- Email: [email protected]
Simultaneous antegrade dual AV node conduction initiates AV nodal re-entrant tachycardia (a rare initiation mechanism)
M. Al Mehairi a,⇑, S.A. Al Ghamdi a, K. Dagriri a, A. Al Fagih a a
Department of Adult Cardiology, Prince Sultan Cardiac Center, Riyadh
a
Saudi Arabia
Typical atrioventricular nodal reentrant tachycardia (AVNRT) is the most common paroxysmal supraventricular tachycardia among adults. The concept of dual pathway physiology remains widely accepted, although this physiology likely results from the functional properties of anisotropic tissue within the triangle of Koch, rather than anatomically distinct tracts of conduction. AVNRT is typically induced with anterograde block over the fast pathway and conduction over the slow pathway, with subsequent retrograde conduction over the fast pathway. On rare occasions, anterograde AV node conduction occurs simultaneously through fast and slow pathways resulting in two ventricular beats in response to one atrial beat. We report a case of AVNRT where the tachycardia is always induced by the same mechanism described above. Successful ablation was achieved by slow pathway modification. Ó 2012 King Saud University. Production and hosting by Elsevier B.V. All rights reserved. Keywords: AVNRT, Fast pathway, Slow pathway, Ablation
Case description
A
49-year-old female with a long-standing history of paroxysmal supra-ventricular tachycardia (PSVT), reported several visits to the emergency room due to SVT that is responsive to intravenous adenosine. Her resting 12-leads electrocardiogram (ECG) and the echocardiography study were both normal. All of her biochemical parameters and hemoglobin level were within normal limits. She underwent an electrophysiological study using two diagnostic catheters, 6F quadripolar right ventricular and 6F octapolar coronary sinus (CS) catheters. Concentric retrograde ventriculo-atrial (VA) activation sequence was
noticed at baseline with faster ventricular pacing. Conduction was maintained 1:1 through AVN down to 370 ms, and anterograde atrio-ventricular (AV) conduction was maintained 1:1 through the AVN down to 390 ms. A narrow complex tachycardia consistent with AVNRT at cycle length (CL) of 380 ms was repeatedly induced using short atrial burst pacing from proximal CS catheter at different coupling intervals. The AVNRT was always initiated by simultaneous anterograde conduction over fast and slow pathway resulting in two ventricular responses, A1H1 = 50 ms corresponding to the fast pathway conduction, and A1H2 = 330 ms corresponding to the slow pathway conduction. The second ventricular response was always followed by retrograde atrial beat
Received 1 April 2012; revised 4 July 2012; accepted 22 July 2012. Available online 22 August 2012
⇑ Corresponding author. Tel.: +966 14777714x8765; fax: +966 14778771. E-mail addresses: [email protected] (M. Al Mehairi), ghamdisas@ hotmail.com (S.A. Al Ghamdi), [email protected] (K. Dagriri), [email protected] (A. Al Fagih).
P.O. Box 2925 Riyadh – 11461KSA Tel: +966 1 2520088 ext 40151 Fax: +966 1 2520718 Email: [email protected] URL: www.sha.org.sa
1016–7315 Ó 2012 King Saud University. Production and hosting by Elsevier B.V. All rights reserved. Peer review under responsibility of King Saud University. URL: www.ksu.edu.sa http://dx.doi.org/10.1016/j.jsha.2012.07.005
Production and hosting by Elsevier
CASE REPORT
Simultaneous antegrade dual AV node conduction initiates AV nodal re-entrant tachycardia (a rare initiation mechanism)
36
AL MEHAIRI ET AL SIMULTANEOUS ANTEGRADE DUAL AV NODE CONDUCTION INITIATES AV NODAL RE-ENTRANT TACHYCARDIA
J Saudi Heart Assoc 2013;25:35–37
CASE REPORT Figure 1. Surface ECG with intra-cardiac tracing shows 1:2 phenomenon. Note, burst atrial pacing from proximal CS 7,8 resulted in simultaneous dual AVN conduction occur after the third atrial paced beat followed by initiation of AVNRT at CL of 380 ms. II, aVF, V1 = surface ECG, HIS-P = HIS proximal, HIS-D = HIS distal, CS 7,8, CS 5,6, CS 3,4 = proximal to distal bipole of coronary sinus catheter.
conducted over the fast pathway which initiated and maintained the re-entrant tachycardia (Fig. 1). Slow pathway modification was performed successfully using a 7F large curve, 4 mm tip ablation catheter (Boson scientific). Total ablation time was 130 s at 50 W and temperature of 60 °C. SVT could not be induced further after ablation. Patient did very well afterwards with no documented recurrences at the one-year follow up.
