Pediatr Cardiol DOI 10.1007/s00246-014-0907-5
ORIGINAL ARTICLE
Exercise Testing in Children With Wolff–Parkinson–White Syndrome: What Is Its Value? M. Dalili • K. Vahidshahi • M. Y. Aarabi-Moghaddam J. Y. Rao • P. Brugada
•
Received: 13 January 2014 / Accepted: 25 March 2014 Ó Springer Science+Business Media New York 2014
Abstract This study was conducted to evaluate the accuracy of exercise testing for predicting accessory pathway characteristics in children with Wolff–Parkinson–White (WPW) syndrome. The study enrolled 37 children with WPW syndrome and candidates for invasive electrophysiologic study (EPS). Exercise testing was performed for all the study participants before the invasive study. Data from the invasive EPS were compared with findings from the exercise testing. The sudden disappearance of the delta (D) wave was seen in 10 cases (27 %). No significant correlation was found between the D wave disappearance and the antegrade effective refractory period of the accessory pathway (AERPAP) or the shortest pre-excited RR interval (SPERRI). The sensitivity, specificity, and positive and negative predictive values of D wave disappearance, based on AERP-AP as gold standard, were respectively 29.4, 80, 71.4, and 40 %. The corresponding values with SPERRI as the gold standard were respectively 23.8, 71.4, 71.4 and 23.8 %. Exercise testing has a medium to low rate of accuracy in detecting low-risk WPW syndrome patients in the pediatric age group. Keywords Arrhythmia Wolff–Parkinson–White syndrome Pre-excitation Children
Introduction The approach to children with ventricular pre-excitation, the so-called Wolff–Parkinson–White (WPW) syndrome, is a
M. Dalili (&) K. Vahidshahi M. Y. Aarabi-Moghaddam J. Y. Rao P. Brugada Rajaie Cardiovascular Medical and Research Center, Tehran, Islamic Republic of Iran e-mail: [email protected]
challenge in the field of pediatric electrophysiology. Individuals with pre-excitation are at risk for sudden cardiac death (SCD), which seems to happen when high-rate atrial tachyarrhythmias, especially atrial fibrillation (AF), are conducted rapidly to the ventricles over an accessory pathway. Findings also have shown that the incidence of AF is higher among patients with ventricular pre-excitation [3, 8]. Clinicians generally agree on the characteristics that put the patient with ventricular pre-excitation in the high-risk group, such as short refractoriness of the pathway, multiple pathways, and arrhythmia inducibility during electrophysiologic study (EPS). Advances in the art and science of electrophysiology offer a low-risk, highly effective, and rapid means for treating the disorder via catheter ablation, even in patients with anatomic heart defects [5, 10, 13, 14]. However fears of the procedural risk, costs, possible emotional effects, and other factors associated with all invasive procedures encourage physicians to find a noninvasive way to predict risk in WPW cases. One of the most focused noninvasive tests for risk stratification in WPW is exercise testing. The logic behind the stress test is that accessory pathways unable to conduct at high sinus rates during exercise cannot conduct rapid atrial tachyarrhythmias to the ventricles. A recent consensus focused on exercise testing in children with asymptomatic WPW [16] supported the sudden disappearance of the delta (D) wave during exercise as a sign of low risk. In this study, we compared persistence or loss of pre-excitation during exercise testing with findings during invasive EPS.
