Orthodromic Reciprocating Tachycardia Research Articles

Orthodromic Reciprocating Tachycardia Relying on Aberrant Conduction: The Need for a Larger Circuit.

Aberrant conduction during orthodromic reciprocating tachycardia (ORT) prolongs the ventriculoatrial conduction time, which can be essential for the maintenance of tachycardia in specific cases. We searched for ORT relying on aberrancy among 220 cases in our center. Three patients showed the phenomenon of aberrancy-dependent ORT. All accessory pathways were located at the lateral regions of the atrioventricular annulus. None of them had a baseline bundle branch block (BBB). Creating a functional BBB was necessary to induce the tachycardias. In two cases, termination of tachycardias was directly associated with resolution of the aberration. In the other case, re-entry required both BBB and slow pathway conduction. We conclude that extra transseptal time caused by aberrancy can be an integral part of the ORT circuit, which explains the infrequent and unsustainable episodes of ORT in certain patients and is useful in understanding the circuit and localizing the pathway.

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

AbstractBackgroundThis study aimed to establish a systematic method for diagnosing atrioventricular nodal reentrant tachycardia (AVNRT) with a bystander concealed nodoventricular pathway (cNVP).MethodsWe 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).ResultsThe 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.ConclusionAVNRT 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.

Discrepant results of the total pacing prematurity in orthodromic reciprocating tachycardia with right bundle branch block.

The total pacing prematurity (TPP) is useful for distinguishing orthodromic reciprocating tachycardia (ORT) from atrioventricular nodal re-entrant tachycardia, but it may not be effective in patients with right bundle branch block (RBBB). We faced this challenge in an elderly woman, as RBBB and a prolonged transseptal conduction made it difficult to diagnose the tachycardia using the TPP. It is important to consider the presence or absence of RBBB when evaluating the results of the TPP.

PO-05-226 ORTHODROMIC RECIPROCATING TACHYCARDIA RELYING ON ABERRANT CONDUCTION: NEED FOR A LAGER CIRCUIT

Aberrant conduction during orthodromic reciprocating tachycardia (ORT) can prolong the ventriculo-atrial conduction time, which is found essential for the reentry in certain situations. To investigate the prevalence and different mechanism of aberrancy-dependent ORT. ORT cases relying on aberrancy from 220 cases in our center were searched using the following criteria: (1) Multiple episodes of ORT with aberrant conduction in ECG ; (2) No baseline BBB during sinus rhythm; (3) Absence of narrow QRS form during tachycardia unless isoproterenol used; (4) Restoration of bundle branch conduction giving rise to tachycardia termination or circuit alteration. ECGs and intracardiac tracings during study were carefully examined. 3 patients from 220 patients (1.4%) with ORT showed the phenomenon of dependence on aberrancy. Clinical tachycardia episodes of the patients were short in time. All accessory pathways (APs) were located at anterolateral regions of atrioventricular annulus. None of them had baseline bundle branch block. Creating functional bundle branch block was necessary to induce the tachycardias. In the first patient with ORT and left bundle branch block (LBBB), a late-delivered premature ventricular contraction (PVC) was able to advance the next A and reset the tachycardia, which was diagnostic for ORT with aberrancy. Meanwhile, left bundle branch conduction was restored which narrowed the next QRS complex. Tachycardia was then terminated by the advanced wavefront reaching the ventricular insertion site of AP which was refractory. In the second case, termination of the tachycardia was always preceded by a spontaneous LBBB restoration, with the V and subsequent A at MA advanced, suggesting anterograde block in the AV node. In the other case was, induction required both right BBB and slow pathway conduction. When isoproterenol was given, fast pathway recovered followed by BBB restoration, which made anterograde limb again switched to slow pathway. All pathways were successfully ablated during the procedure. All patients have been free of arrhythmias for at least 6 months. Extra transseptal time caused by aberrancy can be an integral part of ORT, which can explain the infrequent or late onset and unsustainable episodes of ORT in certain patients and is useful in understanding the circuit and localizing the pathway.

Last Entrainment Sequence: A Novel Diagnostic Technique for Atrial Tachycardia Mimicking Other Supraventricular Tachycardias.

