Author + information
- Received February 9, 2017
- Revision received May 8, 2017
- Accepted May 30, 2017
- Published online September 13, 2017.
- Mitsunori Maruyama, MD, PhDa,∗ (, )
- Shunsuke Uetake, MD, PhDa,
- Yasushi Miyauchi, MD, PhDa,
- Yoshihiko Seino, MD, PhDa and
- Wataru Shimizu, MD, PhDb
- aDepartment of Cardiovascular Medicine, Nippon Medical School Chiba Hokusoh Hospital, Chiba, Japan
- bDepartment of Cardiovascular Medicine, Nippon Medical School, Tokyo, Japan
- ↵∗Address for correspondence:
Dr. Mitsunori Maruyama, Department of Cardiovascular Medicine, Nippon Medical School, Chiba Hokusoh Hospital, 1715 Kamakari, Inzai-city, Chiba, 2701694 Japan.
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 reentrant 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 reentrant 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.
A correct differential diagnosis of paroxysmal supraventricular tachycardia (SVT) is of clinical importance because catheter ablation now offers a definitive cure for the majority of SVTs. Ventricular overdrive pacing (VOP) during an SVT is a key maneuver to distinguish the SVT mechanism. The electrogram sequence upon cessation of the VOP (an atrial–ventricular or atrial–atrial–ventricular response) is useful for diagnosing atrial tachycardias (ATs) (1). In addition, several criteria obtained from VOP provide important clues to distinguish orthodromic reciprocating tachycardia (ORT) by using accessory pathways (APs) from atrioventricular nodal reentrant tachycardia (AVNRT). These criteria include the difference between the stimulus–atrial interval and tachycardia ventriculo-atrial (VA) interval, the difference between the post-pacing interval and tachycardia cycle length (PPI – TCL) (2,3), the difference in the His-atrial intervals during VOP and the tachycardia (4), a constant QRS fusion (5), and orthodromic His-bundle or septal ventricular capture (6). These criteria rely on successful entrainment; however, termination of the SVT during VOP is common.
In contrast, some other VOP criteria, such as atrial capture or tachycardia termination within the transition zone of a QRS fusion (7), and the timing of the atrial capture relative to the advancement of the septal para-Hisian ventricular electrogram (SVE) (8), were suggested to help differentiate ORT from AVNRT even when the SVT was terminated during VOP. However, it is not fully understood how effectively these criteria provide a final diagnosis of the terminated SVT. Recently, Kaiser et al. (9) showed that PPI – TCL could be mathematically predicted if VOP terminated the SVT after the resetting of the SVT. Furthermore, the pacing prematurity needed to reset or terminate an SVT may have a diagnostic value equivalent to PPI – TCL (10), which is also potentially useful in diagnosing terminated SVTs. The aim of the present study was to evaluate the diagnostic yield of the termination analyses in a cohort of patients with SVTs terminated during VOP.
A total of 206 patients were studied who presented to Nippon Medical School Chiba Hokusoh Hospital and Nippon Medical School Hospital for catheter ablation of SVT. The study was approved by our institutional review board. Patients were included if they had SVTs with a 1:1 atrioventricular relationship and underwent VOP from the right ventricular apex (RVA) during the SVT at a pacing cycle length (PCL) 10 to 40 ms shorter than the TCL. SVTs exhibiting spontaneous TCL oscillations >15 ms within 3 cycles before the onset of the VOP were excluded from the study.
Electrophysiological study and catheter ablation
After providing written informed consent, patients underwent an electrophysiological study that was performed under deep sedation. Twelve-lead surface electrocardiograms and intracardiac electrograms from the high right atrium, coronary sinus, His-bundle region, and RVA were recorded and digitally stored. All measurements were made by using on-screen calipers. Intravenous isoproterenol (0.005 to 0.02 μg/kg/min) was administered if no tachycardia was inducible or sustained at baseline. When the sustained SVTs were terminated during VOP, multiple VOP attempts were made, aiming at successful entrainment of the SVTs. The VOP results were classified as a termination response if the VOP terminated the SVT at least twice. Radiofrequency catheter ablation was performed with a nonirrigated catheter for AVNRT and paraseptal AT/ORT or with an open-irrigated catheter for a nonseptal AT/ORT.
