- Email: [email protected]
Incessant “ventricular tachycardia” in a patient with non-ischemic cardiomyopathy. What is the tachycardia mechanism?
Available online at www.sciencedirect.com
ScienceDirect Journal of Electrocardiology xx (2015) xxx – xxx www.jecgonline.com
Incessant “ventricular tachycardia” in a patient with non-ischemic cardiomyopathy. What is the tachycardia mechanism?☆,☆☆ Sandeep Arora, MD, CCDS, FHRS⁎ Cardiac Electrophysiology, Excela Health Westmoreland Hospital, 532 W. Pittsburgh Street, Greensburg, PA, USA
Abstract
We present an uncommon and unique arrhythmia in a patient with non-ischemic cardiomyopathy and dual chamber implantable cardioverter defibrillator presenting with palpitations and dyspnea. While surface electrocardiogram suggested irregular narrow complex tachycardia, evaluation of stored electrograms from implantable cardioverter defibrillator revealed incessant episodes of non-sustained ventricular tachycardia. The patient underwent electrophysiological study and successful ablation of the arrhythmia with complete resolution of symptoms. We discuss the underlying tachycardia mechanism and challenges in the diagnosing and management of this unusual rhythm disorder. © 2015 Elsevier Inc. All rights reserved.
Keywords:
Dual response; Atrio-ventricular; Non-reentrant; Cardiomyopathy
Case presentation A 64-year-old female with history of hypertension, paroxysmal atrial fibrillation (AF) and non-ischemic cardiomyopathy with left ventricular ejection fraction (LVEF) of 35% and congestive heart failure (CHF) presented to our arrhythmia clinic for persistent symptoms of palpitations and dyspnea on exertion. She had undergone implantation of dual chamber implantable cardioverter defibrillator (ICD) 2 years ago for primary prophylaxis of sudden cardiac death. She had no history of ventricular tachycardia prior to ICD implantation and had not received any ICD shock for ventricular arrhythmia. Her presenting electrocardiogram (EKG) showed repetitive burst of irregular tachycardia with narrow but variable QRS width and morphology (Fig. 1). Evaluation of intra-cardiac electrograms from ICD interrogation revealed multiple episodes of non-sustained “ventricular tachycardia” (Fig. 2). What is the underlying arrhythmia mechanism? Commentary This case represents a unique form of arrhythmia where the surface EKG suggested atrial/junctional tachycardia with narrow QRS complexes with intermittent aberrancy in the His–purkinje system. However, intra-cardiac ICD interroga☆
Financial support: None. Conflicts of interests: None. ⁎ 8775 Norwin Ave, Irwin, PA 15642, USA. E-mail address: [email protected]
☆☆
http://dx.doi.org/10.1016/j.jelectrocard.2015.01.013 0022-0736/© 2015 Elsevier Inc. All rights reserved.
tion revealed ventricular events clearly outnumbering atrial counters labeling it as “ventricular tachycardia” (Fig. 2). Differential diagnosis included frequent premature junctional or ventricular complexes, atrio-ventricular (AV) nodal reentrant tachycardia with alternating upper common pathway block, bundle branch reentrant beats or dual AV nodal pathways with double response for every atrial depolarization. Though not present in our case, in a patient with sustained tachycardia, other consideration could be reentrant circuit involving concealed nodofascicular tract with VA block. The patient underwent an electrophysiological study, which revealed sinus rhythm with repetitive two ventricular complexes for single P wave (1:2 AV response). Both ventricular complexes were preceded by His depolarization (arrows, Fig. 3). HV interval of both QRS complexes was similar though second ventricular complex had aberrant conduction resulting in variable QRS morphology. Atrial activation sequence remained unchanged in coronary sinus, His bundle and high right atrial catheters suggesting sinus rhythm and not retrograde conduction. On occasion, the second QRS complex followed immediately after the atrial paced event and therefore triggered ventricular safety pacing (not shown). These findings were consistent with dual AV nodal pathway with conduction over both fast and slow pathways resulting in dual AV response. Intermittent P waves conducted only via the fast pathway with block in the slow pathway (first beat, Fig. 3). Due to intermittent block in the slow pathway, the patient did not have long episodes of “tachycardia” to initiate therapies from ICD. No echo beats were noted. Programmed atrial stimulation was performed with and without isoproterenol
2
S. Arora / Journal of Electrocardiology xx (2015) xxx–xxx
Fig. 1. Surface EKG showing irregular narrow complex tachycardia with intermittent aberrant conduction.
