Electrophysiological features and radiofrequency catheter ablation of accessory pathways associated with atrioventricular discordance.

INTRODUCTION: Although a high prevalence of the presence of an accessory pathway (AP) associated with atrioventricular (AV) discordance has been reported, a case series of its characteristics and the results of catheter ablation (CA) have not been sufficiently documented. METHODS AND RESULTS: We retrospectively examined 11 consecutive patients with atrioventricular discordance who underwent CA for atrioventricular reciprocating tachycardia (AVRT) via an AP and planned cardiac surgery after CA. Orthodromic AVRTs were induced in 10 patients via AP, but no antidromic/duodromic AVRT was induced in any of the cases. A total of 13 APs were identified, and all of them were located around the anatomical tricuspid valve (TV) annulus, including two Ebsteinoid valves. The APs were predominantly located posteriorly, posterolaterally, and posteroseptally on the TV in nine patients (82%). Two patients (18%) had multiple APs or a single broad AP. Four (36%) and three (27%) patients showed twin AVNs and other supraventricular tachycardias (SVTs) except AVRT via the AP. Ten patients (91%) had acute successful CA in the first session, except for one patient with multiple APs who required the third session to eliminate all APs before the planned Fontan surgery. There were no major complications associated with CA. Seven of eight patients who underwent cardiac surgery after CA did not experience peri-/postoperative SVT. CONCLUSION: APs in patients with AV discordance are usually associated with the anatomical TV annulus. CA of an AP in AV discordance is highly effective and recommended to reduce the risk of SVT. The coexistence of twin AVNs and other SVTs should be considered during CA of an AP in AV discordance.

Unusual variants of pre-excitation: From anatomy to ablation: Part III-Clinical presentation, electrophysiologic characteristics, when and how to ablate nodoventricular, nodofascicular, fasciculoventricular pathways, along with considerations of permanent junctional reciprocating tachycardia.

The recognition of the presence, location, and properties of unusual accessory pathways for atrioventricular conduction is an exciting, but frequently a difficult, challenge for the clinical cardiac arrhythmologist. In this third part of our series of reviews, we discuss the different steps required to come to the correct diagnosis and management decision in patients with nodofascicular, nodoventricular, and fasciculo-ventricular pathways. We also discuss the concealed accessory atrioventricular pathways with the properties of decremental retrograde conduction that are associated with the so-called permanent form of junctional reciprocating tachycardia. Careful analysis of the 12-lead electrocardiogram during sinus rhythm and tachycardias should always precede the investigation in the catheterization room. When using programmed electrical stimulation of the heart from different intracardiac locations, combined with activation mapping, it should be possible to localize both the proximal and distal ends of the accessory connections. This, in turn, should then permit the determination of their electrophysiologic properties, providing the answer to the question "are they incorporated in a tachycardia circuit?". It is this information that is essential for decision-making with regard to the need for catheter ablation, and if necessary, its appropriate site.

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.

BACKGROUND: 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. OBJECTIVE: 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. METHODS: 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]. RESULTS: 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. CONCLUSION: 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.

Coexistence of a permanent form of a junctional reciprocating tachycardia and coronary sinus aneurysm: A case report.

A 58-year-old man with a long R-P' narrow QRS tachycardia underwent an electrophysiological study. The tachycardia was diagnosed as a permanent form of junctional reciprocating tachycardia (PJRT), and the earliest atrial activation site during tachycardia was coronary sinus (CS) ostium. Radiofrequency ablation at the site was initially not successful because the tip impedance and temperature were unstable. After changing of the ablation catheter to that with contact force sensor, the accessory pathway was immediately ablated and the PJRT was no longer induced. A retrograde CS angiogram revealed a fusiform aneurysm, which was located at the earliest activation site during the tachycardia.

Noninvasive predictors of perioperative atrial arrhythmias in patients with tetralogy of Fallot undergoing pulmonary valve replacement.

