Utility of preoperative electrophysiologic studies in patients with Ebstein’s anomaly undergoing the Cone procedure Jill K.L. Shivapour, MD,*† Elizabeth D. Sherwin, MD,*† Mark E. Alexander, MD, FHRS,*† Frank Cecchin, MD,*† Douglas Y. Mah, MD,*† John K. Triedman, MD, FHRS,*†1 Gerald R. Marx, MD,*† Pedro J. del Nido, MD,*† Edward P. Walsh, MD, FHRS*† From the *Departments of Cardiology and Cardiac Surgery, Boston Children’s Hospital, and †Departments of Pediatrics and Surgery, Harvard Medical School, Boston, Massachusetts. BACKGROUND Ebstein’s anomaly is associated with a high incidence of atrial and ventricular arrhythmias. The Cone procedure has become an effective hemodynamic intervention for this malformation. In response to two late postoperative sudden deaths in our early institutional Cone experience, a standardized plan for aggressive rhythm evaluation was instituted, including preoperative electrophysiologic studies (EPS) and intraoperative implantable loop recorder (ILR) placement. OBJECTIVE The purpose of this study was to measure the yield of this diagnostic protocol for patients with Ebstein’s anomaly undergoing surgical repair and to describe its influence on patient management. METHODS All patients at Boston Children’s Hospital with Ebstein’s anomaly who underwent the Cone procedure from December 2006 to September 2012 were reviewed. Pre- and postoperative arrhythmias and therapies were documented. For patients who underwent preoperative EPS, all arrhythmia substrates and interventions were recorded. RESULTS A total of 74 patients were included, 42 of whom underwent preoperative EPS. Significant findings were documented during EPS in 29 of the 42 patients (69%), including eight patients
Introduction Ebstein’s anomaly is a relatively rare disorder accounting for less than 1% of all congenital heart defects. Its hallmark anatomic feature is apical displacement of the tricuspid valve, which can result in tricuspid regurgitation and/or stenosis, right atrial and right ventricular dilation, cyanosis (if the atrial septum is not intact), and even biventricular failure in severe cases.1 Displacement of the tricuspid valve is also associated with some portion of the right ventricular inflow being thin and “atrialized,” with histologically and electrically abnormal myocardium spanning the region from Address reprint requests and correspondence: Dr. Edward P. Walsh, Boston Children’s Hospital, 300 Longwood Ave, Boston, MA 02115. E-mail address: [email protected]. 1 Dr. Triedman is a consultant to Biosense Webster.
1547-5271/$-see front matter B 2014 Heart Rhythm Society. All rights reserved.
with no prior suspicion of arrhythmias. Seventeen patients had successful catheter ablation during EPS, and EPS data guided one or more intraoperative rhythm interventions for the remainder. During follow-up, diagnostic yield from ILR was low. Since implementing a more aggressive diagnostic strategy, no further sudden deaths have occurred. CONCLUSION Preoperative EPS has a high diagnostic and therapeutic yield in patients with Ebstein’s anomaly undergoing the Cone operation. It is reasonable to recommend EPS as a routine preoperative test for this population. KEYWORDS Arrhythmia surgery; Catheter ablation; Cone procedure; Congenital heart disease; Ebstein’s anomaly; Electrophysiologic study; Wolff-Parkinson-White syndrome; Ventricular tachycardia ABBREVIATIONS AV ¼ atrioventricular; EPS ¼ electrophysiologic study; ILR ¼ implantable loop recorder; ICD ¼ implantable cardioverter-defibrillator; VT ¼ ventricular tachycardia; WPW ¼ Wolff-Parkinson-White syndrome (Heart Rhythm 2014;11:182–186) I 2014 Heart Rhythm Society. All rights reserved.
the true right atrioventricular (AV) groove to the mobile edge of the tricuspid valve leaflets.2 As a consequence of these hemodynamic and electrical derangements, patients with Ebstein’s anomaly have a high incidence of atrial and ventricular arrhythmias, including the highest frequency of Wolff-Parkinson-White (WPW) syndrome for any congenital heart defect.3,4 Surgical techniques for Ebstein’s anomaly have evolved, and the Cone procedure developed by da Silva et al has now been adopted by many centers.5–7 Perioperative management may be complicated by arrhythmias, many of which involve mechanisms that can be addressed with preoperative catheter ablation or intraoperative surgical ablation.2,5,8 Early in our institutional Cone experience, we encountered two patients with good hemodynamic outcomes who suffered sudden death (presumed arrhythmic) within 60 days of surgery that http://dx.doi.org/10.1016/j.hrthm.2013.10.045
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was unanticipated based on history and noninvasive rhythm observations.7 This prompted a more systematic evaluation for arrhythmia substrates in patients with Ebstein’s anomaly undergoing the Cone procedure at our center, using preoperative electrophysiologic studies (EPS) and ablation whenever possible, as well as intraoperative placement of an implantable loop recorder (ILR) to monitor for postoperative arrhythmias.9 This report describes the frequency of arrhythmias detected with this diagnostic strategy and outlines the interventions used to address the substrates so identified.