Discussion AVNRT represents the most common paroxysmal supraventricular tachycardia of which typically (slow–fast) is the most common form. During the electrophysiological study (EPS), demonstration of discontinuous refractory periodic curves (Jump) between the fast and slow pathways is considered diagnostic for typical (slow– fast) AVNRT [1]. Interestingly, an uncommon form of typical AVNRT induction has been described in the literature as 1 for 2 phenomena. This simultaneous form of dual AVN anterograde conduction is considered a rare mechanism of AVNRT induction, with incidence of 1.5–4% of patients with AVNRT [2,3]. It is more prevalent after the fifth decade and predominant in females [2]. Two proposed mechanisms for this rare form of
tachycardia induction have been suggested in the literature; the first mechanism is the retrograde block on the slow pathway impeding the activation of the impulse coming down the fast pathway. The second mechanism is a critical slowing of conduction in the slow pathway that allows the full recovery of His bundle excitability from the fast pathway activation [4]. One of the earliest descriptions of simultaneous conduction through both atrioventricular (AV) nodal pathways was by Csapo G. [5]. However, triple AV nodal pathways conduction properties have also been described in the literature as fast, intermediate and slow pathways [6,7]. Interestingly, dual or triple AVN pathways as an SVT substrate does not always imply a reentrant form of SVT. Other rare forms of SVT’s can utilize the same substrate by different activation phenomena and different manifestation of the tachycardia in the surface ECG. An incessant non-reentrant supraventricular tachycardia is an example of such SVT’s that is constantly conducted with 1:2 phenomena. This form has been described in the literature, in which the R–R interval might be irregular and mistakenly labeled as atrial fibrillation in case the dual response is intermittent [8]. Two basic requirements were explained as a mechanism for this form of SVT that utilizes dual AVN pathways as
AL MEHAIRI ET AL SIMULTANEOUS ANTEGRADE DUAL AV NODE CONDUCTION INITIATES AV NODAL RE-ENTRANT TACHYCARDIA
37
CASE REPORT
J Saudi Heart Assoc 2013;25:35–37
Figure 2. Ladder diagram with intracardiac tracing indicates 1:2 atrioventricular conduction in the presence of dual atrioventricular nodal pathways and initiation of supraventricular tachycardia. A = atrium, dAVN = AV node with dual conduction properties, V = ventricle, HISP = HIS proximal, HIS-D = HIS distal, CS 7,8 = proximal bipole of coronary sinus catheter, A = Atrial, H = HI, V = Ventricular, S1 = Atrial stimulation.
a substrate; the first is the absence of retrograde ventriculoatrial conduction via the fast pathway as well as the slow pathway. The second one is the time difference between the anterograde conduction over the slow pathway and the fast pathway has to be longer than the effective refractory period of the infra-nodal conduction system [9]. Slow pathway modification remains the treatment of choice in such cases [10]. Atrial bigeminy on the surface electrogram can also mimic this phenomenon in case the PAC superimposes the T wave mimicking a simultaneous ventricular activation from the preceding beat. Careful attention to an extreme Wenckebach phenomena during atrial pacing during EPS is required to avoid misinterpretation of 1 for 2 activation phenomena. AVNRT is commonly induced with anterograde block over the fast pathway and conduction over the slow pathway, with subsequent retrograde conduction over the fast pathway. Our case, represents dual AVN physiology with 1:2 phenomena (Fig. 2), in which atrial burst pacing repeatedly induced AVNRT in the same manner with different coupling intervals. Simultaneous conduction over both slow and fast pathway was repeatedly noticed during the tachycardia induction. Slow pathway modification has successfully prevented the re-induction of the tachycardia. In conclusion, despite that the concept of 1 for 2 phenomena of AVNRT induction is rare, it remains diagnostic for typical AVNRT (slow–fast) that can be sufficiently treated by slow pathway modification.
