Concealed Pathway Research Articles

Cellular immunity analysis by a modular acoustofluidic platform: CIAMAP.

The study of molecular mechanisms at the single-cell level holds immense potential for enhancing immunotherapy and understanding neuroinflammation and neurodegenerative diseases by identifying previously concealed pathways within a diverse range of paired cells. However, existing single-cell pairing platforms have limitations in low pairing efficiency, complex manual operation procedures, and single-use functionality. Here, we report a multiparametric cellular immunity analysis by a modular acoustofluidic platform: CIAMAP. This platform enables users to efficiently sort and collect effector-target (i.e., NK92-K562) cell pairs and monitor the real-time dynamics of immunological response formation. Furthermore, we conducted transcriptional and protein expression analyses to evaluate the pathways that mediate effector cytotoxicity toward target cells, as well as the synergistic effect of doxorubicin on the cellular immune response. Our CIAMAP can provide promising building blocks for high-throughput quantitative single-cell level coculture to understand intercellular communication while also empowering immunotherapy by precision analysis of immunological synapses.

Systematic observation-based diagnosis of atrioventricular nodal reentrant tachycardia with a bystander concealed nodoventricular pathway.

This study aimed to establish a systematic method for diagnosing atrioventricular nodal reentrant tachycardia (AVNRT) with a bystander concealed nodoventricular pathway (cNVP). We analyzed 13 cases of AVNRT with a bystander cNVP, 11 connected to the slow pathway (cNVP-SP) and two to the fast pathway (cNVP-FP), along with two cases of cNVP-related orthodromic reciprocating tachycardia (ORT). The diagnostic process was summarized in three steps. Step 1 was identification of the presence of an accessory pathway by resetting the tachycardia with delay (n = 9) and termination without atrial capture (n = 4) immediately after delivery of a His-refractory premature ventricular contraction (PVC). Step 2 was exclusion of ORT by atrio-His block during the tachycardia (n = 4), disappearance of the reset phenomenon after the early PVC (n = 7), or dissociation of His from the tachycardia during ventricular overdrive pacing (n = 1). Moreover, tachycardia reset/termination without the atrial capture (n = 2/2) 1 cycle after the His-refractory PVC was specifically diagnostic. Exceptionally, the disappearance of the reset phenomenon was also observed in the two cNVP-ORTs. Step 3 was verification of the AVN as the cNVP insertion site, evidenced by an atrial reset/block preceding the His reset/block in fast-slow AVNRT with a cNVP-SP and slow-fast AVNRT with a cNVP-FP or His reset preceding the atrial reset in slow-fast AVNRT with a cNVP-SP. AVNRT with a bystander cNVP can be diagnosed in the three steps with few exceptions. Notably, tachycardia reset/termination without atrial capture one cycle after delivery of a His-refractory PVC is specifically diagnostic.

Phenylalanine treatment generates scent in flowers by increased production of phenylpropanoid-benzenoid volatiles

Fragrance is a desirable characteristic for cut flowers, but is rare among commercial cultivars. To date, there are no transformed commercial flower cultivars with increased fragrance, despite the fact that genetic engineering can generate fragrance in ornamentals without compromising on other commercial traits. One of the major volatile groups responsible for fragrance of flowers such as roses, petunia, snapdragon and clarkia, are the phenylalanine-derived benzenoid phenylpropanoids (BPVs). Here we show that a variety of commercial flowers, belonging to taxonomically distant plant species have the potential of producing fragrant BPVs when treated with exogenous phenylalanine. This group of flowers includes chrysanthemums, roses, anemones, Ornithogalum dubium and gerberas. Chrysanthemums, among the five leading flowers in the cut flower industry, lack flowery fragrance. However, treatment of cut chrysanthemums with phenylalanine resulted in an increase in BPVs preexisting in the flowers, producing a flowery fragrance clearly distinguished by a sensory panel. Similarly, phenylalanine treatment of anemones, also lacking fragrance, resulted in fragrant flowers. However, unlike chrysanthemums, in anemones, in addition to increasing preexisting BPVs, phenylalanine treatment resulted in production of new BPVs, not detected in non-treated flowers. Production of novel compounds due to phenylalanine treatment suggests that concealed metabolic pathways do exist in plants, may be activated by increased substrate availability. This study presents the potential of phenylalanine treatment as a way for increasing flowery fragrance in a large variety of non-fragrant commercially important plants.