Patients and Methods The study population consisted of all children (ages 5–14 years) with the diagnosis of WPW who were admitted
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to the Rajai Heart Center, Tehran (a tertiary academic national and regional heart center) for interacardiac electrophysiologic study from June 2012, to September 2013. The exclusion criteria ruled out clinical inability to perform the exercise test and lack of parental consent. For all the cases, exercise testing based on the modified Bruce protocol was performed using a treadmill (Cardiotest; h/p Cosmos, Traunstein, Germany). The exercise testing was performed to the patient’s maximum tolerance. The standard 12-lead electrocardiogram was recorded continuously from rest until termination of the exercise and continued for 5 min into the recovery. The total test duration and the maximum heart rates were recorded. The entire study was reviewed for D wave changes and arrhythmia. In all cases, EPS was performed within a few days after exercise testing. The EPS was conducted by a single pediatric electrophysiologist blinded to the exercise test results. The Bard EP system (Lowell, MA, USA) was used for the EPS. The electrophysiologic parameters during sinus rhythm including cycle length, P-delta interval, QRS duration, and QT, AH, and HV intervals were recorded in milliseconds. In 34 cases, the drive cycle of 500 ms was used to measure the anterograde refractory period of the accessory pathway (AERP-AP). In the remaining three cases with baseline cycle lengths shorter than 500 ms, a drive cycle length of 450 ms was used. The shortest preexcited RR interval (SPERRI) was measured with atrial incremental pacing. The SPERRI also was measured in cases with inducible AF. The location of the accessory pathway was defined in all cases. Recorded electrophysiologic parameters were compared with the findings of the exercise test. Data were analyzed with SPSS software version 18.00 (SPSS, Chicago, IL, USA) using appropriate descriptive and analytical statistical tools. A P value lower than 0.05 was considered significant.
Results The study investigated 37 pediatric WPW patients (73 % female) with mean age of 9.81 ± 2.70 years (range, 5–14 years) and a mean weight of 40.32 ± 17.17 kg (range, 17–85 kg). The majority of the patients were symptomatic. The symptoms included palpitations in 29 patients, chest pain in 3 patients, and syncope in 1 patient. The cardiac anatomy was normal in 89.2 % of the patients. The exercise test characteristics are shown in Table 1. No patient had arrhythmia or symptoms (inappropriate palpitation or dyspnea) during the exercise test. In ten cases (27 %), the D wave disappeared suddenly during the test (Fig. 1). In three additional cases, the D wave intermittently disappeared, and in 24 patients, it persisted until the end of the exercise.
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Table 1 Exercise test results in 37 cases of Wolff–Parkinson–White syndrome (WPW) Exercise test characteristics
Resultsa
Duration (min)
14.48 ± 2.70 (9–19)
Exercise capacity (METs)
12.87 ± 1.81 (10.1–17.2)
Minimum heart rate (bpm)
97.94 ± 15.47 (65–127)
Maximum heart rate (bpm)
178.10 ± 16.87 (161–211)
Delta wave sudden disappearance: n (%) Yes
10 (27)
No
27 (73)b
METs metabolic equivalent of the tasks, bpm beats per minute a
Results are expressed as mean ± standard deviation (range)
b
Including the cases with intermittently disappeared delta wave
During EPS, the baseline ECG characteristics were measured. An arrhythmia was induced in 26 patients (70.3 %). The most common arrhythmia was orthodromic atrioventricular reentrant tachycardia (ORT: 23 cases), followed by antidromic atrioventricular reentrant tachycardia (two cases). In three cases, we were able to induce atrial fibrillation (as the only inducible arrhythmia in 1 case and in addition to the ORT in two cases). Arrhythmia inducibility did not allow all measurements in several patients. Exact AERP-AP and SPERRI could be measured in 27 and 28 cases, respectively. In three cases with inducible AF, the SPERRI was measured both with atrial decremental pacing and during AF, yielding similar results. In 67.6 % of the cases, the pathway was located in the septal region. Radiofrequency ablation was performed in 36 cases, with a success rate of 94.5 %. In one case, ablation was not performed due to anteroseptal location, a high anterograde refractory period and SPERRI of the accessory pathway, arrhythmia noninducibility, and nonavailability of the cryo system. One unsuccessful ablation was performed for a child with a midseptal pathway in whom ablation was attempted only with low energy. In another child, abnormal situs and complex cardiac anatomy prevented procedural success. Table 2 demonstrates the relationship between D wave disappearance and some important demographic, clinical, and EP data. As shown, D wave disappearance was not significantly correlated with clinical (including symptoms) or EPS data. Based on our findings, the sensitivity, specificity, positive predictive value, and negative predictive values of sudden D wave disappearance compared with an AERP-AP C250 ms or longer were 29.4, 80, 71.4, and 40 % respectively. The corresponding values were 23.8, 71.4, 71.4, and 23.8 % when sudden D wave disappearance was compared with a SPERRI longer than 250 ms. The accuracy of exercise testing in predicting an AERP-AP of 250 ms or longer was 48.1 % and a SPERRI longer than 250 ms was 35.7 %.