Adenosine-sensitive re-entrant atrial tachycardia (AT) originating from near the atrioventricular (AV) node or AV annulus resembles other supraventricular tachycardias (SVTs), and the differential diagnosis is sometimes challenging. This study sought to develop a novel technique to distinguish adenosine-sensitive re-entrant AT from AV nodal re-entrant tachycardia (AVNRT) and orthodromic reciprocating tachycardia (ORT). The study retrospectively studied 117 re-entrant SVTs that were successfully entrained by atrial overdrive pacing (AOP) (27 adenosine-sensitive re-entrant ATs, 63 AVNRTs, 27 ORTs). If the second atrial electrogram after AOP (A2) at the earliest atrial activation site (EAAS) accelerated to the pacing cycle length, the EAAS was considered orthodromically activated. Then, we compared the sequence of A2 and the last entrained His bundle (H∗) and QRS complex (V∗). The study hypothesized that the last entrained impulse would activate the EAAS before it enters the AV node, His bundle, and ventricle during AT (A2-H∗-V∗) but would activate the EAAS after the His bundle activation during AVNRT and ORT (H∗-V∗-A2 or H∗-A2-V∗). Orthodromic EAAS activation was documented during AOP in 84 SVTs (72%) when performing AOP from sites proximal to the entrance of SVTs. A2-H∗-V∗ responses were observed in 21 of 25 ATs, but were never for AVNRTs or ORTs. All ORTs and fast-slow AVNRTs had H∗-V∗-A2 responses. Eleven of 21 slow-fast AVNRTs had H∗-A2-V∗ responses. The sensitivity, specificity, and positive and negative predictive values of the A2-H∗-V∗ response for diagnosing AT were 84%, 100%, 100%, and 94%, respectively. The last entrainment sequence was useful for differentiating ATs with diagnostic difficulties.

PO-672-01 RIGHT SIDED ANTEROSEPTAL ACCESSORY PATHWAY INDUCED CARDIOMYOPATHY

We describe 2 patients with right anteroseptal accessory pathway (ASAP) who developed new left ventricular systolic dysfunction (LVSD) due to worsening AV node conduction which resulted in more pre-excitation and frequent orthodromic reciprocating tachycardia (ORT).

Unusual response to ventricular pacing maneuvers in narrow complex tachycardia-What is the mechanism?

two ventricular pacing maneuvers confirm the presence of a concealed NV/NF AP, however, whether it is a bystander during AVNRT or actively participating in the tachycardia mechanism remains unclear. The response of VOP entraining the tachycardia could not be obtained due to repeated termination of the tachycardia. Although, the presence of dual-AV nodal pathways and consistent VA relation during the tachycardia favor AVNRT as most likely etiology, orthodromic reciprocating tachycardia (ORT) using concealed NV/NF AP cannot be excluded This article is protected by copyright. All rights reserved.

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.

Novel Diagnostic Observations of Nodoventricular/Nodofascicular Pathway-Related Orthodromic Reciprocating Tachycardia Differentiating From Atrioventricular Nodal Re-Entrant Tachycardia.

This study sought to assess the performance of current diagnostic criteria and identify additional electrophysiological features differentiating orthodromic reciprocating tachycardia (ORT) with a concealed nodoventricular/nodofascicular (NV/NF) pathway from atrioventricular nodal re-entrant tachycardia (AVNRT). Diagnosing sustained supraventricular tachycardia (SVT) despite the occurrence of ventriculoatrial block (VAB) is challenging. We analyzed electrograms of 25 sustained SVTs (9 NV/NF-ORTs [n=7/2] and 16 AVNRTs) with VAB and 91 AVNRTs without VAB (for reference). More than 1 SVT, each with a different ventriculoatrial interval, was commonly induced in AVNRT cases (75%) but not in NV/NF-ORT cases (0%; p=0.0005). Wenckebach VAB was common in NV/NF-ORTs (78%), but VAB patterns varied in AVNRTs. The His-His interval transiently prolonged in the following beat after the VAB in most AVNRTs but rarely did in NV/NF-ORTs (79% vs. 22%; p=0.01). NV/NF-ORT was diagnosed by His-refractory premature ventricular contractions (n=5) and the findings during right ventricular overdrive pacing showing an uncorrected/corrected post-pacing interval (PPI)-tachycardia cycle length (TCL) ≤115/110 ms (n = 5/5), orthodromic His capture (n=6), and V-V-A (ventricle-ventricle-atrial response) response (n=3). A single form of induced SVT (positive predictive value [PPV]: 69%; negative predictive value [NPV]: 100%), Wenckebach VAB (PPV: 70%; NPV: 87%), stable His-His interval despite VAB (PPV: 70%; NPV: 85%), orthodromic His capture (PPV: 100%; NPV: 97%), and V-V-A response (PPV: 100%; NPV: 95%) characterized NV/NF-ORT, and a PPI-TCL of≤125ms (PPV: 100%; NPV: 100%) characterized NV-ORT. Induction of a single SVT form, Wenckebach VAB, stable His-His interval despite VAB, orthodromic His capture, and V-V-A response appeared to discriminate NV/NF-ORT from AVNRT, with a PPI-TCL of≤125ms discriminating NV-ORT from NF-ORT and AVNRT.