Exercise-Induced Arrhythmias.

Scenario: This single-lead II rhythm strip was obtained from a 70-year-old woman during an exercise stress test done as part of screening for participation in a research trial. Her medical conditions included being overweight (body mass index [weight in kilograms divided by height in meters squared], 28.8), pharmacologically managed hypertension, and hypercholesterolemia. To be eligible to participate in the research trial, the patient had to complete a recumbent bike exercise stress test to demonstrate that she could exercise safely. The 10-second strip shown below was her electrocardiogram (ECG) during peak exercise. Although the patient was asymptomatic during this rhythm, do you think it is safe for her to exercise without further medical evaluation?Normal sinus rhythm at 80/min with a sudden onset of supraventricular tachycardia (SVT) at 150/min induced by exercise stress test.Supraventriculat tachycardias are a category of cardiac rhythms originating at or above the atrioventricular (AV) node; thus, SVTs have a narrow QRS complex with a rapid heart rate greater than150/min that is typically faster than sinus tachycardia. The heart rate with SVTs is often so fast that it is difficult to distinguish whether atrial activity (presence of P wave) is occurring. Paroxysmal SVT, or PSVT, is characterized by rapid onset and offset of SVT, which may occur during vigorous exercise. In this case, the PSVT was triggered by a premature atrial contraction (PAC) as indicated by the arrow on the strip above. In the absence of accessory or concealed pathways between the atria and ventricles, a PAC can initiate a reentry pathway with different refractory and conduction speeds in the AV node (called AV nodal reentry tachycardia [AVNRT]). Such AV nodal reentry manifests hidden or inverted P waves and leads to a very fast heart rate (150-240/min), which can dramatically reduce ventricular filling and may lead to symptoms and/or myocardial ischemia in patients with coronary artery disease.In this case, the patient was asymptomatic and the PSVT abruptly stopped after exercise testing was terminated. Typically, PSVTs due to an accessory pathway are seen in young people and are not necessarily dangerous but rather unpleasant when cardiac palpitations are sensed. In such cases, the treatment of choice is catheter ablation, which can be curative. On the other hand, PSVT due to AVNRT is seen in cases of enhanced automaticity of the AV node mediated by stimulants (eg, excessive caffeine), medications (eg, β-blockers), or psychological factors (eg, stress) as seen in this patient. However, given that this patient is an older person with cardiac risk factors, she may not tolerate the sudden decrease in cardiac output associated with rapid heart rates, thus putting her at risk of falling during exercise. Therefore, a full cardiac evaluation is needed before this patient is enrolled in the research trial.

Electrophysiologic approach to diagnosis and ablation of patients with permanent junctional reciprocating tachycardia associated with complex anatomy and/or physiology.

Permanent junctional reciprocating tachycardia (PJRT) is a rare supraventricular tachycardia (SVT), typically involving a single decremental posteroseptal accessory pathway (AP). Four patients with long RP SVT underwent electrophysiology (EP) study and ablation. The cases were reviewed. Case 1 recurred despite 3 prior ablations at the site of earliest retrograde atrial activation during orthodromic reciprocating tachycardia (ORT). Mapping during a repeat EP study demonstrated a prepotential in the coronary sinus (CS). Ablation over the earliest atrial activation in the CS resulted in dissociation of the potential from the atrium during sinus rhythm. The potential was traced back to the CS os and ablated. Case 2 underwent successful ablation at 6 o'clock on the mitral annulus (MA). ORT recurred and successful ablation was performed at 1 o'clock on the MA. Case 3 had tachycardia with variation in both V-A and A-H intervals which precluded the use of usual maneuvers so we used simultaneous atrial and ventricular pacing and introduced a premature atrial contraction with a closely coupled premature ventricular contraction. Case 4 had had two prior atrial fibrillation ablations with continued SVT over a decremental atrioventricular bypass tract that was successfully ablated at 5 o'clock on the tricuspid annulus. A second SVT consistent with a concealed nodoventricular pathway was successfully ablated at the right inferior extension of the AV nodal slow pathway. We describe challenging cases of PJRT by virtue of complex anatomy, diagnostic features, and multiple arrhythmia mechanisms.