Pediatr Cardiol Fig. 1 Sudden delta (D) wave disappearance during exercise testing. After the red arrow, atrioventricular conduction is over the normal pathway
Table 2 Relationship between delta (D) wave disappearance and some demographic and electrophysiologic (EP) data Variable
D Wave sudden disappearance Yes n (%)
No n (%)
P Value
Male
4 (40)
6 (60)
0.248
Female
6 (22.2)
21 (77.8)
Gender
Age group (years) \9
6 (33.3)
12 (66.7)
0.319
[9 PR interval (ms)
4 (21.1) 82.70 ± 18.36
15 (78.9) 86.18 ± 18.19
0.581
QRS duration (ms)
127.00 ± 14.39
131.88 ± 20.85
0.501 0.328
Arrhythmia inducibility Yes
6 (23.1)
20 (76.9)
No
4 (36.4)
7 (63.6)
\250
2 (20)
8 (80)
C250
5 (29.4)
12 (70.6)
\250
2 (28.6)
5 (71.4)
C250
5 (23.8)
16 (76.2)
AERP-AP (ms) 0.475
SPERRI (ms) 0.581
AERP-AP antegrade effective refractory period of accessory pathway, SPERRI shortest pre-excited RR interval
Discussion Most electrophysiologists concur in using an invasive approach for WPW syndrome in children 8–18 years of age. The challenge is in dealing with asymptomatic children who have incidental detection of the WPW pattern on
surface ECG. Multiple accessory pathways, arrhythmia inducibility in the EP lab, and short refractoriness of the accessory pathways have been traditionally considered high-risk features for many years. To date, the only tool for detecting the number of accessory pathways is invasive EPS. For arrhythmia inducibility as well, the standard accepted tool is invasive EPS using different pacing maneuvers. The only important variable to be validated by noninvasive tests is the pathway refractoriness determined by AERP-AP and SPERRI. Based on research into this aspect, the 2012 consensus [16] proposed that the sudden D wave disappearance during exercise testing of asymptomatic children is a sign of low-risk WPW syndrome. Before that consensus, most pediatric electrophysiologists conventionally considered EPS to be the only reliable method for risk stratification of WPW patients [2]. We designed the current study before the consensus report was published. The levels of evidence in that article were B and C, which encouraged us to continue this research. We reinforced the safety of exercise testing and EPS for pediatric WPW patients. However, performing an optimal exercise test for a child is not very easy. One of the important concerns is familial consent. Some families limited their child’s activity after hearing that he or she had a cardiac problem. Some other patients did not comply to continue the exercise until the maximal heart rate was achieved because of noncardiac reasons. Again, fear of complications is a common problem. Failure to achieve the maximal heart rate is an important issue that can affect the sensitivity of exercise testing. Even if the value of exercise testing is established, a unique
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exercise protocol with a certain target of the maximal heart rate should be used. The diagnosis of sudden D wave disappearance is not so easy on a treadmill tracing because of the movement artifacts. This aspect may be responsible for differences among studies, and if this is true, it could restrict the value of exercise testing. The rate of D wave disappearance was higher in our study (26.3 %) than in the studies of Czosek et al. [4] and others [12]. One major area of concern is the interpretation of exercise test results, including interobserver differences. The rate of arrhythmia inducibility and the types of arrhythmia in our study were similar to those in the study of Sarubbi et al. [18]. We measured both AERP-AP and SPERRI to identify low-risk patients in EPS. The studies of Dubin et al. [7], Santinelli et al. [17], and Pappone et al. [15] used AERP-AP, whereas the studies of others such as Bromberg et al. [1] and Fenici et al. [9] used SPERRI as the main factor. The findings have differed significantly among studies. Wackel et al. [20] found a specificity of 94 % and positive predictive value of 92 % for exercise testing in predicting an AERP-AP of 250 ms or less. Sharma et al. [19] and Gaita et al. [11] compared D wave disappearance in the exercise test with SPERRI. They found higher sensitivity and lower specificity values. The study of Daubert et al. [6], as in our study, indicated that exercise testing was not appropriate for risk stratification of WPW patients. The discordant results between the study by Wakel et al. [20] and our study and the studies of Sharma et al. [19], Gaita et al. [11], and Daubert et al. [6] may be explained by differences in the detection of sudden (but not gradual) D wave disappearance in the measurement of EPS data or probably in the patient sample.
