50 is the new 70: Short ventriculoatrial times are common in children with atrioventricular reciprocating tachycardia Scott R. Ceresnak, MD,* Lan N. Doan, MPH, CPH,*† Kara S. Motonaga, MD,* Kishor Avasarala, MD,* Anthony V. Trela, PNP,* Charitha D. Reddy, MD,* Anne M. Dubin, MD, FHRS* From the *Lucile Packard Children’s Hospital–Stanford University, Pediatric Cardiology, Pediatric Electrophysiology–Department of Pediatrics, Palo Alto, California and †Lucille Packard Children’s Hospital–Stanford University, Stanford Center for Clinical & Translational Research & Education and Stanford Child Health Research Institute Spectrum Child Health, Division of Pediatric Cardiology, Palo Alto, California. BACKGROUND One of the basic electrophysiological principles of atrioventricular reciprocating tachycardia (AVRT) is that ventriculoatrial (VA) times during tachycardia are 470 ms. We hypothesized, however, that children may commonly have VA times o70 ms in AVRT. OBJECTIVE This study sought to determine the incidence and characteristics associated with short-VA AVRT in children. METHODS A retrospective single-center review of children with AVRT from 2000 to 2014 was performed. All patients r18 years of age with AVRT at electrophysiology study were included. Patients with persistent junctional reciprocating tachycardia, atrioventricular nodal reentry tachycardia, and tachycardia not unequivocally proven to be AVRT were excluded. VA time was defined as the time between earliest ventricular activation and earliest atrial activation in any lead and was confirmed by 2 electrophysiologists. Patients with VA times o70 ms (SHORT-VA) and those with standard VA times Z70 ms (STD-VA) were compared. Logistic regression analysis identified characteristics of SHORT-VA patients. RESULTS A total of 495 patients with AVRT were included (mean age 11.7 ⫾ 4.1 years). There were 265 patients (54%) with concealed accessory pathways (APs) and 230 (46%) with WolffParkinson-White syndrome. AP location was left-sided in 301 patients (61%) and right-sided in 194 (39%). The mean VA time in AVRT was 100 ⫾ 33 ms. A total of 63 patients (13%) had VA times o70 ms (SHORT-VA). The shortest VA time during AVRT was 50 ms. There was no difference in age, AV nodal block cycle, or body surface
Introduction Atrioventricular reciprocating tachycardia (AVRT) is the most common cause of supraventricular tachycardia (SVT) Funding: NIH-NCATS-CTSA grant #UL1 TR001085, Lucile Packard Foundation for Children’s Health, and the Child Health Research Institute. Address reprint requests and correspondence: Dr Scott R. Ceresnak, Lucile Packard Children’s Hospital–Stanford University, Pediatric Cardiology, Pediatric Electrophysiology–Department of Pediatrics, 750 Welch Rd, Suite 305, Palo Alto, CA 94304. E-mail address: [email protected].
1547-5271/$-see front matter B 2015 Heart Rhythm Society. All rights reserved.
area between SHORT-VA and STD-VA patients, but SHORT-VA patients had lower weight (43 ⫾ 17 vs 51 ⫾ 23 kg, P ¼ .02), lower AV nodal effective refractory period (AVNERP; 269 ⫾ 50 vs 245 ⫾ 52 ms, P o .01), and more left-sided APs (50 [79%] vs 251 [58%]; P o .01]. On multivariate logistic regression, factors associated with SHORT-VA included left-sided AP (odds ratio [OR] 5.79, confidence interval [95% CI] 2.21–15.1, P o .01), shorter AVNERP (OR 0.99, CI 0.98– 0.99, P o .01), and lower weight (OR 0.97, CI 0.95–0.99, P o .01). CONCLUSIONS Children with AVRT can frequently have VA times o70 ms, with 50 ms being the shortest VA time. This finding debunks the classic electrophysiology principle that VA times in AVRT must be 470 ms. SHORT-VA AVRT was more common in children with left-sided APs. KEYWORDS Ablation; Atrioventricular reciprocating tachycardia; Children; Electrophysiology study; Pediatrics; Supraventricular tachycardia; Ventriculoatrial times ABBREVIATIONS AP ¼ accessory pathway; AVNERP ¼ AV nodal effective refractory period; AVNRT ¼ atrioventricular nodal reentry tachycardia; AVRT ¼ atrioventricular reciprocating tachycardia; CI ¼ confidence interval; CS ¼ coronary sinus; EPS ¼ electrophysiology study; LV ¼ left ventricle/ventricular; OR ¼ odds ratio; SD ¼ standard deviation; SVT ¼ supraventricular tachycardia; VA ¼ ventriculoatrial (Heart Rhythm 2015;12:1541–1547) I 2015 Heart Rhythm Society. All rights reserved.
in children.1,2 One of the basic electrophysiological principles of AVRT is that ventriculoatrial (VA) times during tachycardia are typically 470 ms, because this is the minimum time needed for the electrical impulse to travel through the ventricle and return to the atria to sustain tachycardia.3–7 This 70-ms delineation is often the cutoff point for distinguishing AVRT from atrioventricular nodal reentry tachycardia (AVNRT), although this delineation was largely derived from classic studies on adult patients.3,4,8 http://dx.doi.org/10.1016/j.hrthm.2015.03.047
1542 Assessments of VA times during AVRT in children undergoing invasive electrophysiology testing have been performed only in very small studies, and normal values for the VA interval during AVRT in children have not been established.4,6 Therefore, we sought to determine normative values for VA times during SVT in a large cohort of children and adolescents undergoing electrophysiology study (EPS) for AVRT, and we hypothesized that children may commonly have VA times o70 ms during AVRT. In addition, we sought to determine the shortest VA time in a large cohort of children with AVRT and to determine factors that may be associated with short VA times during AVRT in children.