BACKGROUND: Patients with tetralogy of Fallot (TOF) have increased risk of atrial arrhythmias. HYPOTHESIS: A measure of atrial dispersion, the P-wave vector magnitude (Pvm), can identify patients at risk for perioperative atrial flutter (AFL) or intra-atrial re-entrant tachycardia (IART) in a large TOF cohort. METHODS: We performed a blinded, retrospective analysis of 158 TOF patients undergoing pulmonary valve replacement between 1997 and 2015. History of AFL/IART was documented using electrocardiogram, Holter monitor, exercise stress test, implanted cardiac device, and electrophysiology study. P-R intervals, Pvm, QRS duration, and QRS vector magnitude were assessed from resting sinus-rhythm 12-lead electrocardiograms and identification of those with AFL/IART was determined. RESULTS: Fourteen patients (8.9%) were found to have AFL/IART. Pvm, QRS duration, and QRS vector magnitude significantly differentiated those with AFL/IART from those without on univariate analysis: 0.09 ± 0.04 vs 0.18 ± 0.07 mV, 161.3 ± 21.9 vs 137.7 ± 31.4 ms, and 1.2 (interquartile range, 1.0-1.2) vs 1.6 mV (1.0-2.3), respectively (P < 0.05 for each). The Pvm had the highest area under the ROC curve (0.88) and was the only significant predictor on multivariate analysis, with odds ratio of 0.02 (95% confidence interval: 0.01-0.53). P-R duration, MRI volumes, and right-heart hemodynamics did not significantly differentiate those with vs those without AFL/IART. CONCLUSIONS: In TOF patients undergoing pulmonary valve replacement, Pvm has significant value in predicting those with perioperative AFL/IART. These clinical features may help further evaluate TOF patients at risk for perioperative atrial arrhythmias. Prospective studies are warranted.

Utility of Pre-Induction Ventriculoatrial Response to Adenosine in the Diagnosis of Orthodromic Reciprocating Tachycardia.

OBJECTIVES: This study sought to evaluate the utility of ventriculoatrial (VA) conduction patterns in response to adenosine in predicting inducibility of orthodromic reciprocating tachycardia (ORT). BACKGROUND: Adenosine is known to consistently block atrioventricular (AV) nodal conduction. We hypothesized that persistent VA conduction despite administration of adenosine would have a high predictive value for identifying the presence of a retrograde accessory pathway (AP) and associated ORT. METHODS: A total of 168 patients undergoing electrophysiological study for supraventricular tachycardia (SVT) had assessment of VA conduction during ventricular pacing and adenosine administration. Standard pacing maneuvers were then used for induction and diagnosis of the SVT mechanism. RESULTS: Absence of VA block to adenosine (doses up to 24 mg) had 88% sensitivity and 91% specificity for identifying ORT (positive predictive value 76%, negative predictive value 96%). Four patients with adenosine-induced VA block and inducible ORT had decremental APs. Adenosine caused VA block in 6 patients with eccentric VA activation due to atypical AV nodal conduction, and concentric VA conduction persisted in all 12 patients with a septal AP. Adenosine unmasked free-wall APs in 10 patients by blocking AV nodal conduction, shifting VA activation from concentric to eccentric. CONCLUSIONS: The response of VA conduction to adenosine is a highly sensitive and specific method for detecting retrograde AP conduction and inducible ORT. Adenosine-induced VA block rules out inducible ORT due to a nondecremental AP. In cases of VA fusion, adenosine-induced block of AV nodal conduction can delineate the location of the AP atrial insertion site.

Analyses of the Mode of Termination During Diagnostic Ventricular Pacing to Differentiate the Mechanisms of Supraventricular Tachycardias.