infusion, which did not induce AV nodal reentry. Burst atrial pacing at 600 ms resulted in block in the slow pathway with 1:1 AV conduction. With His depolarization clearly preceding every ventricular complex with similar HV interval, ventricular premature complexes originating from ventricular myocardium were essentially excluded. His extrasystole with retrograde VA block could not be completely excluded but were felt unlikely considering the consistent “linking” with prior ventricular complex. Though there was no left bundle recording catheter to completely exclude bundle branch reentry, the presence of normal HV interval (at baseline and during apparent tachycardia) and relatively normal QRS complex of the “reentrant beat” made it improbable. AV nodal reentrant tachycardia with intermittent upper common pathway block was ruled out based upon atrial activation sequence and lack of VA association. Moreover, no AH delay was seen prior to “tachycardia” initiation in our patient to suggest AVNRT. In patients with sustained narrow complex tachycardia and variable/absent VA conduction, reentrant circuit involving antegrade conduction over His bundle and retrograde conduction over concealed nodo-fascicular pathway is a
diagnostic consideration. In these patients, atrium is not part of the circuit and VA conduction can be completely absent. Also there could be alternating bundle branch block without change in VA (if VA conduction is present) or HH interval [1]. These patients usually have regular sustained tachycardia with fixed H-H interval. Our patient never had any sustained tachycardia and H-H interval was variable. The patient underwent slow pathway modification by radiofrequency ablation performed in the slow pathway region anterior to coronary sinus Os as done traditionally for typical AV nodal reentrant tachycardia. Ablation was performed during atrial pacing since evaluation of retrograde conduction was difficult in the presence of dual AV conduction. At the end of the procedure, no conduction over the slow pathway was noted with only 1:1 AV conduction. On follow-up, her symptoms dramatically improved and no arrhythmia was detected on ICD interrogation. A follow-up echocardiography 6 months later revealed complete normalization of left ventricular ejection fraction to 60% with no heart failure symptoms. Dual AV nodal conduction represents an uncommon form of non-reentrant arrhythmia, first described by Csapo [2] in
Fig. 2. Intra-cardiac electrograms and marker channels from ICD interrogation showing episodes of non-sustained “ventricular tachycardia”.
S. Arora / Journal of Electrocardiology xx (2015) xxx–xxx
3
Fig. 3. Electrophysiology study showing dual ventricular response from single atrial depolarization (arrows) due to simultaneous conduction over both fast and slow pathways.