Diagnosis of SVT
AT was diagnosed if the ventricular activation was not linked to the atrial activation, which was demonstrated by atrial overdrive pacing from multiple atrial sites (differential atrial overdrive pacing) with a maximal difference in the post-pacing VA interval among the different atrial sites >20 ms (11). An atrial–atrial–ventricular response after VOP was considered diagnostic for AT in a short-RP tachycardia but not in a long-RP tachycardia because of the possibility of dual atrial responses (12). AT was excluded when any of the following were observed: 1) an atrial–ventricular response after VOP; 2) reproducible spontaneous termination of the tachycardia with atrioventricular block; 3) occurrence of VA block despite perpetuation of the tachycardia; 4) tachycardia termination without capturing the atrium during the VOP or ventricular extrastimulus; and 5) atrial cycle prolongation with atrial capture from a ventricular extrastimulus (post-excitation).
ORT was diagnosed if any of the following criteria were satisfied: 1) an eccentric atrial activation during the tachycardia that was reproducible by ventricular pacing, with the earliest atrial activation beyond the left posterolateral mitral annulus that excluded a “left-variant” AVNRT (13,14); 2) an increase in the VA interval >20 ms with the development of ipsilateral bundle branch block (15); 3) resetting or reproducible termination of the tachycardia with a ventricular extrastimulus applied when the His-bundle was refractory; 4) constant QRS fusion during VOP (5); 5) orthodromic His-bundle or septal ventricular capture during VOP (6); 6) a PPI – TCL corrected by an atrioventricular nodal conduction delay <110 ms or a stimulus–atrial interval minus tachycardia VA interval <85 ms measured by VOP (2,3); and 7) a shorter His–atrial interval during the VOP than the His–atrial interval during the tachycardia (4). ORT was excluded if either spontaneous second-degree atrioventricular block during the tachycardia or VA dissociation during VOP was observed.
AVNRT was diagnosed if the tachycardia was capable of being induced and terminated by pacing, and both AT and ORT were excluded. AVNRT was considered typical when the septal VA interval was ≤70 ms and the earliest atrial activation was in the His-bundle region.
A final diagnosis was made based on a combination of the tachycardia features, results of diagnostic pacing maneuvers, and the outcome of the catheter ablation.
Total pacing prematurity and prediction of PPI – TCL
We measured the prematurity of the pacing needed to first reset or terminate the tachycardia as the total pacing prematurity (TPP). The TPP was defined as the sum of the prematurity of each stimulus (TCL-PCL) until the first atrial resetting or tachycardia termination, calculated by the TCL-PCL multiplied by the number (n) of stimuli needed to reset the atrium or to terminate the tachycardia (9).
To prevent a potential error from minor variations in the TCL and coupling of the first stimulus, and to make the calculation simpler, we directly measured the nTCL and nPCL with on-screen calipers as the sum of the TCL and PCL, respectively (TCLsum and PCLsum) (Figures 1 to 3⇓⇓⇓).
PPI – TCL could be predicted by subtracting the amount of the tachycardia advancement during the first atrial reset from the TPP (9).
To exclude spontaneous termination during the VOP, we confirmed the reproducibility of the tachycardia termination by repeating the VOP and did not analyze the data if the atrial rate displayed a progressive slowing before the tachycardia termination.
Other diagnostic criteria for a terminated tachycardia during VOP
We examined the presence or absence of atrial capture or tachycardia termination within the “transition zone,” which was reported to be useful for the diagnosis of ORTs even when the tachycardia was terminated during VOP (7). Here, the transition zone was defined as the time period from the beginning of the VOP with fused QRS complexes and the first paced complex with a stable QRS morphology. The “fusion period” was defined as the time period with fused QRS complexes but not including the first stable QRS complex (Figure 1).
The number of stable QRS complexes required to reset the tachycardia was also counted. A number of stable QRS complexes ≤1 were shown to be diagnostic for ORT, similar to the transition zone criterion (16).
It was reported that atrial capture simultaneous with or before advancement of the SVE helped differentiate ORT by using a septal AP from AVNRT when the tachycardia terminated during VOP (8). Thus, the differential response of the SVE and atrium was analyzed in septal ORTs and AVNRTs (Figure 1).
