EDITORIAL COMMENTARY
PVCs arising from the moderator band: An under-recognized trigger for idiopathic VF? Andrea M. Russo, MD, FACC, FHRS From the Cooper Medical School of Rowan University, Camden, New Jersey. Idiopathic ventricular fibrillation (VF) occurs in the absence of underlying structural heart disease or ECG abnormalities and accounts for a minority of patients who survive out-of-hospital cardiac arrest. Although implantable cardioverter-defibrillator therapy typically is recommended for patients who have been resuscitated from cardiac arrest, arrhythmias may recur and even can lead to electrical storms. Recent advances in the understanding of the mechanisms and triggers responsible for VF have resulted in the use of catheter ablation strategies aimed at ablation of monomorphic focal premature ventricular contractions (PVCs) responsible for triggering ventricular arrhythmias. In many cases, these triggers of VF may be related to potentials arising from His–Purkinje fibers.1-6 In patients without structural heart disease, idiopathic VF/polymorphic ventricular tachycardia (VT) also may arise from triggers located in the right ventricular outflow tract,1,6 anterior wall of the right ventricle,1,7 papillary muscles,5 left ventricular outflow tract,5 or right ventricular moderator band (MB).8 However, ablation of arrhythmias in some regions, including the papillary muscles or MB, may be challenging because of issues of catheter contact or stability, thus limiting effective energy delivery. In addition, these potential sources of triggers may be under-recognized without a tool that allows direct visualization of endocardial structures during the ablation procedure. In this issue of HeartRhythm, Sadek et al8 report an MB source of PVCs in 10 patients presenting with monomorphic VT or idiopathic VF and eloquently describe ECG and procedural findings in these patients undergoing catheter ablation. Although the initial success rates for VF ablation KEYWORDS Idiopathic ventricular fibrillation; Premature ventricular contractions; Intracardiac echocardiography; Catheter ablation ABBREVIATIONS ECG ¼ electrocardiography; ICE ¼ intracardiac echocardiography; MB ¼ moderator band; PVC ¼ premature ventricular contraction; RF ¼ radiofrequency; VF ¼ ventricular fibrillation; VT ¼ ventricular tachycardia (Heart Rhythm 2015;12:76–77) Dr. Russo has received honoraria from Medtronic, St. Jude Medical, Biotronik, and Boston Scientific; research support from Medtronic and Boston Scientific; and fellowship support from Medtronic and Boston Scientific. Address reprint requests and correspondence: Dr. Andrea M. Russo, Electrophysiology and Arrhythmia Services, 393 Dorrance Bldg, 1 Cooper Plaza, Cooper University Hospital, Camden, NJ 08103. E-mail address: [email protected].
1547-5271/$-see front matter B 2015 Heart Rhythm Society. All rights reserved.
aimed at targeting the critically timed PVCs responsible for triggering VF have been reported to be 81% to 100%, similar to the immediate success rate of 100% in the present study, short-term recurrence rates were up to 11% to 18%,1,2,6 which are higher than recurrence rates typically seen with other forms of idiopathic ventricular arrhythmias. In the current study, 60% of patients with an MB source of PVCs required a second ablation procedure days to months after the initial procedure.8 Radiofrequency (RF) ablation of PVCs localized to endocardial structures may be particularly challenging. In addition, these potential sources of triggers for VT/VF may be under-recognized.
Prevalence of MB PVCs Information about the prevalence, ECG features, and results of ablation of MB PVCs is limited. In the present study, 10 of 394 patients (2.5%) with idiopathic ventricular arrhythmias had an MB source. Although an MB source of PVCs that trigger VF has only been reported recently, this source of triggers likely has been previously under-recognized because fluoroscopic or current computerized mapping modalities cannot visualize this structure. In addition, the prevalence of MB PVCs leading to idiopathic VF may be underestimated because most survivors of cardiac arrest/VF do not under electrophysiologic study with provocation of PVCs to assess inducibility. The utilization of intracardiac echocardiography (ICE) has greatly advanced the understanding of the source of arrhythmias, providing an enhanced appreciation of the correlation between electrophysiologic findings and anatomic structures.