Conclusion Based on our findings, exercise testing has limited (medium to low) accuracy in detecting low-risk WPW patients in the pediatric population. Larger studies with more patients and longer follow-up periods could clarify the role of exercise testing in risk stratification of pediatric WPW patients. Until then, EPS remains the gold standard for risk stratification.
Study Limitations The limitations of our study included the small sample size and the lack of follow-up evaluation.
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References 1. Bromberg BI, Lindsay BD, Cain ME, Cox JL (1996) Impact of clinical history and electrophysiologic characterization of accessory pathways on management strategies to reduce sudden death among children with Wolff–Parkinson–White syndrome. J Am Coll Cardiol 27:690–695 2. Campbell RM, Strieper MJ, Frias PA, Collins KK, Van Hare GF, Dubin AM (2003) Survey of current practice of pediatric electrophysiologists for asymptomatic Wolff–Parkinson–White syndrome. Pediatrics 111:6245–6247 3. Centurio´n OA, Shimizu A, Isomoto S, Konoe A (2008) Mechanisms for the genesis of paroxysmal atrial fibrillation in the Wolff–Parkinson–White syndrome: intrinsic atrial muscle vulnerability vs electrophysiological properties of the accessory pathway. Europace 10:294–302 4. Czosek RJ, Anderson JB, Marino BS, Mellion K, Knilans TK (2011) Noninvasive risk stratification techniques in pediatric patients with ventricular preexcitation. PACE 34:555–562 5. Dalili M, Rao JY, Brugada P (2013) Radiofrequency ablation of accessory pathways in children with complex congenital cardiac lesions: a report of three cases. J Tehran Heart Cent 8:111–115 6. Daubert C, Ollitrault J, Descaves C, Mabo P, Ritter P, Gouffault J (1988) Failure of the exercise test to predict the anterograde refractory period of the accessory pathway in Wolff–Parkinson– White syndrome. Pacing Clin Electrophysiol 11:1130–1138 7. Dubin AM, Collins KK, Chiesa N, Hanisch D, Van Hare GF (2002) Use of electrophysiologic testing to assess risk in children with Wolff–Parkinson–White syndrome. Cardiol Young 12: 245–252 8. Duckeck W, Kuck KH (1993) Atrial fibrillation in Wolff–Parkinson–White syndrome: development and therapy. Herz 18:60–66 9. Fenici R, Ruggieri MP, di Lillo M, Fenici P (1996) Reproducibility of transesophageal pacing in patients with Wolff–Parkinson–White syndrome. Pacing Clin Electrophysiol 19:1951–1957 10. Friedman RA, Walsh EP, Silka MJ, Calkins H, Stevenson WG, Rhodes LA, Deal BJ, Wolff GS, Demaso DR, Hanisch D, Van Hare GF (2002) NASPE Expert Consensus Conference: radiofrequency catheter ablation in children with and without congenital heart disease: report of the writing committee, North American Society of Pacing and Electrophysiology. Pacing Clin Electrophysiol 25:1000–1017 11. Gaita F, Giustetto C, Riccardi R, Mangiardi L, Brusca A (1989) Stress and pharmacologic test as methods to identify patients with Wolff–Parkinson–White syndrome at risk of sudden death. Am J Card 64:487–490 12. Jezior MR, Kent SM, Atwood JE (2005) Exercise testing in Wolff–Parkinson–White syndrome: case report with ECG and literature review. Chest 127:1454–1457 13. Mosaed P, Dalili M, Emkanjoo Z (2012) Interventional electrophysiology in children: a single-center experience. Iran J Pediatr 22:333–338 14. Nielsen JC, Kottkamp H, Piorkowski C, Gerds-Li JH, Tanner H, Hindricks G (2006) Radiofrequency ablation in children and adolescents: results in 154 consecutive patients. EP Europace 8:323–329 15. Pappone C, Santinelli V, Rosanio S, Vicedomini G, Nardi S, Pappone A, Tortoriello V, Manguso F, Mazzone P, Gulletta S, Oreto G, Alfieri O (2003) Usefulness of invasive electrophysiologic testing to stratify the risk of arrhythmic events in asymptomatic patients with Wolff–Parkinson–White pattern: results from a large prospective long-term follow-up study. J Am Coll Cardiol 41:239–244 16. Pediatric and Congenital Electrophysiology Society (PACES), Heart Rhythm Society (HRS), American College of Cardiology
