The precise timing of tachycardia entrainment is determined by the postpacing interval, the tachycardia cycle length, and the pacing rate: Theoretical insights and practical applications

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.

Unusual response to His-synchronous ventricular stimulation during a supraventricular tachycardia: Atrial advancement with or without resetting?

The delivery of ventricular extra-stimulus when the His bundle is refractory is the most important maneuver in the diagnosis of an accessory pathway conduction.The "reset" indicates that the extra-stimulus has penetrated the circuit to alter the "subsequent cycle'. The advanced atrial activation time is expected to affect (reset or terminate) the tachycardia to the next cycle. However, some pitfalls should be kept in mind in the evaluation of the resetting response. This article is protected by copyright. All rights reserved.

Importance of the Activation Sequence of the His or Right Bundle for Diagnosis of Complex Tachycardia Circuits

In this review, we emphasize the unique value of recording the activation sequence of the His bundle or right bundle branch (RB) for diagnoses of various supraventricular and fascicular tachycardias. A close analysis of the His to RB (H-RB) activation sequence can help differentiate various forms of supraventricular tachycardias, namely atrioventricular nodal reentry tachycardia from concealed nodofascicular tachycardia, a common clinical dilemma. Furthermore, bundle branch reentry tachycardia and fascicular tachycardias often are included in the differential diagnosis of supraventricular tachycardia with aberrancy, and the use of this technique can help the operator make the distinction between supraventricular tachycardias and these other forms of ventricular tachycardias using the His-Purkinje system. We show that this technique is enhanced by the use of multipolar catheters placed to span the proximal His to RB position to record the activation sequence between proximal His potential to the distal RB potential. This allows the operator to fully analyze the activation sequence in sinus rhythm as compared to that during tachycardia and may help target ablation of these arrhythmias. We argue that 3 patterns of H-RB activation are commonly identified-the anterograde H-RB pattern, the retrograde H-RB (right bundle to His bundle) pattern, and the chevron H-RB pattern (simultaneous proximal His and proximal RB activation)-and specific arrhythmias tend to be associated with specific H-RB activation sequences. We show that being able to record and categorize this H-RB relationship can be instrumental to the operator, along with standard pacing maneuvers, to make an arrhythmia diagnosis in complex tachycardia circuits. We highlight the importance of H-RB activation patterns in these complex tachycardias by means of case illustrations from our groups as well as from prior reports.

Limitations of ventricular pacing maneuvers to differentiate orthodromic reciprocating tachycardia from atrioventricular nodal reentry tachycardia

PURPOSE

Various ventricular pacing maneuvers have been developed to differentiate orthodromic reciprocating tachycardia (ORT) from atrioventricular nodal reentry tachycardia (AVNRT). We aimed to evaluate the diagnostic value of ventricular pacing maneuvers in patients undergoing catheter ablation for AVNRT/ORT.

METHODS

Sixty patients with supraventricular tachycardia (SVT) undergoing invasive EP study were included (ORT: 31, typical AVNRT: 18, atypical AVNRT: 11). Ventricular overdrive pacing (VOP) and resetting by premature ventricular stimulation (PVS) during SVT were analyzed by 3 independent observers blinded to the ultimate diagnosis. We determined intraclass correlation coefficient (ICC) for interobserver agreement and the diagnostic accuracy of consensual results.

RESULTS

Although specificity of all parameters was high (96-100%) for ORT, semi-quantitative parameters of VOP (requiring the recognition of specific ECG patterns) had lower interobserver reliability (ICC: 0.32-0.66) and sensitivity (16.1-77.4%). In contrast, most quantitative measurements of VOP and PVS showed good reproducibility (ICC: 0.93-0.95) and sensitivity (74.2-89.3%), but post-pacing interval after VOP needed correction with AV nodal conduction slowing. False negative results for diagnosing ORT were more common with left free wall vs. right free wall or septal, and slowly vs. fast-conducting septal APs. False positivity was only seen with a bystander, concealed nodo-fascicular/nodo-ventricular (NF/NV) AP in a case of AVNRT.