OBJECTIVES: The goal of this study was to determine the diagnostic yield of analyzing the mode of termination during ventricular overdrive pacing (VOP) to differentiate the mechanisms of supraventricular tachycardias (SVTs). BACKGROUND: The majority of the diagnostic criteria for VOP rely on successful entrainment, but termination of SVTs is common during VOP. METHODS: We studied 225 SVTs with a 1:1 atrioventricular relationship, including 34 atrial tachycardias, 67 orthodromic reciprocating tachycardias (ORTs) (including 4 ORTs using accessory pathways [APs] with decremental properties), and 124 atrioventricular nodal re-entrant tachycardias. The total pacing prematurity (TPP) needed to reset or terminate the SVT was calculated by using a simplified method, and the post-pacing interval minus the tachycardia cycle length (PPI - TCL) was predicted from the TPP. RESULTS: VOP terminated 87 SVTs (39%). No atrial tachycardias were terminated by VOP in this study. SVT termination occurred after (n = 71) or before (n = 16) atrial resetting. The predicted PPI - TCL was highly correlated with the measured PPI - TCL (r = 0.96; p < 0.001). The TPP had diagnostic accuracy equivalent to the predicted PPI - TCL. The TPP was measurable irrespective of the termination mode and correctly diagnosed ORTs with decremental APs. All ORTs using septal APs and no atrioventricular nodal re-entrant tachycardias had a TPP <125 ms. Considering other criteria evaluable in terminated SVTs, a combined criteria of a TPP <125 ms and atrial capture/termination within the fusion period were specific for ORTs using free-wall APs, except for left anterolateral/lateral sites. CONCLUSIONS: The termination analyses were useful for differential diagnoses of SVTs terminated during VOP.

Characteristics of Decremental Accessory Pathways in Children.

BACKGROUND: Although retrograde decremental accessory pathways (DAPs) are thought to typically present as permanent junctional reciprocating tachycardia (permanent junctional reciprocating tachycardia), they may also be diagnosed unexpectedly during electrophysiology study. We aimed to compare the clinical and electrophysiological characteristics of patients with DAPs to an age-matched cohort with nondecremental accessory pathways. METHODS AND RESULTS: We retrospectively studied pediatric patients (<21 years of age) with retrograde DAPs and an age-matched control population with nondecremental accessory pathways who underwent electrophysiology study between 2005 and 2014. Decrement was defined as rate-dependent prolongation of the local ventriculo-atrial time by >30 ms. Twenty-six patients with DAPs were compared with 73 controls (mean age at electrophysiology study 9.8±5.7 and 10.3±5.2 years, respectively [P=nonsignificant]). Compared with controls, patients with DAPs had more frequent syncope (5/26 [19%] versus 3/73 [4%]; P=0.02) and ventricular dysfunction (6/26 [23%] versus 4/73 [6%]; P=0.04). Only 11 (42%) DAP patients manifested clinical permanent junctional reciprocating tachycardia, and these patients had more syncope (5/11 [45%] versus 0/15 [0%]; P<0.01), slower orthodromic reciprocating tachycardia (176±44 beats per minute versus 229±31 beats per minute; P=0.001), and longer ventriculo-atrial times (mean maximum ventriculo-atrial times of 283±116 ms versus 208±42 ms; P=0.02) compared with those with DAPs without clinical permanent junctional reciprocating tachycardia. DAPs and controls had similar rates of acute ablation success (23/26 [89%] versus 67/73 [92%]; P=nonsignificant) and recurrences (1/23 [4%] versus 2/67 [3%]; P=nonsignificant). CONCLUSIONS: The majority of pediatric patients with DAPs do not present with clinical permanent junctional reciprocating tachycardia. DAPs are associated with more severe symptoms, but ablation outcomes are similar to those of age-matched controls.

Long Postpacing Interval After Entrainment of Tachycardia Including a Slow Conduction Zone Within the Circuit.