Pediatr Cardiol Foundation (ACCF), American Heart Association (AHA), American Academy of Pediatrics (AAP), Canadian Heart Rhythm Society (CHRS), Cohen MI, Triedman JK, Cannon BC, Davis AM, Drago F, Janousek J, Klein GJ, Law IH, Morady FJ, Paul T, Perry JC, Sanatani S, Tanel RE (2012) PACES/HRS expert consensus statement on the management of the asymptomatic young patient with a Wolff–Parkinson–White (WPW, ventricular preexcitation) electrocardiographic pattern: developed in partnership between the Pediatric and Congenital Electrophysiology Society (PACES) and the Heart Rhythm Society (HRS). Endorsed by the governing bodies of PACES, HRS, The American College of Cardiology Foundation (ACCF), The American Heart Association (AHA), The American Academy of Pediatrics (AAP), and The Canadian Heart Rhythm Society (CHRS). Heart Rhythm 9: 1006–1024 17. Santinelli V, Radinovic A, Manguso F, Vicedomini G, Gulletta S, Paglino G, Mazzone P, Ciconte G, Sacchi S, Sala S, Pappone C
(2009) The natural history of asymptomatic ventricular preexcitation: a long-term prospective follow-up study of 184 asymptomatic children. J Am Coll Cardiol 53:275–280 18. Sarubbi B, D’Alto M, Vergara P, Calvanese R, Mercurio B, Russo MG, Calabro` R (2005) Electrophysiological evaluation of asymptomatic ventricular pre-excitation in children and adolescents. Int J Card 98:207–214 19. Sharma AD, Yee R, Guiraudon G, Klein GJ (1987) Sensitivity and specificity of invasive and noninvasive testing for risk of sudden death in Wolff–Parkinson–White syndrome. J Am Coll Cardiol 10:373–381 20. Wackel P, Irving C, Webber S, Beerman L, Arora G (2012) Risk stratification in Wolff–Parkinson–White syndrome: the correlation between noninvasive and invasive testing in pediatric patients. PACE 35:1451–1457
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ORIGINAL ARTICLE
Exercise Testing in Children With Wolff–Parkinson–White Syndrome: What Is Its Value? M. Dalili • K. Vahidshahi • M. Y. Aarabi-Moghaddam J. Y. Rao • P. Brugada
•
Received: 13 January 2014 / Accepted: 25 March 2014 Ó Springer Science+Business Media New York 2014
Abstract This study was conducted to evaluate the accuracy of exercise testing for predicting accessory pathway characteristics in children with Wolff–Parkinson–White (WPW) syndrome. The study enrolled 37 children with WPW syndrome and candidates for invasive electrophysiologic study (EPS). Exercise testing was performed for all the study participants before the invasive study. Data from the invasive EPS were compared with findings from the exercise testing. The sudden disappearance of the delta (D) wave was seen in 10 cases (27 %). No significant correlation was found between the D wave disappearance and the antegrade effective refractory period of the accessory pathway (AERPAP) or the shortest pre-excited RR interval (SPERRI). The sensitivity, specificity, and positive and negative predictive values of D wave disappearance, based on AERP-AP as gold standard, were respectively 29.4, 80, 71.4, and 40 %. The corresponding values with SPERRI as the gold standard were respectively 23.8, 71.4, 71.4 and 23.8 %. Exercise testing has a medium to low rate of accuracy in detecting low-risk WPW syndrome patients in the pediatric age group. Keywords Arrhythmia Wolff–Parkinson–White syndrome Pre-excitation Children
Introduction The approach to children with ventricular pre-excitation, the so-called Wolff–Parkinson–White (WPW) syndrome, is a
M. Dalili (&) K. Vahidshahi M. Y. Aarabi-Moghaddam J. Y. Rao P. Brugada Rajaie Cardiovascular Medical and Research Center, Tehran, Islamic Republic of Iran e-mail: [email protected]
