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Efficacy and safety of atrioventricular nodal modification for atrioventricular nodal reentrant tachycardia in the pediatric population
Efficacy and safety of atrioventricular nodal modification for atrioventricular nodal reentrant tachycardia in the pediatric population The safety and efficacy of radiofrequency catheter modification of the atrioventricular node for atrioventricular nodal reentrant tachycardia in the pediatric population is described. Twenty-one patients with a mean age of 14.9 + 3.0 years underwent slow-pathway atrioventricular nodal modification with a stepwise anatomic approach. The average cumuletlve fluoroscopy exposure time (22 procedures in 21 patients) inclusive of the electrophysiologic study was 38.1 + 22 minutes. Noninducibility of tachycardia was achieved in all patients with one procedural complication (hemothorax). Durlng a mean follow-up of 15 + 9.08 months, tachycardla recurred in one patient. Patient and family acceptance and satisfaction with the procedure was high. Because of the curative potential of radiofrequency catheter modification with low associated short- and long-term risks, it may be considered as a primary treatment option in pediatric patients with symptomatic atrioventricular nodal reentrant tachycardia. (AM HEART J 1994;128:993-7.)
Anwer Dhala, MD, Siobhan Bremner, BSN, MPH, Sanjay Deshpande, MD, Zalmen Blanck, MD, Andrea Natale, MD, Jasbir Sra, MD, Mohammad Jazayeri, MD, and Masood Akhtar, MD Milwaukee, Wis.
Radiofrequency catheter ablation in the pediatric population has primarily been used in the management of accessory pathway mediated tachycardias and is likely to supersede other modalities as the treatment of choice in this setting.rF 2 Although the majority of paroxysmal supraventricular tachycardias in infancy and early childhood are related to accessory atrioventricular (AV) connections, AV nodal reentrant tachycardia assumes a greater role in its cause with increasing age and may account for a significant proportion of paroxysmal supraventricular tachycardias in the teenage years.3 The initial radiofrequency transcatheter AV nodal modification attempts (primarily in adult patients) targeted the fast pathway of the AV node and were associated with a risk for development of complete heart block of 5 %
to 10 % , thus discouraging its use in the pediatric population. With the advent of slow-pathway ablation/modification, this risk has been considerably reduced. Nevertheless, reported experience with catheter modification of the AV node in the pediatric age group is sparse. Hence it is difficult to define the role of radiofrequency catheter modification of the AV node as a primary treatment modality in these patients. We therefore report our experience in a series of consecutive patients with transcatheter modification of the AV node.
From the Electrophysiology Laboratory, Milwaukee Samaritan Medical Center, and St. Luke’s Medical Wisconsin-Milwaukee Clinical Campus.
4, and syncope in 1. In 18 patients supraventricular tachycardia had been documented electrocardiographically either during visits to the emergency department (12 patients) or during ambulatory monitoring (6). In the remaining patients, although the symptomswere suggestive, rhythm documentation wasunavailable and AV nodal reentrant tachycardia wasdiagnosedduring an electrophys-
Received
for publication
Oct. 4, 1993;
accepted
Dhala, Pkwy.
Health Science Building East, Milwaukee, WI 53215-3660.
Reprint requests: West Kinnickinnic
Anwer River
Copyright @ 1994 0002.8703/94/$3.00
by Mosby-Year + 0 4/l/68140
MD, #470,
Book,
Inc.
Feb.
Heart Institute of Sinai Center, University of 7, 1994. 2901
METHODS Patients.
From June 1990to June 1993,21 consecutive patients with a mean age of 14.9 + 3.65 years (range 5 to 18 years) underwent AV nodal modification for treatment of AV nodal reentrant tachycardia. All patients had symptoms, the worst being uncomfortable palpitations in 6 patients, dizzinessor presyncopein 10, shortness of breath in
903
904
Dhala
et al.