1979. It is both under- and misdiagnosed in clinical practice and can lead to apparent tachycardia due to 1:2 AV conduction. This may cause disabling symptoms and can potentially lead to reversible tachycardia induced cardiomyopathy [3,4]. Surface EKG may be confusing and can be mistaken for atrial tachycardia/premature beats, ventricular tachycardia, or more commonly atrial fibrillation. QRS morphology may be variable due to either aberrancy in the His–purkinje system or fusion of the subsequent atrial complex (spontaneous or paced) with the preceding ventricular beat conducted over the slow pathway. If sustained, surface EKG reveals narrow complex tachycardia with cycle length alterans due to linking of slow pathway conduction with preceding fast pathway [5]. Occasionally, patients may have alternating 1:1 and 1:2 AV conduction and in patients with implantable electronic devices, right atrial pacing can suppress this arrhythmia by conduction block in the slow pathway [6]. Management of these patients is difficult due to both delay in making the correct diagnosis and poor response with anti-arrhythmic medications. Electrophysiological study can diagnose and can provide long term cure for this unique form of arrhythmia with high success rate. Catheter ablation may be challenging in these cases since conduction over the slow pathway during sinus rhythm can be mistaken as junctional beat without retrograde conduction, which is usually considered as an indication to stop ablation. Also slow pathway may be located on the left atrial aspect at the
region of mitral annulus requiring transseptal puncture for successful ablation [7]. Careful analysis of the EKG and intracardiac electrocardiograms in patients with implantable devices is required to help make the diagnosis. References [1] Hamdan MH, Kalman JM, Lesh MD, Lee RJ, Saxon LA, Dorostkar P, et al. Narrow complex tachycardia with VA block. Diagnostic and therapeutic implications. PACE 1998;21:1196–206. [2] Csapo G. Paroxysmal nonreentrant tachycardias due to simultaneous conduction in dual atrioventricular nodal pathways. Am J Cardiol 1979;43(5):1033–45. [3] Clementy N, Casset-Senon D, Giraudeau C, Cosnay P. Tachycardiomyopathy secondary to nonreentrant atrioventricular nodal tachycardia: recovery after slow pathway ablation. PACE 2007;30:925–8. [4] Anselme F, Frederiks J, Boyle NG, Papageorgiou P, Josephson ME. An unusual cause of tachycardia-induced myopathy. Pacing Clin Electrophysiol 1996;19:115–9. [5] Zimmermann M, Testuz A, Schmutz M, Burri H. Narrow complex tachycardia with cycle length alterans: what is the mechanism? Heart Rhythm 2009;6:1238–9. [6] Wang NC, Shah H, Jain SK, Saba S. Dual atrioventricular nodal nonreentrant tachycardia with alternating 1:1 and 1:2 AV conduction: mechanistic hypotheses and total suppression using right atrial pacing. Ann Noninvasive Electrocardiol 2013;18:199–203. [7] Lockwood D, Nakagawa H, Jackman WM. Electrophysiological characteristics of atrioventricular nodal reentrant tachycardia: implications for reentrant circuits. In: Zipes DP, Jalife J, editors. Cardiac electrophysiology: from cell to bedside. 5th ed. Philadelphia: WB Saunders; 2009. p. 615–46.
ScienceDirect Journal of Electrocardiology xx (2015) xxx – xxx www.jecgonline.com
Incessant “ventricular tachycardia” in a patient with non-ischemic cardiomyopathy. What is the tachycardia mechanism?☆,☆☆ Sandeep Arora, MD, CCDS, FHRS⁎ Cardiac Electrophysiology, Excela Health Westmoreland Hospital, 532 W. Pittsburgh Street, Greensburg, PA, USA
Abstract
We present an uncommon and unique arrhythmia in a patient with non-ischemic cardiomyopathy and dual chamber implantable cardioverter defibrillator presenting with palpitations and dyspnea. While surface electrocardiogram suggested irregular narrow complex tachycardia, evaluation of stored electrograms from implantable cardioverter defibrillator revealed incessant episodes of non-sustained ventricular tachycardia. The patient underwent electrophysiological study and successful ablation of the arrhythmia with complete resolution of symptoms. We discuss the underlying tachycardia mechanism and challenges in the diagnosing and management of this unusual rhythm disorder. © 2015 Elsevier Inc. All rights reserved.
Keywords:
Dual response; Atrio-ventricular; Non-reentrant; Cardiomyopathy
Case presentation A 64-year-old female with history of hypertension, paroxysmal atrial fibrillation (AF) and non-ischemic cardiomyopathy with left ventricular ejection fraction (LVEF) of 35% and congestive heart failure (CHF) presented to our arrhythmia clinic for persistent symptoms of palpitations and dyspnea on exertion. She had undergone implantation of dual chamber implantable cardioverter defibrillator (ICD) 2 years ago for primary prophylaxis of sudden cardiac death. She had no history of ventricular tachycardia prior to ICD implantation and had not received any ICD shock for ventricular arrhythmia. Her presenting electrocardiogram (EKG) showed repetitive burst of irregular tachycardia with narrow but variable QRS width and morphology (Fig. 1). Evaluation of intra-cardiac electrograms from ICD interrogation revealed multiple episodes of non-sustained “ventricular tachycardia” (Fig. 2). What is the underlying arrhythmia mechanism? Commentary This case represents a unique form of arrhythmia where the surface EKG suggested atrial/junctional tachycardia with narrow QRS complexes with intermittent aberrancy in the His–purkinje system. However, intra-cardiac ICD interroga☆
Financial support: None. Conflicts of interests: None. ⁎ 8775 Norwin Ave, Irwin, PA 15642, USA. E-mail address: [email protected]
☆☆
http://dx.doi.org/10.1016/j.jelectrocard.2015.01.013 0022-0736/© 2015 Elsevier Inc. All rights reserved.