challenge in the field of pediatric electrophysiology. Individuals with pre-excitation are at risk for sudden cardiac death (SCD), which seems to happen when high-rate atrial tachyarrhythmias, especially atrial fibrillation (AF), are conducted rapidly to the ventricles over an accessory pathway. Findings also have shown that the incidence of AF is higher among patients with ventricular pre-excitation [3, 8]. Clinicians generally agree on the characteristics that put the patient with ventricular pre-excitation in the high-risk group, such as short refractoriness of the pathway, multiple pathways, and arrhythmia inducibility during electrophysiologic study (EPS). Advances in the art and science of electrophysiology offer a low-risk, highly effective, and rapid means for treating the disorder via catheter ablation, even in patients with anatomic heart defects [5, 10, 13, 14]. However fears of the procedural risk, costs, possible emotional effects, and other factors associated with all invasive procedures encourage physicians to find a noninvasive way to predict risk in WPW cases. One of the most focused noninvasive tests for risk stratification in WPW is exercise testing. The logic behind the stress test is that accessory pathways unable to conduct at high sinus rates during exercise cannot conduct rapid atrial tachyarrhythmias to the ventricles. A recent consensus focused on exercise testing in children with asymptomatic WPW [16] supported the sudden disappearance of the delta (D) wave during exercise as a sign of low risk. In this study, we compared persistence or loss of pre-excitation during exercise testing with findings during invasive EPS.
Patients and Methods The study population consisted of all children (ages 5–14 years) with the diagnosis of WPW who were admitted
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to the Rajai Heart Center, Tehran (a tertiary academic national and regional heart center) for interacardiac electrophysiologic study from June 2012, to September 2013. The exclusion criteria ruled out clinical inability to perform the exercise test and lack of parental consent. For all the cases, exercise testing based on the modified Bruce protocol was performed using a treadmill (Cardiotest; h/p Cosmos, Traunstein, Germany). The exercise testing was performed to the patient’s maximum tolerance. The standard 12-lead electrocardiogram was recorded continuously from rest until termination of the exercise and continued for 5 min into the recovery. The total test duration and the maximum heart rates were recorded. The entire study was reviewed for D wave changes and arrhythmia. In all cases, EPS was performed within a few days after exercise testing. The EPS was conducted by a single pediatric electrophysiologist blinded to the exercise test results. The Bard EP system (Lowell, MA, USA) was used for the EPS. The electrophysiologic parameters during sinus rhythm including cycle length, P-delta interval, QRS duration, and QT, AH, and HV intervals were recorded in milliseconds. In 34 cases, the drive cycle of 500 ms was used to measure the anterograde refractory period of the accessory pathway (AERP-AP). In the remaining three cases with baseline cycle lengths shorter than 500 ms, a drive cycle length of 450 ms was used. The shortest preexcited RR interval (SPERRI) was measured with atrial incremental pacing. The SPERRI also was measured in cases with inducible AF. The location of the accessory pathway was defined in all cases. Recorded electrophysiologic parameters were compared with the findings of the exercise test. Data were analyzed with SPSS software version 18.00 (SPSS, Chicago, IL, USA) using appropriate descriptive and analytical statistical tools. A P value lower than 0.05 was considered significant.