Methods Data source and study population Record review was approved by the Committee for Clinical Investigation at Boston Children’s Hospital. All patients with the diagnosis of Ebstein’s anomaly who underwent the Cone procedure at our center from December 2006 to September 2012 were included. Analysis involved demographics, preoperative rhythm history, preoperative EPS (if performed), catheter ablation procedures, intraoperative arrhythmia interventions, early postoperative arrhythmias, and follow-up arrhythmias (including ILR data if a device was implanted). Patients were dichotomized into those who had a preoperative EPS and those who did not. For patients who underwent preoperative EPS, the diagnostic study included standard investigation for manifest or concealed accessory pathways, atriofascicular fibers, and inducible supraventricular tachycardias. In addition, a relatively nonaggressive ventricular stimulation protocol (S4 at one drive cycle length, at one right ventricular site, minimal coupling interval 200 ms, off isoproterenol) was performed. Induced ventricular tachycardias (VTs) were scored as “sustained” if duration was 430 seconds and/or caused hemodynamic compromise or as “nonsustained” if 45 beats but o30 seconds. Catheter ablation usually was attempted if a suitable substrate was present at preoperative EPS, although in some cases the procedure was restricted to mapping as a guide for later surgical ablation at the discretion of the electrophysiologist and cardiac surgeon. The Cone procedure was performed using surgical techniques described previously.5,7 Operative reports were reviewed for all arrhythmia interventions, including cryoablation or division of accessory pathways, right atrial or biatrial maze procedures, and cryoablation of right ventricular tissue involved in monomorphic VT. In addition, note was made of all rhythm-related hardware implants, including ILRs, epicardial implantable cardioverter-defibrillator (ICD) leads, and ICD generators. Records were examined for all postoperative arrhythmias causing patient instability that required intervention prior to hospital discharge. All available outpatient follow-up records were reviewed for later arrhythmias and sudden death.
Study design and analysis This was a descriptive study designed primarily to measure the yield of an aggressive arrhythmia detection strategy and
183
to evaluate the influence of this strategy on antiarrhythmic interventions. Comparisons of gross clinical features between subgroups of patients with and without preoperative EPS were performed, but strong selection bias and small subject numbers prevented meaningful statistical conclusions from this comparison. Continuous variables are expressed as median and range. Categorical variables are reported as counts and percentages.
Results Patient characteristics A total of 74 patients with Ebstein’s anomaly underwent the Cone operation at our center between December 2006 and September 2012. Early in this experience, patients did not undergo preoperative EPS unless there were clinical indications such as manifest preexcitation or a documented arrhythmia thought to be amenable to ablation therapy. Nearly all recent patients underwent EPS as a standard preoperative test whether or not there was an obvious clinical indication. Ultimately, 42 subjects (57%) had preoperative EPS performed. Median age at the time of the Cone procedure was 12.1 years (range 0.2–56.2 years), and 61% of the patients were female. Of the 42 who underwent EPS prior to the Cone procedure (Table 1), the preoperative arrhythmia history was positive for 23 (55%); the remaining 19 were studied proactively to rule out cryptic arrhythmia substrates that might require treatment prior to or during surgery. Of the 32 patients without preoperative EPS, only 3 (9%) had any prior rhythm concerns (atrial flutter in one, remote history of neonatal supraventricular tachycardia without recurrence in one, and one asymptomatic patient who was genotype positive for long QT syndrome type 1).
Preoperative EPS findings Of the 42 patients who underwent preoperative EPS (Figure 1), significant arrhythmia substrates were found in Table 1
Demographics and preoperative arrhythmia history Preop EPS (n ¼ 42)
Age at Cone procedure (years) Female gender Preoperative rhythm concern Atrial flutter Atrial fibrillation Ectopic atrial tachycardia WPW syndrome/tachycardia WPW syndrome/asymptomatic SVT (undetermined mechanism) Ventricular tachycardia Other
No Preop EPS (n ¼ 32)
13.8 (0.4, 55.9) 10.9 (0.2, 56.2) 23 (55%) 22 (69%) 23 (55%) 3 (9%) 2 1 1 — 3 — 6 — 3 — 5 1 3 —
— 1
Data are expressed as median (minimum, maximum) for continuous variables and as number (percentage) for categorical variables. EPS ¼ electrophysiologic study; SVT ¼ supraventricular tachycardia; WPW ¼ Wolff-Parkinson-White.
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Figure 1 Flowchart showing positive findings at electrophysiologic study according to preoperative rhythm history. It is noteworthy that significant arrhythmia substrates were identified in as many as 42% of patients with Ebstein’s anomaly with a benign rhythm history prior to surgery. AP ¼ accessory pathway; AV ¼ atrioventricular; EPS ¼ electrophysiologic study; VT ¼ ventricular tachycardia; WPW ¼ Wolff-Parkinson-White.
29 (69%), involving a total of 56 discrete mechanisms. Of note, EPS was positive in 8 of the 19 patients (42%) who had no preoperative arrhythmia concerns and were only studied as a precaution under the aggressive diagnostic strategy. For the 23 patients who had prior documented or suspected arrhythmias, EPS was positive in 21 (91%). The two negative studies involved one patient with asymptomatic ventricular ectopy on ambulatory monitoring and another with a history of possible ectopic atrial tachycardia. For the majority of the 21 patients with a prior arrhythmia history and positive EPS, the principal clinical concern was manifest preexcitation, and accessory pathways were indeed identified in all such cases. However, 14 of these 21 (66%) were found to have additional arrhythmia mechanisms, including multiple accessory pathways, atriofascicular fibers, AV nodal reentry, atrial flutter, atrial fibrillation, or VT.