Table I. Clinical dergoing
AVN
American
characteristics modification
of pediatric
No. of patients Age (~4 Mean + SD Range Sex Men Women Duration of symptoms (yr) Mean f SD Range Structural heart disease Worst symptoms Palpitations Dizziness/presyncope Shortness of breath Syncope No. of medications tried 0
patients
un-
14.9 k 3.6 5-18 14 I 2.5 f 2.4 0.25 to 11 None 6 10 4 1 5 11 5
1 2
*Hemothorax,
iologic study. The meanduration of symptomswas2.5 f 2.4
years, range 2 months to 11 years. Of the 16 patients who had previously received ant&rhythmic therapy, catheter ablation wasdone either for inadequate symptom control (12 patients) or side effects (4). The clinical features of these patients are summarized in Table I. Ablative procedure. At the time of the planned catheter ablation procedure, all patients underwent a baseline electrophysiologic evaluation in the drug-free state. The ablative procedure wasperformed with general anesthesia in 18patients and intravenous midazolamhydrochloride in three patients who were older and able to cooperate. Electrode catheters were positioned in the high right atrium acrossthe tricuspid valve for His bundle recordings, coronary sinus, and right
ventricular
apex. The
stimulation
protocol consisted of atrial and ventricular incremental pacing
and extrastimulation.
When
AV nodal
reentrant
tachycardia could not be induced or sustainedat baseline, an infusion
of isoproterenol
at 0.5 pg/min
was started
and
incremented until sustained tachycardia was inducible. The maximum
isoproterenol
dosage required
was 2 rg/min.
In patients requiring isoproterenol administration, all electrophysiologicparameterswereremeasuredboth before and after ablation. Intravenous heparin wasadministered at an initial
dose of 2000 U at the onset of the procedure;
subsequently 1000U were given hourly for the duration of the procedure. Radiofrequency current was delivered between the distal electrode of a 7F deflectable quadripolar catheter with a 4 mm bulbous-tip electrode and an external adhesive patch electrode placed below the right scapula. Slow-pathway modification was performed with a stepwise anatomic approach, as previously described from our laboratory.4 In this approach the part of the tricuspid annulus in relation to the septal leaflet of the tricuspid
valve (baseof the triangle of Koch) is divided into six regions labeled
Pl, P2, Ml,
Table II. Ablation sessiondata and follow-up No. of lesions Mean +- SD Range Successful ablation site PI P2 Ml M2 Fluoroscopic time (mm) Mean -t SD Range Success Redo Complications* Atrioventricular block Length of follow-up (mo) Mean + SD Range
21
M2, Al, and A2, with Pl being
November 1994 Heart Journal
6.8 * 5.3 1-18
36.1 3~ 22 8-85 21(100%)
1 1 0 15 of: 9.06 5-37
1 patient.
Table Ill. Electrophysiologic characteristics before and after ablation
1:l AV 1:l VA
308.9 312.8
Tachycardia cycle length
312.5 f 62.9
AV, Atrioventricular duction.
+ 59.9 + 81.4
conduction;
p Value
After
Before 317.8 318.2
f 61.8 + 122.6
NS NS
-
NS, not signifkmt;
VA, ventricular
con-
most posteroinferior and A2 most anterosuperior (Fig. 1). For slow-pathway ablation, the ablating catheter was initially placed in the Pl location. An annular position was confirmed by electrograms that showed a small atrial deflection and a larger ventricular deflection, with an AV electrogram ratio of 0.1 to 0.5. After application of radiofrequency energy (30 to 35W for 40 to 65 seconds)attempts were made to induce AV nodal reentrant tachycardia. If tachycardia was still inducible, the tip of the catheter was repositioned in an anterior-superior manner progressing from Pl to Ml
location.
After
application
of each lesion,
attempts were made to induce tachycardia. The endpoint of the procedure was noninducibility of the tachycardia. Atrial and ventricular pacing protocols had appeared at 30 minutes, both at baselineand after isoproterenol infusion in all patients,
and 24 to 48 hours after ablation.