The various manifestations of concealed nodofascicular/nodoventricular bypass tracts

The various arrhythmic manifestations of concealed nodofascicular (NF)/nodoventricular (NV) bypass tracts (BPTs) are poorly understood. The purpose of the study was to define diagnostic criteria for supraventricular tachycardias (SVTs) associated with concealed nodal pathways (NPs). We reviewed 11 patients with concealed NPs who underwent electrophysiology study and ablation for symptomatic SVT. Of 11 patients 7 (64% women; mean age 54 ± 16 years), NF/NV BPTs were active bystanders during atrioventricular nodal reentrant tachycardia (atypical [n = 4]; typical [n =2]) or participants during orthodromic NF/NV reentrant tachycardia (n = 5). The majority (10 of 11 [91%]) had nodal origin in the slow pathway (SP) and 7 of 11 (64%) presented as long RP SVT. Ablation of the SP targeting the right (n = 10) or left (n = 1) inferior extension eliminated concealed NP-associated SVTs in all patients. Concealed NF/NV BPTs are active bystanders equally as common as participants during SVT. They typically insert into the SP and often present as long RP SVT. SP ablation eliminates concealed NF/NV BPT-associated SVTs regardless of the mechanism.

A novel pacing maneuver to verify the postpacing interval minus the tachycardia cycle length while adjusting for decremental conduction: Using “dual-chamber entrainment” for improved supraventricular tachycardia discrimination

The postpacing interval (PPI) minus the tachycardia cycle length (TCL) is frequently used to investigate tachycardias. However, a variety of issues (eg, failure to entrain, decremental conduction, and oscillating TCLs) can make interpretation of the PPI-TCL challenging. The purpose of this study was to investigate a novel maneuver to confirm the PPI-TCL value without using either the ventricular PPI or the TCL interval and to assess the ability of this maneuver to identify decremental conduction and differentiate supraventricular tachycardias. We analyzed 77 intracardiac recordings from patients (age 25 ± 20 years; 40 female) who underwent catheter ablation of atrioventricular nodal reentrant tachycardia (AVNRT) or orthodromic reciprocating tachycardia (ORT) with a concealed pathway. We calculated the PPI-TCL, the AH-corrected PPI-TCL, and estimated the PPI-TCL using "dual-chamber entrainment" calculated as [PPIV - TCL = Stim(A→V) + Stim(V→A) - PPIA]. The PPI-TCL calculated by dual-chamber entrainment highly correlated with the observed and AH-corrected PPI-TCL (R2= 0.79 and 0.96, respectively; P <.001]. A dual-chamber entrainment PPI-TCL value of 80 ms correctly differentiated all AVNRT from septal ORT cases, whereas the standard PPI-TCL and AH-corrected PPI-TCL methods were incorrect in 14% and 6% of cases, respectively. Dual-chamber entrainment identified 3 ± 10 ms of additional decremental conduction beyond AH prolongation, including 4 pathways with significant (>10 ms) decrement. Dual-chamber entrainment estimates the PPI-TCL value without using either the ventricular PPI or the TCL interval. This maneuver adjusts for all decremental conduction, including within concealed pathways, where a dual-chamber entrainment PPI-TCL value >80 ms favors AVNRT over ORT. This maneuver can be used to verify the observed PPI-TCL value in challenging cases.

Unmasking of a concealed slow pathway by atrioventricular simultaneous basic pacing

A 71-year-old woman with narrow QRS tachycardia was referred for catheter ablation. The clinical tachycardia was diagnosed as slow/fast form of atrioventricular (AV) nodal reentrant tachycardia (AVNRT) with the upper common pathway. Although neither conventional nor double atrial programmed extrastimulation (APS) showed any evidence of a dual AV nodal pathway, AV simultaneous pacing during basic stimulation preceding APS (AVSP-APS) reproducibly revealed a dual AV nodal pathway as a double ventricular response. The AVSP-APS pacing method may be helpful to unmask a "concealed slow pathway" in patients with AVNRT.

