Node Modification Research Articles

Catheter ablation of inappropriate sinus tachycardia.

Catheter ablation for inappropriate sinus tachycardia (IST) is recommended for patients symptomatic for palpitations and refractory to other treatments. The current approach consists in sinus node modification (SNM), achieved by ablation of the cranial part of the sinus node to eliminate faster sinus rates while trying to preserve chronotropic competence. This approach has a limited efficacy, with a very modest long-term clinical success. To overcome this, proper patient selection is crucial and an epicardial approach should always be considered. This brief review will discuss the current role and limitations of catheter ablation in the management of patients with IST.

Targeted Single-Site MOF Node Modification: Trivalent Metal Loading via Atomic Layer Deposition

Postsynthetic functionalization of metal organic frameworks (MOFs) enables the controlled, high-density incorporation of new atoms on a crystallographically precise framework. Leveraging the broad palette of known atomic layer deposition (ALD) chemistries, ALD in MOFs (AIM) is one such targeted approach to construct diverse, highly functional, few-atom clusters. We here demonstrate the saturating reaction of trimethylindium (InMe3) with the node hydroxyls and ligated water of NU-1000, which takes place without significant loss of MOF crystallinity or internal surface area. We computationally identify the elementary steps by which trimethylated trivalent metal compounds (ALD precursors) react with this Zr-based MOF node to generate a uniform and well characterized new surface layer on the node itself, and we predict a final structure that is fully consistent with experimental X-ray pair distribution function (PDF) analysis. We further demonstrate tunable metal loading through controlled number density of t...

Database System of Business Case Based on Network Perspective

School enterprise cooperation mode is the double oriented education model based on enterprises needs and teaching goal, and is an effective way of improving the universities teaching quality and cultivating students' practice innovation ability. Based on the network perspective and enterprise demand, the paper designs a kind of new business English teaching cases computer system, and the system uses the internet interactivity make enterprise staff and teachers can achieve real-time interaction. In order to optimize the teaching case system, this paper uses parabolic interpolation to carry on multi node modification for the network transmission signal, and then a single objective network nodes optimization model will be established, and the use of VB software carries out visual programming for the system, it can enhance the system easy to operate and real-time interaction, which provides a new method for the design of computer English teaching case.

Insights from preclinical ultra high-density electroanatomical sinus node mapping

Although sinus node modification by catheter ablation is an established therapy for the treatment of inappropriate sinus tachycardia, there is incomplete understanding of sinus node anatomy and function but also limited electroanatomical mapping data. Recently, an automatic, ultra high-resolution mapping system has been presented to accurately and quickly identify right atrial (RA) geometry and activation patterns but detailed assessment of sinus node activation has not been performed which was one aim of this study. Preclinical experiences are compared with previous sinus node mapping studies in animals and humans, and potential clinical implications for catheter ablation are discussed. In anaesthetized and ventilated 14 pigs, 30 endocardial and 2 eipcardial RA maps were generated using the Rhythmia™ mapping system without complications and earliest activation sites (EAS) and sinus break-out (SBO) were determined. At baseline, EAS and SBO were located anterior to the middle (n = 6) or lower third (n = 8) of the crista terminalis exhibiting a unicentric activation pattern in all cases. Conduction pathways were directed anterior, posterior, superior, or inferior with substantial inter-individual variation in direction, pathway distance, and conduction time. Orciprenaline, propranolol, or amiodarone shifted endocardial activation with considerable variation between animals with inconsistent patterns. Multicentric activation was found in one case after orciprenaline infusion. Sequential endocardial and epicardial high-density mapping of the RA was performed in two animals and showed a high congruence of the sinus node activation in the endo- and the epicardial map. Ultra high-density mapping allows fast, simple, and very detailed assessment of sinus node activation. Future studies are clearly needed to evaluate novel mapping and ablation strategies for an improved understanding of sinus node disease and better outcomes.