Pa-
tients underwent two-dimensionalechocardiography/Doppler studies 24 to 48 hours after the procedure.
RESULTS Twenty patients had inducible sustained AV nodal reentrant tachycardia of the common variety (mean cycle length 312.5 + 62.9 msec; range 240 to 460
Volume 128, Number 5 American Heart Journal
B Septal cusp of Tricuspid Valve
/
1-ricuspid Valve
Fig. 1. Anatomic location of slow pathway ablation sites in right anterior oblique projection (A). Tricuspid annulus along septal leaflet of tricuspid valve extending from coronary sinus ostium to most proximal His bundle recording site is divided into three zones: posterior (P), medial 00, and anterior (A). Each zone is further subdivided into two sites (PI, Ps; Ml, Ms; Al, As). For slow pathway ablation, only the posterior and medial sites are targeted. 8, Location of successful ablation sites in study group.
msec) induced either at baseline (16 patients) or after isoproterenol infusion (5). Two of these patients also had inducible uncommon AV nodal reentrant t,achycardia, and one patient had only the uncommon variety induced. Atrioventricular conduction characteristics before and after ablation are summarized in Table II. The ablation session data are summarized in Table III. The successful ablation sites were Pl in 4 patients, P2 in 9, Ml in 5, and M2 in 4. The mean cumulative fluoroscopy time per patient (22 procedures in 21 patients) was 36.19 + 22 min, range 8 to 85 min, median 30 min. Total number of lesions delivered were 6.8 f 5.3, range 1 to 18, median 6. Noninducibility of AV nodal reentrant tachycardia was obtained in all patients. However, single AV nodal ethos remained inducible in 5 patients with the atria1 extrastimulus technique (Fig. 2). In 4 of these patients, at the same or longer coupling interval of the extrastimulus, the conduction time via the slow pathway as measured by the As to HZ or Hi to Hz interval of the AV nodal echo beat after ablation was longer than that before ablation by 40 to 140 msec, mean 90 msec. In the fifth patient these intervals remained unchanged after ablation. No recurrence of symptoms was seen in any of these patients.
Complications. Immediately after the procedure, one patient had right-sided chest pain and was found to have a hemothorax probably caused by internal jugular vein cannulation. The hemothorax was treated with percutaneous thoracocentesis without need for blood transfusion. No patient had transient or permanent AV block. Follow-up. Twenty of 21 patients had no inducible tachycardia at the predischarge electrophysiologic evaluation. The patient who had inducible AV nodal reentrant tachycardia underwent a second ablation procedure immediately after the electrophysiologic study and has remained without symptoms for > 1 year of follow-up. All patients also underwent a predischarge two-dimensional echocardiogram with Doppler and color flow imaging to assess catheterinduced trauma. No patient had pericardial effusion, intracardiac thrombi, or structural abnormality of the tricuspid valve. Trace tricuspid regurgitation by Doppler color flow imaging was seen in nine patients and mild tricuspid regurgitation in one patient. Preprocedure echocardiograms with color flow imaging were available for comparison in only a few patients. However, the degree of tricuspid regurgitation seen in these patients was believed to be within the range of tricuspid insufficiency seen in normal subjects with
906
Dhulu et al.
American
A
A
A
November 1994 Heart Journal
IL
CSPI csp,+Jn-+q--
csp
HB&@, ACP : ACd e
‘!
-
.
