Anterograde Conduction Research Articles

Low-dose dexmedetomidine sedation in patients undergoing electrophysiological study and ablation of supraventricular tachycardias in a same day setting

Abstract Background Catheter ablation for supraventricular tachycardias (SVT) can frequently cause patient discomfort, anxiety or pain. Through the years different drugs have been employed to provide an optimal sedation without interfere with inducibility of tachyarrhythmia. Moreover, the increasing number of patients with this clinical condition and the growing demand of catheter ablation, makes same day discharge mandatory. For this purpose, drugs that guarantee minimal sedation and reduce adverse events should be used. Dexedetomidine (DEX) is a selective alpha-2 agonist with analgesic and sedating effect without significant respiratory depression. Its electrophysiological effects include the sinus node and atrioventricular (AV) node depression and an increased atrial refractoriness. Albeit there is a reduction of side effects of most commonly used sedation drugs, data on the efficacy and safety profile of DEX during SVT ablation of adult patients are unclear and conflicting. Purpose The aim of this study was to assess whether optimal sedation and patient’s comfort can be achieved with a low-dose DEX without interfering with electrophysiological parameters during catheter ablation of SVT in adult population. Methods This is a single-center prospective study. Study population consisted of patients undergoing mapping and catheter ablation of SVT from January to September 2023 divided into DEX group (periprocedural infusion of Dexedetomidine 0.07-0.11 mcg/kg/h without loading dose) and non-DEX group (midazolam 1-2 mg periprocedural). Clinical and procedural data were recorded for all patients, as well as all measurements taken during electrophysiological study. Results The study population was predominantly female (60%) with a mean age of 56 ± 13.7 years. Hypotension occurred in only one patient, in the DEX group. No cases of desaturation were observed in both groups. Most of the induced tachyarrhythmias were the slow-fast type of atrioventricular nodal reentrant tachycardia (75%), whereas atrioventricular reentrant tachycardia and atrial tachycardia were less common (7.1% and 7.1%). No significant differences were recorded in relation to AV node refractoriness, atrial refractoriness, anterograde and retrograde conduction. (Table 1) Isoproterenol was required to induce tachyarrhythmia in both groups. Arrhythmia inducibility and aberrancy in tachycardia was not significantly influenced by DEX. The jump phenomenon was recorded more frequently in the DEX group (86.4% vs. 46.7%; p=0.004). The mean duration of the procedure did not differ between the two groups. All patients were discharged on the same day after 3 hours of observation. Conclusions The use of low-dose Dexedetomidine was succesful in improving periprocedural patient comfort, without reducing tachyarrhythmia inducibility or major electrophysiological parameters.

Wolf–Parkinson–White Syndrome: Diagnosis, Risk Assessment, and Therapy—An Update

Wolf–Parkinson–White (WPW) syndrome is a disorder characterized by the presence of at least one accessory pathway (AP) that can predispose people to atrial/ventricular tachyarrhythmias and even sudden cardiac death. It is the second most common cause of paroxysmal supraventricular tachycardia in most parts of the world, affecting about 0.1–0.3% of the general population. Most patients with WPW syndrome have normal anatomy, but it may be associated with concomitant congenital heart disease or systemic diseases. Although many individuals are asymptomatic, during supraventricular arrhythmia episodes, they may experience severe symptoms, including syncope or even sudden cardiac death (mainly due to pre-excited atrial fibrillation over rapidly conducting AP). In addition to arrhythmia-related symptoms, for some specific locations of the APs with overt anterograde conduction, there might be a reduction in exercise capacity mediated by a reduction in LV systolic performance due to anomalous LV depolarization. Although it is typically diagnosed through electrocardiography (ECG), additional tests are necessary for risk assessment. Management of WPW syndrome may be quite challenging and can vary from only acknowledging the presence of the accessory pathway to pharmacological treatment or radiofrequency ablation. Early diagnosis, risk assessment, and appropriate treatment are critical steps in the management of WPW syndrome, aiming to improve the quality of life and reduce the risk of life-threatening arrhythmias.