Is There a Difference in Tachycardia Cycle Length during SVT in Children with AVRT and AVNRT?

There are limited adult data suggesting the tachycardia cycle length (TCL) of atrioventricular reentry tachycardia (AVRT) is shorter than atrioventricular nodal reentry tachycardia (AVNRT), though little data exist in children. We sought to determine if there is a difference in TCL between AVRT and AVNRT in children. A single-center retrospective review of children with supraventricular tachycardia (SVT) from 2000 to 2015 was performed. Age ≤ 18 years, invasive electrophysiology study (EPS) confirming AVRT or AVNRT. Atypical AVNRT, congenital heart disease, antiarrhythmic medication use at time of EPS. Data were compared between patients with AVRT and AVNRT via t-test, χ2 test, and linear regression. A total of 835 patients were included (12 ± 4 years, 52 ± 31 kg, TCL 321 ± 55 ms), 539 (65%) with AVRT (270 Wolff-Parkinson-White, 269 concealed pathways) and 296 (35%) with AVNRT. Patients with AVRT were younger (11.7 ± 4.1 years vs 13.0 ± 3.6 years, P < 0.001) and smaller (49 ± 22 kg vs 57 ± 43 kg, P < 0.001). In the baseline state, the TCL was shorter in AVRT than AVRNT (329 ± 51 ms vs 340 ± 60 ms, P = 0.04). In patients requiring isoproterenol to induce SVT, there was no difference in TCL (290 ± 49 ms vs 297 ± 49 ms, P = 0.26). When controlling for age, there was no difference in TCL between AVRT and AVNRT at baseline or on isoproterenol. The regression equation for TCL in the baseline state was TCL = 290 + 4 (age), indicating the TCL will increase by 4 ms above a baseline of 290 ms for each year of life. When controlling for age, there is no difference in the TCL between AVRT and AVNRT in children. Age, not tachycardia mechanism, is the most significant factor in predicting TCL.

Same-day cardiac catheter ablation is safe and cost-effective: Experience from a UK tertiary center.

Catheter ablation is a curative intervention for common arrhythmias such as supraventricular tachycardia and atrial flutter. Many centers still admit patients overnight after this procedure. This study was performed to evaluate the safety and cost-effectiveness of same-day standard catheter ablation. We conducted a retrospective study of all consecutive elective same-day procedures performed between 2010 and 2014. Data were collected on baseline parameters, procedure details and success, postoperative complications, unplanned overnight hospital admissions, and clinical outcome (including mortality) at 4-month follow-up. A cost analysis of potential savings was also performed. A total of 1142 patients underwent planned same-day electrophysiological study with or without ablation. Radiofrequency ablation was performed in 897 of these patients (mean age ± standard error 56 ± 0.6 years, range 16-95 years, 467 males), with 921 arrhythmias ablated and with complete procedural success in 883 cases (96%). There were 92 unplanned admissions (10.3%): 50 for concealed pathways that required transseptal puncture, 19 for immediate complications (including 9 femoral bleeds and 5 pacemakers for heart block), 12 admitted at the operator's discretion, and 11 for other clinical reasons. All had transthoracic echocardiography after the procedure, and none had significant pericardial effusion. At 4-month follow-up, there were 16 readmissions (1 deep vein thrombosis, 3 pericarditic chest pain, 2 femoral hematomas, 7 palpitations, and 3 others) and 1 death (unrelated to ablation). An overnight stay at our center costs $450 (£300); same-day ablation over this period saved our institution $365,000 (£240,000). Same-day standard catheter ablation is safe and cost-effective, with significant benefits for patients and health care providers. This is particularly important given the current financial climate.

Bundle branch aberrancy in predicting mechanism of SVT

A 26 year old lady with structurally normal heart underwent electrophysiological study (EPS) and radiofrequency ablation for recurrent supraventricular tachycardia (SVT). EPS revealed orthodromic atrioventricular reciprocating tachycardia (AVRT) involving a left sided concealed pathway. This report demonstrates the clues provided by spontaneous bundle branch aberrancy during SVT in predicting the mechanism of tachycardia.