Importance of ECG characteristics It is important to characterize ECG features of ventricular arrhythmias that help to localize the site of origin before the procedure because this can help guide ablation and assist with preprocedural planning, which may enhance efficacy. Because most centers may not routinely use ICE during ablation of PVCs or idiopathic VT, appropriate recognition of this potential focus may help with procedural preparation. In addition, preprocedural diagnostic clues may have important implications for counseling patients regarding expectations, including success rates and potential risks of the procedure. http://dx.doi.org/10.1016/j.hrthm.2014.10.001
Russo
Editorial Commentary
Value of imaging during ablation With the increase in complexity of ablation procedures, ICE has become a powerful tool that allows visualization of the cardiac anatomy, which is not provided by fluoroscopy. It typically is used in conjunction with computerized mapping systems, and it complements information obtained by electroanatomic mapping. ICE provides good visualization of intracardiac soft tissue structures, including valves, papillary muscles, and the MB. In addition, ICE has been used for obtaining transeptal access, placing catheters, observing catheter–tissue contact, and visualizing lesion formation, as well as monitoring for complications during ablation procedures. The utility of ICE has been demonstrated during ablation of idiopathic ventricular arrhythmias arising from the left ventricular papillary muscles.9,10 The complex anatomic structure of the papillary muscles may cause difficulty with catheter manipulation during mapping and ablation. In addition, the arrhythmia may be located deeply beneath the endocardium.10 Sadek et al8 now describe the utility of ICE during catheter ablation in the right ventricle in a series of patients with an MB source of ventricular arrhythmias. The site of successful ablation along the MB varied, including sites along the septal insertion, free-wall insertion, or along the body of the MB, with ablation extending to the right bundle in 1 patient. Sadek et al also describe potential challenges related to catheter contact and stability when ablating on the MB, which may contribute to high recurrence rates.
Future directions In addition to potential issues related to stability and contact, the inability to determine effective lesion creation, including the size or intramural depth of ablation lesions, may hamper success. Prior investigation using magnetic resonance imaging with delayed enhancement found that clinical outcome after ablation was related to ineffective creation of RF lesions.11 Ideally, it would be useful to assess “real-time” lesion creation during the ablation procedure. Myocardial contrast echocardiography was used in an animal model to differentiate RF ablation lesions from normal myocardium, demonstrating that this technique accurately localized and quantified RF lesions in a normal left ventricle.12 Instantaneous anatomic feedback regarding the effects of RF delivery on anatomy might provide additional information regarding potential reasons for ineffective lesion creation during the procedure, perhaps also reducing recurrence rates.
Clinical implications The study by Sadek et al provides important clinical information for operators performing ablation procedures, including the following: 1. The MB is clearly described as a source of PVCs triggering monomorphic VT or idiopathic VF in the absence of underlying structural heart disease.
77 2. ECG features of MB ventricular arrhythmias may be useful in identifying the arrhythmia focus and planning for the procedure. 3. ICE can be helpful in guiding mapping and ablation aimed at arrhythmias located on endocardial structures. Sadek et al provide important insights into the need to correlate cardiac anatomy with electrophysiologic findings during complex ablation procedures, highlighting ways to overcome challenges by using ICE, in conjunction with an advanced mapping system and an irrigated catheter, to help ensure ablation success. Even with the availability of advanced technology and procedures performed by internationally renowned experts, 60% of patients with an MB source of ventricular arrhythmias required a second ablation procedure, possibly because of unstable catheter–tissue contact, inadequate lesion depth, and/or changing exit sites along the MB. Further investigation is needed to determine the mechanism of failure and whether other technologic advancements, such as cryoablation, use of catheters that can assess “contact force,” or real-time feedback related to lesion creation, might further improve long-term outcome after ablation on endocardial structures.