Methods The study was a single-center retrospective cohort study of patients with AVRT. Institutional Review Board approval was obtained for this investigation. All patients r18 years of age who underwent invasive EPS between January 1, 2000, and November 1, 2014, who were diagnosed unequivocally with AVRT in the electrophysiology laboratory and had intracardiac tracings available for review were included. Patients with persistent junctional reciprocating tachycardia, AVNRT, and tachycardia not unequivocally proven to be AVRT were excluded. The diagnosis of AVRT was made on the basis of established standard criteria outlined by Josephson et al,4,9,10 and the diagnosis in each patient was confirmed by combinations of the following findings: (1) initiation and termination of the tachycardia with pacing; (2) 1:1 pattern of ventricular and atrial activation during tachycardia; (3) nondecremental VA conduction during ventricular extrastimulus testing; (4) eccentric VA conduction; (5) early activation of the atrium when premature ventricular beats were delivered in tachycardia during His bundle refractoriness; (6) parahisian pacing with a stimulus to atrial activation time o40 ms; and (7) an increase in the VA time during tachycardia in bundle branch block in the bundle ipsilateral to the accessory pathway (AP). Throughout the study period, electrophysiology procedural techniques were consistent, with catheters typically placed in the high right atrium, coronary sinus (CS), right ventricular apex, and His position. In a very small subset of infants requiring EPS, invasive testing was performed solely with an esophageal electrode. VA time in AVRT was defined as the time between earliest ventricular activation in any surface or intracardiac lead and the earliest atrial activation in any surface or intracardiac lead during orthodromic AVRT. All tracings from patients with VA times o70 ms were reviewed and measured independently by 2 electrophysiologists. All measurements were made digitally on a GE CardioLab recording system (General Electric, Inc, Fairfield, CT) at a sweep speed of 200 ms with digital calipers, using standard electrophysiology laboratory settings, with high-pass and low-pass filters set at 30 and 500 Hz, respectively. A random sampling of 10% of the patients with VA times 470 ms
Heart Rhythm, Vol 12, No 7, July 2015 were also reviewed, and VA times were measured to confirm accuracy of the data.
Data collection Data collected for this investigation included patient-specific demographic information, invasive electrophysiology testing findings and measurements, and location of the AP.
Data and Statistical Analysis Statistical analysis was performed with Stata (version 12, Stata Corp LP, College Station, TX). All data were checked for normality of distribution, and categorical and dichotomous variables were expressed as numbers and percentages, whereas continuous variables were expressed as mean ⫾ standard deviation (SD). A random sample of VA time measurements, made by the 2 pediatric electrophysiologists, were evaluated via interobserver variability via kappa statistic. Patients with VA times o70 ms (SHORT-VA) and those with standard VA times Z70 ms (STD-VA) were compared with χ2 test for categorical variables, Student t tests for normally distributed continuous data, and Mann-Whitney U test for non-normally distributed continuous data. One-way analysis of variance was used to compare mean VA times during AVRT between right lateral, septal, and left lateral locations. A multivariable logistic regression model was then created with the SHORT-VA group as the primary outcome variable of interest. Variables with P values r.05 in the univariate model were included in the multivariate model. Hosmer-Lemeshow tests were used to assess logistic regression model fit. All 2-sided P values o.05 were considered statistically significant.
Results Patient population During the 14-year study period, a total of 495 patients met inclusion criteria with inducible AVRT and tracings available for review (Table 1). There were 265 patients (54%) with concealed APs and 230 (46%) with Wolff-Parkinson-White syndrome who underwent invasive intracardiac testing. The APs were left-sided in 301 patients (61%) and right-sided in 194 (39%). Measurements of VA times made by the 2 electrophysiologists demonstrated good reliability, with a kappa statistic of 0.84. The mean VA time for all patients during AVRT was 100 ⫾ 33 ms. Data on the entire study population are shown in Table 1. A total of 63 patients (13%) had VA times o70 ms (SHORT-VA), and the shortest VA time during AVRT found in any patient during the study period was 50 ms. Examples of SHORT-VA tachycardias are demonstrated in Figure 1 and the AP locations in SHORTVA patients are shown in Figure 2. Among the 63 SHORT-VA patients, the anatomic locations of the APs were left lateral in 41 (65%), left posterolateral in 7 (11%), left anterolateral in 1 (2%), right posteroseptal in 8 (13%), right anterolateral in 4 (6%), and right midseptal in 2 (3%). Only 10 SHORT-VA patients (16%) had a septal pathway, with the majority of pathways noted to be left-sided (78%). When we compared VA times between the lateral locations on the tricuspid annulus
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Figure 1 Intracardiac tracings of short ventriculoatrial (VA) times in atrioventricular reciprocating tachycardia (AVRT). A: A 13-year-old with a left lateral accessory pathway, with earliest atrial activation in tachycardia noted in the coronary sinus (CS) 3,4 pair and a VA time in AVRT of 56 ms. B: A 10-year-old with a right posteroseptal pathway, with earliest atrial activation in tachycardia in the CS 7,8 pair and a VA time in AVRT of 55 ms. d ¼ distal; HIS ¼ His bundle; HRA ¼ high right atrium; m ¼ mid; p ¼ proximal; RVa ¼ right ventricular apex; Stim 2 ¼ stimulus channel.
(right anterolateral, right lateral, and right posterolateral), lateral locations on the mitral annuls (left anterolateral, left lateral, and left posterolateral), and septal locations (right anteroseptal, right midseptal, right posteroseptal, and left posteroseptal), the VA times in tachycardia were significantly longer in the lateral region of the tricuspid annulus (Table 2). This finding, however, may be related in part to use of a diagnostic catheter in the high right atrial position instead of along the tricuspid annulus.
Comparison of SHORT-VA to STD-VA patients Patients with short VA times in AVRT (SHORT-VA) were compared with patients with VA times 470 ms (STD-VA). There was no difference in age, AV nodal block cycle, or body surface area between SHORT-VA and STD-VA patients, but SHORT-VA patients had lower weights (43 ⫾ 17 vs 51 ⫾ 23 kg, P o .01) and more left-sided APs (50 [79%] vs 251 [58%], P o .01). A comparison of the STD-VA and SHORT-VA patients is given in Table 1.