Continuous variables are expressed as the mean ± SD and were compared by using the Student t test. A 1-way analysis of variance combined with a Bonferroni procedure was used for multiple comparisons, and the Fisher exact test was used to analyze the categorical data. The correlation was examined by using a Pearson's correlation. A p value <0.05 was considered statistically significant.
A total of 225 SVTs in 206 patients (including 34 ATs, 67 ORTs, and 124 AVNRTs) were studied. The baseline patient characteristics are shown in Table 1. Male sex was more prevalent in the ORT patients than in the AVNRT and AT patients. The mechanisms of AT were reentrant in 21 and non-reentrant in 13. The origins of 19 ATs were paraseptal regions (adenosine-sensitive reentrant AT arising from near the atrioventricular node [n = 11] or coronary sinus ostium [n = 3], and non-reentrant focal septal AT [n = 5]). Three ATs were related to previous cardiac surgery. The mean cycle length of AT was longer than that of ORT or AVNRT. In the ORTs, the locations of the APs were septal in 14 (8 right APs [2 superoparaseptal APs, 1 midseptal AP, and 5 posteroseptal APs] and 6 left posteroseptal APs), left free-wall in 48 (1 anterior APs, 13 anterolateral APs, 21 lateral APs, 7 posterolateral APs, and 6 posterior APs), and right free-wall in 5 (1 anterior AP, 2 anterolateral APs, and 2 lateral APs). Four APs had a decremental conduction property, defined as a VA interval during the tachycardia >40% of the TCL (17) (1 septal AP and 3 free-wall APs). Eighty-five AVNRTs were typical (slow–fast form) and 39 were atypical (23 fast–slow form and 16 slow–slow form).
Responses of SVT to VOP
Of 225 SVTs, VOP resulted in successful entrainment with 1:1 VA conduction in 103 (46%), VA dissociation in 35 (15%), and termination of the tachycardia in 87 (39%). Although the TCL-PCL was similar among ORT, AVNRT, and AT, the responses to VOP substantially differed according to the cause of the SVT (Table 1). Because the ventricle is a critical part of ORT, VA dissociation never occurred with VOP during the ORT. VA dissociation was frequently observed in ATs (85%) but was also seen in some AVNRTs (5%). In 55% of the ORT cases and 40% of AVNRT cases, the tachycardia terminated during the VOP. The VOP terminated 3 (75%) of 4 ORTs with a decremental AP. There were no ATs that terminated during the VOP. Hence, either ORT or AVNRT was responsible for the SVTs terminated by VOP in the subjects of this study.
Two modes of tachycardia termination were observed: 1) termination after an atrial reset (type 1: n = 71 [82%]) (Figure 2); or 2) termination without any perturbation of the atrial cycle (type 2: n = 16 [18%]) (Figure 3). During 3.1 ± 1.2 (range: 2 to 7) attempts of VOP, the type of termination was consistent in 34 (39%) SVTs, both types of termination were observed in 5 (6%) SVTs, and successful entrainment was finally obtained in 48 (55%) SVTs. Either type of termination was observed when the tachycardia was terminated with conduction block in the retrograde limb (type 1 [n = 17], type 2 [n = 16]), whereas only type 1 termination occurred when the tachycardia was terminated with conduction block in the anterograde limb (n = 54). In ORTs with a decremental AP, all the terminations were type 2, whereas only 3 (9%) of 34 ORTs with a nondecremental AP exhibited type 2 termination (p < 0.01). In AVNRT, the incidence of type 2 termination was higher in atypical AVNRTs than in typical AVNRTs (54% vs. 8%; p < 0.01).
Predicted PPI – TCL
PPI – TCL was able to be predicted by the formula shown in the Methods section if the SVT was successfully entrained or terminated after atrial resetting (i.e., 1:1 VA conduction or type 1 termination). Figure 4A shows a correlation between the predicted PPI – TCL and measured PPI – TCL corrected by an atrioventricular nodal conduction delay (3) in 103 successfully entrained SVTs. The predicted PPI – TCL was highly correlated with the corrected PPI – TCL derived from actual measurements (r = 0.96; p < 0.001).