A simple maneuver to determine if septal accessory pathway ablation requires a left atrial approach.

Septal accessory pathway (AP) ablation can be challenging due to the complex anatomy of the septal region. The decision to access the left atrium (LA) is often made after failure of ablation from the right. We sought to establish whether the difference between ventriculo-atrial (VA) time during right ventricular (RV) apical pacing versus the VA during tachycardia would help establish the successful site for ablation of septal APs. Intracardiac electrograms of patients with orthodromic reciprocating tachycardia (ORT) using a septal AP with successful catheter ablation were reviewed. The ∆VA was the difference between the VA interval during RV apical pacing and the VA interval during ORT. The difference in the VA interval during right ventricular entrainment and ORT (StimA-VA) was also measured. The median ∆VA time was significantly less in patients with a septal AP ablated on the right side compared with patients with a septal AP ablated on the left side (12 ± 19 vs. 56 ± 10 ms, p < .001). The StimA-VA was significantly different between the two groups (22 ± 14 vs. 53 ± 9 ms, p < .001). The ∆VA and StimA-VA were always 40 ms in patients with non-decremental septal APs ablated from the right side and always greater than 40 ms in those with septal APs ablated from the left. ΔVA and StimA-VA values identified with RV apical pacing in the setting of ORT involving a septal AP predict when left atrial access will be necessary for successful ablation.

Catheter ablation of orthodromic reciprocating tachycardia and atrioventricular nodal reentrant tachycardia in children with hypoplastic left heart syndrome.

Experience with catheter ablation of orthodromic reciprocating tachycardia (ORT) and atrioventricular nodal reentrant tachycardia (AVNRT) in young children with hypoplastic left heart syndrome (HLHS) is limited. We report the feasibility, safety, and outcomes of catheter ablation of ORT and AVNRT in children with HLHS. This was a retrospective review of patients with HLHS who underwent catheter ablation for reentrant supraventricular tachycardias (excluding atrial tachycardias) between 2005 and 2017 at a single center. Descriptive data including demographics, clinical history, procedural data, and outcomes were recorded. Ten children with HLHS underwent elevencatheter ablation procedures. Median age and weight at ablation were 2.7 years (range: 0.1-10.5) and 11.4 kg (range: 3.6-30.4), respectively. Tachycardia mechanism was AVNRT in four, ORT in five (two with preexcitation), and both in one. Acute procedural success was 100% and there was no spontaneous recurrence of tachycardia orpreexcitationin median 92 months (range: 21-175 months) follow-up. Five patients underwent subsequent EP studies at catheterization (intracardiac) or after surgery (via epicardial wires): three were noninducible, one after AVNRT ablation had inducible atrial tachycardia, and one after initial ORT ablation had inducible ORT at fenestration closure and underwent successful repeat ablation. Thus, long-term freedom from clinical tachycardia was 100% and from inducible AVNRT or ORT was 80%. Transcatheter ablation for ORT and AVNRT in children with HLHS can be performed with excellent acute and long-term success without major complications.

A Simple Method to Differentiate Atrioventricular Node Reentrant Tachycardia from Orthodromic Reciprocating Tachycardia.