1544 Table 1
Heart Rhythm, Vol 12, No 7, July 2015 Patient population and comparison of SHORT-VA (o70 ms) and STD-VA (Z70 ms) patients
Age (years) Gender (male, %) Weight (kg) Height (cm) BSA (m2) Diagnosis WPW (n, %) Concealed AP (n, %) AP Location Left Sided (n, %) Right Sided (n, %) Multiple AP (n, %) Congenital heart disease (n, %) AV nodal WB CL (ms) AVNERP (ms) QRS duration (ms) Tachycardia induction state Baseline (n, %) Isoproterenol (n, %) AVRT cycle length (ms) VA time in AVRT (ms) HV interval in AVRT (ms)
All patients (n ¼ 495)
STD-VA (n ¼ 432)
11.7 ⫾ 4.1 293 (59%) 49.6 ⫾ 22.3 149 ⫾ 23 1.42 ⫾ 0.43
11.8 256 50.5 150 1.43
230 (46%) 265 (54%)
200 (46%) 232 (54%)
30 (48%) 33 (52%)
301 (61%) 194 (39%) 19 (3.9%) 17 (2.5%) 300 ⫾ 60 265 ⫾ 51 78 ⫾ 25
251 (58%) 181 (42%) 18 (4.2%) 16 (3.7%) 302 ⫾ 60 269 ⫾ 50 79 ⫾ 22
50 (79%) 13 (21%) 1 (1.6%) 1 (1.6%) 288 ⫾ 55 245 ⫾ 52 76 ⫾ 37
419 (85%) 76 (15%) 327 ⫾ 60 100 ⫾ 33 44 ⫾ 17
371 (86%) 61 (14%) 328 ⫾ 60 107 ⫾ 32 43 ⫾ 14
48 15 318 63 49
⫾ 4.2 (59%) ⫾ 22.9 ⫾ 23 ⫾ 0.42
SHORT-VA (n ¼ 63)
p-value*
11.1 ⫾ 3.9 37 (59%) 43.2 ⫾ 16.5 146 ⫾ 20 1.38 ⫾ 0.50
0.24 0.94 0.02 0.27 0.46 0.84 o0.01 0.32 0.39 0.10 o0.01 0.50 0.04
(76%) (24%) ⫾ 59 ⫾5 ⫾ 27
0.24 o0.01 0.03
WB ¼ Wenckebach, CL ¼ Cycle length * Comparison between STD-VA and SHORT-VA tachycardia patients
Multivariate model On multivariate logistic regression, predictors of SHORTVA AVRT were left-sided AP (odds ratio [OR] 5.79, confidence interval [95% CI] 2.21–15.1, P o .01), a shorter AV nodal effective refractory period (OR 0.99, CI 0.98–0.99, P o .01), and lower weight (OR 0.97, CI 0.95–0.99, P o .01). These data are shown in Table 3.
Discussion One of the core electrophysiological principles of AVRT is that the VA time during tachycardia is typically 470 ms.3 This central principle has been shown to help rule out AVRT and be a reliable cutoff point in distinguishing AVRT from AVNRT during invasive electrophysiology testing. In this
Table 2
Right lateral Septal Mean VA time (ms) 117 ⫾ 40
Left lateral p-value*
97 ⫾ 37 97 ⫾ 24
o0.01
* P-value reflect an ANOVA comparison of the mean VA time during AVRT between the right lateral, septal and left lateral locations
large series of children with AVRT confirmed in the electrophysiology laboratory, however, we have demonstrated that 13% of children had VA times o70 ms during AVRT, and the VA time during AVRT was as short as 50 ms. Thus, the 70-ms cutoff point to distinguish AVRT from AVNRT is a fundamental electrophysiological principle that should be revised in pediatric electrophysiology. The 70-ms rule has been demonstrated in studies in adults and in small studies in children to be a reliable cutoff point in helping to differentiate AVRT from AVNRT.3,8,9,11,12 One small study in children demonstrated that use of this 70-ms cutoff carries a 94% positive predictive value and 100% negative predictive value for distinguishing AVNRT from AVRT.13 Although 70 ms appears fairly reliable for distinguishing AVRT from AVNRT in these small series, others have postulated that children may have VA times of less than 70 ms during AVRT. This in part may be related to faster Table 3
Figure 2 This illustration demonstrates a typical left anterior oblique view of the tricuspid and mitral valves and shows the anatomic locations of the accessory pathways in the 63 patients with atrioventricular reciprocating tachycardia with ventriculoatrial times o70 ms (SHORT-VA). Note the majority were in the left lateral region of the mitral annulus. LAL ¼ left anterolateral; LL ¼ left lateral; LPL ¼ left posterolateral; RAL ¼ right anterolateral; RMS ¼ right midseptal; RPS ¼ right posteroseptal.
Comparison of VA times in AVRT based on location
Multivariable model for odds of SHORT-VA AVRT Odds ratio
Left-sided AP Weight AVNERP HV interval in AVRT Isoproterenol
5.79 0.97 0.99 1.01 2.00
95% CI
p-value
2.21 – 15.1 0.95 – 0.99 0.98 – 0.99 0.99 – 1.03 0.68 – 5.87
o0.01 o0.01 o0.01 0.17 0.21
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Short VA AVRT in Children
Figure 3 Anatomy of the conduction system. In this series, patients with leftsided accessory pathways had shorter ventriculoatrial times. This may be explained in part by the anatomy of the conduction system, with the main portion of the left bundle branch being shorter than the right bundle branch and branches of the left posterior fascicle enabling rapid conduction through the ventricle.