A Comparison of Clustering and Modification based Graph Anonymization Methods with Constraints

this paper a comparison is performed on two of the key methods for graph anonymization and their behavior is evaluated when constraints are incorporated into the anonymization process. The two methods tested are node clustering and node modification and are applied to online social network (OSN) graph datasets. The constraints implement user defined utility requirements for the community structure of the graph and major hub nodes. The methods are benchmarked using three real OSN datasets and different levels of kanonymity. The results show that the constraints reduce the information loss while incurring an acceptable disclosure risk. Overall, it is found that the modification method with constraints gives the best results for information loss and risk of disclosure.

GW24-e1770 Radiofrequency catheter ablation of superior ventricular tachycardia in patients with persistent left superior vena cava

ObjectivesRadiofrequency catheter ablation of superior ventricular tachycardia (SVT) is unusual because of the anatomy. The aim of this study is to discuss the strategy of radiofrequency catheter ablation of SVT...

ASSA13-02-13 Radiofrequency Catheter Ablation of Superior Ventricular Tachycardia in Patients with Persistent Left Superior Vena Cava

<h3>Background</h3> Radiofrequency catheter ablation of superior ventricular tachycardia (SVT) is unusual because of the anatomy. <h3>Objective</h3> The aim of this study is to discuss the strategy of radiofrequency catheter ablation of SVT in patients with persistent left superior vena cava (PLSVC). <h3>Methods</h3> From June 2008 to June 2011, 17 patients with PLSVC and SVT underwent one of the following RFCA: AV node modification (8 patients), left accessory pathway (6 patients), paroxysmal atrial fibrillation (3 patient). <h3>Results</h3> Coronary sinus access through left subclavian vein in each patient. AV node modification was carried out in 8 patients. Four patients with left accessory pathway were ablated through aortic retrograde approach, and the other two patients with left side accessory pathway were accomplished through transseptal approach. Three patients with PAF were cured through circumferential pulmonary vein isolation after atrium septum puncture. The success rate was 100%, and complication was not occurred. <h3>Conclusions</h3> Even though the success rate of RFCA with PLSVC and SVT was high and the complication rate was low, the recognization of PLSVA, the skills of ablation and the precaution of complications should be payed attention.

Stellate ganglion block: A therapeutic alternative for patients with medically refractory inappropriate sinus tachycardia?

Inappropriate sinus tachycardia (IST) is a clinical syndrome characterized by presence of non-paroxysmal tachyarrhythmia manifesting with increased resting heart rate and exaggerated or persistent response to exercise or position. When IST is intolerable and medically refractory, invasive therapies such as sinus node modification or atrioventricular node ablation with placement of permanent pacemaker are tried to control symptoms. We present a 34 year old patient with symptomatic IST unresponsive to medical therapy who underwent anesthetic block of the right and left stellate ganglia. At four month follow up the patient demonstrated sustained improvement in heart rate and reported freedom from previous symptoms.

Inappropriate Sinus Tachycardia

Inappropriate sinus tachycardia (IST) is a syndrome in which the sinus heart rate is inexplicably faster than expected and associated symptoms are present. The heart rate at rest, even in a supine position, can exceed 100 beats/min; minimal activity accelerates the rate rapidly and substantially. Patients with IST may require restriction from physical activity. Mechanisms responsible for IST are understood incompletely. It is important to distinguish IST from so-called appropriate sinus tachycardia and from postural orthostatic tachycardia syndrome, with which overlap may occur. Because the long-term outcome seems to be benign, treatment may be unnecessary or may be as simple as physical training. However, for patients with intolerable symptoms, therapeutic measures are warranted. Even at high doses, β-adrenergic blockers, the first-line therapy, often are ineffective; the same is true for most other medical therapies. In rare instances, catheter- or surgically- based right atrial or sinus node modification may be helpful, but even this is fraught with limited efficacy and potential complications. Overtreatment, in an attempt to reduce symptoms, can be difficult to avoid, but is discouraged.