tion revealed ventricular events clearly outnumbering atrial counters labeling it as “ventricular tachycardia” (Fig. 2). Differential diagnosis included frequent premature junctional or ventricular complexes, atrio-ventricular (AV) nodal reentrant tachycardia with alternating upper common pathway block, bundle branch reentrant beats or dual AV nodal pathways with double response for every atrial depolarization. Though not present in our case, in a patient with sustained tachycardia, other consideration could be reentrant circuit involving concealed nodofascicular tract with VA block. The patient underwent an electrophysiological study, which revealed sinus rhythm with repetitive two ventricular complexes for single P wave (1:2 AV response). Both ventricular complexes were preceded by His depolarization (arrows, Fig. 3). HV interval of both QRS complexes was similar though second ventricular complex had aberrant conduction resulting in variable QRS morphology. Atrial activation sequence remained unchanged in coronary sinus, His bundle and high right atrial catheters suggesting sinus rhythm and not retrograde conduction. On occasion, the second QRS complex followed immediately after the atrial paced event and therefore triggered ventricular safety pacing (not shown). These findings were consistent with dual AV nodal pathway with conduction over both fast and slow pathways resulting in dual AV response. Intermittent P waves conducted only via the fast pathway with block in the slow pathway (first beat, Fig. 3). Due to intermittent block in the slow pathway, the patient did not have long episodes of “tachycardia” to initiate therapies from ICD. No echo beats were noted. Programmed atrial stimulation was performed with and without isoproterenol
2
S. Arora / Journal of Electrocardiology xx (2015) xxx–xxx
Fig. 1. Surface EKG showing irregular narrow complex tachycardia with intermittent aberrant conduction.
infusion, which did not induce AV nodal reentry. Burst atrial pacing at 600 ms resulted in block in the slow pathway with 1:1 AV conduction. With His depolarization clearly preceding every ventricular complex with similar HV interval, ventricular premature complexes originating from ventricular myocardium were essentially excluded. His extrasystole with retrograde VA block could not be completely excluded but were felt unlikely considering the consistent “linking” with prior ventricular complex. Though there was no left bundle recording catheter to completely exclude bundle branch reentry, the presence of normal HV interval (at baseline and during apparent tachycardia) and relatively normal QRS complex of the “reentrant beat” made it improbable. AV nodal reentrant tachycardia with intermittent upper common pathway block was ruled out based upon atrial activation sequence and lack of VA association. Moreover, no AH delay was seen prior to “tachycardia” initiation in our patient to suggest AVNRT. In patients with sustained narrow complex tachycardia and variable/absent VA conduction, reentrant circuit involving antegrade conduction over His bundle and retrograde conduction over concealed nodo-fascicular pathway is a
diagnostic consideration. In these patients, atrium is not part of the circuit and VA conduction can be completely absent. Also there could be alternating bundle branch block without change in VA (if VA conduction is present) or HH interval [1]. These patients usually have regular sustained tachycardia with fixed H-H interval. Our patient never had any sustained tachycardia and H-H interval was variable. The patient underwent slow pathway modification by radiofrequency ablation performed in the slow pathway region anterior to coronary sinus Os as done traditionally for typical AV nodal reentrant tachycardia. Ablation was performed during atrial pacing since evaluation of retrograde conduction was difficult in the presence of dual AV conduction. At the end of the procedure, no conduction over the slow pathway was noted with only 1:1 AV conduction. On follow-up, her symptoms dramatically improved and no arrhythmia was detected on ICD interrogation. A follow-up echocardiography 6 months later revealed complete normalization of left ventricular ejection fraction to 60% with no heart failure symptoms. Dual AV nodal conduction represents an uncommon form of non-reentrant arrhythmia, first described by Csapo [2] in
Fig. 2. Intra-cardiac electrograms and marker channels from ICD interrogation showing episodes of non-sustained “ventricular tachycardia”.