1545 atrial, AV nodal, His-Purkinje, and ventricular conduction times in children than in adults. In 1979, Benditt et al8 compared 15 patients with AVNRT to 15 patients with AVRT and hypothesized that a VA time of 61 ms would be the lowest likely VA time during AVRT, because 61 ms was 2 standard deviations (SD) below the mean VA time in AVRT in their study population; however, none of the 15 patients in that series had a VA time of less than 70 ms, and the shortest VA time was 75 ms. In 1991, Schaffer et al9 identified 5 of 28 patients with AVRT who had VA times shorter than 70 ms, with the shortest VA time identified as 60 ms. They hypothesized that the lowest likely VA time during AVRT in children could be as low as 45 ms, because this was 2 SDs below the mean for the 28 patients in their series. All VA intervals in that study were performed on hard-copy recordings, and measurements were made with hand calipers. Although the cutoff point of 70 ms may carry strong predictive value for distinguishing AVRT from AVNRT, we have demonstrated in this report that short VA times are commonly seen in children, and VA times o70 ms certainly do not preclude AVRT as the cause of tachycardia. It is also interesting to note that in our study, it was less common to
Figure 4 Normal activation of the left ventricle. Early activation (pink regions) is seen in the inferior left ventricular septal region, as well as in the left lateral basal region. Early activation in the left lateral basal region may help explain why the majority of the atrioventricular reciprocating tachycardia with ventriculoatrial times o70 ms occurred with an accessory pathway in the left lateral region of the mitral annulus. Reprinted with permission from Durrer et al.16
1546 see a short VA interval in a septal pathway (the main alternative in the differential diagnosis for AVNRT), because the vast majority of SHORT-VA tachycardias were secondary to eccentric left-sided pathways. Thus, the shortest VA time identified during AVRT in children in this large cohort was 50 ms, and these short VA tachycardias were rarely secondary to septal pathways. The physiological explanation for shorter VA times during AVRT occurring predominantly in patients with left-sided APs is likely multifactorial. The left bundle branch has been shown to typically have a longer refractory period and may have faster conduction velocity than the right bundle branch.14,15 The conduction properties of the right and left bundle branches also explain why right bundle branch block occurs more commonly in atrial fibrillation (Ashman phenomenon), and activation of the left ventricular (LV) endocardial surface has been demonstrated to occur 5 to 10 ms earlier than activation of the right ventricular endocardial surface, which indicates more brisk conduction through the left bundle branch than the right bundle branch.14,16 Another explanation may be related to the anatomic difference between the right and left bundle branches and electrical activation of the LV. The left bundle branch is usually shorter than the right, and the early takeoff and long course of the posterior fascicle may enable rapid conduction through the LV and early arrival of the electrical impulse in the posterolateral region of the mitral annulus (Figure 3). In 1970, Durrer et al16 demonstrated that there are typically 3 areas of early activation in the LV: high on the anterior paraseptal wall just below the attachment of the mitral valve, the central surface of the interventricular septum, and the posterior paraseptal region approximately one third of the distance from apex to base (Figure 4). Josephson4(p32) also demonstrated early activation of the superior-basal aspect of the LV free wall with the use of 3dimensional electroanatomic mapping. Thus, quicker conduction through the left bundle branch and early activation of the LV near a left lateral AP may explain the preponderance of SHORT-VA tachycardias with left-sided pathways. Finally, an additional explanation may be related to the distance of the AP from the compact AV node. It is possible that longer VA times are required for septal APs because of their close proximity to the AV node, and shorter VA times may not allow for recovery of the AV node enough to sustain SVT in children. Left-sided APs, however, are located farther from the AV node and can therefore have shorter conduction times and still facilitate SVT. The shorter VA times with left-sided pathways during AVRT thus appears to be related to anatomic and conduction properties of the right and left bundle branches coupled with activation patterns of the LV and distance of the AP from the compact AV node.
Conclusions In this large series of children with AVRT confirmed during EPS, we have demonstrated that children can have VA times
Heart Rhythm, Vol 12, No 7, July 2015 o70 ms during AVRT; the shortest VA time found was 50 ms. This finding debunks the classic electrophysiology principle that VA times in AVRT are 470 ms. SHORTVA AVRT was also more common in children with leftsided APs (OR 5.79) and only rarely occurred in children with septal pathways. We hypothesize that the high occurrence of short VA times in patients with left-sided APs may be secondary to the faster conduction velocity of the left bundle branch, longer refractory period of the right ventricle, anatomic difference between the left and right bundle branches, distance from the compact AV node, and the activation pattern of the LV.
Acknowledgment Medical illustrations (Figures 2 and 3) were done by Charitha Reddy, MD.
References 1. Van Hare GF, Javitz H, Carmelli D, Saul JP, Tanel RE, Fischbach PS, Kanter RJ, Schaffer M, Dunnigan A, Serwer G, and participating members of the Pediatric Electrophysiology Society. Prospective assessment after pediatric cardiac ablation: demographics, medical profiles, and initial outcomes. J Cardiovasc Electrophysiol 2004;15:759–770. 2. Ko JK, Deal BJ, Strasburger JF, Benson DW Jr. Supraventricular tachycardia mechanisms and their age distribution in pediatric patients. Am J Cardiol 1992;69:1028–1032. 3. Gallagher JJ, Smith WM, Kasell J, Smith WM, Grant AO, Benson DW Jr. Use of the esophageal lead in the diagnosis of mechanisms of reciprocating supraventricular tachycardia. Pacing Clin Electrophysiol 1980;3:440–451. 4. Josephson ME. Clinical Cardiac Electrophysiology: Techniques and Interpretations. In: Philadelphia, PA: Lippencott Williams & Wilkins; 2008. 5. Benson DW Jr, Dunnigan A, Benditt DG, Pritzker MR, Thompson TR. Transesophageal study of infant supraventricular tachycardia: electrophysiologic characteristics. Am J Cardiol 1983;52:1002–1006. 6. Walsh EP, Saul JP, Triedman JK. Cardiac Arrhythmias in Children and Young Adults with Congenital Heart Disease. In: Philadelphia, PA: Lippencott Williams & Wilkins; 2001:184. 7. Deal B, Wolff G, Gelband H. Current Concepts in Diagnosis and Management of Arrhythmias in Infants and Children. In: Armonk, NY: Futura; 1998. 8. Benditt DG, Pritchett EL, Smith WM, Gallagher JJ. Ventriculoatrial intervals: diagnostic use in paroxysmal supraventricular tachycardia. Ann Intern Med 1979;91:161–166. 9. Schaffer MS, Gillette PC. Ventriculoatrial intervals during narrow complex reentrant tachycardia in children. Am Heart J 1991;121(pt 1):1699–1702. 10. Reddy VY, Jongnarangsin K, Albert CM, Sabbour H, Keane D, Mela T, McGovern B, Ruskin JN. Para-Hisian entrainment: a novel pacing maneuver to differentiate orthodromic atrioventricular reentrant tachycardia from atrioventricular nodal reentrant tachycardia. J Cardiovasc Electrophysiol 2003;14: 1321–1328. 11. Braunschweig F, Christel P, Jensen-Urstad M, Andersson M, Schwieler J, Tapanainen J, Bastani H, Gadler F, Linde C, Schöls W, Bergfeldt L. Paroxysmal regular supraventricular tachycardia: the diagnostic accuracy of the transesophageal ventriculo-atrial interval. Ann Noninvasive Electrocardiol 2011;16:327–335. 12. Harte MT, Teo KK, Horgan JH. The diagnosis and management of supraventricular tachycardia by transesophageal cardiac stimulation and recording. Chest 1988;93:339–344. 13. Samson RA, Deal BJ, Strasburger JF, Benson DW Jr. Comparison of transesophageal and intracardiac electrophysiologic studies in characterization of supraventricular tachycardia in pediatric patients. J Am Coll Cardiol 1995;26: 159–163. 14. Gouaux JL, Ashman R. Auricular fibrillation with aberration simulating ventricular paroxysmal tachycardia. Am Heart J 1947;34:366–373. 15. Chaudry R II, Ramsaran EK, Spodick DH. Observations on the reliability of the Ashman phenomenon. Am Heart J 1994;128:205–209. 16. Durrer D, van Dam RT, Freud GE, Janse MJ, Meijler FL, Arzbaecher RC. Total excitation of the isolated human heart. Circulation 1970;41:899–912.