Influence of EPS on preoperative and intraoperative arrhythmia interventions Positive findings at EPS influenced perioperative management in nearly all cases (Table 2). Catheter ablation of 40 discrete substrates was attempted in 17 patients. Ablation was successful for targeted substrates in 16 of 17 patients (94%), with the single failure involving a cautious cryoablation attempt in a 3-year-old child with AV nodal reentry in whom the risk of nodal damage was deemed high. Three interesting patients had sustained monomorphic VT circuits induced within atrialized right ventricular tissue that were sufficiently slow and hemodynamically tolerated to allow formal mapping. Catheter ablation was successful in eliminating VT in two of these cases (Figure 2). Ablation was deferred until the operating room in the third case because of young age (6 months) and concern for potential perforation through the thin atrialized ventricular tissue. For three other patients with induced monomorphic VT, rapid rates caused
prompt hemodynamic compromise and detailed mapping could not be performed. Multiple intraoperative arrhythmia interventions were performed. For 35 of the 42 patients (83%) with preoperative EPS, an atrial maze procedure was carried out using cryosurgical techniques based on the results of their EPS and clinical history. Data from EPS influenced surgical approach in the sense that a biatrial maze was recommended over a simple right atrial maze if sustained atrial fibrillation had been induced. In some instances, atrial maze procedures were done simply at the surgeon’s discretion based on severe degrees of atrial enlargement, even when EPS did not induce Table 2
Catheter and intraoperative rhythm interventions
Catheter ablation* Total accessory pathways Atriofascicular fiber AV nodal reentry Ectopic atrial tachycardia Total atrial flutter circuits Monomorphic VT Arrhythmia surgery* Atrial maze Monomorphic VT cryoablation Accessory pathway division Device implants* Epicardial ICD lead alone Epicardial ICD lead & generator ILR
Preop EPS (n ¼ 42)
No Preop EPS (n ¼ 32)
17 (40%) 21 2 4 2 9 2 36 (86%) 35 1 1 23 (55%) 5 1 20
— — — — — — — 13 (41%) 13 — — 2 (6%) — — 2
Data are expressed as number (percentage). AV ¼ atrioventricular; EPS ¼ electrophysiologic study; ICD ¼ implantable cardioverter-defibrillator; ILR ¼ implantable loop recorder; VT ¼ ventricular tachycardia. * Note that some patients had ablation or surgical intervention for more than one substrate, or more than one device implanted.
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Figure 2 Radiofrequency catheter ablation of monomorphic ventricular tachycardia in a child with Ebstein’s anomaly prior to the Cone procedure. Anteroposterior (AP) and lateral (LAT) fluoroscopic projections show catheter tip (arrows) at the site of successful ablation on the diaphragmatic surface of right ventricular inflow where muscle was thin and atrialized. The tachycardia had left bundle branch block and superior axis compatible with an exit in this region and stopped abruptly 4 seconds into radiofrequency ablation.
flutter or fibrillation. Other interventions included one case of successful cryosurgical interruption for an accessory pathway that had not been addressed with catheter ablation and one case of successful cryosurgery for macroreentrant VT arising from atrialized right ventricular tissue in the 6month-old mentioned earlier. Based on the VT substrates found at the time of preoperative EPS, coupled with hesitation to consider transvenous ICD leads across a reconstructed tricuspid valve, 5 of the 42 patients (12%) had placement of epicardial ICD leads for potential future use, and one patient had a full ICD system with generator implant at the time of Cone procedure. Twenty of the 42 patients also had ILR implant to monitor for postoperative arrhythmias. 10
Postoperative arrhythmias and follow-up Early postoperative arrhythmias (Table 3) needing active treatment occurred in 6 of the 42 patients who had preoperative EPS, including two cases of frequent nonsustained VT and one case each of ectopic atrial tachycardia, atrial fibrillation, atrial flutter, and ventricular fibrillation (in the setting of low serum potassium of 2.4 mEq/L). Except for atrial fibrillation in one patient who had undergone a biatrial maze, there were no other recurrences of arrhythmia substrates that had been addressed with catheter ablation or cryosurgery. Of the 32 patients without preoperative EPS, 3 (9%) experienced significant arrhythmias in the early postoperative period, including one case each of atrial fibrillation, atrial flutter, and ectopic atrial tachycardia. Follow-up rhythm status was ascertained at a median of 367 days (range 0–1910 days) for the 42 patients with preoperative EPS. During this time, 3 (7%) had
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documentation of significant arrhythmias, including atrial fibrillation in two (requiring electrical cardioversion) and nonsustained VT with positive follow-up EPS in one (who went on to have an ICD generator added to the lead placed at the time of Cone surgery). There were no patient deaths in this group. Follow-up rhythm status was ascertained at a median of 630 days (range 0–1924 days) for the 32 patients who did not undergo EPS. During this time, 3 (10%) had documentation of significant arrhythmias, including one case each of ectopic atrial tachycardia (treated medically), atrial flutter (requiring electrical cardioversion), and nonsustained VT with positive EPS (treated medically). There were two unexpected sudden deaths in this group that were presumed arrhythmic. A total of 22 patients (20 from the EPS group and 2 from the non-EPS group) underwent ILR implant in conjunction with their Cone procedure. The ultimate yield from this device was low. Only one patient had an arrhythmia recorded (slow ectopic atrial tachycardia) that would not have been detected by conventional means.