BACKGROUNDS: Postpacing interval (PPI) measured after entrainment pacing describes the distance between pacing site and reentrant circuit. However, the influential features to PPI remain to be elucidated. METHODS AND RESULTS: This study included 22 cases with slow/fast atrioventricular (AV) nodal reentrant tachycardia (AVNRT), 14 orthodromic AV reciprocating tachycardia (AVRT) using an accessary pathway, 22 typical atrial flutter (AFL), and 18 other macroreentrant atrial tachycardia (atypical AFL). Rapid pacing at a pacing cycle length (PCL) 5% shorter than tachycardia cycle length (TCL) was done from a site on or close to the reentry circuit. Pacing sites included the coronary sinus ostium in AVNRT, earliest atrial activation site in AVRT, and cavotricuspid isthmus in typical AFL. In atypical AFL, tachycardia circuit was determined on the basis of CARTO mapping, and then the pacing site was. TCL was significantly longer in AVNRT and AVRT than in typical AFL and atypical AFL (both P < 0.05). PCL minus TCL value was similar among the 4 groups. PPI minus TCL value (milliseconds) was significantly longer in AVNRT (median, 40 [IQR, 29-60.8]) and AVRT (34 [20-47]) than in typical AFL (0 [0-4]) and atypical AFL (3.5 [0-8]) (both P < 0.05). Furthermore, PPI minus TCL was prolonged with shortening of PCL in AVNRT and AVRT (both P < 0.05), whereas it was unchanged in typical AFL (P = 0.50). CONCLUSION: PPI after concealed entrainment is prolonged compared with TCL when the reentry circuit involves a slow conduction zone with a decremental conduction property such as the AV node.

Determining the Site of Accessory Pathways in Orthodromic Reciprocating Tachycardia by Using the Response to Right Ventricular Pacing.

BACKGROUND: Postpacing interval (PPI) after right ventricular (RV) pacing entrainment minus tachycardia cycle length (TCL) with a correction for atrioventricular (AV) node delay (corrected PPI-TCL) was useful to differentiate atrioventricular node reentrant tachycardia (AVNRT) from orthodromic reciprocating tachycardia (ORT). However, the value of corrected PPI-TCL in determining the site of the accessory pathway (AP) in ORT has not been investigated. The purpose of this study was to assess whether the corrected PPI-TCL is useful in differentiating ORT using a left-sided AP from a right-sided AP. METHODS: We studied 52 patients with ORT using a left-sided AP and 13 patients with a right-sided AP. The PPI was measured upon cessation of the RV pacing at a cycle length 10-40 ms shorter than the TCL. The corrected PPI-TCL was calculated from the subtraction of the increment in AV nodal conduction time of the first PPI from the PPI-TCL. RESULTS: The mean corrected PPI-TCL was 83 ± 20 ms in patients with ORT using a left-sided AP and 27 ± 19 ms in patients with a right-sided AP (P ≤ 0.001). All patients with ORT using a left-sided AP except three patients with left septal AP and none of the patients with ORT using a right-sided AP had a corrected PPI-TCL > 55 ms. CONCLUSIONS: The corrected PPI-TCL after the RV pacing entrainment is useful to guide differentiating ORT using a left-sided AP from a right-sided AP.

Mecanismos electrofisiológicos y diagnóstico de la fibrilación auricular / Electrophysiological mechanisms and diagnosis of atrial fibrillation

Pese a ser la arritmia cardiaca sostenida más frecuente y que se describió hace más de 100 años, la fibrilación auricular es, junto con la fibrilación ventricular, prácticamente la única cuyo mecanismo aún se desconoce. Este desconocimiento tiene profundas implicaciones clínicas más allá de un mero interés académico. Así, el desconocimiento sobre el mecanismo hace que el diagnóstico de esta arritmia siga siendo básicamente electrocardiográfico. Esto origina que se planteen dudas diagnósticas con cierta frecuencia, tanto en el ECG de superficie como en registros electrofisiológicos intracavitarios. Además, el desconocimiento de su mecanismo limita el desarrollo de terapias farmacológicas e invasivas más dirigidas y medidas preventivas que la eviten o al menos la retrasen. En este artículo se revisan las teorías más aceptadas sobre el mecanismo de esta arritmia, como la de las múltiples reentradas funcionales coexistentes o la de los rotores madre, así como la de los factores que pueden influir en él, como el remodelado auricular, la presencia de fibrosis y cicatrices auriculares, la masa auricular, el papel de las venas pulmonares y los hechos que respaldan una relación con la reentrada. Asimismo, se revisan los criterios diagnósticos de esta arritmia, sus tipos y las exploraciones diagnósticas que se debe realizar a estos pacientes (AU)