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CLINICAL PERSPECTIVES AVRT is the most common arrhythmia in children, and one of the basic principles of electrophysiology is that VA times in tachycardia are typically less than 70 ms. In this report, we demonstrate in a large number of children undergoing invasive EPS over a 14-year period, short VA times (o70 ms) were commonly seen in children with AVRT. The shortest VA time identified was 50 ms and, somewhat surprisingly, the short VA tachycardias were common with left-sided accessory pathways and were seen less frequently with septal pathways. This finding is important for electrophysiologists performing ablations of accessory pathways in children, because the main differential diagnosis for short VA tachycardias in children is AVNRT, and the short VA tachycardias seen in this series were only rarely seen in septal accessory pathways. The findings from this report thus suggest the classic electrophysiology principle that VA times in AVRT must be 470 ms should be revised in pediatric electrophysiology.
Introduction Atrioventricular reciprocating tachycardia (AVRT) is the most common cause of supraventricular tachycardia (SVT) Funding: NIH-NCATS-CTSA grant #UL1 TR001085, Lucile Packard Foundation for Children’s Health, and the Child Health Research Institute. Address reprint requests and correspondence: Dr Scott R. Ceresnak, Lucile Packard Children’s Hospital–Stanford University, Pediatric Cardiology, Pediatric Electrophysiology–Department of Pediatrics, 750 Welch Rd, Suite 305, Palo Alto, CA 94304. E-mail address: [email protected].
1547-5271/$-see front matter B 2015 Heart Rhythm Society. All rights reserved.
area between SHORT-VA and STD-VA patients, but SHORT-VA patients had lower weight (43 ⫾ 17 vs 51 ⫾ 23 kg, P ¼ .02), lower AV nodal effective refractory period (AVNERP; 269 ⫾ 50 vs 245 ⫾ 52 ms, P o .01), and more left-sided APs (50 [79%] vs 251 [58%]; P o .01]. On multivariate logistic regression, factors associated with SHORT-VA included left-sided AP (odds ratio [OR] 5.79, confidence interval [95% CI] 2.21–15.1, P o .01), shorter AVNERP (OR 0.99, CI 0.98– 0.99, P o .01), and lower weight (OR 0.97, CI 0.95–0.99, P o .01). CONCLUSIONS Children with AVRT can frequently have VA times o70 ms, with 50 ms being the shortest VA time. This finding debunks the classic electrophysiology principle that VA times in AVRT must be 470 ms. SHORT-VA AVRT was more common in children with left-sided APs. KEYWORDS Ablation; Atrioventricular reciprocating tachycardia; Children; Electrophysiology study; Pediatrics; Supraventricular tachycardia; Ventriculoatrial times ABBREVIATIONS AP ¼ accessory pathway; AVNERP ¼ AV nodal effective refractory period; AVNRT ¼ atrioventricular nodal reentry tachycardia; AVRT ¼ atrioventricular reciprocating tachycardia; CI ¼ confidence interval; CS ¼ coronary sinus; EPS ¼ electrophysiology study; LV ¼ left ventricle/ventricular; OR ¼ odds ratio; SD ¼ standard deviation; SVT ¼ supraventricular tachycardia; VA ¼ ventriculoatrial (Heart Rhythm 2015;12:1541–1547) I 2015 Heart Rhythm Society. All rights reserved.
in children.1,2 One of the basic electrophysiological principles of AVRT is that ventriculoatrial (VA) times during tachycardia are typically 470 ms, because this is the minimum time needed for the electrical impulse to travel through the ventricle and return to the atria to sustain tachycardia.3–7 This 70-ms delineation is often the cutoff point for distinguishing AVRT from atrioventricular nodal reentry tachycardia (AVNRT), although this delineation was largely derived from classic studies on adult patients.3,4,8 http://dx.doi.org/10.1016/j.hrthm.2015.03.047
1542 Assessments of VA times during AVRT in children undergoing invasive electrophysiology testing have been performed only in very small studies, and normal values for the VA interval during AVRT in children have not been established.4,6 Therefore, we sought to determine normative values for VA times during SVT in a large cohort of children and adolescents undergoing electrophysiology study (EPS) for AVRT, and we hypothesized that children may commonly have VA times o70 ms during AVRT. In addition, we sought to determine the shortest VA time in a large cohort of children with AVRT and to determine factors that may be associated with short VA times during AVRT in children.
Methods The study was a single-center retrospective cohort study of patients with AVRT. Institutional Review Board approval was obtained for this investigation. All patients r18 years of age who underwent invasive EPS between January 1, 2000, and November 1, 2014, who were diagnosed unequivocally with AVRT in the electrophysiology laboratory and had intracardiac tracings available for review were included. Patients with persistent junctional reciprocating tachycardia, AVNRT, and tachycardia not unequivocally proven to be AVRT were excluded. The diagnosis of AVRT was made on the basis of established standard criteria outlined by Josephson et al,4,9,10 and the diagnosis in each patient was confirmed by combinations of the following findings: (1) initiation and termination of the tachycardia with pacing; (2) 1:1 pattern of ventricular and atrial activation during tachycardia; (3) nondecremental VA conduction during ventricular extrastimulus testing; (4) eccentric VA conduction; (5) early activation of the atrium when premature ventricular beats were delivered in tachycardia during His bundle refractoriness; (6) parahisian pacing with a stimulus to atrial activation time o40 ms; and (7) an increase in the VA time during tachycardia in bundle branch block in the bundle ipsilateral to the accessory pathway (AP). Throughout the study period, electrophysiology procedural techniques were consistent, with catheters typically placed in the high right atrium, coronary sinus (CS), right ventricular apex, and His position. In a very small subset of infants requiring EPS, invasive testing was performed solely with an esophageal electrode. VA time in AVRT was defined as the time between earliest ventricular activation in any surface or intracardiac lead and the earliest atrial activation in any surface or intracardiac lead during orthodromic AVRT. All tracings from patients with VA times o70 ms were reviewed and measured independently by 2 electrophysiologists. All measurements were made digitally on a GE CardioLab recording system (General Electric, Inc, Fairfield, CT) at a sweep speed of 200 ms with digital calipers, using standard electrophysiology laboratory settings, with high-pass and low-pass filters set at 30 and 500 Hz, respectively. A random sampling of 10% of the patients with VA times 470 ms
Heart Rhythm, Vol 12, No 7, July 2015 were also reviewed, and VA times were measured to confirm accuracy of the data.
