Author + information
- Received March 15, 2017
- Revision received June 22, 2017
- Accepted July 13, 2017
- Published online November 1, 2017.
- Frederick T. Han, MD∗ (, )
- Eric M. Riles, MD, MPH,
- Nitish Badhwar, MD and
- Melvin M. Scheinman, MD
- Department of Medicine, University of Utah Health Sciences Center, Division of Cardiovascular Medicine, Salt Lake City, Utah
- ↵∗Address for correspondence:
Dr. Frederick T. Han, University of Utah Health Sciences Center, Division of Cardiovascular Medicine, 30 North 1900 East, Room 4A-100 SOM, Salt Lake City, Utah 84132.
Objectives The authors sought to describe the clinical features and sites of successful ablation for incessant nodofascicular (NF) and nodoventricular (NV) tachycardias.
Background Incessant supraventricular tachycardias have been associated with tachycardia-induced cardiomyopathies and have been previously attributed to permanent junctional reciprocating tachycardias, atrial tachycardias, and atrioventricular nodal re-entrant tachycardias. Incessant concealed NF and NV tachycardias have not been described previously.
Methods Three cases of incessant concealed NF and NV re-entrant tachycardias were identified from 2 centers.
Results The authors describe 3 cases with incessant supraventricular tachycardia resulting from NV (2 cases) and NF (1 case) pathways. Atrioventricular nodal re-entrant tachycardia was excluded by His synchronous premature ventricular complexes that either delayed or terminated the tachycardia. Ventricular pacing showed constant and progressive fusion in cases 1 and 3. In 2 cases, there was spontaneous initiation with a 1:2 response (cases 1 and 3); the presence of retrograde longitudinal dissociation or marked decremental pathway conduction in cases 1 and 3 sustains these tachycardias. The NV pathway was successfully ablated in the slow pathway region in case 3 and at the right bundle branch in case 1. The NF pathway was successfully ablated within the proximal coronary sinus in case 2.
Conclusions This is the first report of incessant supraventricular tachycardia using concealed NF or NV pathways. These tachycardias demonstrated spontaneous initiation from sinus rhythm with a 1:2 response and retrograde longitudinal dissociation or marked decremental pathway conduction. Successful ablation was achieved at either right-sided sites or within the coronary sinus.
Incessant supraventricular tachycardias (SVTs) have been well described for patients with permanent junctional reciprocating tachycardia (1–4), atrial tachycardia (5,6), and, more recently, for those with atrioventricular (AV) nodal re-entrant tachycardia (AVNRT) (7). To our knowledge, there are no prior reports of incessant SVT in patients with nodofascicular (NF) or nodoventricular (NV) pathways. This study describes the electrophysiologic characteristics and sites for ablation in patients with incessant SVT resulting from concealed NF and NV tachycardias.
From 2014 to 2016, 3 cases with incessant concealed NF or NV tachycardia were prospectively identified from the University of Utah Health Sciences Center and the University of California, San Francisco Medical Center. The tachycardia characteristics of the 3 cases are presented in Table 1. Incessant tachycardia is defined as tachycardia present during >50% of the observed monitoring period, either on inpatient telemetry or outpatient ambulatory monitoring. All 3 patients underwent electrophysiology study and ablation. During the electrophysiology study, catheters were placed in the right atrium, right ventricle, His bundle, and coronary sinus (CS). Diagnostic maneuvers and ablation were performed at the discretion of the electrophysiologist. The clinical findings and ablation details are presented below.
Diagnostic criteria for a concealed NF/NV tachycardia included: 1) tachycardia with orthodromic activation of the His bundle; 2) evidence of late premature ventricular complexes (PVCs) resetting (evidenced by advancing or delaying the next His bundle activation) or terminating the tachycardia; and 3) dissociation of the atrium from the tachycardia. Concealed NV tachycardia was differentiated from a concealed NF tachycardia by the presence of constant and progressive fusion with ventricular pacing during the tachycardia, indicating the participation of the ventricle in the tachycardia circuit with an NV tachycardia (8–10). NF tachycardia fails to demonstrate constant or progressive fusion during ventricular overdrive pacing because the circuit is confined to the specialized conduction system and the ventricular myocardium is not part of the circuit.