Results The study investigated 37 pediatric WPW patients (73 % female) with mean age of 9.81 ± 2.70 years (range, 5–14 years) and a mean weight of 40.32 ± 17.17 kg (range, 17–85 kg). The majority of the patients were symptomatic. The symptoms included palpitations in 29 patients, chest pain in 3 patients, and syncope in 1 patient. The cardiac anatomy was normal in 89.2 % of the patients. The exercise test characteristics are shown in Table 1. No patient had arrhythmia or symptoms (inappropriate palpitation or dyspnea) during the exercise test. In ten cases (27 %), the D wave disappeared suddenly during the test (Fig. 1). In three additional cases, the D wave intermittently disappeared, and in 24 patients, it persisted until the end of the exercise.
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Table 1 Exercise test results in 37 cases of Wolff–Parkinson–White syndrome (WPW) Exercise test characteristics
Resultsa
Duration (min)
14.48 ± 2.70 (9–19)
Exercise capacity (METs)
12.87 ± 1.81 (10.1–17.2)
Minimum heart rate (bpm)
97.94 ± 15.47 (65–127)
Maximum heart rate (bpm)
178.10 ± 16.87 (161–211)
Delta wave sudden disappearance: n (%) Yes
10 (27)
No
27 (73)b
METs metabolic equivalent of the tasks, bpm beats per minute a
Results are expressed as mean ± standard deviation (range)
b
Including the cases with intermittently disappeared delta wave
During EPS, the baseline ECG characteristics were measured. An arrhythmia was induced in 26 patients (70.3 %). The most common arrhythmia was orthodromic atrioventricular reentrant tachycardia (ORT: 23 cases), followed by antidromic atrioventricular reentrant tachycardia (two cases). In three cases, we were able to induce atrial fibrillation (as the only inducible arrhythmia in 1 case and in addition to the ORT in two cases). Arrhythmia inducibility did not allow all measurements in several patients. Exact AERP-AP and SPERRI could be measured in 27 and 28 cases, respectively. In three cases with inducible AF, the SPERRI was measured both with atrial decremental pacing and during AF, yielding similar results. In 67.6 % of the cases, the pathway was located in the septal region. Radiofrequency ablation was performed in 36 cases, with a success rate of 94.5 %. In one case, ablation was not performed due to anteroseptal location, a high anterograde refractory period and SPERRI of the accessory pathway, arrhythmia noninducibility, and nonavailability of the cryo system. One unsuccessful ablation was performed for a child with a midseptal pathway in whom ablation was attempted only with low energy. In another child, abnormal situs and complex cardiac anatomy prevented procedural success. Table 2 demonstrates the relationship between D wave disappearance and some important demographic, clinical, and EP data. As shown, D wave disappearance was not significantly correlated with clinical (including symptoms) or EPS data. Based on our findings, the sensitivity, specificity, positive predictive value, and negative predictive values of sudden D wave disappearance compared with an AERP-AP C250 ms or longer were 29.4, 80, 71.4, and 40 % respectively. The corresponding values were 23.8, 71.4, 71.4, and 23.8 % when sudden D wave disappearance was compared with a SPERRI longer than 250 ms. The accuracy of exercise testing in predicting an AERP-AP of 250 ms or longer was 48.1 % and a SPERRI longer than 250 ms was 35.7 %.