Discussion This study sought to measure the impact of an aggressive diagnostic strategy for identifying and addressing all arrhythmia substrates in patients with Ebstein’s anomaly undergoing major cardiac surgical interventions such as the Cone procedure. The central finding was a high overall yield (69%) at preoperative EPS for significant arrhythmia substrates. Not surprisingly, this yield was highest (91%) among patients with previously documented rhythm abnormalities, but it is noteworthy that the rate of positive testing still was remarkably high (42%) for patients with Ebstein’s anomaly with no prior arrhythmia concerns based on history and noninvasive testing alone. Moreover, even among those with a previously documented arrhythmia substrate, there was a high likelihood of uncovering secondary and tertiary arrhythmia mechanisms that were unrelated to the primary substrate.
Table 3
Postoperative and follow-up arrhythmias Preop EPS No Preop EPS (n ¼ 42) (n ¼ 32)
Early arrhythmias Atrial flutter Atrial fibrillation Ectopic atrial tachycardia Nonsustained VT Ventricular fibrillation (low potassium) Follow-up arrhythmias/events Atrial flutter Atrial fibrillation Ectopic atrial tachycardia Nonsustained VT and þV-stim Sudden death (presumed arrhythmia)
6 (14%) 1 1 1 2 1
3 (9%) 1 1 1 — —
3 (7%) — 2 — 1 —
5 (16%) 1 — 1 1 2
Data expressed as number (percentage). EPS ¼ electrophysiologic study; þV-stim ¼ positive ventricular stimulation at EPS; VT ¼ ventricular tachycardia.
186 Findings at preoperative EPS exerted a strong influence on patient management in this series by (1) allowing many substrates to be eliminated by preoperative catheter ablation, (2) guiding surgical interventions for certain atrial and ventricular arrhythmias, and (3) alerting clinicians to the potential need for epicardial ICD hardware. It is important to emphasize that any subsequent catheter ablation procedures along the tricuspid annulus, as well as transvenous placement of ventricular pacing or ICD leads, may be difficult or contraindicated in patients with Ebstein’s anomaly following tricuspid valve reconstruction. Subsequent catheter ablation for residual accessory pathways or atrial flutter involving the cavotricuspid isthmus can be especially difficult when an annuloplasty ring has been incorporated into the repair. Hence, all efforts must be made to intervene for arrhythmias prior to or during such operations. This descriptive series supports routine preoperative EPS as a useful method to ensure that all relevant tachycardia substrates have been properly identified. Ebstein’s anomaly is well known to be associated with a high incidence of accessory pathways around the tricuspid valve ring, as well as an assortment of other atrial tachycardias.3,4,11,12 Catheter ablation of such targets has been described in multiple prior reports.2,13–16 Most data suggest that the recurrence rate after accessory pathway ablation in patients with Ebstein’s anomaly is relatively high. We were fortunate that no recurrences were encountered in this series, although it may be that surgical manipulation around the tricuspid annulus during the Cone repair reinforced catheter lesions or otherwise disrupted residual accessory pathways to account for this favorable outcome. Ventricular arrhythmias in Ebstein’s anomaly are less well understood, and it has long been unclear whether reentrant VT circuits in this population were intrinsic to congenitally abnormal right ventricular muscle, a consequence of degenerative remodeling, or a result of surgical scarring. Observations from this series suggest that at least some macroreentrant VT circuits are likely to be intrinsic to Ebstein’s malformation itself. We observed and successfully mapped three circuits arising from atrialized right ventricular tissue in young patients who had not undergone prior surgery, and these circuits seem to be amenable to catheter and surgical ablation.2,17 Routine use of an ILR was considered for a time at our institution as a way to monitor for serious postoperative arrhythmias following the Cone operation. The device was implanted in 22 patients but revealed only a single asymptomatic arrhythmia event that would have been missed by conventional means. Based on this low return, we have abandoned ILR implant unless there are patient-specific indications.
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Study limitations The main limitation of this study was lack of a control group to accurately measure the influence of preoperative EPS on patient outcomes. The non-EPS subgroup did not represent a valid comparison for this purpose because it was made up almost exclusively of patients from our early Cone experience who did not have preexistent rhythm concerns. These descriptive data are too limited to infer a strong protective effect of preoperative EPS.
Conclusion Patients with Ebstein’s anomaly carry a heavy arrhythmia burden that must be well delineated in advance of major surgical interventions such as the Cone procedure. Comprehensive EPS helps detect these arrhythmias and guide therapy. It is reasonable to recommend EPS as a standard preoperative test in this setting, even in patients who do not have prior documented arrhythmias.