Unresponsive to Cardioversion Pre-excited Irregular Rhythm

Highlights: 1. Atrial fibrillation in the presence of an accessory pathway may present with confounding electrocardiographic signs. 2. The clinical recognition of WPW may be hindered by the presence of pre-excited AF. - Case Summary: A 46-year-old man without known past medical history was referred to the tertiary hospital emergency department after being found collapsed at home. There are no any complaints of any headache, nausea, chest pain, or paralysis of extremities before losing consciousness. His chest examination to bilateral auscultation was clear. Chest X-ray, routine blood work, and transthoracic echocardiography did not reveal any abnormalities. The initial heart rate before referral was 250-300/min and the ECG shows irregular wide QRS complex tachycardia. The ECG after cardioversions shows sinus rhythm 86 bpm with WPW type A pattern. The patient got intravenous amiodarone and intravenous lidocaine during the transfer. And the ECG on arrival at the emergency department, the heart rate was 50-150 bpm irregularly and the ECG shows atrial fibrillation with a narrow QRS complex. Discussion: Rapid anterograde accessory pathway conduction during atrial fibrillation (AF) can result in sudden cardiac death. During pre-excited AF, delta waves as the key feature of Wolff-Parkinson-White (WPW) syndrome might be obscured. We should keep in mind the diagnosis of pre-excited AF in patients presenting with irregular and wide complex tachycardia.

Radiofrequency Catheter Ablation of Mahaim Tachycardia in Adult Patients

Mahaim pathways causing reentrant tachycardia are rare but potentially dangerous arrhythmia. Catheter ablation is the definitive treatment option for individuals with this kind of tachycardia. Objective: To evaluate the efficacy and safety of radiofrequency catheter ablation of mahaim tachycardia in adult patients. Methods: A retrospective study investigated total of 40 adult patients referred to the Cardiac Electrophysiology Department of Hayatabad medical Complex Peshawar from 4th January 2017 to 21st September 2022 were enrolled. Patient’s age (20-68 years) of both male and female genders referred for radiofrequency ablation of mahaim tachycardia were studied. The tachycardia was invariably antidromic, resulting from anterograde conduction via the Mahaim pathway. All the cases were followed for complications. Results: The overall mean age was 43.60 ± 12.4 years. The mean ablation and flouro time was 9.44± 6.93 minutes and 20.64 ± 9.77 minutes respectively. Hypertension and diabetes were found in 11 (27.5%) and 6 (15%) patients respectively. The successful ablation was achieved in 31 (77.5%) patients whereas 1 case was abandoned. During follow-up, one patient developed femoral hematoma as a complication. Typical Atrioventricular nodal reentry tachycardia (AVNRT) and atrial fibrillation were other tachycardia found in 3 (7.5%) and 4 (10%) respectively. The incidence of congenital anomalies such as ASD Secundum, HOCM, DCM, and Ebstein Anomaly was 2 (5%), 1 (2.5%), 1 (2.5%), and 1 (2.5%) respectively. Conclusion: The present study found that Radiofrequency ablation is effective and safe for treating Mahaim tachycardia. The success rate of RFA was 77.5%.

A compact multi-functional model of the rabbit atrioventricular node with dual pathways.

The atrioventricular node (AVN) is considered a "black box", and the functioning of its dual pathways remains controversial and not fully understood. In contrast to numerous clinical studies, there are only a few mathematical models of the node. In this paper, we present a compact, computationally lightweight multi-functional rabbit AVN model based on the Aliev-Panfilov two-variable cardiac cell model. The one-dimensional AVN model includes fast (FP) and slow (SP) pathways, primary pacemaking in the sinoatrial node, and subsidiary pacemaking in the SP. To obtain the direction-dependent conduction properties of the AVN, together with gradients of intercellular coupling and cell refractoriness, we implemented the asymmetry of coupling between model cells. We hypothesized that the asymmetry can reflect some effects related to the complexity of the real 3D structure of AVN. In addition, the model is accompanied by a visualization of electrical conduction in the AVN, revealing the interaction between SP and FP in the form of ladder diagrams. The AVN model demonstrates broad functionality, including normal sinus rhythm, AVN automaticity, filtering of high-rate atrial rhythms during atrial fibrillation and atrial flutter with Wenckebach periodicity, direction-dependent properties, and realistic anterograde and retrograde conduction curves in the control case and the cases of FP and SP ablation. To show the validity of the proposed model, we compare the simulation results with the available experimental data. Despite its simplicity, the proposed model can be used both as a stand-alone module and as a part of complex three-dimensional atrial or whole heart simulation systems, and can help to understand some puzzling functions of AVN.