In 71 SVTs with type 1 termination during VOP, all AVNRT cases had a predicted PPI – TCL >110 ms (range: 132 to 286 ms), and all ORT cases using a septal AP had a predicted PPI – TCL <110 ms (range: 25 to 94 ms) (Figure 4B), as in the previous study identifying a measured corrected PPI – TCL >110 ms in AVNRTs and <110 ms in septal ORTs (3). Seven of 22 ORT cases with type 1 termination using a left free-wall AP (4 left anterolateral APs, 1 left lateral AP, and 2 left posterolateral APs) had a predicted PPI – TCL >110 ms, probably because these locations of the AP were relatively remote from the pacing site, at the RVA. The prediction of PPI – TCL was not feasible in ORT using a decremental AP because all of them exhibited type 2 termination (Figure 3).
The predicted PPI – TCL was not available for type 2 termination, whereas the calculation of the TPP was possible independently of the type of tachycardia termination. In 87 SVTs terminated during VOP, all AVNRT cases had a TPP >125 ms (range: 140 to 331 ms), and all ORT cases using a septal AP had a TPP <125 ms (range: 40 to 104 ms) (Figure 5). Similar to PPI – TCL, 9 of 26 terminated ORT cases using a left free-wall AP (4 left anterolateral APs, 3 left lateral APs, and 2 left posterolateral APs) had a TPP >125 ms. The TPP results were consistent within the same SVT even when different responses to VOP were observed during multiple VOP attempts.
Comparisons of the diagnostic performance among the criteria for ORT in terminated SVT
The present study confirmed that the criterion (atrial capture or tachycardia termination within the transition zone) had a favorable sensitivity and specificity for a diagnosis of ORT (Table 2). The number of stable QRS complexes required to reset the tachycardia was 0.5 ± 0.7 in ORT and 3.7 ± 1.9 in AVNRT (p < 0.01). The diagnostic yield of the criterion (the number of stable QRS complexes ≤1) was substantially the same as the transition zone criterion for a diagnosis of ORT. These criteria were not diagnostic for ORTs due to 11 false-positives in AVNRT cases (Figure 6). Because all the false-positives in the AVNRT cases exhibited atrial capture at the timing of the first stable QRS complex, the criteria redefined as atrial capture or tachycardia termination within the fusion period, and the absence of a stable QRS complex, were specific for ORT, although the sensitivity was substantially diminished.
Calvo et al. (8) reported that atrial capture simultaneous with or preceding the SVE advancement was specific for ORT using a septal AP. Because this criterion is not applicable to ORT using a free-wall AP, its availability was limited. Of 14 septal ORTs, 6 false-negatives were noted (5 left posteroseptal APs and 1 right posteroseptal AP with a decremental conduction property). When combined with other criteria, an additional diagnostic yield by using the SVE criterion could not be found.
When the TPP criterion was combined with the criterion of the fusion period (or no stable QRS complex), the sensitivity for diagnosing ORT was maximized, although it remained specific (Table 2). All false-negatives with the combined criteria were observed in patients with ORTs using an AP beyond the left posterolateral mitral annulus (6 anterolateral APs and 7 lateral APs) that did not require a differentiation from AVNRT.
Because the RVA is closer to the reentrant circuit of ORT, PPI – TCL measured at the RVA should be a smaller value in ORT than it would for AVNRT or AT. A corrected PPI – TCL <110 ms is specific for ORT (3), but it cannot be measured when VOP terminates the SVT. The incidence of SVT termination during VOP is reported to be 8% to 56% (7,8,16,18) and was 39% in this study. As shown in a recent study (9), PPI – TCL was accurately predicted, provided that the atrium was reset during VOP. Thus, the prediction of PPI – TCL is feasible when the mode of the SVT termination is type 1, and its diagnostic values in the terminated SVT are consistent with the values in the SVT that is successfully entrained (2,3). Furthermore, we found that the TPP, obtained by using our simplified method, had a diagnostic value similar to PPI – TCL for the ORT diagnosis, but the TPP was measurable irrespective of the mode of the SVT termination. Bennett et al. (17) described that the PPI – TCL criterion was invalid in approximately 50% of ORT cases with a decremental AP because a conduction delay in the AP caused a prolongation of PPI – TCL. In this study, 3 of 4 ORTs with a decremental AP displayed type 2 termination during VOP, in which a conduction block in the AP was responsible for the tachycardia termination. Interestingly, the TPP correctly differentiated all the ORTs with decremental APs. This finding suggests that the TPP might be less affected by a decremental conduction property because it should reflect the characteristics of the conducting path from the pacing site to the tachycardia circuit rather than that of the tachycardia circuit itself. Figure 7 represents how the TPP and PPI – TCL were demonstrated in SVTs with a prominent decremental conduction property in the retrograde limb of the tachycardia circuit. This example exhibits a prolongation of the atrial cycle at the first atrial reset (i.e., post-excitation), resulting in a longer predicted PCL-TCL than the TPP. Hence, the TPP might be a better criterion than PPI – TCL in ORTs using decremental APs.