References [1] Demosthenes G, Katritsis A, John Camm. Classification and differential diagnosis of atrioventricular nodal reentrant tachycardia. Europace 2006;8:29–36. [2] Tomasi C, De Ponti R, Tritto M, et al. Simultaneous dual fast and slow pathway conduction upon induction of typical atrioventricular nodal reentrant tachycardia: electrophysiologic characteristics in a series of patients. J Cardiovasc Electrophysiol 2005;16(6):594–600. [3] Kertesz NJ, Fogel RI, Prystowsky EN, et al. Mechanism of induction of atrioventricular node reentry by simultaneous anterograde conduction over the fast and slow pathways. J Cardiovasc Electrophysiol 2005;16(3):251–5. [4] Calò L, Riccardi R, Scaglione M, et al. Unusual induction of slow–fast atrioventricular nodal reentrant tachycardia. Report of two cases. G Ital Cardiol 1999;29(11):1318–22. [5] Csapo G. Paroxysmal nonreentrant tachycardias due to simultaneous conduction in dual atrioventricular nodal pathways. Am J Cardiol 1979;43:1033–45. [6] Yokoshiki H, Sasaki K, Shimokawa J, et al. Nonreentrant atrioventricular nodal tachycardia due to triple nodal pathways manifested by radiofrequency ablation at coronary sinus ostium. J Electrocardiol 2006;39:395–9. [7] Arena G, Bongiorni MG, Soldati E, Gherarducci G, Mariani M. Incessant nonreentrant atrioventricular nodal tachycardia due to multiple nodal pathways treated by radiofrequency ablation of the slow pathways. J Cardiovasc Electrophysiol 1999;10:1636–42. [8] Dixit S, Callans DJ, Gerstenfeld EP, Marchlinski FE. Reentrant and nonreentrant forms of atrio-ventricular nodal tachycardia mimicking atrial fibrillation. J Cardiovasc Electrophysiol 2006;17:312–6. [9] Neumann T et al. Double ventricular excitation in dual atrioventricular node conduction physiology: catheter ablation of the slow conduction pathway of the dual atrioventricular node. Z Kardiol 2000;89:1014–8. [10] Francis Johnson, Krishnan MN. Dual ventricular response or 1:2 atrioventricular conduction in dual atrioventricular nodal physiology. Indian Pacing Electrophysiol J 2008;8(2):77–9.
Department of Adult Cardiology, Prince Sultan Cardiac Center, Riyadh
a
Saudi Arabia
Typical atrioventricular nodal reentrant tachycardia (AVNRT) is the most common paroxysmal supraventricular tachycardia among adults. The concept of dual pathway physiology remains widely accepted, although this physiology likely results from the functional properties of anisotropic tissue within the triangle of Koch, rather than anatomically distinct tracts of conduction. AVNRT is typically induced with anterograde block over the fast pathway and conduction over the slow pathway, with subsequent retrograde conduction over the fast pathway. On rare occasions, anterograde AV node conduction occurs simultaneously through fast and slow pathways resulting in two ventricular beats in response to one atrial beat. We report a case of AVNRT where the tachycardia is always induced by the same mechanism described above. Successful ablation was achieved by slow pathway modification. Ó 2012 King Saud University. Production and hosting by Elsevier B.V. All rights reserved. Keywords: AVNRT, Fast pathway, Slow pathway, Ablation
Case description
A
49-year-old female with a long-standing history of paroxysmal supra-ventricular tachycardia (PSVT), reported several visits to the emergency room due to SVT that is responsive to intravenous adenosine. Her resting 12-leads electrocardiogram (ECG) and the echocardiography study were both normal. All of her biochemical parameters and hemoglobin level were within normal limits. She underwent an electrophysiological study using two diagnostic catheters, 6F quadripolar right ventricular and 6F octapolar coronary sinus (CS) catheters. Concentric retrograde ventriculo-atrial (VA) activation sequence was
noticed at baseline with faster ventricular pacing. Conduction was maintained 1:1 through AVN down to 370 ms, and anterograde atrio-ventricular (AV) conduction was maintained 1:1 through the AVN down to 390 ms. A narrow complex tachycardia consistent with AVNRT at cycle length (CL) of 380 ms was repeatedly induced using short atrial burst pacing from proximal CS catheter at different coupling intervals. The AVNRT was always initiated by simultaneous anterograde conduction over fast and slow pathway resulting in two ventricular responses, A1H1 = 50 ms corresponding to the fast pathway conduction, and A1H2 = 330 ms corresponding to the slow pathway conduction. The second ventricular response was always followed by retrograde atrial beat
Received 1 April 2012; revised 4 July 2012; accepted 22 July 2012. Available online 22 August 2012
⇑ Corresponding author. Tel.: +966 14777714x8765; fax: +966 14778771. E-mail addresses: [email protected] (M. Al Mehairi), ghamdisas@ hotmail.com (S.A. Al Ghamdi), [email protected] (K. Dagriri), [email protected] (A. Al Fagih).