Not Just a One-Way: Mahaim Accessory Pathway Concomitantly Supporting Orthodromic Atrioventricular Re-Entrant Tachycardia

We report the case of a 41-year-old female with documented narrow QRS tachycardia. During electrophysiological study, both orthodromic and antidromic atrioventricular reentry tachycardia (AVRT) were demonstrated as well as short episodes of pre-excited atrial fibrillation. Programmed atrial stimulation resulted in decremental anterograde conduction on the AP, thus confirming an unexpected Mahaim accessory pathway (AP) diagnosis. Limited 3D activation maps of the right atrium during orthoAVRT, respectively, and the right ventricle (RV) during antiAVRT were constructed and helped accurately describe the atrial and ventricular insertion points, which were superposed on the tricuspid ring, confirming the existence of a single short atrio-ventricular right free wall AP. Short atrioventricular APs with anterograde Mahaim-type conduction concomitantly sustaining orthodromic AVRT are extremely rare. Electroanatomical 3D mapping may help both to clarify the diagnosis and increase the success rate by accurately describing the insertion points of complex accessory pathways.

112 A CASE OF INCESSANT SLOW-FAST AVNRT TREATED WITH HIS BUNDLE PACING

Abstract Introduction Slow-fast AVNRT can rarely present as incessant SVT, particularly in patients with increased HV interval. We describe a case of incessant typical AVNRT, treated without transcatheter ablation. Case Presentation An 83-year-old man, with history of PAF, was admitted to our ICU complaining of dyspnea, dizziness and amaurosis. His ECG at presentation depicted sinus bradycardia, first degree AVB (PQ=400 ms) and RBBB (Fig 1A). After betablocker wash-out period, we decided to perform CSP using HBP to ensure AV synchrony and restore physiological pacing. During wash-out period, an incessant regular wide complex tachycardia with RBBB morphology and ventricular rate of 110 bpm occurred: the tracing showed a P wave immediately after the QRS, with RP < PR (Fig 1B). The tachycardia was incessant also in the EP lab. By means of 2 pacing leads (RV lead in the apical septum and RA lead in right appendage) and one diagnostic decapolar catheter (Inquiry, 2-2-2 Abbott) in His region, all connected to the polygraph, we performed an EPS. HV interval in sinus rhythm was 60 ms, AH 340 ms. The electrograms during tachycardia showed HVA sequence and 1:1 VA association, VA< 70 ms, cycle length 520 ms. Pacing from RV lead, we performed the ventricular overdrive pacing maneuver obtaining a VAV response; PPI-TCL was 280 ms and SA-VA difference was 205 ms (Fig 2A). We also noted a VA linking response to atrial overdrive pacing, and AHA response at the end of maneuver excluding JT (Fig 2B). In addition, pacing by the His catheter during tachycardia, we interrupted the arrythmia: the V signal after the last paced beat was not followed by retro-conducted A signal (Fig 2C). Finally, by administrating adenosine 12 mg the tachycardia interrupted with A as last signal recorded (Fig 2D). All these findings were consistent with an incessant typical AVNRT. We chose to treat AVRNT with sequential atrial-His pacing, placing a third lead in His region and programming the device in DDD 70-120, with selective His bundle capture, not correcting the RBBB (Fig 1C, D). Discussion In patients with poor anterograde AV nodal conduction, also slow-fast AVNRT can present as incessant tachycardia. In fact, a shorter sinus cycle length or atrial extrasystole could initiate sufficient delay in anterograde conduction to allow for recovery in conduction in the retrograde direction led to a persistent tachycardia. This case highlights the value of performing EPS diagnostic maneuvers also during PM implantations in order to personalize therapy and programming.

804 WOLF PARKINSON WHITE SYNDROME OR ASYMPTOMATIC VENTRICULAR PRE-EXITATION IN CHILDREN: EVALUATION OF ELECTROPHYSIOLOGICAL PROPERTIES CHANGES IN TWO DIFFERENT TIMING