-lqp/..-
H1-HP=
440
Fig. 2. Induction of commonAV nodal reentrant tachycardia, electrogramsat successfulablation site, and persistenceof single AV node echo after radiofrequency modification of AV node. Tracings from top to bottom are surface ECG leads (I, II, V), proximal and distal coronary sinus records (CSP and CSd, His bundle recording (HP), and time line CT). In 6, AC, and ACd are obtained from deflectable mapping catheter capable of delivering radiofrequency energy. A, Programmed atria1 stimulation at drive cycle of 400 msecand premature coupling interval of 240 msecinitiates commonAV nodal reentrant tachycardia. Note HI, Ha interval of tachycardia initiating beat is 360 msec.B, After delivery of radiofrequency energy, AV nodal reentrant tachycardia wasno longer inducible. However, it may be appreciated that when a drive cycle (400msec)and coupling interval (240 msec)similar to that shown in A are used,only oneAV node echo is induced with longer Hi, Hs interval of 460 msec.
this imaging modality.5 All but two of the patients were discharged within 36 hours of admission. Over a mean follow-up of 15 -+ 9.96 months (range 5 to 37 months), recurrence of symptoms was noted in one patient. All other patients remain symptom free, expressed satisfaction with the procedure and improvement in lifestyle, and would recommend the procedure to others with similar problems. DISCUSSION
This study demonstrates modification of the AV node nodal reentrant tachycardia cedure-related complications lation.
the efficacy of catheter in the treatment of AV with a low risk for proin the pediatric popu-
The approaches used for AV nodal modification in this study reflect an evolution in the method of this procedure.6l 7 In the early experience with AV nodal modification, the fast pathway was targeted. Because the catheter access to fast-pathway ablation is close to the region of the compact AV node, this approach is associated with an increased risk of AV block. With a catheter-ablation approach to the AV node, which involved modification of conduction through the slow pathway alone, preservation of antegrade AV nodal conduction was seen in all patients. However, unlike fast-pathway ablation, where abolition of retrograde conduction via the fast pathway is used to determine successful fast pathway ablation, endpoints for slowpathway ablation are less clear. The current under-
Volume American
128,
Number 5 Heart Journal
standing of AV nodal physiologic mechanisms suggests the existence of multiple antegrade and retrograde fast and slow AV nodal pathways8 We have therefore used noninducibility of tachycardia rather than abolition of dual physiologic mechanisms as the endpoint of the procedure. Even inducibility of single AV nodal echoes does not necessarily indicate that the tachycardia circuit has not been interrupted, because this may merely indicate the presence of a slow pathway (other than that used during sustained tachycardia) that is incapable of sustaining tachycardia. Aggressive attempts to ablate these persistent single AV nodal echoes prolongs procedure t,ime and may result in damage to the compact AV node with resultant AV block. During the period of follow-up in the present series, recurrence of tachycardia was seen in only one patient; no patient had heart block. The other major concern is the long-term consequences of radiation exposure. The typical radiation exposure times seen in this study are comparable to those of other radiographic imaging procedures which have been shown to be associated with low risk of development of malignancies.g We have had a reduction in fluoroscopy time with increasing experience, and improvements in x-ray equipment and catheter design are expected to shorten radiation times even further. The severity of symptoms in AV nodal reentrant tachycardia may range from occasional, brief, selflimited episodes where no treatment is warranted to symptoms that are frequent or severe enough to affect their lifestyles and therefore require therapeutic intervention. When such intervention is required, radiofrequency catheter ablation compares favorably with the other available treatment options for AV nodal reentrant tachycardia. Pharmacologic therapy may be associated with noncompliance, inefficacy, intolerable side effects, or with the potential for lifethreatening proarrhythmia.‘O Furthermore, drug effects may be reversed during periods of increased sympathetic tone such as during the physical activity expected in this young population.lr Surgical treatment requires cardiopulmonary bypass with its attendant morbidity. Cost-benefit analysis also appears to favor catheter ablation over the other treatment modalities.r2