A 50-year-old woman with history of a baseline left bundle branch block (LBBB) and prior thoracic osteosarcoma with surgical resection and chemotherapy presented with persistent palpitations. Her baseline electrocardiogram showed sinus rhythm with a LBBB pattern. An electrocardiogram performed for palpitations identified a sustained LBBB pattern wide complex tachycardia at 195 beats/min, precordial transition between V4 and V5, and inferior axis, replicating her baseline LBBB. The tachycardia was incessant and was associated with hypotension and acute congestive heart failure. Intravenous adenosine (12 mg) terminated the tachycardia (Online Figure 1A); however, the tachycardia immediately recurred after the adenosine effect resolved (Online Figure 1B). An echocardiogram during sinus rhythm revealed left ventricular systolic dysfunction, with a left ventricular ejection fraction of 29%.
During the electrophysiology study, the baseline atrial-His (AH) and His-ventricular (HV) intervals were 93 and 61 ms, respectively. The tachycardia occurred spontaneously with a 2 for 1 initiation pattern and was associated with AV dissociation (Figure 1). The HV interval prolonged during the tachycardia to 75 ms; this prolongation provided a critical delay in the right bundle branch to initiate and maintain the tachycardia. His synchronous premature ventricular complexes (PVCs) consistently advanced the next beat of tachycardia (Online Figure 2). Entrainment from both the right ventricular base (Figure 2) and the right ventricular apex (Online Figure 3) provided evidence of a re-entrant mechanism with the finding of progressive fusion during pacing at different cycle lengths and confirmed that both the basal (Online Figure 4) and apical (Online Figure 5) right ventricle were close to the circuit with a post-pacing interval (PPI) approximately 30 ms longer than the tachycardia cycle length (TCL).
Bundle branch reentry tachycardia was excluded by: 1) entrainment mapping from the right ventricle base identifying the basal right ventricle muscle to be within the circuit and 2) the effect of adenosine reliably terminating the tachycardia confirming that the AV node was a critical part of the tachycardia circuit. Reproducible tachycardia termination with adenosine provides strong evidence against bundle branch re-entrant tachycardia in which adenosine would not be expected to have any effect on the tachycardia. AV nodal re-entrant tachycardia with upper common pathway block was excluded by: 1) evidence of a pathway participating in the tachycardia circuit with His synchronous PVCs delaying the subsequent beat of tachycardia; and 2) entrainment mapping from the right ventricular base and apex producing evidence of progressive fusion. With AV nodal re-entrant tachycardia, progressive fusion would not occur because of the circuit being confined to the AV junction.
Entrainment mapping and ablation were performed sequentially beginning from an apical location at sites where entrainment mapping identified the ventricle to be part of the circuit, starting with the distal right bundle potential. After ablation at the distal right bundle potential, the baseline HV interval prolonged from 61 to 105 ms (Online Figure 6), but the tachycardia remained inducible with an HV interval of 120 ms during tachycardia.
Progressive entrainment mapping at sites more proximal in the right bundle potential identified a site to be within the tachycardia circuit (Online Figure 7). Ablation at this site during sinus rhythm produced infraHisian complete block (Online Figure 8) and rendered it noninducible. No junctional beats were noted during the ablation. Because of finding complete heart block and class 2 congestive heart failure with left ventricular systolic dysfunction, a cardiac resynchronization therapy defibrillator was implanted. In this case, we intended to ablate the distal right bundle in an area where tachycardia entrainment confirmed the site to be close to the circuit at the distal NV insertion site. After ablation of the distal right bundle, the LBBB was still present with an increase in the HV interval. Subsequent ablation at the proximal right bundle branch (RBB) potential resulted in complete infrahisian AV block. This was early in our experience; with our current knowledge, we would have attempted ablation at the slow pathway region for our initial approach.