Abstract Background In patients with Wolf Parkinson White (WPW) syndrome or asymptomatic ventricular pre-excitation (VP), electrophysiologic study (EPS) is recommended to assess and to stratify the risk of life - threatening arrhythmias and SCD. However, little information exist on the timing of EPS study. In particular, the electrophysiological properties variations of accessory pathway (AP) in patients with asymptomatic or symptomatic VP remain to be defined. Recently, the evolution of electrophysiological data was observed in a cohort of patients by including children and adults, although a transcatheter ablation (TCA) was performed during the evaluation among the two EPS. According to our knowledge, no study exists related to the changes over time in the conductive properties of an atrioventricular accessory pathway (AP) and arrhythmic vulnerability in the pediatric - young adult population. Aims The aim of our study was to investigate the evolution of clinical and electrophysiological datas of the manifest PV (intermittent or persistent), the arrhythmic vulnerability and any modifications in the features of AP anterograde conduction in symptomatic or asymptomatic children, examined on two separate timing, at least 2 years apart from one EPS to the next. Method This is a retrospective monocentric observational study performed at Bambino Gesu` Children's Hospital, Rome, Italy. Between January 2011 and July 2022, we enrolled forty-four children and young adults (32 male, mean age 10 years± 2,42) with manifest ventricular preexcitation underwent, as our standard management, at two electrophysiolgical studies (EPS, transesophageal and/or endocavitary), both at rest and during adrenergic stress (exercise testing or isoproterenol infusion) in two different timing (T0 and T1) within a minimal interval of 2 year. No transchateter ablation was performed between two EPS. Clinical and electrophysiological data were collected and compared. Results We observed a significant modification in atrioventricular accessory pathway conductive properties from T0 to T1 in basal study. In particular, at the baseline, preAVA value and 1/1 conduction VA time were respectively 306,59±43 and 292,61±61,7 and significatively decreased on occasion of second EPS evalutation (T1) (respectively to 279,51±41 with p 0,004 and 267,13±51,6, with p 0,003). Furthermore, an ARVT were induced in 14 patients in T1 respect 9 patient in T0 (p<0,03) and AF in 16 patients in T1 respect 7 patients in T0 (p 0,24). This results were not confirmed on adrenergic test during EPS evaluation. We also reported a clinically but not statistically relevant reduction of SPERRI time evaluated during EPS with stress test from T0 to T1 (from 251,44±47,9 to 206,9±36,7; p= 0,18). Conclusion There were significant and clinically rilevant changes of electrophysiological datas in young patients with symptomatic and asymptomatic VP underwent two EPS in two different timing. Therefore, in our opinion, a systematic evaluation with repeated EPS should be considered in this population.

The characteristics of pre-excitation syndrome concomitant with atrial tachyarrhythmia and the effect of radiofrequency ablation.

Wolff-Parkinson-White (WPW) concomitant with atrial tachyarrhythmia (ATA) has not been systemically characterized. Detailed electroanatomical mapping of the right atrium (RA) and/or left atrium (LA) was performed using three-dimensional mapping and the accessory pathway (AP) was mapped. WPW syndrome with ATA was diagnosed in 11 patients (median age 60 years). The characteristic of unidirectional anterograde conduction over the AP was displayed in nine patients, six of whom were intermittent. Sustained atrial tachycardia, that is, counterclockwise atrial flutter (AFL) with a median tachycardia cycle length (TCL) of 225 (220-275) ms, was mapped in eight patients; furthermore, "figure 8" right atrial reentry was mapped with TCL 250ms in one patient with a surgical history of ventricular septal defect repair. The remaining two patients underwent mitral annulus-dependent AT after paroxysmal atrial fibrillation (PAF) ablation and LA micro-reentry AT, respectively. In four patients, the location of the APs was left posterior. Left-lateral APs were identified in four patients. The locations of the APs in the remaining three patients were the right posterior and middle septum. All ATAs and APs were successfully ablated. After a median follow-up of 37 (15-72) months, no anterograde conduction over the AP was recorded, new onset of PAF was recorded in three patients, and all of them underwent circumferential pulmonary vein isolation. WPW with concomitant ATA frequently had continuous anterograde conduction over the AP with a rapid ventricular rate. Most WPWs displayed the characteristic of unidirectional anterograde conduction.

High temperature and hyperkalemia cause exit block of action potentials at the atrioventricular junction of rainbow trout (Oncorhynchus mykiss) heart

At critically high temperatures, atrioventricular (AV) block causes ventricular bradycardia and collapse of cardiac output in fish. Here, the possible role of the AV canal in high temperature-induced heart failure was examined. To this end, optical mapping was used to measure action potential (AP) conduction in isolated AV junction preparations of the rainbow trout (Oncorhynchus mykiss) heart during acute warming/cooling in the presence of 4 or 8 mM external K+ concentration. The preparation included the AV canal and some atrial and ventricular tissue at its edges, and it was paced either from atrial or ventricular side at a frequency of 0.67 Hz (40 beats min−1) to trigger forward (anterograde) and backward (retrograde) conduction, respectively. The propagation of AP was fast in atrial and ventricular tissues, but much slower in the AV canal, causing an AV delay. Acute warming from 15 °C to 27 °C or cooling from 15 °C to 5 °C did not impair AP conduction in the AV canal, as both anterograde and retrograde excitations propagated regularly through the AV canal. In contrast, anterograde conduction through the AV canal did not trigger ventricular excitation at the boundary zone between the AV canal and the ventricle when extracellular K+ concentration was raised from 4 mM to 8 mM at 27 °C. Also, the retrograde conduction was blocked at the border between the AV canal and the atrium in high K+ at 27 °C. These findings suggest that the AV canal is resistant against high temperatures (and high K+), but the ventricular muscle cannot be excited by APs coming from the AV canal when temperature and external K+ concentration are simultaneously elevated. Therefore, bradycardia at high temperatures in fish may occur due to inability of AP of the AV canal to trigger ventricular AP at the junctional zone between the AV canal and the proximal part of the ventricle.