Frequent Additional Tachyarrhythmias in Patients with Inappropriate Sinus Tachycardia Undergoing Sinus Node Modification: An Important Cause of Symptom Recurrence

Symptom recurrence following sinus node modification (SNM) for inappropriate sinus tachycardia (IST) remains significant despite achieving acute procedural success. The impact of non-IST tachyarrhythmias on symptom recurrence remains poorly characterized. The objective was to determine the prevalence and nature of additional tachyarrhythmias preceding and following SNM for IST. Consecutive patients with IST undergoing SNM at the University of Pennsylvania were studied. SNM was initially performed using an anatomic approach targeting the superolateral crista terminalis under intracardiac echocardiographic guidance and later using an electrophysiologic approach, targeting the site of the earliest right atrial activation during maximum heart rate (HR) with isoproterenol infusion. An effort was made to shift the site more caudally until a decrease of >25% in resting HR was achieved, with a blunted response to isoproterenol and flattening of the P-wave axis in leads III and aVF. Patients were followed for arrhythmia recurrence. Tachyarrhythmias were documented with electrocardiographic monitoring and then characterized during EP study. Thirty-three patients underwent SNM and were followed for a mean of 2.0 ± 1.5 years. During follow-up, 27% developed a non-IST tachyarrhythmia and 18% developed recurrent IST. Additionally, 42% of patients had a non-IST tachyarrhythmia prior to SNM. Non-IST tachyarrhythmias are common in patients with IST before and after SNM. A major reason for symptom recurrence following SNM is development of a non-IST tachyarrhythmia. These tachyarrhythmias should be detected and treated to optimize patient outcomes.

156 A single centre experience of Ivabradine and Clonidine for inappropriate sinus tachycardia

<h3>Introduction</h3> Inappropriate sinus tachycardia (IST) is a relatively rare disease that manifests with resting tachycardia, a rapid increase in heart rate (HR) with minimal exertion, a normal ECG and absence of structural heart disease. Treatment options include β-blockade or sinus node modification which are not 100% successful. Newer agents like sinus node inhibitor (Ivabradine) or a centrally acting α-2 sympathomimetic (Clonidine) can be used but there is no success outcome data for either and there is also no evidence that one is better than the other. We present our experience of managing 6 patients with a diagnosis of IST with either Ivabradine or Clonidine or both. <h3>Methods</h3> We identified 6 patients from 2005 to 2009 with a diagnosis of IST (according to accepted international guidelines) who had been treated with either Ivabradine or Clonidine or both. Medical case records were reviewed for each patient. <h3>Results</h3> 5 out of 6 patients were women with a mean age of 27.5 years (range 16–40 years). All patients had been symptomatic for alteast 6 months before presentation to our tertiary centre. 2 patients had associated symptoms of hyperadrenergic surges. Holter monitoring prior to treatment demonstrated sinus tachycardia. Resting pre-treatment mean 24 h HR was 94±10 (range 75–100) and mean HR on minimal exertion was 157±20 (range 130–176). All patients had a structurally normal heart on echocardiogram. Tilt table testing was considered in 3 patients due to their symptoms and it excluded postural orthostatic tachycardia syndrome. Pre-treatment with β-blockers had been unsuccessful in 5/6 patients. The remaining patient had symptomatic asthma and was therefore unable to tolerate β-blockers. Ivabradine was exclusively used in 3 patients and clonidine in 2. 1 patient was started with Ivabradine but later switched over to clonidine as it was ineffective. All 4 patients taking Ivabradine failed to gain symptom relief with no significant reduction in mean 24-h HR parameters. Mean resting HR after 3 months of Ivabradine therapy was 95±9 (range 88–105) and mean HR on exertion was 159±23 (range 128–180). 2/4 patients subsequently had complete sinus node ablation and AAIR pacemaker. In contrast, the 3 patients on clonidine had greater symptom resolution and fall in resting and exercise heart rates at 3 months follow-up. Resting mean HR was 81±3 (range 78–83) and mean HR with exertion was 144±18 (range 132–164). The HR variability pre and post treatment is shown in Abstract 156 figure 1. <h3>Discussion</h3> In our case series of 6 patients, Clonidine was more effective than Ivabradine both in terms of reducing heart rate and treating symptoms for patients with inappropriate sinus tachycardia. Patients with coexisting hyperadrenergic symptoms may benefit the most. A trial of Clonidine can be recommended before considering sinus node ablation. Formal randomised controlled trials are needed to confirm our findings.