A 38-year-old woman with rheumatoid arthritis presented with incessant SVT correlating with daily episodes of near syncope. A Holter monitor identified an incessant symptomatic short RP (QRS complex - P wave interval) tachycardia at 137 beats/min. A narrow QRS complex short RP tachycardia (tachycardia 1; cycle length [CL]: 538 ms) was reproducibly induced with spontaneous atrial complexes conducted via the slow pathway. With attempted right ventricular overdrive pacing, tachycardia 1 terminated, and a long RP tachycardia (tachycardia 2, CL: 547 to 600 ms) with earliest atrial activation at the proximal CS was observed. Tachycardia 1 was also noted to spontaneously convert to tachycardia 2 with the absence of retrograde atrial conduction (Online Figure 9), with a change from a short ventricular atrial (VA) interval to markedly prolonged VA interval. During extended periods of tachycardia, we noted the presence of spontaneous VA block during tachycardia with conversion from tachycardia 1 to tachycardia 2. With the change in the VA relationship, there was also a change in the site of earliest retrograde atrial activation. Because the atrium is not a critical part of the circuit, we hypothesize that retrograde conduction occurred via both the fast pathway and the anterior inferior extension of the AV node. For the short RP tachycardia, the impulse traveled retrograde from the AV node to the atrium via the anterior inferior extension with earliest activation in the region of the CS ostium. Conversely, for the long RP tachycardia retrograde conduction from the AV node to the atrium via the fast pathway would exhibit earliest activation at the His bundle region. Because the atrium is activated as a bystander in this case, it can be activated in a varying relationship to the ventricle depending on the relative speed of conduction of the fast pathway versus the anterior inferior extension.
Because right ventricular overdrive pacing reproducibly terminated tachycardia 1, entrainment mapping could not be performed. Pacing from the basal right ventricle versus the apical right ventricle failed to produce evidence of fusion, thus supporting the finding of a concealed NF pathway.
The His synchronous PVCs both delayed the subsequent His and terminated the tachycardia (Online Figure 10), proving the presence of a concealed NF pathway and its participation as the retrograde limb of the tachycardia (tachycardia 1). Activation mapping of the NF tachycardia identified a discrete potential at the roof of the CS ostium that preceded the His activation (Figure 3A). We confirmed the presence of this potential in sinus rhythm before ablation (Figure 3B). Ablation at this site terminated the tachycardia (Online Figure 11) and subsequently produced junctional complexes during ablation in sinus rhythm. After ablation, neither tachycardias 1 or 2 were induced. The findings of: 1) a spontaneous marked change in the VA interval with persistence of tachycardia at different cycle lengths; and 2) elimination of both tachycardia 1 and 2 with ablation at a single site are consistent with longitudinal dissociation of the retrograde limb of the concealed NF pathway.
Evidence against AV nodal re-entrant tachycardia with a bystander NF pathway in this case is termination of the tachycardia with His synchronous PVCs.
A 37-year-old woman presented with a history of frequent palpitations since childhood. Ambulatory monitoring revealed an incessant narrow complex tachycardia, which was initiated by a 2 for 1 response. The baseline rhythm was sinus and baseline AH and HV intervals were normal. There was no evidence of dual AV nodal pathway conduction or ventricular pre-excitation. A sustained long-RP narrow complex tachycardia occurred spontaneously during sinus rhythm.
Atrial activation during tachycardia was concentric. PVCs delivered during His-refractoriness consistently terminated the tachycardia (Online Figure 12). Ventricular overdrive pacing produced a V-A-H-V (Ventricular - Atrial - His - Ventricular) response. The AH interval during tachycardia was shorter than the AH interval during sinus rhythm and during atrial pacing at the TCL (Online Figure 13). Entrainment with fusion and orthodromic His bundle capture were noted during ventricular overdrive pacing (Figure 4). The findings of the His synchronous PVCs terminating the tachycardia and the presence of fusion with ventricular overdrive pacing provide evidence of a pathway participating as the retrograde limb of the tachycardia circuit. The observation that the AH interval was shorter during the tachycardia indicates that the atria and the ventricles were being activated in parallel from the AV node (concealed NV re-entrant tachycardia) as opposed to in series (expected with an orthodromic AV re-entrant tachycardia). This finding excludes AV re-entrant tachycardia.
The TCL alternated spontaneously between 380 and 480 ms (Figure 5). Abrupt alternations in the tachycardia CL corresponded to alternations in the VA interval with a fixed AH interval, and the changes in the VA interval preceded changes in the atrial-atrial and His-His interval. This may be explained by either longitudinal dissociation of the retrograde NV limb of the tachycardia or marked decremental conduction of the pathway.
Ablation at the slow pathway region rendered the tachycardia noninducible. Junctional beats with VA conduction were noted during the ablation.
This report describes the first series of patients with incessant concealed NF and NV tachycardias. This series highlights several features that characterize and may explain the mechanism of the incessant nature of these tachycardias.