Discrimination between atrioventricular node reentry tachycardia (AVNRT) and orthodromic reciprocating tachycardia (ORT) during an electrophysiological study is sometimes challenging. This study aimed to investigate if the difference in the local VA (ventricle-atrium) interval during ventricular entrainment pacing and during tachycardia (DVA, defined as the shortest local VA interval of coronary sinus [CS] during entrainment minus the shortest local VA interval of CS during tachycardia) was different in patients with AVNRT and patients with ORT.Diagnoses of AVNRT or ORT through a concealed accessory pathway (AP) were made according to conventional electrophysiological criteria and ablation results. Entrainment by right ventricular (RV) pacing was performed in each patient before ablation and patients with successful entrainment were included in the study. The DVA was compared between patients with AVNRT and patients with ORT. The DVA in patients with AVNRT was significantly longer than that in patients with ORT (120 ± 20 versus 5.7 ± 9; P < 0.001). In each patient with AVNRT of slow-fast type, fast-slow type, and slow-slow type, the DVA was more than 48 ms. In each patient with ORT using a left free wall accessory pathway (AP), right free wall AP, and septal AP, the DVA was less than 20 ms.DVA was found to be a rapid, useful test in distinguishing patients with AVNRT from those with ORT.

Validation of right ventricular pacing response during supraventricular tachycardia in mechanistic diagnosis (transition zone)

Background Right ventricular pacing (RVP) during supraventricular tachycardia (SVT) produces progressive QRS fusion before the QRS morphology becomes stable. This transition zone (TZ) may provide useful information for differentiating orthodromic reciprocating tachycardia (ORT) from atrioventricular nodal re-entrant tachycardia and atrial tachycardia independent of entrainment success. Methods and results We studied the effect of properly timed RVP on atrial timing during the TZ in 63 patients with SVT who had RVP within 40 ms of the tachycardia cycle length. The TZ during RVP includes progressively fused QRS complexes and the first paced complex with a stable QRS morphology based on analysis of the 12-lead ECG. We also measured the stimulus–atrial (SA) interval from the end of the TZ and with each QRS complex thereafter until pacing was terminated or ventriculoatrial block occurred. A fixed SA interval was defined as variation less than or equal to 10 ms during RVP. Atrial pre-excitation, postexcitation, or SVT termination with abrupt ventriculoatrial block was observed within the TZ in 19 of 22 patients with ORT. A fixed SA interval was established within the TZ in 22 of 22 patients with ORT. At least one of these two responses was observed in all patients with ORT. Only four patients out of 36 with atrioventricular nodal re-entrant tachycardia showed atrial pre-excitation within TZ and only four patients showed fixed SA within TZ. None of the atrial tachycardia patients had atrial timing perturbed or a fixed SA interval established within the TZ. Conclusion During RVP within 40 ms of the tachycardia cycle length, ORT is the likely mechanism when atrial timing is perturbed or a fixed SA interval is established within the TZ.

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

This study sought to evaluate the utility of ventriculoatrial (VA) conduction patterns in response to adenosine in predicting inducibility of orthodromic reciprocating tachycardia (ORT). 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. 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. 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 andinducible 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. 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.

16-31: Successful ablation of parahisian atrial tachycardia and pathway mediated tachycardia via non coronary cusp

Purpose: Atrial tachycardias (AT), antidromic reciprocating tachycardias and orthodromic reciprocating tachycardias (ORT) with parahisian origin are not uncommon. Catheter ablation at this area posed significant risk of heart block. Ablation at non- coronary cusp (NCC) was proposed to be safe and effective. We sought to investigate electrophysiological characteristics and catheter ablation in this area with various types of arrhythmia. Method: This study included 8 patients with focal AT, 4 patients with Wolff Parkinson White Syndrome (WPW) and 4 patients with concealed orthodromic reciprocating tachycardia (ORT). Activation mapping was performed during tachycardia in all cases. In WPW without tachycardia or retrograde atrial conduction, mapping ventricular insertion during maximal pre-excitation was done. Aortogram was done in all cases in order to confirm catheter position. Echocardiogram was done after procedure to look for new onset aortic regurgitation. Result: Four cases of AT (50%) and 4 cases of ORT (100%) were incessant during procedure. All cases of WPW had atrial fibrillation before index procedure. Parahisian origin were confirmed in all cases by pacing manoeuvre. In AT group, activation mapping demonstrated an earliest atrial activation preceded the atrial activation at the His Bundle by 18 ± 3 msec. All accessory pathway in WPW and ORT group were confirmed by parahisian pacing. Detailed mapping showed earliest atrial potential (ORT group) and ventricular potential (WPW group) during tachycardia was located superoposterior to His Bundle. During ablation in all cases, mapping was performed in aortic sinus and all cusps. Irrigation catheter was required to eliminate tachycardia in 8 cases. His potential were not found at the target ablation site. AT were terminated in all cases within 5 second and all accessory pathway was eliminated within 5 second. Neither junctional beats nor PR prolongation was found during ablation. No complication occurred. Post procedure echocardiography did not show new aortic regurgitation. All patients were arrhythmia free after 1 year follow up. Conclusion: In patient with AT, ORT or WPW near the His bundle, mapping in NCC is an viable option and catheter ablation is safe and effective.