P.O. Box 2925 Riyadh – 11461KSA Tel: +966 1 2520088 ext 40151 Fax: +966 1 2520718 Email: [email protected] URL: www.sha.org.sa
1016–7315 Ó 2012 King Saud University. Production and hosting by Elsevier B.V. All rights reserved. Peer review under responsibility of King Saud University. URL: www.ksu.edu.sa http://dx.doi.org/10.1016/j.jsha.2012.07.005
Production and hosting by Elsevier
CASE REPORT
Simultaneous antegrade dual AV node conduction initiates AV nodal re-entrant tachycardia (a rare initiation mechanism)
36
AL MEHAIRI ET AL SIMULTANEOUS ANTEGRADE DUAL AV NODE CONDUCTION INITIATES AV NODAL RE-ENTRANT TACHYCARDIA
J Saudi Heart Assoc 2013;25:35–37
CASE REPORT Figure 1. Surface ECG with intra-cardiac tracing shows 1:2 phenomenon. Note, burst atrial pacing from proximal CS 7,8 resulted in simultaneous dual AVN conduction occur after the third atrial paced beat followed by initiation of AVNRT at CL of 380 ms. II, aVF, V1 = surface ECG, HIS-P = HIS proximal, HIS-D = HIS distal, CS 7,8, CS 5,6, CS 3,4 = proximal to distal bipole of coronary sinus catheter.
conducted over the fast pathway which initiated and maintained the re-entrant tachycardia (Fig. 1). Slow pathway modification was performed successfully using a 7F large curve, 4 mm tip ablation catheter (Boson scientific). Total ablation time was 130 s at 50 W and temperature of 60 °C. SVT could not be induced further after ablation. Patient did very well afterwards with no documented recurrences at the one-year follow up.
Discussion AVNRT represents the most common paroxysmal supraventricular tachycardia of which typically (slow–fast) is the most common form. During the electrophysiological study (EPS), demonstration of discontinuous refractory periodic curves (Jump) between the fast and slow pathways is considered diagnostic for typical (slow– fast) AVNRT [1]. Interestingly, an uncommon form of typical AVNRT induction has been described in the literature as 1 for 2 phenomena. This simultaneous form of dual AVN anterograde conduction is considered a rare mechanism of AVNRT induction, with incidence of 1.5–4% of patients with AVNRT [2,3]. It is more prevalent after the fifth decade and predominant in females [2]. Two proposed mechanisms for this rare form of
tachycardia induction have been suggested in the literature; the first mechanism is the retrograde block on the slow pathway impeding the activation of the impulse coming down the fast pathway. The second mechanism is a critical slowing of conduction in the slow pathway that allows the full recovery of His bundle excitability from the fast pathway activation [4]. One of the earliest descriptions of simultaneous conduction through both atrioventricular (AV) nodal pathways was by Csapo G. [5]. However, triple AV nodal pathways conduction properties have also been described in the literature as fast, intermediate and slow pathways [6,7]. Interestingly, dual or triple AVN pathways as an SVT substrate does not always imply a reentrant form of SVT. Other rare forms of SVT’s can utilize the same substrate by different activation phenomena and different manifestation of the tachycardia in the surface ECG. An incessant non-reentrant supraventricular tachycardia is an example of such SVT’s that is constantly conducted with 1:2 phenomena. This form has been described in the literature, in which the R–R interval might be irregular and mistakenly labeled as atrial fibrillation in case the dual response is intermittent [8]. Two basic requirements were explained as a mechanism for this form of SVT that utilizes dual AVN pathways as
AL MEHAIRI ET AL SIMULTANEOUS ANTEGRADE DUAL AV NODE CONDUCTION INITIATES AV NODAL RE-ENTRANT TACHYCARDIA
37
CASE REPORT
J Saudi Heart Assoc 2013;25:35–37
Figure 2. Ladder diagram with intracardiac tracing indicates 1:2 atrioventricular conduction in the presence of dual atrioventricular nodal pathways and initiation of supraventricular tachycardia. A = atrium, dAVN = AV node with dual conduction properties, V = ventricle, HISP = HIS proximal, HIS-D = HIS distal, CS 7,8 = proximal bipole of coronary sinus catheter, A = Atrial, H = HI, V = Ventricular, S1 = Atrial stimulation.