References 1. Attenhofer Jost CH, Connolly HM, Dearani JA, Edwards WD, Danielson GK. Ebstein’s anomaly. Circulation 2007;115:277–285. 2. Walsh EP. Interventional electrophysiology in patients with congenital heart disease. Circulation 2007;115:3224–3234. 3. Attenhofer Jost CH, Connolly HM, Edwards WD, Hayes D, Warnes CA, Danielson GK. Ebstein's anomaly: review of a multifaceted congenital cardiac condition. Swiss Med Wkly 2005;135:269–281. 4. Zachariah JP, Walsh EP, Triedman JK, et al. Multiple accessory pathways in the young: the impact of structural heart disease. Am Heart J 2013;165:87–92. 5. da Silva JP, Baumgratz JF, da Fonseca L, et al. The Cone reconstruction of the tricuspid valve in Ebstein’s anomaly. The operation: early and midterm results. J Thorac Cardiovasc Surg 2007;133:215–223. 6. da Silva JP, da Silva Lda F. Ebstein’s anomaly of the tricuspid valve: the Cone repair. Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu 2012;15:38–45. 7. Vogel M, Marx GR, Tworetzky W, et al. Ebstein’s malformation of the tricuspid valve: short-term outcomes of the “Cone procedure” versus conventional surgery. Congenit Heart Dis 2012;7:50–58. 8. Stulak JM, Dearani J, Puga FJ, Zehr KJ, Schaff HV, Danielson GK. Right-sided Maze procedure for atrial tachyarrhythmias in congenital heart disease. Ann Thorac Surg 2006;81:1780–1784. 9. Shivapour JK, Sherwin ED, Jordao L, et al. The utility of preoperative electrophysiology studies and Reveal implantation in patients with Ebstein’s anomaly undergoing Cone procedure (abstract). Heart Rhythm 2012;9:S94. 10. Stulak JM, Dearani JA, Puga FJ, Zehr KJ, Schaff HV, Danielson GK. Right-sided Maze procedure for atrial tachyarrhythmias in congenital heart disease. Ann Thorac Surg 2006;81:1780–1784. 11. Delhaas T, Sarvaas GJ, Rijlaarsdam ME, et al. A multicenter, long-term study on arrhythmias in children with Ebstein anomaly. Pediatr Cardiol 2010;31:229–233. 12. Khositseth A, Danielson GK, Dearani JA, Munger TM, Porter CJ. Supraventricular tachyarrhythmias in Ebstein anomaly: management and outcome. J Thorac Cardiovasc Surg 2004;128:826–833. 13. Reich JD, Auld D, Hulse E, Sullivan K, Campbell R. The Pediatric Radiofrequency Ablation Registry’s experience with Ebstein’s anomaly. Pediatric Electrophysiology Society. J Cardiovasc Electrophysiol 1998;9:1370–1377. 14. Chetaille P, Walsh EP, Triedman JK. Outcomes of radiofrequency catheter ablation of atrioventricular reciprocating tachycardia in patients with congenital heart disease. Heart Rhythm 2004;1:168–173. 15. Roten L, Lukac P, De Groot N, et al. Catheter ablation in Ebstein’s anomaly: a multicenter study. J Cardiovasc Electrophysiol 2011;22:1391–1396. 16. Sherwin ED, Walsh EP, Abrams DJ. Variable QRS morphologies in Ebstein’s anomaly: what is the mechanism? Heart Rhythm 2013;10:933–937. 17. Obioha-Ngwu O, Milliez P, Richardson A, Pittaro M, Josephson ME. Ventricular tachycardia in Ebstein’s anomaly. Circulation 2001;104:E92–E94.
Introduction Ebstein’s anomaly is a relatively rare disorder accounting for less than 1% of all congenital heart defects. Its hallmark anatomic feature is apical displacement of the tricuspid valve, which can result in tricuspid regurgitation and/or stenosis, right atrial and right ventricular dilation, cyanosis (if the atrial septum is not intact), and even biventricular failure in severe cases.1 Displacement of the tricuspid valve is also associated with some portion of the right ventricular inflow being thin and “atrialized,” with histologically and electrically abnormal myocardium spanning the region from Address reprint requests and correspondence: Dr. Edward P. Walsh, Boston Children’s Hospital, 300 Longwood Ave, Boston, MA 02115. E-mail address: [email protected]. 1 Dr. Triedman is a consultant to Biosense Webster.
1547-5271/$-see front matter B 2014 Heart Rhythm Society. All rights reserved.
with no prior suspicion of arrhythmias. Seventeen patients had successful catheter ablation during EPS, and EPS data guided one or more intraoperative rhythm interventions for the remainder. During follow-up, diagnostic yield from ILR was low. Since implementing a more aggressive diagnostic strategy, no further sudden deaths have occurred. CONCLUSION Preoperative EPS has a high diagnostic and therapeutic yield in patients with Ebstein’s anomaly undergoing the Cone operation. It is reasonable to recommend EPS as a routine preoperative test for this population. KEYWORDS Arrhythmia surgery; Catheter ablation; Cone procedure; Congenital heart disease; Ebstein’s anomaly; Electrophysiologic study; Wolff-Parkinson-White syndrome; Ventricular tachycardia ABBREVIATIONS AV ¼ atrioventricular; EPS ¼ electrophysiologic study; ILR ¼ implantable loop recorder; ICD ¼ implantable cardioverter-defibrillator; VT ¼ ventricular tachycardia; WPW ¼ Wolff-Parkinson-White syndrome (Heart Rhythm 2014;11:182–186) I 2014 Heart Rhythm Society. All rights reserved.
the true right atrioventricular (AV) groove to the mobile edge of the tricuspid valve leaflets.2 As a consequence of these hemodynamic and electrical derangements, patients with Ebstein’s anomaly have a high incidence of atrial and ventricular arrhythmias, including the highest frequency of Wolff-Parkinson-White (WPW) syndrome for any congenital heart defect.3,4 Surgical techniques for Ebstein’s anomaly have evolved, and the Cone procedure developed by da Silva et al has now been adopted by many centers.5–7 Perioperative management may be complicated by arrhythmias, many of which involve mechanisms that can be addressed with preoperative catheter ablation or intraoperative surgical ablation.2,5,8 Early in our institutional Cone experience, we encountered two patients with good hemodynamic outcomes who suffered sudden death (presumed arrhythmic) within 60 days of surgery that http://dx.doi.org/10.1016/j.hrthm.2013.10.045
Shivapour et al
Preoperative Electrophysiologic Studies in Ebstein’s Anomaly
was unanticipated based on history and noninvasive rhythm observations.7 This prompted a more systematic evaluation for arrhythmia substrates in patients with Ebstein’s anomaly undergoing the Cone procedure at our center, using preoperative electrophysiologic studies (EPS) and ablation whenever possible, as well as intraoperative placement of an implantable loop recorder (ILR) to monitor for postoperative arrhythmias.9 This report describes the frequency of arrhythmias detected with this diagnostic strategy and outlines the interventions used to address the substrates so identified.