References 1. Haissaguerre M, Shoda M, Jais P, et al. Mapping and ablation of idiopathic ventricular fibrillation. Circulation 2002;106:962–967. 2. Haissaguerre M, Shah DC, Jais P, et al. Role of Purkinje conducting system in triggering of idiopathic ventricular fibrillation. Lancet 2002;359:677–678. 3. Haissaguerre M, Derval N, Sacher F, et al. Sudden cardiac arrest associated with early repolarization. N Engl J Med 2008;358:2016–2023. 4. Srivathsan K, Gami AS, Ackerman MJ, Asirvatham SJ. Treatment of ventricular fibrillation in a patient with prior diagnosis of long QT syndrome: importance of precise electrophysiologic diagnosis to successfully ablate the trigger. Heart Rhythm 2007;4:1090–1093. 5. Van Herendael H, Zado ES, Haqqani H, et al. Catheter ablation of ventricular fibrillation: importance of left ventricular outflow tract and papillary muscle triggers. Heart Rhythm 2014;11:566–573. 6. Knecht S, Sacher F, Wright M, et al. Long-term follow-up of idiopathic ventricular fibrillation ablation: a multicenter study. J Am Coll Cardiol 2009;54:522–528. 7. Pasquié JL, Sanders P, Hocini M, Hsu LF, Scavée C, Jais P, Takahashi Y, Rotter M, Sacher F, Victor J, Clémenty J, Haïssaguerre M. Fever as a precipitant of idiopathic ventricular fibrillation in patients with normal hearts. J Cardiovasc Electrophysiol 2004;15:1271–1276. 8. Sadek MM, Benhayon D, Sureddi R, et al. Idiopathic ventricular arrhythmias originating from the moderator band: electrocardiographic characteristics and treatment by catheter ablation. Heart Rhythm 2014;12:67–75. 9. Yamada T, Doppalapudi H, McElderry HT, et al. Idiopathic ventricular arrhythmias originating from the papillary muscles in the left ventricle: prevalence, electrocardiographic and electrophysiological characteristics, and results of the radiofrequency catheter ablation. J Cardiovasc Electrophysiol 2010;21:62–69. 10. Yamada T, Doppalapudi H, McElderry HT, et al. Electrocardiographic and electrophysiological characteristics in idiopathic ventricular arrhythmias originating from the papillary muscles in the left ventricle: relevance for catheter ablation. Circ Arrhythm Electrophysiol 2010;3:324–331. 11. Ilg K, Baman TS, Gupta SK, Swanson S, Good E, Chugh A, Jongnarangsin K, Pelosi F Jr, Crawford T, Oral H, Morady F, Bogun F. Assessment of radiofrequency ablation lesions by CMR imaging after ablation of idiopathic ventricular arrhythmias. JACC Cardiovasc Imaging 2010;3:278–285. 12. Khoury DS, Rao L, Ding C, Sun H, Youker KA, Panescu D, Nagueh SF. Localizing and quantifying ablation lesions in the left ventricle by myocardial contrast echocardiography. J Cardiovasc Electrophysiol 2004;15:1078–1087.
PVCs arising from the moderator band: An under-recognized trigger for idiopathic VF? Andrea M. Russo, MD, FACC, FHRS From the Cooper Medical School of Rowan University, Camden, New Jersey. Idiopathic ventricular fibrillation (VF) occurs in the absence of underlying structural heart disease or ECG abnormalities and accounts for a minority of patients who survive out-of-hospital cardiac arrest. Although implantable cardioverter-defibrillator therapy typically is recommended for patients who have been resuscitated from cardiac arrest, arrhythmias may recur and even can lead to electrical storms. Recent advances in the understanding of the mechanisms and triggers responsible for VF have resulted in the use of catheter ablation strategies aimed at ablation of monomorphic focal premature ventricular contractions (PVCs) responsible for triggering ventricular arrhythmias. In many cases, these triggers of VF may be related to potentials arising from His–Purkinje fibers.1-6 In patients without structural heart disease, idiopathic VF/polymorphic ventricular tachycardia (VT) also may arise from triggers located in the right ventricular outflow tract,1,6 anterior wall of the right ventricle,1,7 papillary muscles,5 left ventricular outflow tract,5 or right ventricular moderator band (MB).8 However, ablation of arrhythmias in some regions, including the papillary muscles or MB, may be challenging because of issues of catheter contact or stability, thus limiting effective energy delivery. In addition, these potential sources of triggers may be under-recognized without a tool that allows direct visualization of endocardial structures during the ablation procedure. In this issue of HeartRhythm, Sadek et al8 report an MB source of PVCs in 10 patients presenting with monomorphic VT or idiopathic VF and eloquently describe ECG and procedural findings in these patients undergoing catheter ablation. Although the initial success rates for VF ablation KEYWORDS Idiopathic ventricular fibrillation; Premature ventricular contractions; Intracardiac echocardiography; Catheter ablation ABBREVIATIONS ECG ¼ electrocardiography; ICE ¼ intracardiac echocardiography; MB ¼ moderator band; PVC ¼ premature ventricular contraction; RF ¼ radiofrequency; VF ¼ ventricular fibrillation; VT ¼ ventricular tachycardia (Heart Rhythm 2015;12:76–77) Dr. Russo has received honoraria from Medtronic, St. Jude Medical, Biotronik, and Boston Scientific; research support from Medtronic and Boston Scientific; and fellowship support from Medtronic and Boston Scientific. Address reprint requests and correspondence: Dr. Andrea M. Russo, Electrophysiology and Arrhythmia Services, 393 Dorrance Bldg, 1 Cooper Plaza, Cooper University Hospital, Camden, NJ 08103. E-mail address: [email protected].