S. Arora / Journal of Electrocardiology xx (2015) xxx–xxx
3
Fig. 3. Electrophysiology study showing dual ventricular response from single atrial depolarization (arrows) due to simultaneous conduction over both fast and slow pathways.
1979. It is both under- and misdiagnosed in clinical practice and can lead to apparent tachycardia due to 1:2 AV conduction. This may cause disabling symptoms and can potentially lead to reversible tachycardia induced cardiomyopathy [3,4]. Surface EKG may be confusing and can be mistaken for atrial tachycardia/premature beats, ventricular tachycardia, or more commonly atrial fibrillation. QRS morphology may be variable due to either aberrancy in the His–purkinje system or fusion of the subsequent atrial complex (spontaneous or paced) with the preceding ventricular beat conducted over the slow pathway. If sustained, surface EKG reveals narrow complex tachycardia with cycle length alterans due to linking of slow pathway conduction with preceding fast pathway [5]. Occasionally, patients may have alternating 1:1 and 1:2 AV conduction and in patients with implantable electronic devices, right atrial pacing can suppress this arrhythmia by conduction block in the slow pathway [6]. Management of these patients is difficult due to both delay in making the correct diagnosis and poor response with anti-arrhythmic medications. Electrophysiological study can diagnose and can provide long term cure for this unique form of arrhythmia with high success rate. Catheter ablation may be challenging in these cases since conduction over the slow pathway during sinus rhythm can be mistaken as junctional beat without retrograde conduction, which is usually considered as an indication to stop ablation. Also slow pathway may be located on the left atrial aspect at the
region of mitral annulus requiring transseptal puncture for successful ablation [7]. Careful analysis of the EKG and intracardiac electrocardiograms in patients with implantable devices is required to help make the diagnosis. References [1] Hamdan MH, Kalman JM, Lesh MD, Lee RJ, Saxon LA, Dorostkar P, et al. Narrow complex tachycardia with VA block. Diagnostic and therapeutic implications. PACE 1998;21:1196–206. [2] Csapo G. Paroxysmal nonreentrant tachycardias due to simultaneous conduction in dual atrioventricular nodal pathways. Am J Cardiol 1979;43(5):1033–45. [3] Clementy N, Casset-Senon D, Giraudeau C, Cosnay P. Tachycardiomyopathy secondary to nonreentrant atrioventricular nodal tachycardia: recovery after slow pathway ablation. PACE 2007;30:925–8. [4] Anselme F, Frederiks J, Boyle NG, Papageorgiou P, Josephson ME. An unusual cause of tachycardia-induced myopathy. Pacing Clin Electrophysiol 1996;19:115–9. [5] Zimmermann M, Testuz A, Schmutz M, Burri H. Narrow complex tachycardia with cycle length alterans: what is the mechanism? Heart Rhythm 2009;6:1238–9. [6] Wang NC, Shah H, Jain SK, Saba S. Dual atrioventricular nodal nonreentrant tachycardia with alternating 1:1 and 1:2 AV conduction: mechanistic hypotheses and total suppression using right atrial pacing. Ann Noninvasive Electrocardiol 2013;18:199–203. [7] Lockwood D, Nakagawa H, Jackman WM. Electrophysiological characteristics of atrioventricular nodal reentrant tachycardia: implications for reentrant circuits. In: Zipes DP, Jalife J, editors. Cardiac electrophysiology: from cell to bedside. 5th ed. Philadelphia: WB Saunders; 2009. p. 615–46.