Coexistence of a Classical Nodoventricular Accessory Pathway With a Left-Sided Mahaim Accessory Pathway

The coexistence of 2 Mahaim pathways represents a diagnostic challenge. We present a case in which the SH/HA intervals were useful for identifying concealed nodoventricular or His-ventricular pathways.

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.

Anteroseptal accessory pathways: Killing one bird with two stones

BACKGROUND AND AIMS

Ablation of anteroseptal accessory pathways (AS-AP) is challenging, with lower success and more complications compared to other APs. AS-APs can be successfully ablated from the right atrium (RA) or the aortic valve's noncoronary cusp (NCC). We report two patients who required a hybrid ablation approach to achieve successful abolition of both anterograde and retrograde AS-AP conduction.

METHODS AND RESULTS

A 21-year-old female with supraventricular tachycardia (SVT) and pre-excitation on electrocardiogram (ECG) underwent electrophysiology study (EPS) confirming an AS-AP with anterograde and retrograde conduction. Ablation in the NCC achieved immediate and persistent anterograde conduction block. Electrophysiological maneuvers showed persistent retrograde AP conduction and orthodromic reciprocating tachycardia (ORT) remained easily inducible. Additional ablation in the NCC did not eliminate retrograde conduction. Further ablation in the RA opposite the NCC at the site of earliest retrograde atrial activation during ORT restored sinus and eliminated retrograde AP conduction. A 52-year-old male with SVT and ECG with pre-excitation underwent EPS that confirmed an AS-AP with anterograde and retrograde conduction. Ablation was performed in the NCC resulting in immediate elimination of pre-excitation. Retrograde conduction was still present and confirmed by repeating electrophysiological maneuvers. Ablation was performed in the RA opposite the successful ablation site in the NCC, eliminating retrograde AP conduction.

CONCLUSION

Two cases of AS-AP with anterograde and retrograde conduction and successful elimination of pathway conduction required a hybrid ablation approach from the NCC and RA. This approach may be helpful in other cases to improve success rates without using excessive ablation near the normal conduction system.

An Incessant Tachycardia: What Is the Mechanism?

A 39-year-old man presented with lifelong palpitations, a mildly reduced left ventricular ejection fraction, and incessant tachycardia. Electrocardiography revealed a regular, one-to-one supraventricular tachycardia with superiorly directed P-waves and a long R–P interval. The differential diagnosis of the tachycardia, response to invasive electrophysiologic maneuvers, and treatment with catheter ablation are discussed.

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

INTRODUCTION

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.

METHODS AND RESULTS

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 eleven catheter 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%.

CONCLUSION

Transcatheter ablation for ORT and AVNRT in children with HLHS can be performed with excellent acute and long-term success without major complications.

The "hidden" concealed left-sided accessory pathway: An uncommon cause of SVT in young people

BACKGROUND

Concealed left-sided accessory pathways (CLAP) are a cause of supraventricular tachycardia (SVT) in the young. Most are mapped with right ventricular (RV) apical/outflow pacing. Rarely, alternative means of mapping are required. We review our experience from three pediatric electrophysiology (EP) centers with a rare form of "hidden" CLAP.

METHODS

All patients <21 years undergoing EP study from 2008 to 2014 with a "hidden" CLAP (defined as an accessory pathway [AP] for which RV pacing at cycle lengths [CL] stable for mapping did not demonstrate eccentric retrograde conduction) were included.

EXCLUSION CRITERIA

preexcitation. Demographic, procedural, and follow-up data were collected.

RESULTS

A total of 23 patients met the criteria (median age, 14.3 years [range 7-21], weight, 51 kg [31-99]). 21 (96%) had SVT and one AFIB (4%). APs were adenosine sensitive in 7/20 patients (35%) and VA conduction was decremental in six (26%). CLAP conduction was demonstrable with orthodromic reentrant tachycardia in all patients, with RV extrastimulus testing in seven (30%) and with rapid RV pacing (<CL 300) in three (13%). Left ventricular (LV) pacing demonstrated CLAP conduction in 17/17 (100%) patients in whom it was used. All 23 CLAPs were successfully ablated (100%) via transseptal approach with radiofrequency energy. Specific ablation techniques included: 16 (70%) during LV paced rhythm, four (17%) during orthodromic reciprocating tachycardia (ORT; 3/4 ventricular entrained), and three (13%) with brief rapid RV pacing. There were no complications. At 18 months (range 3-96), there was one recurrence (4%).

CONCLUSIONS

Some CLAPs are only demonstrable with LV pacing, entrained ORT, or rapid RV pacing. LV pacing facilitated preferential AP conduction, allowing for mapping while maintaining stable hemodynamics.

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.

Change in cycle length during narrow complex tachycardia: what is the mechanism?

Major spontaneous variation in cycle length during supraventricular tachycardia is quite an uncommon phenomenon, which sometimes can mislead a correct diagnosis. We describe a patient who developed spontaneous variation in cycle length during electrophysiologic study in whom the coronary sinus cannulation was extremely difficult. In this situation, careful inspection of the mechanisms associated with this variation and classic pacing maneuvers are important to make a correct diagnosis of the supraventricular tachycardia.