1547-5271/$-see front matter B 2015 Heart Rhythm Society. All rights reserved.
aimed at targeting the critically timed PVCs responsible for triggering VF have been reported to be 81% to 100%, similar to the immediate success rate of 100% in the present study, short-term recurrence rates were up to 11% to 18%,1,2,6 which are higher than recurrence rates typically seen with other forms of idiopathic ventricular arrhythmias. In the current study, 60% of patients with an MB source of PVCs required a second ablation procedure days to months after the initial procedure.8 Radiofrequency (RF) ablation of PVCs localized to endocardial structures may be particularly challenging. In addition, these potential sources of triggers for VT/VF may be under-recognized.
Prevalence of MB PVCs Information about the prevalence, ECG features, and results of ablation of MB PVCs is limited. In the present study, 10 of 394 patients (2.5%) with idiopathic ventricular arrhythmias had an MB source. Although an MB source of PVCs that trigger VF has only been reported recently, this source of triggers likely has been previously under-recognized because fluoroscopic or current computerized mapping modalities cannot visualize this structure. In addition, the prevalence of MB PVCs leading to idiopathic VF may be underestimated because most survivors of cardiac arrest/VF do not under electrophysiologic study with provocation of PVCs to assess inducibility. The utilization of intracardiac echocardiography (ICE) has greatly advanced the understanding of the source of arrhythmias, providing an enhanced appreciation of the correlation between electrophysiologic findings and anatomic structures.
Importance of ECG characteristics It is important to characterize ECG features of ventricular arrhythmias that help to localize the site of origin before the procedure because this can help guide ablation and assist with preprocedural planning, which may enhance efficacy. Because most centers may not routinely use ICE during ablation of PVCs or idiopathic VT, appropriate recognition of this potential focus may help with procedural preparation. In addition, preprocedural diagnostic clues may have important implications for counseling patients regarding expectations, including success rates and potential risks of the procedure. http://dx.doi.org/10.1016/j.hrthm.2014.10.001
Russo
Editorial Commentary
Value of imaging during ablation With the increase in complexity of ablation procedures, ICE has become a powerful tool that allows visualization of the cardiac anatomy, which is not provided by fluoroscopy. It typically is used in conjunction with computerized mapping systems, and it complements information obtained by electroanatomic mapping. ICE provides good visualization of intracardiac soft tissue structures, including valves, papillary muscles, and the MB. In addition, ICE has been used for obtaining transeptal access, placing catheters, observing catheter–tissue contact, and visualizing lesion formation, as well as monitoring for complications during ablation procedures. The utility of ICE has been demonstrated during ablation of idiopathic ventricular arrhythmias arising from the left ventricular papillary muscles.9,10 The complex anatomic structure of the papillary muscles may cause difficulty with catheter manipulation during mapping and ablation. In addition, the arrhythmia may be located deeply beneath the endocardium.10 Sadek et al8 now describe the utility of ICE during catheter ablation in the right ventricle in a series of patients with an MB source of ventricular arrhythmias. The site of successful ablation along the MB varied, including sites along the septal insertion, free-wall insertion, or along the body of the MB, with ablation extending to the right bundle in 1 patient. Sadek et al also describe potential challenges related to catheter contact and stability when ablating on the MB, which may contribute to high recurrence rates.
Future directions In addition to potential issues related to stability and contact, the inability to determine effective lesion creation, including the size or intramural depth of ablation lesions, may hamper success. Prior investigation using magnetic resonance imaging with delayed enhancement found that clinical outcome after ablation was related to ineffective creation of RF lesions.11 Ideally, it would be useful to assess “real-time” lesion creation during the ablation procedure. Myocardial contrast echocardiography was used in an animal model to differentiate RF ablation lesions from normal myocardium, demonstrating that this technique accurately localized and quantified RF lesions in a normal left ventricle.12 Instantaneous anatomic feedback regarding the effects of RF delivery on anatomy might provide additional information regarding potential reasons for ineffective lesion creation during the procedure, perhaps also reducing recurrence rates.