The initiation of these tachycardias occurred frequently and spontaneously with a 2 for 1 initiation pattern in cases 1 and 3 or with premature atrial extrastimuli as seen in case 2. The ease with which these tachycardias were initiated indicates the presence of a wide excitable gap contributing to their frequent initiation as well as their incessant nature (11–14). The variable and abrupt change in VA interval in case 2 and the 2 distinct VA intervals in case 3 are consistent with longitudinal dissociation of the retrograde NF and NV limbs of these tachycardias. We hypothesize that switching from the short VA to a longer VA interval extends the excitable gap and serves to support perpetuation of the tachycardia. In addition, case 1 had a longer His-ventricular interval during tachycardia contributing to a critical delay in the right bundle, giving rise to a wide excitable gap and the incessant tachycardia. We hypothesize that these physiologic findings correlate with a longer path length for the tachycardia circuit.
This case series of incessant NF and NV tachycardias show that these tachycardias can present with VA dissociation, a 1:1 short RP relationship, or a 1:1 long RP relationship. These variations are a function of the NF/NV insertion into the AV node as well as the properties of the retrograde limb of the NF/NV pathway. This report illustrates the importance of using His synchronous PVCs to assess for the presence of NF and NV pathways based on tachycardia resetting or termination. All 3 tachycardias in this series were reset/terminated by His synchronous PVCs, proving the presence and the participation of these NF and NV pathways in the tachycardia. Because the atrium is not part of the circuit for these tachycardias, analyzing the His-His interval for evidence of resetting is the key feature of these tachycardias.
The use of adenosine can be a useful diagnostic maneuver for distinguishing a concealed NF/NV tachycardia from ventricular tachycardia resulting from bundle to bundle reentry. Administration of intravenous adenosine in this case terminated the tachycardia, with AV block indicating the involvement of the AV node as a critical part of the tachycardia circuit. This is in contrast to bundle branch reentry ventricular tachycardia in which the AV node is not part of the circuit, and adenosine would not be expected to have any effect upon the tachycardia. Of further interest for case 1, ablation of the distal RBB potential over a more lateral portion of the moderator band increased the H-V (His - Ventricular) interval and prolonged the tachycardia CL, whereas ablation of the proximal RBB block resulted in tachycardia termination. This suggests that ablation distal to the N-V (nodoventricular) insertion site is associated with failed ablation.
Cases 2 and 3
Case 2 showed variable VA intervals and 2 different tachycardias (short RP and long RP tachycardias). In case 3, there were changes in the TCL corresponding to discrete changes in the VA interval, whereas the AH interval remains fixed. Longitudinal dissociation of retrograde conduction has been rarely described in patients with accessory pathways (11,12,15). Successful ablation at a single site (slow pathway) would argue for a discrete N-V pathway as opposed to 2 separate pathways; however, marked decremental pathway conduction cannot be excluded.
Differentiation of an NF from an NV pathway can be achieved by entrainment mapping with ventricular overdrive pacing from the right ventricular base and the right ventricular apex (8). As shown in case 1, a concealed NV tachycardia will produce constant and progressive fusion with pacing from these 2 different sites because of the ventricle being part of the circuit (PPI – TCL <30 ms). With an NF tachycardia, the circuit involves the AV node, His-Purkinje system, and the retrograde NF pathway. Entrainment from the right ventricular base and apex would fail to produce constant or progressive fusion as occurred in case 2. Bundle branch reentry tachycardia would be expected to produce manifest fusion during entrainment from the right ventricular base and apex; however, the right ventricular base would be out of the circuit (i.e., PPI – TCL >30 ms).
Right ventricular overdrive pacing for AV nodal re-entrant tachycardia typically produces a PPI – TCL >115 ms (16,17). Although we used a PPI within 30 ms of the TCL to identify the NF/NV pathway locations with entrainment mapping, this criterion must be used judiciously. Our attempts at entrainment focused on a paced cycle length within 10 ms of the TCL. Because the right ventricular pacing sites are typically close to the NF/NV pathway insertion sites, using a PPI – TCL ≤30 ms proved to be reliable in our experience for entrainment mapping of NF/NV pathways. However, we did note that entrainment at faster cycle lengths in case 1 produced progressively longer PPIs; this reflects potential decremental conduction through the AV node, His Purkinje system, and likely the NV pathway and thus consistent pacing at cycle lengths within 10 ms of the TCLs are recommended for entrainment mapping of these pathways.