Utility of open window mapping using high-density mapping approach in accessory pathways ablation

Abstract Introduction and purpose We sought to described a new protocol of open window mapping (OW) utilizing high-density mapping in accessory pathways (AP) in CARTO® 3 system. This protocol automatically map conventional electrophysiology criteria for AP location, as shorter local EGM AV interval (extended early meets late tool), earliest local activation time (LAT)and annotation at unipolar signal (wavefront annotation). Methods This was a single center, prospective and observational trial of 21 consecutive patients who underwent an AP catheter ablation. Results We included 16 men and 5 women, with a mean age of 32.6±17.9 years. The characteristics of AP, including mapping and ablation were described in Table 1. Twelve AP were of left location and 9 in right location. Mapping was performed in anterograde conduction in 17 patients (80.9%), retrograde in 9 patients (42.9%) and orthodromic tachycardia in 7 patients (33.3%). Mean mapping points were 3205±2034, with 29.2 min±12.5 min of mapping. All 21 patients had a successful ablation after OW mapping and mean radiofrequency time until complete AP elimination was 2.76 s. We present an example of a Left lateral AP OW mapping in antegrade and retrograde conduction in Figure 1, which shows EEML mapping tool, targeting shorter interval EGM AV or VA and color adjust to determine earliest LAT in chamber of exit. Conclusions In our experience, automatically mapping of conventional electrophysiology criteria for AP diagnostic is feasible to localize AP insertion, suggesting an increasing in effectiveness of procedure, and reducing mapping time, ablation time and X-ray exposure time. More studies should be performed to corroborate these conclusions. Funding Acknowledgement Type of funding sources: None.

A manifest nodoventricular accessory pathway with unusual electrophysiological manifestations.

A nodoventricular accessory pathway showing the degree of anterograde decremental conduction was more than the atrioventricular node.

Ebstein's Anomaly between Valve Damage and Cardiac Arrhythmia

Ebstein’s anomaly (E.A) is a congenital malformation that represents less than 1% of all congenital heart disease. They are predisposed to arrhythmias because of abnormal cardiac anatomy. We report the case of a 60-year-old female with a history of early infancy diagnosis of E.A, admitted for tachycardia with wide QRS complex. An electrophysiology study revealed an atrial rhythm and programmed atrial stimulation induced atrial tachycardia identical to the clinical tachycardia with multiple circuits. Radiofrequency ablation was not performed because of technical difficulties. At two months follow-up, the patient’s cardiac condition worsened and echocardiography revealed worsening tricuspid regurgitation. She underwent surgical repair. The postoperative course was uneventful. The diagnosis of this anomaly is mainly made by transthoracic echocardiogram, which constitutes the cornerstone of imaging examinations. Diagnosis is made when there is an apical displacement of the tricuspid septal leaflets past 8mm/m². Cardiac arrhythmias are frequent with Ebstein malformation; sudden death and accessory pathway fast-conducting AV with anterograde and retrograde conduction are commonly described in most patients. While, wide-QRS tachycardia, ventricular tachycardia (VT), or flutter through the para-septal pathway may occur. The management of tachyarrhythmias associated with E.A remains a real challenge. Even if it can be difficult given the atrial dilatation, electrophysiological exploration with possible radiofrequency ablation of symptomatic supraventricular tachyarrhythmias remains necessary. Otherwise, supraventricular tachyarrhythmia in E.A, can also be ablated surgically.