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

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. 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. 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. 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.

Diagnosis and Ablation of Long RP Supraventricular Tachycardias

Long RP tachycardias are a unique collection of arrhythmias that include atypical (fast-slow) atrio-ventricular nodal reentrant tachycardia (AVNRT) with and without a concealed, bystander nodo-fascicular/ventricular accessory pathway (AP), orthodromic reciprocating tachycardia (ORT) using a concealed, slowly conducting, and decremental atrio-ventricular (AV) AP (PJRT), ORT using a concealed nodo-fascicular/ventricular AP (NFRT), and atrial tachycardia (AT)-all but the last being dependent upon the AV node. These tachycardias respond differently to pacing maneuvers than their short RP counterparts and can manifest: (1) both true and pseudo-AAV responses, (2) long uncorrected and corrected post-pacing intervals, (3) prolonged delta ventriculo-atrial (∆VA) and delta His bundle-atrial (∆HA) values, and (4) resetting with delay. Diagnosis requires analysis of available clues from spontaneous transition zones as well as atrial and ventricular pacing maneuvers to delineate the upper and lower limbs of each circuit, respectively. Establishing the exact mechanism of tachycardia is important for safe and successful ablation. With activation mapping to localize AT or the AV AP of ORT and slow pathway (SP) ablation of atypical AVNRT and NF APs inserting into the SP, the majority of long RP tachycardias can be successfully treated.

Differentiation of Atrioventricular Nodal Reentrant Tachycardia from Orthodromic Reciprocating Tachycardia by the Resetting Response to Ventricular Extrastimuli: Comparison to Response to Continuous Ventricular Pacing

The usefulness of ventricular entrainment to differentiate AV nodal reentrant tachycardia (AVNRT) from orthodromic reciprocating tachycardia (ORT) by substracting the corrected postpacing interval (cPPI) from the tachycardia cycle length (TCL) or the ventriculoatrial interval during stimulation (SA) from that during tachycardia (VA) have been widely validated. However, some tachycardias are interrupted by pacing trains but may not be so by ventricular extrastimuli resulting in resetting. To validate prospectively the diagnostic yield of cPPI-TCL and SA-VA measurements after resetting and to determine the proportion of AVNRT and ORT that can be entrained and/or reset from the right ventricular apex (RVA). 223 consecutive patients with inducible AVNRT or ORT underwent pacing trains and single extrastimulus (also double extrastimuli if singles did not reset tachycardia) at the RVA. We calculated cPPI-TCL and SA-VA during entrainment and resetting. Entrainment could not be achieved in 15.2% of tachycardias because of consistent tachycardia interruption by pacing; resetting was observed in 99.5%. Values of cPPI-TCL and SA-VA > 110 milliseconds after resetting identified AVNRT as accurately as after entrainment. Values for cPPI-TCL/ SA-VA were: sensitivity: 98/100%; specificity: 96/98%; positive predictive value: 98/99%; negative predictive value: 98/100%. Determinations of cPPI-TCL and SA-VA after resetting with single or double RVA extrastimuli are useful maneuvers to differentiate AVNRT from ORT and can be used for nearly every inducible AVNRT or ORT, even if they are interrupted by ventricular trains.

Choice and Utility of Pacing Maneuver in Establishing the Mechanism of Supraventricular Tachycardia: A Single Center Experience.