Modification of cardiovascular ion channels by gene therapy

Delivery of genes to the heart and vasculature for therapeutic purposes is an exciting strategy that is approaching clinical reality. Abnormalities of expression or function of ion channels is central to many cardiovascular diseases and gene delivery to modify ion channels is an appealing alternative to traditional therapy with small-molecule drugs. Potential therapeutic targets include hypertrophy and heart failure, atrioventricular node modification in atrial fibrillation, ventricular tachycardia and hypertension. Numerous approaches for gene delivery are under development, including use of tissue-specific promoters in viral vectors. For other applications, such as development of biological pacemakers, cells can be transduced with pacemaker genes in vitro, and then the cells implanted within the heart. There are short-term hurdles to therapeutic gene delivery to modify cardiovascular ion channels, but in the intermediate and longer term, the outlook is promising.

A Novel Method for Sinus Node Modification and Phrenic Nerve Protection in Resistant Cases

This is a case report of inappropriate sinus tachycardia in a patient who had a previous unsuccessful endocardial ablation, which had been limited due to concerns of phrenic nerve injury. The patient required a repeat ablation that utilized a novel combined epicardial and endocardial approach for sinus node modification and simultaneous protection of the phrenic nerve via an epicardial balloon.

Reduction in Ventricular Pacing After AV Node Modification in a Patient with Dual‐Chamber Pacemaker: What is the Mechanism?

Reduction in Ventricular Pacing After AV Node Modification in a Patient with Dual‐Chamber Pacemaker: What is the Mechanism?

Superior vena cava obstruction caused by repeated radiofrequency sinus node modification procedures

A 26-year-old woman was referred for implantation of a pacemaker for symptomatic bradycardia. She had undergone 3 prior radiofrequency (RF) sinus node modification procedures for symptomatic sinus tachycardia 28, 27, and 16 months before referral, respectively. As a result, her underlying rhythm was an accelerated junctional rhythm. She was dyspneic with minimal exertion and reported fatigue, palpitations, atypical chest pain, and headaches. Her heart rate and symptoms were refractory to medical trials of theophylline and hyoscymine.

Partial Cardiac Denervation and Sinus Node Modification for Inappropriate Sinus Tachycardia

We describe a case of inappropriate sinus tachycardia refractory to medical therapy and catheter sinus node ablation, which was successfully treated by surgery with approaches on both the sinus node and cardiac autonomic ganglia.

Superior vena cava syndrome: an increasingly frequent complication of cardiac procedures

A 29-year-old woman presented with chest pressure, progressive dyspnea, fatigue, and swelling of her face, neck and upper extremities. Four days earlier, she had undergone a procedure for treatment of inappropriate sinus tachycardia, during which atrioventricular node ablation and implantation of a single-lead VVI pacemaker had been performed following an unsuccessful attempt at sinus node modification. Physical examination, contrast-enhanced CT of the chest, Doppler ultrasonography of the upper extremities, venography, coagulation studies, echocardiography. Superior vena cava syndrome due to thrombotic obstruction-a complication of a cardiac procedure. Anticoagulation, catheter-directed thrombolytic therapy, mechanical thrombectomy, pericardiocentesis.