Feasibility of open window mapping approach in accessory pathways ablation

Abstract Funding Acknowledgements Type of funding sources: None. Introduction and Objectives We described a new protocol of open window mapping (OW) in accessory pathways (AP) in CARTO® 3 system. This protocol automatically mapping conventional electrophysiology criteria of AP diagnostic, as shorter local EGM AV interval (extended early meets late tool), earliest local activation time (LAT) and annotation at unipolar signal (wavefront annotation). Methods Single center, prospective and observational study of 17 consecutive patients underwent AP catheter ablation. Results Mapping was performed in anterograde conduction in 13 patients (76.5%), retrograde in 5 patients(29,4%) and orthodromic tachycardia in 2 patients (11,7%). Mean of numbers of points were 3092±2246, with 30min ± 13min of mapping. Ablation was effective in 17 patients( 100%) and RF time until complete AP elimination was 2.6s. Image 1 show representation of EEML tool, targeting shorter interval EGM AV or VA and color adjust to determine earliest LAT. Image 1 show representation of EEML tool, targeting shorter interval EGM AV or VA and color adjust to determine earliest LAT. Conclusions In our experience, automatically mapping of conventional electrophysiology criteria for AP diagnostic is able to localize AP insertion, suggesting an increasing in effectiveness of procedure, a reducing in mapping time, ablation time and X-ray exposure time.

Emergency catheter ablation: A feasible option for acute treatments of patients with unstable pre-excited atrial fibrillation.

Pre-excited atrial fibrillation (AF) is associated with increased risk of life-threatening events. However, at times, patients with pre-excited AF still repetitively suffer from hemodynamic disturbance, with resistance to acute treatments of antiarrhythmic therapy and cardioversion. To evaluate the feasibility in correcting hemodynamic disturbance, patients with pre-excited AF who underwent catheter ablation of accessory pathway as an emergency procedure, were retrospectively collected from two centers of China. The medical records of patients were analyzed and summarized in this case series. Five patients with pre-excited AF who received emergency catheter ablation of accessory pathway, were collected from two contributor centers and reported in this case series. All collected patients still repetitively suffered from hemodynamic disturbance induced by rapid anterograde conduction of AF via pathway, even guideline recommended acute interventions of intravenous antiarrhythmic therapy and cardioversion had been performed. Finally, as an emergency procedure, catheter ablation of accessory pathway was performed in collected patients. Correspondingly, the hemodynamic unstable status was greatly relieved. Meanwhile, all collected patients with high risk of pre-excited AF were combined with left-sided accessory pathway, with shortest RR interval of widened pre-excited QRS complex less than 250 ms. Thus, combination with left-sided pathway is proposed as an indicator for the increased risk of life-threatening events in patients with high risk of pre-excited AF. Emergency catheter ablation of accessory pathway is an effective option for the acute managements of patients with high risk of pre-excited AF in unstable hemodynamics, which is resistant to antiarrhythmic therapy and cardioversion.