Methods Data source and study population Record review was approved by the Committee for Clinical Investigation at Boston Children’s Hospital. All patients with the diagnosis of Ebstein’s anomaly who underwent the Cone procedure at our center from December 2006 to September 2012 were included. Analysis involved demographics, preoperative rhythm history, preoperative EPS (if performed), catheter ablation procedures, intraoperative arrhythmia interventions, early postoperative arrhythmias, and follow-up arrhythmias (including ILR data if a device was implanted). Patients were dichotomized into those who had a preoperative EPS and those who did not. For patients who underwent preoperative EPS, the diagnostic study included standard investigation for manifest or concealed accessory pathways, atriofascicular fibers, and inducible supraventricular tachycardias. In addition, a relatively nonaggressive ventricular stimulation protocol (S4 at one drive cycle length, at one right ventricular site, minimal coupling interval 200 ms, off isoproterenol) was performed. Induced ventricular tachycardias (VTs) were scored as “sustained” if duration was 430 seconds and/or caused hemodynamic compromise or as “nonsustained” if 45 beats but o30 seconds. Catheter ablation usually was attempted if a suitable substrate was present at preoperative EPS, although in some cases the procedure was restricted to mapping as a guide for later surgical ablation at the discretion of the electrophysiologist and cardiac surgeon. The Cone procedure was performed using surgical techniques described previously.5,7 Operative reports were reviewed for all arrhythmia interventions, including cryoablation or division of accessory pathways, right atrial or biatrial maze procedures, and cryoablation of right ventricular tissue involved in monomorphic VT. In addition, note was made of all rhythm-related hardware implants, including ILRs, epicardial implantable cardioverter-defibrillator (ICD) leads, and ICD generators. Records were examined for all postoperative arrhythmias causing patient instability that required intervention prior to hospital discharge. All available outpatient follow-up records were reviewed for later arrhythmias and sudden death.
Study design and analysis This was a descriptive study designed primarily to measure the yield of an aggressive arrhythmia detection strategy and
183
to evaluate the influence of this strategy on antiarrhythmic interventions. Comparisons of gross clinical features between subgroups of patients with and without preoperative EPS were performed, but strong selection bias and small subject numbers prevented meaningful statistical conclusions from this comparison. Continuous variables are expressed as median and range. Categorical variables are reported as counts and percentages.
Results Patient characteristics A total of 74 patients with Ebstein’s anomaly underwent the Cone operation at our center between December 2006 and September 2012. Early in this experience, patients did not undergo preoperative EPS unless there were clinical indications such as manifest preexcitation or a documented arrhythmia thought to be amenable to ablation therapy. Nearly all recent patients underwent EPS as a standard preoperative test whether or not there was an obvious clinical indication. Ultimately, 42 subjects (57%) had preoperative EPS performed. Median age at the time of the Cone procedure was 12.1 years (range 0.2–56.2 years), and 61% of the patients were female. Of the 42 who underwent EPS prior to the Cone procedure (Table 1), the preoperative arrhythmia history was positive for 23 (55%); the remaining 19 were studied proactively to rule out cryptic arrhythmia substrates that might require treatment prior to or during surgery. Of the 32 patients without preoperative EPS, only 3 (9%) had any prior rhythm concerns (atrial flutter in one, remote history of neonatal supraventricular tachycardia without recurrence in one, and one asymptomatic patient who was genotype positive for long QT syndrome type 1).
Preoperative EPS findings Of the 42 patients who underwent preoperative EPS (Figure 1), significant arrhythmia substrates were found in Table 1
Demographics and preoperative arrhythmia history Preop EPS (n ¼ 42)
Age at Cone procedure (years) Female gender Preoperative rhythm concern Atrial flutter Atrial fibrillation Ectopic atrial tachycardia WPW syndrome/tachycardia WPW syndrome/asymptomatic SVT (undetermined mechanism) Ventricular tachycardia Other
No Preop EPS (n ¼ 32)
13.8 (0.4, 55.9) 10.9 (0.2, 56.2) 23 (55%) 22 (69%) 23 (55%) 3 (9%) 2 1 1 — 3 — 6 — 3 — 5 1 3 —
— 1
Data are expressed as median (minimum, maximum) for continuous variables and as number (percentage) for categorical variables. EPS ¼ electrophysiologic study; SVT ¼ supraventricular tachycardia; WPW ¼ Wolff-Parkinson-White.
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Figure 1 Flowchart showing positive findings at electrophysiologic study according to preoperative rhythm history. It is noteworthy that significant arrhythmia substrates were identified in as many as 42% of patients with Ebstein’s anomaly with a benign rhythm history prior to surgery. AP ¼ accessory pathway; AV ¼ atrioventricular; EPS ¼ electrophysiologic study; VT ¼ ventricular tachycardia; WPW ¼ Wolff-Parkinson-White.