Clinical implications The study by Sadek et al provides important clinical information for operators performing ablation procedures, including the following: 1. The MB is clearly described as a source of PVCs triggering monomorphic VT or idiopathic VF in the absence of underlying structural heart disease.
77 2. ECG features of MB ventricular arrhythmias may be useful in identifying the arrhythmia focus and planning for the procedure. 3. ICE can be helpful in guiding mapping and ablation aimed at arrhythmias located on endocardial structures. Sadek et al provide important insights into the need to correlate cardiac anatomy with electrophysiologic findings during complex ablation procedures, highlighting ways to overcome challenges by using ICE, in conjunction with an advanced mapping system and an irrigated catheter, to help ensure ablation success. Even with the availability of advanced technology and procedures performed by internationally renowned experts, 60% of patients with an MB source of ventricular arrhythmias required a second ablation procedure, possibly because of unstable catheter–tissue contact, inadequate lesion depth, and/or changing exit sites along the MB. Further investigation is needed to determine the mechanism of failure and whether other technologic advancements, such as cryoablation, use of catheters that can assess “contact force,” or real-time feedback related to lesion creation, might further improve long-term outcome after ablation on endocardial structures.
References 1. Haissaguerre M, Shoda M, Jais P, et al. Mapping and ablation of idiopathic ventricular fibrillation. Circulation 2002;106:962–967. 2. Haissaguerre M, Shah DC, Jais P, et al. Role of Purkinje conducting system in triggering of idiopathic ventricular fibrillation. Lancet 2002;359:677–678. 3. Haissaguerre M, Derval N, Sacher F, et al. Sudden cardiac arrest associated with early repolarization. N Engl J Med 2008;358:2016–2023. 4. Srivathsan K, Gami AS, Ackerman MJ, Asirvatham SJ. Treatment of ventricular fibrillation in a patient with prior diagnosis of long QT syndrome: importance of precise electrophysiologic diagnosis to successfully ablate the trigger. Heart Rhythm 2007;4:1090–1093. 5. Van Herendael H, Zado ES, Haqqani H, et al. Catheter ablation of ventricular fibrillation: importance of left ventricular outflow tract and papillary muscle triggers. Heart Rhythm 2014;11:566–573. 6. Knecht S, Sacher F, Wright M, et al. Long-term follow-up of idiopathic ventricular fibrillation ablation: a multicenter study. J Am Coll Cardiol 2009;54:522–528. 7. Pasquié JL, Sanders P, Hocini M, Hsu LF, Scavée C, Jais P, Takahashi Y, Rotter M, Sacher F, Victor J, Clémenty J, Haïssaguerre M. Fever as a precipitant of idiopathic ventricular fibrillation in patients with normal hearts. J Cardiovasc Electrophysiol 2004;15:1271–1276. 8. Sadek MM, Benhayon D, Sureddi R, et al. Idiopathic ventricular arrhythmias originating from the moderator band: electrocardiographic characteristics and treatment by catheter ablation. Heart Rhythm 2014;12:67–75. 9. Yamada T, Doppalapudi H, McElderry HT, et al. Idiopathic ventricular arrhythmias originating from the papillary muscles in the left ventricle: prevalence, electrocardiographic and electrophysiological characteristics, and results of the radiofrequency catheter ablation. J Cardiovasc Electrophysiol 2010;21:62–69. 10. Yamada T, Doppalapudi H, McElderry HT, et al. Electrocardiographic and electrophysiological characteristics in idiopathic ventricular arrhythmias originating from the papillary muscles in the left ventricle: relevance for catheter ablation. Circ Arrhythm Electrophysiol 2010;3:324–331. 11. Ilg K, Baman TS, Gupta SK, Swanson S, Good E, Chugh A, Jongnarangsin K, Pelosi F Jr, Crawford T, Oral H, Morady F, Bogun F. Assessment of radiofrequency ablation lesions by CMR imaging after ablation of idiopathic ventricular arrhythmias. JACC Cardiovasc Imaging 2010;3:278–285. 12. Khoury DS, Rao L, Ding C, Sun H, Youker KA, Panescu D, Nagueh SF. Localizing and quantifying ablation lesions in the left ventricle by myocardial contrast echocardiography. J Cardiovasc Electrophysiol 2004;15:1078–1087.