BackgroundTo evaluate the choice and utility of pacing maneuvers in the electrophysiology (EP) laboratory in establishing supraventricular tachycardia (SVT) mechanism.MethodsWe retrospectively examined a cohort of 160 consecutive patients with SVT presenting for invasive EP evaluation to a single center with 8 electrophysiologists. We analyzed the utility of the two most commonly used pacing maneuvers: (1) ventricular entrainment (VE) and (2) His-refractory premature ventricular stimuli (HRPVC) during SVT.ResultsVE was performed in 96 patients: atrial tachycardia (AT) 12, atrioventricular nodal reentrant tachycardia (AVNRT) 66, and orthodromic reciprocating tachycardia (ORT) 18. During VE, AT patients were most likely to have ventriculo-atrial (VA) dissociation (AT 58%, AVNRT 18%, ORT 0%, P < 0.001) and had a tendency towards less SVT termination (AT 0%, AVNRT 9%, ORT 11%, P = 0.19). HRPVCs were delivered in 39 patients: AT 1, AVNRT 24, and ORT 14. Advancement of atrial signal with HRPVC was only observed in ORT (AT 0%, AVNRT 0%, ORT 79%, P < 0.001) and SVT termination was also mostly observed in ORT (AT 0%, AVNRT 4%, ORT 21%, P = 0.33). The overall diagnostic utility of VE was lowest in AT (AT 42%, AVNRT 71%, ORT 83%, P = 0.04), while HRPVC was rarely used in AT. Furthermore, the utilization of maneuvers varied extensively (0% to100%) among the 8 electrophysiologists.ConclusionThere is great variation in the utilization of pacing maneuvers and their utility in ascertaining the mechanism of SVT. Our results support the fact that discerning AT from AVNRT mechanism remains the most challenging task in SVT diagnosis.

To the editor: Differentiating orthodromic reciprocating tachycardia from atrioventricular nodal reentrant tachycardia

I read the article by Dandamudi et al 1 Dandamudi G. Mokabberi R. Assal C. et al. A novel approach to differentiating orthodromic reciprocating tachycardia from atrioventricular nodal reentrant tachycardia. Heart Rhythm. 2010; 7: 1326-1329 Abstract Full Text Full Text PDF PubMed Scopus (53) Google Scholar with great interest. Congratulations for exploiting a very well known phenomenon in the electrophysiology laboratory and setting up criteria on the basis of that, and then validating this on a good number of patients to differentiate orthodromic reciprocating tachycardia (ORT) and atrioventricular nodal reentrant tachycardia (AVNRT). A few points are worth mentioning. 1It would be difficult to differentiate between completely paced right ventricular (RV) complex and mildly less completely paced complex; the criteria depend highly upon identifying the first beat with either completely paced or fixed fusion, and this may give rise to spurious results. 2If the tachycardia terminates before acceleration of A, which is common in cases of ORT, then the criteria are not valid. It is surprising that in 23 cases of ORT the tachycardia did not terminate in a single case before acceleration of A. In this scenario, the mode of termination is quite helpful. If the tachycardia terminates without producing a complete RV pacing complex (this can be documented by comparing the RV pacing morphology during tachycardia and RV pacing once the tachycardia has terminated), then the tachycardia is ORT because the only way the tachycardia can be terminated in AVNRT is an RV paced complex penetrating through the His bundle, which will produce a complete RV pacing complex. (Unless coincidentally the tachycardia terminates spontaneously, which is uncommon if tachycardia is reasonably sustained.) A novel approach to differentiating orthodromic reciprocating tachycardia from atrioventricular nodal reentrant tachycardiaHeart RhythmVol. 7Issue 9PreviewVarious diagnostic maneuvers have been proposed to help differentiate orthodromic reciprocating tachycardia (ORT) from atrioventricular nodal reentrant tachycardia (AVNRT) prior to ablation. However, not all criteria are applicable in every situation as each has limitations. Full-Text PDF To the Editor—Response: Orthodromic reciprocating tachycardiaHeart RhythmVol. 8Issue 3PreviewWe would like to thank the author for the kind comments. We agree with the author that care needs to be taken when assessing electrocardiographic (ECG) morphologies. All 12 ECG leads would need to be reviewed carefully to ascertain the first purely paced right ventricular (RV) beat or fixed fusion RV beat. However, in most of our cases of orthodromic reciprocating tachycardia (ORT), the tachycardia cycle length (TCL) was advanced to the paced cycle length (PCL) even before achieving fixed fusion in patients with right-sided as well as septal accessory pathways (AP). Full-Text PDF