Chiral and Isotope Analyses for Assessing the Degradation of Organic Contaminants in the Environment: Rayleigh Dependence

The Rayleigh equation is frequently used to describe isotope fractionation as a function of conversion. In this article we propose to draw a parallel between isotope and enantiomeric enrichments and derive a set of conditions that allow the use of the Rayleigh approach to describe the enantiomeric enrichment-conversion dependencies. We demonstrate an implementation of the Rayleigh equation for the enantioselective enzymatic hydrolysis of Mecoprop-methyl, Dichlorprop-methyl, and dimethyl-methylsuccinate by lipases from Pseudomonas fluorescens, Pseudomonas cepacia, and Candida rugosa. The data obtained for all the studied reactions gave good fits to the Rayleigh equation, with a linear regression R(2) > 0.96. In addition to that, our analysis of four microcosm studies on the hydrolysis of the individual enantiomers of Dichloroprop methyl, Lactofen, Fenoxaprop-ethyl, and Metalaxyl reported in the literature by other research groups revealed a suitability of the Rayleigh dependence. Two dimensional plots describing the isotope fractionation versus enantiomeric enrichment are demonstrated for all studied cases. Processes not accompanied by enantiomeric enrichment (acid and base hydrolysis) and by isotope enrichment (transesterification) are demonstrated, their 2-D plots are either horizontal or vertical which can illuminate concealed degradation pathways.

Catheter ablation of drug resistant supraventricular tachycardia in neonates and infants

The aim of this study was to evaluate the indications, results and complications of radiofrequency ablation (RFA) and transcatheter cryoablation (TCA) in neonates and infants with incessant drug-resistant supraventricular tachycardia (SVT). Out of 225 patients who underwent RFA and TCA at our center between January2010 and February 2012, 5 patients under the age of 1 (4 male, 1 female) were evaluated. The indication for RFA/TCA was recurrent hemodynamically compromising drug-resistant SVT. Over a 2-year period, 6 ablation procedures were performed in 5 patients. Average patient age was 3.3 ± 3.9 months (12 days - 9.5 months); average patient weight was 5.4 ± 2.2 kg (3.5-9 kg). One patient had ventricular septal defect, 1 had corrected transposition of great arteries, ventricular septal defect, right ventricular hypoplasia and pulmonary hypertension, while 3 had only patent foramen ovale. Electrophysiology study showed 1 accessory pathway in each patient (right posteroseptal in 2, left posteroseptal in 2 and left lateral in 1). The pathway was manifest in 1 patient with Wolff-Parkinson-White syndrome (WPW) and concealed in the rest. Two of the concealed pathways had slow conduction time and decremental properties (the permanent form of junctional reciprocating tachycardia). Two patients underwentTCA and 3 - RFA, with an acute success rate of 100%. In the first week after the procedure, the patient with the complex cardiac anomaly and WPW developed recurrence and under went ablation again. Four of the procedures were carried out using an electroanatomic mapping system besides fluoroscopy. Average procedure time was 167 min (100-234); fluoroscopy time was 8.2 min (0.7-19.7). None of the patients developed major complications. After the average follow-upperiod of 6.5 months (3-18), all patients were symptom-free without medication. RFA and TCA can be performed successfully in neonates and infants within cessant medically refractory SVT.

Reducing Patient Radiation Dosage during Pediatric SVT Ablations Using an “ALARA” Radiation Reduction Protocol in the Modern Fluoroscopic Era