29 (69%), involving a total of 56 discrete mechanisms. Of note, EPS was positive in 8 of the 19 patients (42%) who had no preoperative arrhythmia concerns and were only studied as a precaution under the aggressive diagnostic strategy. For the 23 patients who had prior documented or suspected arrhythmias, EPS was positive in 21 (91%). The two negative studies involved one patient with asymptomatic ventricular ectopy on ambulatory monitoring and another with a history of possible ectopic atrial tachycardia. For the majority of the 21 patients with a prior arrhythmia history and positive EPS, the principal clinical concern was manifest preexcitation, and accessory pathways were indeed identified in all such cases. However, 14 of these 21 (66%) were found to have additional arrhythmia mechanisms, including multiple accessory pathways, atriofascicular fibers, AV nodal reentry, atrial flutter, atrial fibrillation, or VT.
Influence of EPS on preoperative and intraoperative arrhythmia interventions Positive findings at EPS influenced perioperative management in nearly all cases (Table 2). Catheter ablation of 40 discrete substrates was attempted in 17 patients. Ablation was successful for targeted substrates in 16 of 17 patients (94%), with the single failure involving a cautious cryoablation attempt in a 3-year-old child with AV nodal reentry in whom the risk of nodal damage was deemed high. Three interesting patients had sustained monomorphic VT circuits induced within atrialized right ventricular tissue that were sufficiently slow and hemodynamically tolerated to allow formal mapping. Catheter ablation was successful in eliminating VT in two of these cases (Figure 2). Ablation was deferred until the operating room in the third case because of young age (6 months) and concern for potential perforation through the thin atrialized ventricular tissue. For three other patients with induced monomorphic VT, rapid rates caused
prompt hemodynamic compromise and detailed mapping could not be performed. Multiple intraoperative arrhythmia interventions were performed. For 35 of the 42 patients (83%) with preoperative EPS, an atrial maze procedure was carried out using cryosurgical techniques based on the results of their EPS and clinical history. Data from EPS influenced surgical approach in the sense that a biatrial maze was recommended over a simple right atrial maze if sustained atrial fibrillation had been induced. In some instances, atrial maze procedures were done simply at the surgeon’s discretion based on severe degrees of atrial enlargement, even when EPS did not induce Table 2
Catheter and intraoperative rhythm interventions
Catheter ablation* Total accessory pathways Atriofascicular fiber AV nodal reentry Ectopic atrial tachycardia Total atrial flutter circuits Monomorphic VT Arrhythmia surgery* Atrial maze Monomorphic VT cryoablation Accessory pathway division Device implants* Epicardial ICD lead alone Epicardial ICD lead & generator ILR
Preop EPS (n ¼ 42)
No Preop EPS (n ¼ 32)
17 (40%) 21 2 4 2 9 2 36 (86%) 35 1 1 23 (55%) 5 1 20
— — — — — — — 13 (41%) 13 — — 2 (6%) — — 2
Data are expressed as number (percentage). AV ¼ atrioventricular; EPS ¼ electrophysiologic study; ICD ¼ implantable cardioverter-defibrillator; ILR ¼ implantable loop recorder; VT ¼ ventricular tachycardia. * Note that some patients had ablation or surgical intervention for more than one substrate, or more than one device implanted.
Shivapour et al
Preoperative Electrophysiologic Studies in Ebstein’s Anomaly
Figure 2 Radiofrequency catheter ablation of monomorphic ventricular tachycardia in a child with Ebstein’s anomaly prior to the Cone procedure. Anteroposterior (AP) and lateral (LAT) fluoroscopic projections show catheter tip (arrows) at the site of successful ablation on the diaphragmatic surface of right ventricular inflow where muscle was thin and atrialized. The tachycardia had left bundle branch block and superior axis compatible with an exit in this region and stopped abruptly 4 seconds into radiofrequency ablation.
flutter or fibrillation. Other interventions included one case of successful cryosurgical interruption for an accessory pathway that had not been addressed with catheter ablation and one case of successful cryosurgery for macroreentrant VT arising from atrialized right ventricular tissue in the 6month-old mentioned earlier. Based on the VT substrates found at the time of preoperative EPS, coupled with hesitation to consider transvenous ICD leads across a reconstructed tricuspid valve, 5 of the 42 patients (12%) had placement of epicardial ICD leads for potential future use, and one patient had a full ICD system with generator implant at the time of Cone procedure. Twenty of the 42 patients also had ILR implant to monitor for postoperative arrhythmias. 10
Postoperative arrhythmias and follow-up Early postoperative arrhythmias (Table 3) needing active treatment occurred in 6 of the 42 patients who had preoperative EPS, including two cases of frequent nonsustained VT and one case each of ectopic atrial tachycardia, atrial fibrillation, atrial flutter, and ventricular fibrillation (in the setting of low serum potassium of 2.4 mEq/L). Except for atrial fibrillation in one patient who had undergone a biatrial maze, there were no other recurrences of arrhythmia substrates that had been addressed with catheter ablation or cryosurgery. Of the 32 patients without preoperative EPS, 3 (9%) experienced significant arrhythmias in the early postoperative period, including one case each of atrial fibrillation, atrial flutter, and ectopic atrial tachycardia. Follow-up rhythm status was ascertained at a median of 367 days (range 0–1910 days) for the 42 patients with preoperative EPS. During this time, 3 (7%) had
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documentation of significant arrhythmias, including atrial fibrillation in two (requiring electrical cardioversion) and nonsustained VT with positive follow-up EPS in one (who went on to have an ICD generator added to the lead placed at the time of Cone surgery). There were no patient deaths in this group. Follow-up rhythm status was ascertained at a median of 630 days (range 0–1924 days) for the 32 patients who did not undergo EPS. During this time, 3 (10%) had documentation of significant arrhythmias, including one case each of ectopic atrial tachycardia (treated medically), atrial flutter (requiring electrical cardioversion), and nonsustained VT with positive EPS (treated medically). There were two unexpected sudden deaths in this group that were presumed arrhythmic. A total of 22 patients (20 from the EPS group and 2 from the non-EPS group) underwent ILR implant in conjunction with their Cone procedure. The ultimate yield from this device was low. Only one patient had an arrhythmia recorded (slow ectopic atrial tachycardia) that would not have been detected by conventional means.