Data collection Data collected for this investigation included patient-specific demographic information, invasive electrophysiology testing findings and measurements, and location of the AP.
Data and Statistical Analysis Statistical analysis was performed with Stata (version 12, Stata Corp LP, College Station, TX). All data were checked for normality of distribution, and categorical and dichotomous variables were expressed as numbers and percentages, whereas continuous variables were expressed as mean ⫾ standard deviation (SD). A random sample of VA time measurements, made by the 2 pediatric electrophysiologists, were evaluated via interobserver variability via kappa statistic. Patients with VA times o70 ms (SHORT-VA) and those with standard VA times Z70 ms (STD-VA) were compared with χ2 test for categorical variables, Student t tests for normally distributed continuous data, and Mann-Whitney U test for non-normally distributed continuous data. One-way analysis of variance was used to compare mean VA times during AVRT between right lateral, septal, and left lateral locations. A multivariable logistic regression model was then created with the SHORT-VA group as the primary outcome variable of interest. Variables with P values r.05 in the univariate model were included in the multivariate model. Hosmer-Lemeshow tests were used to assess logistic regression model fit. All 2-sided P values o.05 were considered statistically significant.
Results Patient population During the 14-year study period, a total of 495 patients met inclusion criteria with inducible AVRT and tracings available for review (Table 1). There were 265 patients (54%) with concealed APs and 230 (46%) with Wolff-Parkinson-White syndrome who underwent invasive intracardiac testing. The APs were left-sided in 301 patients (61%) and right-sided in 194 (39%). Measurements of VA times made by the 2 electrophysiologists demonstrated good reliability, with a kappa statistic of 0.84. The mean VA time for all patients during AVRT was 100 ⫾ 33 ms. Data on the entire study population are shown in Table 1. A total of 63 patients (13%) had VA times o70 ms (SHORT-VA), and the shortest VA time during AVRT found in any patient during the study period was 50 ms. Examples of SHORT-VA tachycardias are demonstrated in Figure 1 and the AP locations in SHORTVA patients are shown in Figure 2. Among the 63 SHORT-VA patients, the anatomic locations of the APs were left lateral in 41 (65%), left posterolateral in 7 (11%), left anterolateral in 1 (2%), right posteroseptal in 8 (13%), right anterolateral in 4 (6%), and right midseptal in 2 (3%). Only 10 SHORT-VA patients (16%) had a septal pathway, with the majority of pathways noted to be left-sided (78%). When we compared VA times between the lateral locations on the tricuspid annulus
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Figure 1 Intracardiac tracings of short ventriculoatrial (VA) times in atrioventricular reciprocating tachycardia (AVRT). A: A 13-year-old with a left lateral accessory pathway, with earliest atrial activation in tachycardia noted in the coronary sinus (CS) 3,4 pair and a VA time in AVRT of 56 ms. B: A 10-year-old with a right posteroseptal pathway, with earliest atrial activation in tachycardia in the CS 7,8 pair and a VA time in AVRT of 55 ms. d ¼ distal; HIS ¼ His bundle; HRA ¼ high right atrium; m ¼ mid; p ¼ proximal; RVa ¼ right ventricular apex; Stim 2 ¼ stimulus channel.
(right anterolateral, right lateral, and right posterolateral), lateral locations on the mitral annuls (left anterolateral, left lateral, and left posterolateral), and septal locations (right anteroseptal, right midseptal, right posteroseptal, and left posteroseptal), the VA times in tachycardia were significantly longer in the lateral region of the tricuspid annulus (Table 2). This finding, however, may be related in part to use of a diagnostic catheter in the high right atrial position instead of along the tricuspid annulus.
Comparison of SHORT-VA to STD-VA patients Patients with short VA times in AVRT (SHORT-VA) were compared with patients with VA times 470 ms (STD-VA). There was no difference in age, AV nodal block cycle, or body surface area between SHORT-VA and STD-VA patients, but SHORT-VA patients had lower weights (43 ⫾ 17 vs 51 ⫾ 23 kg, P o .01) and more left-sided APs (50 [79%] vs 251 [58%], P o .01). A comparison of the STD-VA and SHORT-VA patients is given in Table 1.
1544 Table 1
Heart Rhythm, Vol 12, No 7, July 2015 Patient population and comparison of SHORT-VA (o70 ms) and STD-VA (Z70 ms) patients
Age (years) Gender (male, %) Weight (kg) Height (cm) BSA (m2) Diagnosis WPW (n, %) Concealed AP (n, %) AP Location Left Sided (n, %) Right Sided (n, %) Multiple AP (n, %) Congenital heart disease (n, %) AV nodal WB CL (ms) AVNERP (ms) QRS duration (ms) Tachycardia induction state Baseline (n, %) Isoproterenol (n, %) AVRT cycle length (ms) VA time in AVRT (ms) HV interval in AVRT (ms)
All patients (n ¼ 495)
STD-VA (n ¼ 432)
11.7 ⫾ 4.1 293 (59%) 49.6 ⫾ 22.3 149 ⫾ 23 1.42 ⫾ 0.43
11.8 256 50.5 150 1.43
230 (46%) 265 (54%)
200 (46%) 232 (54%)
30 (48%) 33 (52%)
301 (61%) 194 (39%) 19 (3.9%) 17 (2.5%) 300 ⫾ 60 265 ⫾ 51 78 ⫾ 25
251 (58%) 181 (42%) 18 (4.2%) 16 (3.7%) 302 ⫾ 60 269 ⫾ 50 79 ⫾ 22
50 (79%) 13 (21%) 1 (1.6%) 1 (1.6%) 288 ⫾ 55 245 ⫾ 52 76 ⫾ 37
419 (85%) 76 (15%) 327 ⫾ 60 100 ⫾ 33 44 ⫾ 17
371 (86%) 61 (14%) 328 ⫾ 60 107 ⫾ 32 43 ⫾ 14
48 15 318 63 49
⫾ 4.2 (59%) ⫾ 22.9 ⫾ 23 ⫾ 0.42
SHORT-VA (n ¼ 63)
p-value*
11.1 ⫾ 3.9 37 (59%) 43.2 ⫾ 16.5 146 ⫾ 20 1.38 ⫾ 0.50
0.24 0.94 0.02 0.27 0.46 0.84 o0.01 0.32 0.39 0.10 o0.01 0.50 0.04
(76%) (24%) ⫾ 59 ⫾5 ⫾ 27
0.24 o0.01 0.03
WB ¼ Wenckebach, CL ¼ Cycle length * Comparison between STD-VA and SHORT-VA tachycardia patients
Multivariate model On multivariate logistic regression, predictors of SHORTVA AVRT were left-sided AP (odds ratio [OR] 5.79, confidence interval [95% CI] 2.21–15.1, P o .01), a shorter AV nodal effective refractory period (OR 0.99, CI 0.98–0.99, P o .01), and lower weight (OR 0.97, CI 0.95–0.99, P o .01). These data are shown in Table 3.