Long-Term Clinical Outcomes From Catheter Ablation of SVT

Source: Fremed MA, Silver ES, Joong A, et al. Long-term patient experience following acutely successful ablation of supraventricular tachycardia substrate in children. Pediatr Cardiol. 2021;42(1):109-115; doi:10.1007/s00246-020-02459-zInvestigators from Columbia University Medical Center, New York, NY, and Northwestern University Feinberg School of Medicine, Chicago, IL, conducted a cross-sectional survey of pediatric patients who underwent a successful ablation for supraventricular tachycardia (SVT) to assess patient-reported long-term symptoms. Patients who underwent a successful ablation for SVT at the study institution from 2008–2012 were eligible. Participants or their caregivers were administered a survey via email, telephone, or in person that queried their post-ablation events such as recurrence, need for a repeat ablation, and post-ablation symptoms. Demographics, electrophysiologic diagnosis, and modality of the initial ablation were obtained from the participants’ medical record.The primary outcome was patient-reported cure, defined as an affirmative response to the question “Do you consider yourself/your child cured?” Investigators used descriptive statistics to assess patient-reported cure. Variables associated with patient-reported cure also were assessed.There were 269 successful ablations for SVT during the study period in a total of 259 patients, 147 of whom completed the survey. Respondents were mostly male (55%), had an accessory pathway present as the reason for SVT (76%), and received radiofrequency ablation (75%). The mean age of respondents at the time of the initial ablation was 15.2 years, with the mean follow-up time since ablation being 7.2 years.Most (84%) reported themselves cured. Recurrence occurred in 16% of respondents, and 10% required repeat ablation. Patient-reported cure was not associated with electrophysiologic diagnosis or ablation modality, though significantly more had recurrence of SVT after initial success achieved with cryoablation compared to radiofrequency ablation. Significantly more patients who did not feel cured (vs those who did feel cured) reported post-ablation symptoms (87% vs 27%, respectively; P <0.01) and experienced recurrence of arrhythmia (42% vs 10%, respectively; P = 0.01).Investigators conclude that most patients consider themselves cured after an initially successful ablation despite some continuing to report post-ablation symptoms or recurrence of arrhythmia.Dr Spar has disclosed no financial relationship relevant to this commentary. This commentary does not contain a discussion of an unapproved/investigative use of a commercial product/device.SVT is the most common rhythm disturbance in children, occurring in 0.1% to 0.4% of children.1 SVT not only has clinical impact from tachycardia episodes but has been demonstrated to affect quality of life.2 The most common forms of SVT include AV reentrant (AVRT) and AV nodal reentrant tachycardia (AVNRT), with AVRT being more common in patients who undergo catheter ablation. AVRT requires an accessory pathway (AP), which is located on the AV valve annulus, to participate in tachycardia. APs that have anterograde conduction demonstrate ventricular pre-excitation on ECG. AVNRT is the result of dual AV nodal pathways, described as fast and slow AV nodal pathways, that participate in tachycardia. For older children with weights greater than 15kg, catheter ablation is curative therapy and allows patients to avoid antiarrhythmic therapy. In patients with anterograde AP conduction, ablation eliminates risk for sudden death secondary to rapidly conducting atrial fibrillation.3 Typical indications for catheter ablation of SVT include: SVT with ventricular dysfunction, when medical therapy is not effective or not tolerated, family wishes to avoid chronic antiarrhythmic medication, and SVT with hemodynamic compromise.3 Acute success rates of catheter ablation range from 87% to 98%,3,4 with early recurrence ranging from 5% to 20% depending on substrate location and energy used. Risk of serious complication is less than 1%.3 There has been limited investigation of long-term results (years after ablation), with recurrence rates reported to be about 10%.5,6The investigators in the current study reviewed patients who underwent catheter ablation of SVT at a single institution. Of the 280 ablation procedures, 96% were acutely successful. Of these patients, 59% were reached for a median follow-up of 7.2 years. The majority of patients had an ablation for an AP. Subjective cure was reported in 124 of 147 of the study participants. A large percentage of those who reported no cure had documented recurrence. Of interest, 10% of patients who felt cured had recurrence of tachycardia. Patients who did not feel cured were more likely to report symptoms and have experienced arrhythmia. Documented recurrence of tachycardia substrate occurred in 16% of the population, with 73% within the first year and of those 52% within the first 2 months post-procedure.Long-term subjective recurrence after catheter ablation of SVT is relatively low. Recurrence is more likely in patients with persistent symptoms and in those who have had cryoablation rather than radiofrequency ablation.

Evaluation of the Criteria to Distinguish Left Bundle Branch Pacing From LeftVentricular Septal Pacing.

This study sought to assess the predictive value of the proposed electrocardiogram and intracardiac electrogram characteristics for confirmation of left bundle branch (LBB) capture. Previously proposed criteria to distinguish left bundle branch pacing (LBBP) and left ventricular septum (LVS) pacing (LVSP) have not been fully validated. A His bundle pacing lead, an LBBP lead, and a multielectrode catheter at the LVS were placed. Direct LBB capture was defined as demonstration of retrograde His potential on the His bundle pacing lead and/or anterograde left conduction system potentials on the multielectrode catheter during LBBP. The routinely used parameters-His, LBB potential, time from stimulus to peak ventricular activation (Stim-LVAT), and paced QRS morphology during LVSP and LBBP at various depths and outputs were analyzed. Thirty patients (21 non-left bundle branch block [LBBB], 9 LBBB) who demonstrated direct LBB capture using the defined criteria were included. The proportion of paced right bundle branch block was 100% during LBB capture in all patients compared to 23.4% in non-LBBB and 44.4% in LBBB during LVSP. LBB potential was recorded in all patients during intrinsic rhythm (non-LBBB group) or His corrective pacing in LBBB. Paced QRS duration was longer during selective LBBP compared to nonselective LBBP or LVSP only. All patients with characteristics of selective LBBP or abrupt decrease in Stim-LVAT of≥10ms demonstrated LBB capture. Direct LBB capture can be confirmed by recording retrograde His potential and anterograde left conduction system potentials. Abrupt decrease in Stim-LVAT of≥10ms and demonstration of selective LBBP could be used as simple criteria to confirm LBB capture.

Comparison of electrophysiological characteristics of right- and left-sided Mahaim-type accessory pathways.