Discussion This study sought to measure the impact of an aggressive diagnostic strategy for identifying and addressing all arrhythmia substrates in patients with Ebstein’s anomaly undergoing major cardiac surgical interventions such as the Cone procedure. The central finding was a high overall yield (69%) at preoperative EPS for significant arrhythmia substrates. Not surprisingly, this yield was highest (91%) among patients with previously documented rhythm abnormalities, but it is noteworthy that the rate of positive testing still was remarkably high (42%) for patients with Ebstein’s anomaly with no prior arrhythmia concerns based on history and noninvasive testing alone. Moreover, even among those with a previously documented arrhythmia substrate, there was a high likelihood of uncovering secondary and tertiary arrhythmia mechanisms that were unrelated to the primary substrate.
Table 3
Postoperative and follow-up arrhythmias Preop EPS No Preop EPS (n ¼ 42) (n ¼ 32)
Early arrhythmias Atrial flutter Atrial fibrillation Ectopic atrial tachycardia Nonsustained VT Ventricular fibrillation (low potassium) Follow-up arrhythmias/events Atrial flutter Atrial fibrillation Ectopic atrial tachycardia Nonsustained VT and þV-stim Sudden death (presumed arrhythmia)
6 (14%) 1 1 1 2 1
3 (9%) 1 1 1 — —
3 (7%) — 2 — 1 —
5 (16%) 1 — 1 1 2
Data expressed as number (percentage). EPS ¼ electrophysiologic study; þV-stim ¼ positive ventricular stimulation at EPS; VT ¼ ventricular tachycardia.
186 Findings at preoperative EPS exerted a strong influence on patient management in this series by (1) allowing many substrates to be eliminated by preoperative catheter ablation, (2) guiding surgical interventions for certain atrial and ventricular arrhythmias, and (3) alerting clinicians to the potential need for epicardial ICD hardware. It is important to emphasize that any subsequent catheter ablation procedures along the tricuspid annulus, as well as transvenous placement of ventricular pacing or ICD leads, may be difficult or contraindicated in patients with Ebstein’s anomaly following tricuspid valve reconstruction. Subsequent catheter ablation for residual accessory pathways or atrial flutter involving the cavotricuspid isthmus can be especially difficult when an annuloplasty ring has been incorporated into the repair. Hence, all efforts must be made to intervene for arrhythmias prior to or during such operations. This descriptive series supports routine preoperative EPS as a useful method to ensure that all relevant tachycardia substrates have been properly identified. Ebstein’s anomaly is well known to be associated with a high incidence of accessory pathways around the tricuspid valve ring, as well as an assortment of other atrial tachycardias.3,4,11,12 Catheter ablation of such targets has been described in multiple prior reports.2,13–16 Most data suggest that the recurrence rate after accessory pathway ablation in patients with Ebstein’s anomaly is relatively high. We were fortunate that no recurrences were encountered in this series, although it may be that surgical manipulation around the tricuspid annulus during the Cone repair reinforced catheter lesions or otherwise disrupted residual accessory pathways to account for this favorable outcome. Ventricular arrhythmias in Ebstein’s anomaly are less well understood, and it has long been unclear whether reentrant VT circuits in this population were intrinsic to congenitally abnormal right ventricular muscle, a consequence of degenerative remodeling, or a result of surgical scarring. Observations from this series suggest that at least some macroreentrant VT circuits are likely to be intrinsic to Ebstein’s malformation itself. We observed and successfully mapped three circuits arising from atrialized right ventricular tissue in young patients who had not undergone prior surgery, and these circuits seem to be amenable to catheter and surgical ablation.2,17 Routine use of an ILR was considered for a time at our institution as a way to monitor for serious postoperative arrhythmias following the Cone operation. The device was implanted in 22 patients but revealed only a single asymptomatic arrhythmia event that would have been missed by conventional means. Based on this low return, we have abandoned ILR implant unless there are patient-specific indications.
Heart Rhythm, Vol 11, No 2, February 2014
Study limitations The main limitation of this study was lack of a control group to accurately measure the influence of preoperative EPS on patient outcomes. The non-EPS subgroup did not represent a valid comparison for this purpose because it was made up almost exclusively of patients from our early Cone experience who did not have preexistent rhythm concerns. These descriptive data are too limited to infer a strong protective effect of preoperative EPS.
Conclusion Patients with Ebstein’s anomaly carry a heavy arrhythmia burden that must be well delineated in advance of major surgical interventions such as the Cone procedure. Comprehensive EPS helps detect these arrhythmias and guide therapy. It is reasonable to recommend EPS as a standard preoperative test in this setting, even in patients who do not have prior documented arrhythmias.
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