%) from (1.6 ± 1.0%; P < 0.05). Isoprenaline and β1 -blocker showed similar effects on the arrhythmias in catheter lab.

CONCLUSIONS

In some patients with structurally normal heart and ventricular arrhythmias there is a marked reduction of arrhythmias associated with preprocedural anxiety. These patients exhibit a reproducible sequence of β1 -blocker aggravation and catecholamine inhibition of ventricular arrhythmias, including both repetitive ventricular premature beats and monomorphic ventricular tachycardia.

Radiofrequency catheter ablation of idiopathic right ventricular outflow tract arrhythmias

Idiopathic ventricular arrhythmias (VA) consist of various subtypes of VA that occur in the absence of clinically apparent structural heart disease. Affected patients account for approximately 10% of all patients referred for evaluation of ventricular tachycardia (VT). Arrhythmias arising from the outflow tract (OT) are the most common subtype of idiopathic VA and more than 70-80% of idiopathic VTs or premature ventricular contractions (PVCs) originate from the right ventricular (RV) OT. Idiopathic OT arrhythmias are thought to be caused by adenosine-sensitive, cyclic adenosine monophosphate (cAMP) mediated triggered activity and, in general, manifest at a relatively early age. Usually they present as salvos of paroxysmal ventricular ectopic beats and are rarely life-threatening. When highly symptomatic and refractory to antiarrhythmic therapy or causative for ventricular dysfunction, ablation is a recommended treatment with a high success rate and a low risk of complications.

Single-centre experience with an 8-mm tip catheter for radiofrequency catheter ablation of outflow tract ventricular ectopic beats

BACKGROUND

Radiofrequency ablation (RFA) of outflow tract ventricular ectopic beats (OTVEBs) can be performed using a 4-mm or externally-cooled tip RFA catheter, but no data are available concerning the safety and efficacy of a large-tip (8-mm) catheter.

AIMS

To evaluate the feasibility of using an 8-mm tip catheter in patients with OTVEBs.

METHODS

In this prospective cohort study, the 8-mm tip catheter was tested in patients who were referred to our centre for RFA of symptomatic OTVEBs.

RESULTS

The mean age of the 16 patients recruited between September 2008 and March 2010 was 53±18 years and 56.3% were male. Mean left ventricular ejection fraction was 62±9%, mean ventricular ectopic beat width was 144±21 ms, and all patients had left bundle branch block. Fourteen patients had inferior axis QRS morphology and two had superior. The main symptoms were palpitations and pre-syncope. RFA parameters were: procedure time 94±35 min; duration of application 11±10 min; impedance 81±12 Ω; temperature 50±5 °C; and power 46±17 W. RFA succeeded in 15 over 16 patients (93.8%); and recurrence was seen in one patient after a mean follow-up time of 11±6 months. No complications were noted.

CONCLUSIONS

This preliminary study suggests that an 8-mm tip catheter may represent an alternative for RFA in patients with OTVEBs in whom a 4-mm tip was not successful. Larger randomized studies are therefore warranted.

Imaging spectrum of sudden athlete cardiac death

Sudden athlete death (SAD) is a widely publicized and increasingly reported phenomenon. For many, the athlete population epitomize human physical endeavour and achievement and their unexpected death comes with a significant emotional impact on the public. Sudden deaths within this group are often without prior warning. Preceding symptoms of exertional syncope and chest pain do, however, occur and warrant investigation. Similarly, a positive family history of sudden death in a young person or a known family history of a condition associated with SAD necessitates further tests. Screening programmes aimed at detecting those at risk individuals also exist with the aim of reducing fatalities. In this paper we review the topic of SAD and discuss the epidemiology, aetiology, and clinical presentations. We then proceed to discuss each underlying cause, in turn discussing the pathophysiology of each condition. This is followed by a discussion of useful imaging methods with an emphasis on cardiac magnetic resonance and cardiac computed tomography and how these address the various issues raised by the pathophysiology of each entity. We conclude by proposing imaging algorithms for the investigation of patients considered at risk for these conditions and discuss the various issues raised in screening.

Management of ventricular tachycardia in the absence of structural heart disease

Ventricular tachycardia most often arises from the ventricular outflow tracts in patients with apparently structurally normal hearts, and is often termed idiopathic ventricular tachycardia. These tachycardias are characterized by a left bundle branch block, inferior axis QRS morphology, and a unique electropharmacologic profile. The choice of treatment is dictated by the severity of symptoms, and ranges from observation for asymptomatic patients, to antiarrhythmic agents for those who are mildly to moderately symptomatic (eg, palpitations), to catheter-based ablation for those with more troubling symptoms or those who develop tachycardia-mediated cardiomyopathy. Antiarrhythmic therapy can be effective for arrhythmia suppression, and radiofrequency ablation has a high success rate (> 90%) with few procedural complications. In general, ventricular outflow tract tachycardia has a favorable prognosis. Exclusion of arrhythmogenic right ventricular dysplasia/cardiomyopathy is important due to significant disparities in prognosis and treatment.

Magnetic Resonance Imaging Abnormalities in Right Ventricular Outflow Tract Tachycardia and the Prediction of Radiofrequency Ablation Outcome

BACKGROUND

Recent reports have shown abnormalities on cardiac magnetic resonance imaging (MRI) in patients with right ventricular outflow tract (RVOT) tachycardia.

OBJECTIVES

OBJECTIVES of this study were to demonstrate abnormalities on MRI and signal-averaged ECG (SAECG) in patients with RVOT tachycardia and their correlation with the outcome of radiofrequency (RF) ablation.

METHODS

We studied 41 patients with symptomatic RVOT tachycardia and 15 controls. SAECG and cardiac MRI were performed on every subject. An evaluation of structural abnormality, chamber size, function, and wall motion abnormality of the left and right ventricle was performed by MRI. Focal wall thinning was evaluated by the black blood technique and fatty infiltration was evaluated by the T1 image with and without fat suppression.

RESULTS

MRI abnormalities were demonstrated in 24 (58.5%) patients with RVOT tachycardia. The abnormalities included localized wall bulging in 22 (53.7%), focal wall thinning in 10 (24.4%), and fatty replacement in 9 (22%) patients. MRI abnormality was found in only one patient in the control group (P < 0.001). Late potentials from SAECG were demonstrated in six (10.7%) patients but none in the controls (P = 0.117). Among 29 patients who underwent RF ablation, 3 patients had a failed procedure and 3 having arrhythmia recurrence needed repeated ablation. MRI abnormalities and late potentials were associated with an unfavorable outcome of RF ablation.

CONCLUSIONS

MRI abnormalities were frequently found in patients with RVOT tachycardia. MRI abnormalities and late potentials can predict outcomes of RF ablation.

[Molecular basis of primary electrical heart diseases]

The last decade has seen rapid progress in our understanding of the molecular basis of arrhythmias, particularly concerning hereditary arrhythmia syndromes. This has led to significant improvement regarding differentiation, risk stratification and therapy in these patients and their families. However, there is mounting evidence that the knowledge obtained by studying these rare monogenic disorders will also enable us to dissect the molecular mechanisms underlying polygenetic and multi-factorial arrhythmias that are by far more common in clinical practice. The goal of this review is to give a brief overview of current knowledge on the molecular basis of primary electrical heart diseases. A focus is on the long QT syndrome.