In this series, all 3 tachycardias were successfully ablated. For case 1, ablation was performed adjacent to the proximal RBB (where entrainment mapping identified this area to be part of the circuit). This was complicated by complete AV block. Junctional complexes were not present during ablation. This case occurred early in our experience with NF and NV tachycardias, before our finding that these pathways can be successfully ablated from the slow pathway region. Before ablation, the patient was informed of the possibility of AV block with need for a pacemaker; because of the incessant nature of her symptomatic tachycardia, she elected to proceed with ablation despite this risk. Our current approach is to start with ablation at the slow pathway region for NF and NV pathways. If ablation at the slow pathway region fails to render the tachycardia noninducible, activation and entrainment mapping to identify alternative sites for ablation are used. For case 2, successful ablation was achieved just inside the CS ostium and was associated with junctional complexes. Our prior experience has indicated that left-sided NF and NV pathways traverse through the CS, necessitating mapping of the CS for successful ablation. These pathways can exhibit discrete potentials as markers for the site of ablation (18). These left-sided NF pathway extensions have also been identified by other investigators (15).
Case 3 illustrates the finding that ablation in the slow pathway region can successfully treat concealed NV tachycardias. The ablation for case 2 occurred at the roof of the CS ostium. This is consistent with our prior report of left-sided NF pathways being mapped to the CS, guided by discrete potentials following atrial activation in sinus rhythm (18).
We emphasize the importance of His synchronous PVCs, but this depends on a stable TCL.
NF and NV pathways can present as incessant tachycardias. These tachycardias can occur with a 2 for 1 initiation pattern as well as longitudinal VA dissociation. Differentiation of these tachycardias from AVNRT, atrioventricular re-entrant tachycardia, and atrial tachycardia is possible with the use of His synchronous premature ventricular complexes. Ventricular overdrive pacing from the base and apex helps to distinguish between NF and NV tachycardias by assessing for the presence of constant and progressive fusion. Ablation over the right inferior (slow pathway) nodal extension successfully treats these tachycardias. Mapping and ablation of the CS is required for left-sided NF and NV pathways.
COMPETENCY IN MEDICAL KNOWLEDGE: This manuscript addresses clinical competencies of medical knowledge, patient care, and procedural skills with respect to incessant nodofascicular and nodoventricular tachycardias.
TRANSLATIONAL OUTLOOK: This manuscript illustrates the mechanisms and clinical features of nodofascicular and nodoventricular pathways responsible for these incessant supraventricular tachycardias.
The authors thank John Miller, MD, for his gracious assistance with figures for this manuscript.
Dr. Han received research support from Boston Scientific and Abbott and honoraria from Biotronik. Dr. Scheinman is a speaker for St Jude Medical, Boston Scientific, Medtronic, Biosense-Webster, and Biotronik at Fellows Programs. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.
- Abbreviations and Acronyms
- atrioventricular nodal re-entrant tachycardia
- cycle length
- coronary sinus
- left bundle branch block
- premature ventricular complexes
- post-pacing interval
- premature ventricular complexes
- right bundle branch
- QRS complex - P wave
- supraventricular tachycardia
- tachycardia cycle length
- ventricular atrial
- Received March 15, 2017.
- Revision received June 22, 2017.
- Accepted July 13, 2017.
- 2017 American College of Cardiology Foundation
- Dorostkar P.C.,
- Silka M.J.,
- Morady F.,
- Dick M. 2nd.
- Gaita F.,
- Haissaguerre M.,
- Giustetto C.,
- et al.
- Case C.L.,
- Gillette P.C.,
- Oslizlok P.C.,
- Knick B.J.,
- Blair H.L.
- Maury P.,
- Detis N.,
- Duparc A.,
- Mondoly P.,
- Rollin A.,
- Delay M.
- Atie J.,
- Brugada P.,
- Brugada J.,
- et al.
- Lai W.T.,
- Lee C.S.,
- Sheu S.H.,
- Hwang Y.S.,
- Sung R.J.
- Michaud G.F.,
- Tada H.,
- Chough S.,
- et al.
- Badhwar N.J.C.,
- Tchou P.J.,
- Scheinman M.M.