a substrate; the first is the absence of retrograde ventriculoatrial conduction via the fast pathway as well as the slow pathway. The second one is the time difference between the anterograde conduction over the slow pathway and the fast pathway has to be longer than the effective refractory period of the infra-nodal conduction system [9]. Slow pathway modification remains the treatment of choice in such cases [10]. Atrial bigeminy on the surface electrogram can also mimic this phenomenon in case the PAC superimposes the T wave mimicking a simultaneous ventricular activation from the preceding beat. Careful attention to an extreme Wenckebach phenomena during atrial pacing during EPS is required to avoid misinterpretation of 1 for 2 activation phenomena. AVNRT is commonly induced with anterograde block over the fast pathway and conduction over the slow pathway, with subsequent retrograde conduction over the fast pathway. Our case, represents dual AVN physiology with 1:2 phenomena (Fig. 2), in which atrial burst pacing repeatedly induced AVNRT in the same manner with different coupling intervals. Simultaneous conduction over both slow and fast pathway was repeatedly noticed during the tachycardia induction. Slow pathway modification has successfully prevented the re-induction of the tachycardia. In conclusion, despite that the concept of 1 for 2 phenomena of AVNRT induction is rare, it remains diagnostic for typical AVNRT (slow–fast) that can be sufficiently treated by slow pathway modification.
References [1] Demosthenes G, Katritsis A, John Camm. Classification and differential diagnosis of atrioventricular nodal reentrant tachycardia. Europace 2006;8:29–36. [2] Tomasi C, De Ponti R, Tritto M, et al. Simultaneous dual fast and slow pathway conduction upon induction of typical atrioventricular nodal reentrant tachycardia: electrophysiologic characteristics in a series of patients. J Cardiovasc Electrophysiol 2005;16(6):594–600. [3] Kertesz NJ, Fogel RI, Prystowsky EN, et al. Mechanism of induction of atrioventricular node reentry by simultaneous anterograde conduction over the fast and slow pathways. J Cardiovasc Electrophysiol 2005;16(3):251–5. [4] Calò L, Riccardi R, Scaglione M, et al. Unusual induction of slow–fast atrioventricular nodal reentrant tachycardia. Report of two cases. G Ital Cardiol 1999;29(11):1318–22. [5] Csapo G. Paroxysmal nonreentrant tachycardias due to simultaneous conduction in dual atrioventricular nodal pathways. Am J Cardiol 1979;43:1033–45. [6] Yokoshiki H, Sasaki K, Shimokawa J, et al. Nonreentrant atrioventricular nodal tachycardia due to triple nodal pathways manifested by radiofrequency ablation at coronary sinus ostium. J Electrocardiol 2006;39:395–9. [7] Arena G, Bongiorni MG, Soldati E, Gherarducci G, Mariani M. Incessant nonreentrant atrioventricular nodal tachycardia due to multiple nodal pathways treated by radiofrequency ablation of the slow pathways. J Cardiovasc Electrophysiol 1999;10:1636–42. [8] Dixit S, Callans DJ, Gerstenfeld EP, Marchlinski FE. Reentrant and nonreentrant forms of atrio-ventricular nodal tachycardia mimicking atrial fibrillation. J Cardiovasc Electrophysiol 2006;17:312–6. [9] Neumann T et al. Double ventricular excitation in dual atrioventricular node conduction physiology: catheter ablation of the slow conduction pathway of the dual atrioventricular node. Z Kardiol 2000;89:1014–8. [10] Francis Johnson, Krishnan MN. Dual ventricular response or 1:2 atrioventricular conduction in dual atrioventricular nodal physiology. Indian Pacing Electrophysiol J 2008;8(2):77–9.