Discussion One of the core electrophysiological principles of AVRT is that the VA time during tachycardia is typically 470 ms.3 This central principle has been shown to help rule out AVRT and be a reliable cutoff point in distinguishing AVRT from AVNRT during invasive electrophysiology testing. In this
Table 2
Right lateral Septal Mean VA time (ms) 117 ⫾ 40
Left lateral p-value*
97 ⫾ 37 97 ⫾ 24
o0.01
* P-value reflect an ANOVA comparison of the mean VA time during AVRT between the right lateral, septal and left lateral locations
large series of children with AVRT confirmed in the electrophysiology laboratory, however, we have demonstrated that 13% of children had VA times o70 ms during AVRT, and the VA time during AVRT was as short as 50 ms. Thus, the 70-ms cutoff point to distinguish AVRT from AVNRT is a fundamental electrophysiological principle that should be revised in pediatric electrophysiology. The 70-ms rule has been demonstrated in studies in adults and in small studies in children to be a reliable cutoff point in helping to differentiate AVRT from AVNRT.3,8,9,11,12 One small study in children demonstrated that use of this 70-ms cutoff carries a 94% positive predictive value and 100% negative predictive value for distinguishing AVNRT from AVRT.13 Although 70 ms appears fairly reliable for distinguishing AVRT from AVNRT in these small series, others have postulated that children may have VA times of less than 70 ms during AVRT. This in part may be related to faster Table 3
Figure 2 This illustration demonstrates a typical left anterior oblique view of the tricuspid and mitral valves and shows the anatomic locations of the accessory pathways in the 63 patients with atrioventricular reciprocating tachycardia with ventriculoatrial times o70 ms (SHORT-VA). Note the majority were in the left lateral region of the mitral annulus. LAL ¼ left anterolateral; LL ¼ left lateral; LPL ¼ left posterolateral; RAL ¼ right anterolateral; RMS ¼ right midseptal; RPS ¼ right posteroseptal.
Comparison of VA times in AVRT based on location
Multivariable model for odds of SHORT-VA AVRT Odds ratio
Left-sided AP Weight AVNERP HV interval in AVRT Isoproterenol
5.79 0.97 0.99 1.01 2.00
95% CI
p-value
2.21 – 15.1 0.95 – 0.99 0.98 – 0.99 0.99 – 1.03 0.68 – 5.87
o0.01 o0.01 o0.01 0.17 0.21
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Figure 3 Anatomy of the conduction system. In this series, patients with leftsided accessory pathways had shorter ventriculoatrial times. This may be explained in part by the anatomy of the conduction system, with the main portion of the left bundle branch being shorter than the right bundle branch and branches of the left posterior fascicle enabling rapid conduction through the ventricle.
1545 atrial, AV nodal, His-Purkinje, and ventricular conduction times in children than in adults. In 1979, Benditt et al8 compared 15 patients with AVNRT to 15 patients with AVRT and hypothesized that a VA time of 61 ms would be the lowest likely VA time during AVRT, because 61 ms was 2 standard deviations (SD) below the mean VA time in AVRT in their study population; however, none of the 15 patients in that series had a VA time of less than 70 ms, and the shortest VA time was 75 ms. In 1991, Schaffer et al9 identified 5 of 28 patients with AVRT who had VA times shorter than 70 ms, with the shortest VA time identified as 60 ms. They hypothesized that the lowest likely VA time during AVRT in children could be as low as 45 ms, because this was 2 SDs below the mean for the 28 patients in their series. All VA intervals in that study were performed on hard-copy recordings, and measurements were made with hand calipers. Although the cutoff point of 70 ms may carry strong predictive value for distinguishing AVRT from AVNRT, we have demonstrated in this report that short VA times are commonly seen in children, and VA times o70 ms certainly do not preclude AVRT as the cause of tachycardia. It is also interesting to note that in our study, it was less common to
Figure 4 Normal activation of the left ventricle. Early activation (pink regions) is seen in the inferior left ventricular septal region, as well as in the left lateral basal region. Early activation in the left lateral basal region may help explain why the majority of the atrioventricular reciprocating tachycardia with ventriculoatrial times o70 ms occurred with an accessory pathway in the left lateral region of the mitral annulus. Reprinted with permission from Durrer et al.16
1546 see a short VA interval in a septal pathway (the main alternative in the differential diagnosis for AVNRT), because the vast majority of SHORT-VA tachycardias were secondary to eccentric left-sided pathways. Thus, the shortest VA time identified during AVRT in children in this large cohort was 50 ms, and these short VA tachycardias were rarely secondary to septal pathways. The physiological explanation for shorter VA times during AVRT occurring predominantly in patients with left-sided APs is likely multifactorial. The left bundle branch has been shown to typically have a longer refractory period and may have faster conduction velocity than the right bundle branch.14,15 The conduction properties of the right and left bundle branches also explain why right bundle branch block occurs more commonly in atrial fibrillation (Ashman phenomenon), and activation of the left ventricular (LV) endocardial surface has been demonstrated to occur 5 to 10 ms earlier than activation of the right ventricular endocardial surface, which indicates more brisk conduction through the left bundle branch than the right bundle branch.14,16 Another explanation may be related to the anatomic difference between the right and left bundle branches and electrical activation of the LV. The left bundle branch is usually shorter than the right, and the early takeoff and long course of the posterior fascicle may enable rapid conduction through the LV and early arrival of the electrical impulse in the posterolateral region of the mitral annulus (Figure 3). In 1970, Durrer et al16 demonstrated that there are typically 3 areas of early activation in the LV: high on the anterior paraseptal wall just below the attachment of the mitral valve, the central surface of the interventricular septum, and the posterior paraseptal region approximately one third of the distance from apex to base (Figure 4). Josephson4(p32) also demonstrated early activation of the superior-basal aspect of the LV free wall with the use of 3dimensional electroanatomic mapping. Thus, quicker conduction through the left bundle branch and early activation of the LV near a left lateral AP may explain the preponderance of SHORT-VA tachycardias with left-sided pathways. Finally, an additional explanation may be related to the distance of the AP from the compact AV node. It is possible that longer VA times are required for septal APs because of their close proximity to the AV node, and shorter VA times may not allow for recovery of the AV node enough to sustain SVT in children. Left-sided APs, however, are located farther from the AV node and can therefore have shorter conduction times and still facilitate SVT. The shorter VA times with left-sided pathways during AVRT thus appears to be related to anatomic and conduction properties of the right and left bundle branches coupled with activation patterns of the LV and distance of the AP from the compact AV node.