Atrial capture or tachycardia termination within the transition zone and a number of stable QRS complexes ≤1 correctly diagnosed the majority of ORTs even when VOP terminated the SVT. However, because atrial capture was also observed at the timing of the first stable QRS complex in 11 (9%) AVNRTs (Figure 6), we could not make a definitive diagnosis by using only the transition zone criterion. In agreement with our results, the later study noted atrial resetting within the transition zone in 6% to 7% of AVNRT cases (18). Excluding the first stable QRS complex from the transition zone (i.e., fusion period without any stable QRS complexes) made the criteria diagnostic for ORT. However, a modification of the criteria lowered their sensitivity to 58%. When the modified criteria were combined with the TPP criterion, the sensitivity for diagnosing ORT increased to 81% with a 100% specificity (Table 2). The combined criteria did not make a correct diagnosis only in ORT with a left anterolateral or left lateral AP. In general, the differential diagnosis between AVNRT and ORT with this location of the AP has little problem, because a left deviation of the atrioventricular node does not exceed the posterolateral mitral annulus (13,14). In addition, the combined criteria were available unless VA dissociation occurred during the VOP. Because VA dissociation excludes ORT, inclusion of the termination analysis in the diagnostic evaluation would allow us to practically distinguish most ORTs from the other SVTs.
In the present series, VOP did not terminate AT. As a general rule, AT is excluded when the tachycardia is terminated without atrial resetting (i.e., type 2 termination). Thus, a TPP >125 ms diagnoses AVNRT with type 2 termination. In contrast, if the tachycardia is terminated after atrial resetting (i.e., type 1 termination), AT may underlie the mechanism of the SVT. Nonetheless, our results show that VOP rarely terminates AT, suggesting that the occurrence of the tachycardia termination by VOP per se support a diagnosis other than AT.
This study was retrospective in design, and the diagnostic criteria have not been evaluated prospectively. Although inaccurate results were observed exclusively in the left anterolateral and left lateral free-wall APs in this study, diagnosis using termination analyses has potential limitations in ORTs with APs remote from the pacing site. Furthermore, the number of ORTs with decremental APs in our study was too small. Hence, a long TPP should be interpreted with caution if it conflicts with other electrophysiological findings. Our results are not applicable to SVTs terminated spontaneously during VOP. For that reason, we only included SVTs that were sustained at least before the VOP and were terminated reproducibly by VOP. Moreover, cases with a gradual lengthening of the TCL just before the tachycardia termination were not analyzed to avoid an incidental termination during the VOP.
The termination analyses are useful for differential diagnoses of SVTs terminated during VOP. VOP rarely terminates AT. Combining the TPP with the modified resetting criteria during VOP accurately distinguished ORT from the other SVTs.
COMPETENCY IN MEDICAL KNOWLEDGE: An electrophysiological diagnosis of SVT may be challenging when the SVT is terminated during diagnostic pacing. The termination analyses help differentiate the SVT mechanisms and facilitate a successful ablation.
TRANSLATIONAL OUTLOOK: Prospective evaluations in a large-scale cohort are needed to establish the utility of the termination analyses for differential diagnoses of SVTs terminated during diagnostic pacing.
The authors thank Mr. John Martin for his linguistic assistance with the manuscript.
The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
- Abbreviations and Acronyms
- accessory pathways
- atrial tachycardia
- atrioventricular nodal reentrant tachycardia
- orthodromic reciprocating tachycardia
- pacing cycle length
- post-pacing interval
- right ventricular apex
- septal para-Hisian ventricular electrogram
- supraventricular tachycardia
- tachycardia cycle length
- total pacing prematurity
- ventricular overdrive pacing
- Received February 9, 2017.
- Revision received May 8, 2017.
- Accepted May 30, 2017.
- 2017 American College of Cardiology Foundation
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