Use of Noncontact Mapping and Saline‐Cooled Ablation Catheter for Sinus Node Modification in Medically Refractory Inappropriate Sinus Tachycardia

Inappropriate sinus tachycardia (IST) is characterized by heart rate (HR) increase out of proportion to stress level. Radiofrequency (RF) modification of the sinus node (SN) is an accepted treatment modality for medically refractory IST. We describe a new technique using noncontact mapping and a saline irrigated catheter for SN modification. Seven consecutive patients with medically refractory IST were referred for ablation. Intrinsic heart rate (IHR) was calculated with complete autonomic blockade by atropine and propranolol. Isoproterenol (ISO) 1 mcg/min was initiated and increased to 10 mcg/min. Site of earliest activation was tagged at each dose of ISO once stable HR was achieved. RF ablation to target site of earliest activation at peak HR on ISO 10 mcg/min was performed. With any change in P-wave morphology, activation was reassessed and the new site of earliest activation targeted. Endpoint was a decrease in HR and change in P-wave morphology in lead III and aVF. Five of seven patients had abnormal IHR. Mean number of RF lesions was 25 (10-52). All patients had either flattening of the P wave or development of negative P waves in leads III and aVF post RF associated with a decrease in HR of > or = 25% from baseline off ISO. A caudal shift of the site of early activation compared with baseline was observed. One patient who had a prior SN modification developed symptomatic intermittent junctional bradycardia and required an atrial pacemaker 2 weeks later. The other 6 patients in follow-up from 6 to 24 months had no further IST. Noncontact mapping using the described technique in conjunction with the saline-cooled ablation catheter for SN modification in the treatment of IST may provide effective HR control.

Atrioventricular node modification and ablation for ventricular rate control in atrial fibrillation

M A c a i a p H t s e R q e v p f s 6 p a p a n o ntroduction trial fibrillation (AF) may cause embolic stroke and conestive heart failure (CHF) and increases mortality in paients with CHF. AF causes symptoms in some patients but ay be asymptomatic in others. One of the principal causes f symptoms and ventricular dysfunction is the rapid venricular response (RVR) often associated with AF. In some atients, a high vagal tone, or atrioventricular (AV) nodal isease, limits the ventricular response to AF to nearly ormal heart rates at rest and during exercise. These patients re often asymptomatic and do not develop tachycardiaediated ventricular dysfunction. In other patients, howver, AV nodal conduction is rapid, resulting in excessively igh ventricular rates at rest and during exercise. These atients are often highly symptomatic and may have tachyardia-mediated ventricular dysfunction, requiring AV odal blocking drugs such as beta receptor blockers, calium channel blockers, and digitalis, alone or in combinaion, to control ventricular rate. However, pharmacological rate control is often difficult, nd AV node–blocking drugs may cause side effects, inluding hypotension, CHF, and marked bradycardia or auses. Consequently, the nonpharmacological approaches f AV node modification or AV node ablation and paceaker implantation were developed and widely impleented in patients with AF and pharmacologically refracory RVR. This paper will review the role of AV node odification and AV node ablation with pacemaker implanation as methods for ventricular rate control in patients ith AF.

Phrenic Nerve Injury After Catheter Ablation: Should We Worry About This Complication?

Phrenic nerve injury (PNI) is a complication that can occur with catheter ablation. Data from 17 patients with PNI following different catheter ablation techniques were reviewed. PNI was defined as decreased motility (transient) or paralysis (persistent) of the hemi-diaphragm on fluoroscopy or chest X-ray. Patient's recovery was monitored. Normalization of chest images and sniff test would be considered as complete clinical recovery. Out of the 17 PNI patients (16 right, 1 left), 13 (11 persistent, 2 transient) occurred after pulmonary veins isolation with or without superior vena cava ablation. Three patients had persistent PNI after sinus node modification and one other patient experienced PNI after epicardial ventricular tachycardia ablation. Ablation was performed with different energy source including radiofrequency (n = 13), cryothermal (n = 1), ultrasound (n = 2) and laser (n = 1). Patient's symptoms varied broadly from asymptomatic to dyspnea, and even to respiratory insufficiency that required temporary mechanical ventilation support. Two patients with transient PNI resolved immediately after the procedure and the other 15 persistent PNI patients resolved within a mean time of 8.3 +/- 6.6 months. PNI caused by catheter ablation appears to functionally recover over time regardless of the energy sources used for the procedure.