CONCLUSIONS

No single maneuver is 100% sensitive for ORT. Semi-quantitative features have limited reproducibility and all parameters can be misleading in the case of rate-dependent delay during VOP/PVS, ORT circuits remote from the pacing site, or a bystander, concealed NF/NV AP.

A constant postpacing interval in response to overdrive pacing with variable number of beats: An aid in the identification of entrainment for a particular pacing train during macroreentrant atrial tachycardias

BACKGROUND

When pacing trains with a constant cycle length (CL) but increasing number of beats are introduced during a macroreentrant atrial tachycardia (MAT), the postpacing interval (PPI) is expected to increase if entrainment does not occur but could be stable if entrainment occurs. We tested the ability of PPI analysis to detect entrainment.

METHODS

Synchronized pacing trains with increasing number of beats (1-20) were delivered from the coronary sinus (CS) and lateral right atrium (RA) at a CL 20 ms shorter than the MAT CL. Pacing trains were grouped in pairs differing by one-paced beat, and the ∆PPI measured.

RESULTS

In an initial prospective cohort of 21 patients (48% had left atrial flutter) the mean ∆PPI was 21.3 ± 5.6 ms for pairs of pacing trains in which neither entrained the MAT and 2.8 ± 1.4 ms for those in which both entrained the MAT (P < .0001). Results were similar for common vs atypical flutter, PPI-TCL ≤30 ms vs PPI-TCL >30 ms, presence vs absence of antiarrhythmic drugs and faster vs slower MAT. When an index pacing train was compared to one with two-paced beats less, a PPI difference of <19 ms identified entrainment with 95% sensitivity and 98% specificity. In a validation cohort of 16 patients, this cut-off value resulted in sensitivity and specificity of 90% and 94%.

CONCLUSIONS

A relatively constant ∆PPI in response to overdrive pacing with identical CL but different number of beats allows accurate discrimination between trains that entrained vs those which did not entrain a MAT.

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.

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.

Initial Clinical Experience With a New Automated Antitachycardia Pacing Algorithm

Background:

Antitachycardia pacing (ATP) in implantable cardioverter-defibrillators (ICD) decreases patient shock burden but has recognized limitations. A new automated ATP (AATP) based on electrophysiological first principles was designed. The study objective was to assess the feasibility and safety of AATP in ambulatory ICD patients.

Methods and Results:

Enrolled patients had dual chamber or cardiac resynchronization therapy ICDs, history of ≥1 ICD-treated ventricular tachycardias (VT)/ventricular fibrillation episode, or a recorded, sustained monomorphic VT. Detection was set to ventricular fibrillation number of intervals to detect=24/32, VT number of intervals to detect≥16, and a fast VT zone of 240 to 320 ms. AATP prescribed the components and delivery of successive ATP sequences in real time, using the same settings for all patients. ICD datalogs were uploaded every ≈3 months, at unscheduled visits, exit, and death. Episodes and adverse events were adjudicated by separate committees. Results were adjusted (generalized estimating equations) for multiple episodes. AATP was downloaded into the ICDs of 144 patients (121 men), aged 67.4±11.9 years, left ventricular ejection fraction 33.1±13.6% (n=137), and treated 1626 episodes in 49 patients during 14.5±5.1 months of follow-up. Datalogs permitted adjudication of 702 episodes, including 669 sustained monomorphic VT, 20 polymorphic VT, 10 supraventricular tachycardia, and 3 malsensing episodes. AATP terminated 39 of 69 (59% adjusted) sustained monomorphic VT in the fast VT zone, 509 of 590 (85% adjusted) in the VT zone, and 6 of 10 in the ventricular fibrillation zone. No supraventricular tachycardias converted to VT or ventricular fibrillation. No anomalous AATP behavior was observed.

Conclusions:

The new AATP algorithm safely generated ATP sequences and controlled therapy progression in all zones without need for individualized programing.