Conclusions In this large series of children with AVRT confirmed during EPS, we have demonstrated that children can have VA times
Heart Rhythm, Vol 12, No 7, July 2015 o70 ms during AVRT; the shortest VA time found was 50 ms. This finding debunks the classic electrophysiology principle that VA times in AVRT are 470 ms. SHORTVA AVRT was also more common in children with leftsided APs (OR 5.79) and only rarely occurred in children with septal pathways. We hypothesize that the high occurrence of short VA times in patients with left-sided APs may be secondary to the faster conduction velocity of the left bundle branch, longer refractory period of the right ventricle, anatomic difference between the left and right bundle branches, distance from the compact AV node, and the activation pattern of the LV.
Acknowledgment Medical illustrations (Figures 2 and 3) were done by Charitha Reddy, MD.
References 1. Van Hare GF, Javitz H, Carmelli D, Saul JP, Tanel RE, Fischbach PS, Kanter RJ, Schaffer M, Dunnigan A, Serwer G, and participating members of the Pediatric Electrophysiology Society. Prospective assessment after pediatric cardiac ablation: demographics, medical profiles, and initial outcomes. J Cardiovasc Electrophysiol 2004;15:759–770. 2. Ko JK, Deal BJ, Strasburger JF, Benson DW Jr. Supraventricular tachycardia mechanisms and their age distribution in pediatric patients. Am J Cardiol 1992;69:1028–1032. 3. Gallagher JJ, Smith WM, Kasell J, Smith WM, Grant AO, Benson DW Jr. Use of the esophageal lead in the diagnosis of mechanisms of reciprocating supraventricular tachycardia. Pacing Clin Electrophysiol 1980;3:440–451. 4. Josephson ME. Clinical Cardiac Electrophysiology: Techniques and Interpretations. In: Philadelphia, PA: Lippencott Williams & Wilkins; 2008. 5. Benson DW Jr, Dunnigan A, Benditt DG, Pritzker MR, Thompson TR. Transesophageal study of infant supraventricular tachycardia: electrophysiologic characteristics. Am J Cardiol 1983;52:1002–1006. 6. Walsh EP, Saul JP, Triedman JK. Cardiac Arrhythmias in Children and Young Adults with Congenital Heart Disease. In: Philadelphia, PA: Lippencott Williams & Wilkins; 2001:184. 7. Deal B, Wolff G, Gelband H. Current Concepts in Diagnosis and Management of Arrhythmias in Infants and Children. In: Armonk, NY: Futura; 1998. 8. Benditt DG, Pritchett EL, Smith WM, Gallagher JJ. Ventriculoatrial intervals: diagnostic use in paroxysmal supraventricular tachycardia. Ann Intern Med 1979;91:161–166. 9. Schaffer MS, Gillette PC. Ventriculoatrial intervals during narrow complex reentrant tachycardia in children. Am Heart J 1991;121(pt 1):1699–1702. 10. Reddy VY, Jongnarangsin K, Albert CM, Sabbour H, Keane D, Mela T, McGovern B, Ruskin JN. Para-Hisian entrainment: a novel pacing maneuver to differentiate orthodromic atrioventricular reentrant tachycardia from atrioventricular nodal reentrant tachycardia. J Cardiovasc Electrophysiol 2003;14: 1321–1328. 11. Braunschweig F, Christel P, Jensen-Urstad M, Andersson M, Schwieler J, Tapanainen J, Bastani H, Gadler F, Linde C, Schöls W, Bergfeldt L. Paroxysmal regular supraventricular tachycardia: the diagnostic accuracy of the transesophageal ventriculo-atrial interval. Ann Noninvasive Electrocardiol 2011;16:327–335. 12. Harte MT, Teo KK, Horgan JH. The diagnosis and management of supraventricular tachycardia by transesophageal cardiac stimulation and recording. Chest 1988;93:339–344. 13. Samson RA, Deal BJ, Strasburger JF, Benson DW Jr. Comparison of transesophageal and intracardiac electrophysiologic studies in characterization of supraventricular tachycardia in pediatric patients. J Am Coll Cardiol 1995;26: 159–163. 14. Gouaux JL, Ashman R. Auricular fibrillation with aberration simulating ventricular paroxysmal tachycardia. Am Heart J 1947;34:366–373. 15. Chaudry R II, Ramsaran EK, Spodick DH. Observations on the reliability of the Ashman phenomenon. Am Heart J 1994;128:205–209. 16. Durrer D, van Dam RT, Freud GE, Janse MJ, Meijler FL, Arzbaecher RC. Total excitation of the isolated human heart. Circulation 1970;41:899–912.
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CLINICAL PERSPECTIVES AVRT is the most common arrhythmia in children, and one of the basic principles of electrophysiology is that VA times in tachycardia are typically less than 70 ms. In this report, we demonstrate in a large number of children undergoing invasive EPS over a 14-year period, short VA times (o70 ms) were commonly seen in children with AVRT. The shortest VA time identified was 50 ms and, somewhat surprisingly, the short VA tachycardias were common with left-sided accessory pathways and were seen less frequently with septal pathways. This finding is important for electrophysiologists performing ablations of accessory pathways in children, because the main differential diagnosis for short VA tachycardias in children is AVNRT, and the short VA tachycardias seen in this series were only rarely seen in septal accessory pathways. The findings from this report thus suggest the classic electrophysiology principle that VA times in AVRT must be 470 ms should be revised in pediatric electrophysiology.