Despite being the most common sustained cardiac arrhythmia and despite having been first described over 100 years ago, atrial fibrillation is, like ventricular fibrillation, virtually the only arrhythmia whose mechanism is still unknown. This lack of knowledge has profound clinical implications and is not just of academic interest. Firstly, lack of knowledge means that the diagnosis of atrial fibrillation is still based on ECG findings, which can often give rise to doubts about the diagnosis, with both surface ECGs and intracardiac electrophysiological studies. Moreover, lack of knowledge about the underlying mechanism also hampers the development of both better-targeted pharmacological and invasive therapies and preventive measures that can avert, or at least delay, the onset of atrial fibrillation. This article provides a review of the most widely accepted theories about the mechanism underlying this arrhythmia, such as the multiple coexisting functional re-entry circuits theory and the mother rotor theory. In addition, the article examines factors that could influence the condition, such as atrial remodeling, atrial fibrosis and scarring, and the critical atrial mass, and considers the role of the pulmonary veins and the evidence supporting a link with re-entry. Diagnostic criteria for this arrhythmia, its classification and recommended diagnostic investigations are also discussed (AU)

Differential Responses of the Septal Ventricle and the Atrial Signals During Ongoing Entrainment: A Method to Differentiate Orthodromic Reciprocating Tachycardia Using Septal Accessory Pathways From Atypical Atrioventricular Nodal Reentry.

BACKGROUND: Differential diagnosis between tachycardia mediated by septal accessory pathways (AP) and atypical atrioventricular nodal reentry can be challenging. We hypothesized that an immediate versus delayed pace-related advancement of the atrial electrogram, once the local septal parahisian ventricular electrogram (SVE) has been advanced, may help in this diagnosis. METHODS AND RESULTS: We focused on differential timing between SVE and atrial signals at the initiation of continuous right ventricular apical pacing during tachycardia. SVE advancement preceding atrial reset was defined as SVE advanced by the paced wave fronts while atrial signal continued at the tachycardia cycle. We analyzed 51 atypical atrioventricular nodal reentry (45% posterior type) and 80 AP tachycardias (anteroseptal [10], parahisian [18], midseptal [12], and posteroseptal [40]). SVE advancement preceding atrial reset was observed in 98% of atrioventricular nodal reentries during 4±1.1 cycles; this phenomena was observed in 6 (8%) of the atrioventricular reentrant tachycardia mediated by septal AP (P<0.001; sensitivity 98%; specificity 93%; positive predictive value 90%; negative predictive value 99%) and lasted 1 single cycle (P<0.001). Right posteroseptal AP tachycardias were distinctly characterized by atrial reset preceding SVE advancement (with ventricular fusion; specificity 100%; positive predictive value 100%). In 11 cases, it was impossible to achieve sustain entrainment. In all of them, the differential responses at the entrainment attempt allowed for appropriate diagnosis. CONCLUSIONS: The differential response of the SVE and the atrial electrogram at the initiation of continuous right ventricular apical pacing during tachycardia effectively distinguishes between atypical atrioventricular nodal reentry and atrioventricular reentrant tachycardia mediated by septal APs.

50 is the new 70: Short ventriculoatrial times are common in children with atrioventricular reciprocating tachycardia.