Pediatr Cardiol Fig. 1 Sudden delta (D) wave disappearance during exercise testing. After the red arrow, atrioventricular conduction is over the normal pathway
Table 2 Relationship between delta (D) wave disappearance and some demographic and electrophysiologic (EP) data Variable
D Wave sudden disappearance Yes n (%)
No n (%)
P Value
Male
4 (40)
6 (60)
0.248
Female
6 (22.2)
21 (77.8)
Gender
Age group (years) \9
6 (33.3)
12 (66.7)
0.319
[9 PR interval (ms)
4 (21.1) 82.70 ± 18.36
15 (78.9) 86.18 ± 18.19
0.581
QRS duration (ms)
127.00 ± 14.39
131.88 ± 20.85
0.501 0.328
Arrhythmia inducibility Yes
6 (23.1)
20 (76.9)
No
4 (36.4)
7 (63.6)
\250
2 (20)
8 (80)
C250
5 (29.4)
12 (70.6)
\250
2 (28.6)
5 (71.4)
C250
5 (23.8)
16 (76.2)
AERP-AP (ms) 0.475
SPERRI (ms) 0.581
AERP-AP antegrade effective refractory period of accessory pathway, SPERRI shortest pre-excited RR interval
Discussion Most electrophysiologists concur in using an invasive approach for WPW syndrome in children 8–18 years of age. The challenge is in dealing with asymptomatic children who have incidental detection of the WPW pattern on
surface ECG. Multiple accessory pathways, arrhythmia inducibility in the EP lab, and short refractoriness of the accessory pathways have been traditionally considered high-risk features for many years. To date, the only tool for detecting the number of accessory pathways is invasive EPS. For arrhythmia inducibility as well, the standard accepted tool is invasive EPS using different pacing maneuvers. The only important variable to be validated by noninvasive tests is the pathway refractoriness determined by AERP-AP and SPERRI. Based on research into this aspect, the 2012 consensus [16] proposed that the sudden D wave disappearance during exercise testing of asymptomatic children is a sign of low-risk WPW syndrome. Before that consensus, most pediatric electrophysiologists conventionally considered EPS to be the only reliable method for risk stratification of WPW patients [2]. We designed the current study before the consensus report was published. The levels of evidence in that article were B and C, which encouraged us to continue this research. We reinforced the safety of exercise testing and EPS for pediatric WPW patients. However, performing an optimal exercise test for a child is not very easy. One of the important concerns is familial consent. Some families limited their child’s activity after hearing that he or she had a cardiac problem. Some other patients did not comply to continue the exercise until the maximal heart rate was achieved because of noncardiac reasons. Again, fear of complications is a common problem. Failure to achieve the maximal heart rate is an important issue that can affect the sensitivity of exercise testing. Even if the value of exercise testing is established, a unique
123
Pediatr Cardiol
exercise protocol with a certain target of the maximal heart rate should be used. The diagnosis of sudden D wave disappearance is not so easy on a treadmill tracing because of the movement artifacts. This aspect may be responsible for differences among studies, and if this is true, it could restrict the value of exercise testing. The rate of D wave disappearance was higher in our study (26.3 %) than in the studies of Czosek et al. [4] and others [12]. One major area of concern is the interpretation of exercise test results, including interobserver differences. The rate of arrhythmia inducibility and the types of arrhythmia in our study were similar to those in the study of Sarubbi et al. [18]. We measured both AERP-AP and SPERRI to identify low-risk patients in EPS. The studies of Dubin et al. [7], Santinelli et al. [17], and Pappone et al. [15] used AERP-AP, whereas the studies of others such as Bromberg et al. [1] and Fenici et al. [9] used SPERRI as the main factor. The findings have differed significantly among studies. Wackel et al. [20] found a specificity of 94 % and positive predictive value of 92 % for exercise testing in predicting an AERP-AP of 250 ms or less. Sharma et al. [19] and Gaita et al. [11] compared D wave disappearance in the exercise test with SPERRI. They found higher sensitivity and lower specificity values. The study of Daubert et al. [6], as in our study, indicated that exercise testing was not appropriate for risk stratification of WPW patients. The discordant results between the study by Wakel et al. [20] and our study and the studies of Sharma et al. [19], Gaita et al. [11], and Daubert et al. [6] may be explained by differences in the detection of sudden (but not gradual) D wave disappearance in the measurement of EPS data or probably in the patient sample.
Conclusion Based on our findings, exercise testing has limited (medium to low) accuracy in detecting low-risk WPW patients in the pediatric population. Larger studies with more patients and longer follow-up periods could clarify the role of exercise testing in risk stratification of pediatric WPW patients. Until then, EPS remains the gold standard for risk stratification.
Study Limitations The limitations of our study included the small sample size and the lack of follow-up evaluation.
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