Ablation for supraventricular tachycardia (SVT) relies upon fluoroscopy (fluoro), which exposes the patient and staff to ionizing radiation. The objective of this work was to present a new "ALARA--As Low As Reasonably Achievable" protocol with alterations to fluoroscopic x-ray parameters to reduce dose without an electroanatomical (EAM) approach. All patients <21 years of age undergoing ablation of SVT at our institution from June 2011 to April 2012 were included. EAM was not utilized in any case. An ALARA protocol of low frame rates (2 or 3 fps), low fluoro dose/frame (10-18 nGy/frame), and other techniques aimed at reducing use of fluoroscopy were employed. Demographics, procedural, and radiation data were analyzed. Forty-two patients underwent ablation and were studied. Median age was 14.1 years (range 4.8-21.1 years), weight was 51 kg (range 18.2-75 kg), and body surface area was 1.51 m(2) (range 0.72- 1.94 m(2)). Seventeen (41%) had Wolff-Parkinson-White syndrome, 14 (33%) atrioventricular nodal reentrant tachycardia, and 11 (26%) concealed pathways. Median procedural time was 114 minutes (57-246 minutes). Median dose area product (DAP) for posterioanterior and lateral fluoroscopy was 343.2 uGym(2) (range 38.2-3,172 uGym(2)); the median air Kerma product (K) was 45.4 mGy (range 6.7-567.5 mGy). DAP and K are lower than prior data from EAM and fluoroscopy techniques. The acute success rate was 95%; no procedural complications. An ALARA protocol for ablation of SVT reduced radiation to below levels previously reported for combined EAM/fluoro approaches. Success rates were excellent with no complications and without the costs of EAM.

Accessory Pathway Ablation in a 6-Year-Old Girl Using Remote Magnetic Navigation as an Alternative to Cryoablation

A 6-year-old girl with evidence of a parahisian accessory pathway on a baseline electrocardiogram underwent successful catheter ablation using magnetic navigation. Magnetic remote controlled ablation eliminated the parahisian pathway with the first radiofrequency application. A second anterolaterally located concealed pathway was successfully ablated in the same session, resulting in exclusively atrioventricular nodal conduction bidirectionally (total fluoroscopy, 4min; 25μGy).

Catheter Ablation of Two Accessory Pathways in Elusive Ebstein's Anomaly: Procedure Facilitation With Use of a Long Vascular Sheath

A 17-year-old adolescent presenting with multiple episodes of palpitations over the previous 9 months refractory to antiarrhythmic drug therapy and with manifest preexcitation on the 12-lead surface electrocardiogram (type B Wolff-Parkinson-White syndrome) was referred for radiofrequency (RF) catheter ablation. The initial echocardiographic evaluation was reported normal. The first procedure was tedious and prolonged, hampered by the occurrence of mechanical block in the antegrade conduction of the accessory pathway (loss of preexcitation) for the duration of the procedure. There was only retrograde conduction noted via a right lateral accessory pathway and inducible atrioventricular tachycardia with the participation of this concealed pathway, which was successfully ablated after the delivery of 9 radiofrequency energy applications (...excerpt)

Neonatal supraventricular tachycardia: outcomes over a 27‐year period at a single institution

To establish prognosis in neonatal supraventricular tachycardia. All 109 patients <30 days with supraventricular tachycardia due to accessory atrioventricular or atrioventricular nodal reentry from 1971 to 1997 at one institution were retrospectively reviewed. There were seven deaths (6%): five cardiac failure, two not related to arrhythmia. Freedom from arrhythmia, antiarrhythmic medication or late recurrence of arrhythmia was 52% at 1 year, 82% at 5 years and 83% at 10 years. At 10 years 31% of patients with ventricular preexcitation on electrocardiogram had symptoms or medication compared to 6% in those with concealed pathways (p < 0.0001). In patients who needed multiple drugs or more than 6 days to obtain initial arrhythmia control, 50% had arrhythmias at 10 years, compared to 10% of more easily treated cases (p = 0.001). Ventricular preexcitation and initial treatment difficulties, but not foetal presentation, were significant risk factors for prolonged arrhythmia, as confirmed by multivariate analysis. In the remainder, arrhythmia resolved in approximately 90%.