BACKGROUND: One of the basic electrophysiological principles of atrioventricular reciprocating tachycardia (AVRT) is that ventriculoatrial (VA) times during tachycardia are >70 ms. We hypothesized, however, that children may commonly have VA times <70 ms in AVRT. OBJECTIVE: This study sought to determine the incidence and characteristics associated with short-VA AVRT in children. METHODS: A retrospective single-center review of children with AVRT from 2000 to 2014 was performed. All patients ≤18 years of age with AVRT at electrophysiology study were included. Patients with persistent junctional reciprocating tachycardia, atrioventricular nodal reentry tachycardia, and tachycardia not unequivocally proven to be AVRT were excluded. VA time was defined as the time between earliest ventricular activation and earliest atrial activation in any lead and was confirmed by 2 electrophysiologists. Patients with VA times <70 ms (SHORT-VA) and those with standard VA times ≥70 ms (STD-VA) were compared. Logistic regression analysis identified characteristics of SHORT-VA patients. RESULTS: A total of 495 patients with AVRT were included (mean age 11.7 ± 4.1 years). There were 265 patients (54%) with concealed accessory pathways (APs) and 230 (46%) with Wolff-Parkinson-White syndrome. AP location was left-sided in 301 patients (61%) and right-sided in 194 (39%). The mean VA time in AVRT was 100 ± 33 ms. A total of 63 patients (13%) had VA times <70 ms (SHORT-VA). The shortest VA time during AVRT was 50 ms. There was no difference in age, AV nodal block cycle, or body surface area between SHORT-VA and STD-VA patients, but SHORT-VA patients had lower weight (43 ± 17 vs 51 ± 23 kg, P = .02), lower AV nodal effective refractory period (AVNERP; 269 ± 50 vs 245 ± 52 ms, P < .01), and more left-sided APs (50 [79%] vs 251 [58%]; P < .01]. On multivariate logistic regression, factors associated with SHORT-VA included left-sided AP (odds ratio [OR] 5.79, confidence interval [95% CI] 2.21-15.1, P < .01), shorter AVNERP (OR 0.99, CI 0.98-0.99, P < .01), and lower weight (OR 0.97, CI 0.95-0.99, P < .01). CONCLUSIONS: Children with AVRT can frequently have VA times <70 ms, with 50 ms being the shortest VA time. This finding debunks the classic electrophysiology principle that VA times in AVRT must be >70 ms. SHORT-VA AVRT was more common in children with left-sided APs.

His overdrive pacing during supraventricular tachycardia: a novel maneuver for distinguishing atrioventricular nodal reentrant tachycardia from atrioventricular reciprocating tachycardia.

BACKGROUND: Because the His bundle is intrinsic to the circuit in orthodromic reciprocating tachycardia and remote from that of atrioventricular nodal reentrant tachycardia (AVNRT), pacing the His bundle during supraventricular tachycardia (SVT) may be useful to distinguish these arrhythmias. OBJECTIVE: The purpose of this study was to test the hypothesis that His overdrive pacing (HOP) would affect SVT immediately for orthodromic reciprocating tachycardia and in a delayed manner for AVNRT. METHODS: Once SVT was induced, HOP was performed by pacing the His bundle 10-30 ms faster than the SVT cycle length. The maneuver was determined to have entered the tachycardia circuit when a nonfused His-capture beat advanced or delayed the subsequent atrial electrogram by ≥10 ms or when the tachycardia was terminated. The number of beats required to enter each tachycardia with HOP was recorded. RESULTS: HOP was performed during 66 SVTs (26 atrioventricular reciprocating tachycardia [AVRT] and 40 AVNRT). Entry into the tachycardia within 1 beat had sensitivity of 92%, specificity of 92%, positive predictive value (PPV) of 89% and negative predictive value (NPV) of 95% to confirm the diagnosis of AVRT. A cutoff ≥3 beats to enter the circuit had sensitivity of 90%, specificity of 92%, PPV of 95% and NPV of 86% to confirm the diagnosis of AVNRT. HOP had sensitivity, specificity, PPV, and NPV of 100% for distinguishing septal AVRT from atypical AVNRT. CONCLUSION: HOP during SVT is a novel technique for distinguishing orthodromic reciprocating tachycardia from AVNRT. It can reliably distinguish between these arrhythmias with high sensitivity and specificity.