Mahaim-type accessory pathways (MAPs) are generally right-sided due to the embryological differentiation, but left-sided localization is also possible. This study aims to compare the clinical and electrophysiological characteristics of right- and left-sided MAPs. Of 251 patients diagnosed with AP by electrophysiological study between November 2015 and February 2020, 12 patients with MAP were included (right sided n = 8, left sided n = 4). MAP was diagnosed if; (1) no retrograde conduction; (2) anterograde decremental conduction; (3) adenosine sensitivity; and (4) Mahaim potential at successful ablation site were present. Ten of twelve MAPs were clustered on the lateral walls of the mitral (n = 3, 75%) and tricuspid annuli (n = 7, 87.5%). Right-sided MAPs were mostly long pathways extending toward the conduction system whereas left-sided MAPs were short extending toward the neighboring myocardium. For right- and left-sided APs, the median QRS times were 129 and 156 ms (p = .042), the median VAbl -RVApex intervals were -12 and 64 ms (p = .007), the median QRS-V(His) intervals were 16 and 86 ms (p = .120), and the median VAbl -QRS interval was -8 and 12 ms (p = .017), respectively. Coexistence of dual atrioventricular node physiology was observed only in right-sided APs (n = 3, 37.5%). MAPs are more typically located on the right but may rarely be seen on the left. Catheter ablation was associated with high success without complications.

The Effect of Accessory Pathway Location on Cardiac Function in Adult Patients with Wolff-Parkinson-White Syndrome.

Introduction The relationship between ventricular pre-excitation and left ventricular dysfunction has been described in the absence of sustained supraventricular tachycardia in a series of case reports. However, there have been no systematic studies about the effect of ventricular pre-excitation on cardiac function in adult patients with different accessory pathway locations. Methods and Results Patients were divided into four groups based on the type and location of their accessory pathway: septal, right free wall, left free wall, and concealed. N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels, electrocardiogram recordings, electrophysiological properties, and transthoracic echocardiographic data (septal-to-posterior wall motion delay (SPWMD) and interventricular mechanical delay (IVMD) indicating intraventricular and interventricular dyssynchrony) were compared before and after successful ablation. Before radiofrequency catheter ablation, left ventricular ejection fraction (LVEF) was significantly lower in patients with septal and right free wall accessory pathways. Within three months after radiofrequency catheter ablation, NT-proBNP levels decreased, left ventricular function improved, and intraventricular left ventricular dyssynchrony disappeared. There was a negative correlation between initial LVEF with initial QRS duration and initial SPWMD. Notably, SPWMD had a stronger correlation with LVEF than initial QRS duration. Conclusions Anterograde conduction with a septal or right free wall accessory pathway may cause left ventricular dyssynchrony and impair left ventricular function. Intraventricular left ventricular dyssynchrony seems to be responsible for the pathogenesis of left ventricular dysfunction. Radiofrequency catheter ablation results in decreased NT-proBNP levels, normalized QRS duration, mechanical resynchronization, and improved left ventricular function.

Abstract 14912: Sotalol-induced Wide Complex Rhythm: What is the Mechanism?

Introduction: Delta waves associated with atrioventricular accessory pathways (APs) may manifest with autonomic tone, heart rate, and rhythm changes. Rarely, drugs like sotalol can block AV nodal conduction, revealing latent WPW, one treatable cause of sudden death. Case report: A 38-year-old man was admitted for sotalol loading due to frequent typical atrial flutter and SVT and a desire to avoid catheter ablation. He had a history of cardiac arrest with adenosine and tachycardia-induced cardiomyopathy. After recovery, cardiac MRI showed a normal heart without scar. Admission 12-lead ECG ( Figure A ) revealed normal sinus rhythm without other abnormality. With administration of sotalol, the patient developed a wide complex rhythm ( Figure B ). Interpretation of the rhythm indicated presence of a latent AP and a repeat ECG ( Figure C ) confirmed manifest preexcitation. After consenting to electrophysiology study, the patient developed a short RP tachycardia ( Figure D ) which terminated with Valsalva. The patient underwent successful catheter ablation of the pathway located at the anterior floor of the coronary sinus body and the cavotricuspid isthmus. Discussion: The differential diagnosis for a wide complex rhythm in this setting includes rate-related aberrancy, idioventricular rhythm, phase 4 aberrancy, and preexcitation from an AP. Shortened and consistent PR intervals in the tracing lead to preexcitation as the only possible mechanism. APs that are capable of anterograde conduction but are not manifest in sinus rhythm are termed latent APs. Conditions that may cause this phenomenon include opposite autonomic effects on the AP and the AV node, increased atrial conduction time, or concealed retrograde conduction into the AP. Sotalol typically increases the retrograde effective refractory period of the AP but has variable anterograde effect. Sotalol has not previously been reported to reveal a latent AP but may have acted through one of the stated mechanisms.