A new algorithm for concealed accessory pathway localization using T-wave-subtracted retrograde P-wave polarity during orthodromic atrioventricular reentrant tachycardia

AP localization can be predicted by analyzing the polarity of the delta wave, QRS polarity, and R/S ratio in patients with Wolff-Parkinson-White syndrome. However, the estimation of AP location is limited in patients with concealed pathways during atrioventricular reentrant tachycardias (AVRT). Thus, we analyzed retrograde P-wave polarity during orthodromic AVRT and developed an algorithm to predict the localization of concealed accessory pathways (AP). A total number of 131 patients with a single AP and inducible orthodromic AVRT were included. The initial 61 patients were analyzed retrospectively for algorithm development, whereas 70 patients were evaluated prospectively. The retrograde P-wave polarity was analyzed by subtracting the superimposing T-wave during orthodromic AVRT using custom-designed software. Four leads of the surface electrocardiogram (ECG) were identified to accurately distinguish AP locations assigned to four different regions around each AV annulus: I, aVR, aVL, and V(1). Lead V(1) was used to differentiate right (negative or isoelectric) from left (solely positive) APs. Retrograde P-wave in lead I was negative in left posterior APs exclusively and became more positive with an AP location shifting towards right anterior. P-wave polarity in lead aVR demonstrated a shift from a positive polarity from left APs to isoelectric in right APs. The opposite direction (shift from positive to isoelectric) was observed for lead aVL. The subsequently developed algorithm for concealed AP localization using these surface ECG leads demonstrated a high sensitivity, specificity, and positive predictive value particularly for common AP localizations (left posterior and inferior, and right septal) when applied in a prospective fashion. Concealed AP localization can be accurately predicted by the analysis of retrograde P-wave polarity during orthodromic AVRT using the algorithm derived from the presented study.

Pharmacological Therapy in Children with Atrioventricular Reentry: Which Drug?

Atrioventricular reentrant tachycardia (AVRT) is the most common cause of supraventricular tachycardia in young children. In nearly 70% of cases, there is manifest preexcitation on electrocardiogram. In the rest, the accessory pathway is concealed. Drugs control AVRT by affecting conduction through the atrioventricular node (beta-blockers, digoxin, verapamil) or accessory pathway (flecainide, propafenone) or both (sotalol, amiodarone). Adenosine is the drug of choice in acute management of AVRT in hemodynamically stable children. In adenosine-resistant cases, intravenous flecainide, procainamide, esmolol, propafenone and amiodarone are other treatment options. Hypotension and bradycardia can occur during administration of these drugs. Verapamil may be used to treat AVRT using a concealed pathway. Verapamil should be avoided in infants and in patients with decreased cardiac function. In chronic management, catheter ablation is the preferred treatment in older children with frequent AVRT. In infants and small children, ablation is associated with higher risk, and pharmacologic management is recommended. Beta-blockers are the preferred first line drugs for chronic management. In patients with concealed accessory pathway, digoxin and calcium channel blockers are alternative options. Sotalol, flecainide, propafenone and amiodarone can be prescribed in resistant cases. Flecainide and propafenone should be avoided in children with structurally abnormal hearts because of a higher risk of proarrhythmia. The initiation of flecainide, propafenone and sotalol therapy is recommended in an inpatient setting to monitor for proarrhythmias.

Efficacy of Electroanatomical Mapping for Radiofrequency Ablation of Right-sided Accessory Pathways

Introduction: Due to the difficulty in performing detailed mapping around the tricuspid annulus and the high occurrence of mechanical trauma during the procedure, the outcome of right‐sided accessory pathway (AP) ablation still has a relatively high primary failure and recurrence rate.Methods and Results: Six patients with right free‐wall APs underwent electroanatomical mapping. The AP had retrograde unidirectional conduction in 3 patients, anterograde unidirectional conduction in 1 patient, and bidirectional conduction in 2 patients. The right atrial (RA) activation map was constructed during right ventricular (RV) pacing (n = 5), and the RV activation map was constructed during RA pacing (n = 3). During mapping, the AP conduction was interrupted by catheter mechanical trauma in 3 patients. The first RF application successfully eliminated the AP conduction within 2 seconds in 3 patients with concealed pathways. In the remaining 3 patients, rescue RF energy was delivered at the tagged bump site on the map. The mean procedure time was 214 ± 77 minutes, and mean fluoroscopy time 63 ± 23 minutes. No recurrence occurred during 12 ± 3.2 months of followup in any of the patients.Conclusions: With the guidance of an electroanatomical mapping system, right‐sided accessory pathways can be satisfactorily eliminated without later recurrence.