In conclusion, radiofrequency catheter ablation of the slow pathway of the AV node can be performed safely in the pediatric population with low risk for immediate and long-term complications; in patients with AV nodal reentrant tachycardia requiring therapeutic intervention, it could be considered as a primary treatment modality. REFERENCES 1. Saul JP, H&e JE, Wang DE, Weber AT, Rhodes LA, Lock JE, Walsh EP. Catheter ablation of accassory atrioventricular pathways in young patients: use of long vascular sheaths, the transseptal approach and a retrograde left posterior parallel approach. J Am Call Cardiol 1993; 21:571-83. 2. Van Hare GF, Lesh MD, Scheinman M, Langberg JJ. Percutaneous radiofrequency catheter ablation for supraventricular arrhythmias in children. J Am CoU Cardiol 1991;17:1613-20. 3. Ko JK, Deal BJ, Strasburger JF, Benson DW, Donovan M. Supraventricular tachycardia mechanisms and their age distribution in pediatric patients. Am J Cardiol 1992;69:1028-32. 4. Huang SK, Bharati S, Graham AR, Lev M, Marcus FI, Ode11 RC. Closed-chest catheter desiccation of the atrioventricular junction using radiofrequency energy: a new method of catheter ablation. d Am Co11 Cardiol 1987;9:349-58. 5. Yoshida K, Yoshikawa J, Shakudo M, et al. Color Doppler evaluation of valvular regurgitation in normal subjects. Circulation 1988,78:840-7. 6. Lee MA, Morady F, Kadish A, Schamp DJ, Chin MKC, Scheinman MM, Griffin JC, Lash MD, Peterson D, Goldberger J, Calkins H, deBuitleir M, Kou WH, Rosenheck S, Sousa J, Langberg JJ. Catheter modification of the atrioventricular junction with radiofrequency energy for control of atrioventricular nodal reentry tachycardia. Circulation 1991;83:82735. 7. Jazayeri MR, Hempe S, Sra J, Dhala A, Blanck Z, Deshpande S, Avitall B, Krum D, Gilbert C, Akhtar M. Selective transcatheter ablation of the fast and slow pathways using radiofrequency energy in patients with atrioventricular nodal reentrant tachycardia. Circulation 1992;85:131828. 8. Jazayeri M, Sra J, Deshpande S, Blanck Z, Dhala A, Krum D, Avitall B, Akhtar M. Electrophysiologic spectrum of atrioventricular nodal behavior in patients with atrioventricular nodal reentrant tachycardia undergoing selective fast or slow pathway ablation. J Cardiovasc Electrophysiology 1993;4:99-111. 9. Lindsay BD, Eichlins JO, Ambos, Cain ME. Radiation exposure to patients and medical personnel during radiofrequency catheter ablation for supraventricular tachycardia. Am J Cardiol 1992;70:218-23. 10. Ruskin JN, McGovern B, Garan H, DiMarco JP, Kelly E. Antiarrhythmic drugs: a possible cause of out-of-hospital cardiac arrest. N Engl J Med 1983;309:1302-6. 11. Akhtar M, Niasi I, Naccarelli G, Tchou P, Rinkenberger R, Dougherty A, Jazayeri M. Role of adrenergic stimulation by isoproterenol in reversal of effects of encainide in supraventricular tachycardia. Am J Cardiol 1988;62:45L. 12. Kalbfleisch SJ, Calkiis H, Langberg J, El-Atassi R, Leon A. Borganelli M, Morady F. Comparison of the cost of radiofrequency catheter modification of the atrioventricular node and medical therapy for drug-refractory atrioventricular node reentrant tachycardia. J Am Co11 Cardiol 1992:19:1583-7.
Anwer Dhala, MD, Siobhan Bremner, BSN, MPH, Sanjay Deshpande, MD, Zalmen Blanck, MD, Andrea Natale, MD, Jasbir Sra, MD, Mohammad Jazayeri, MD, and Masood Akhtar, MD Milwaukee, Wis.
Radiofrequency catheter ablation in the pediatric population has primarily been used in the management of accessory pathway mediated tachycardias and is likely to supersede other modalities as the treatment of choice in this setting.rF 2 Although the majority of paroxysmal supraventricular tachycardias in infancy and early childhood are related to accessory atrioventricular (AV) connections, AV nodal reentrant tachycardia assumes a greater role in its cause with increasing age and may account for a significant proportion of paroxysmal supraventricular tachycardias in the teenage years.3 The initial radiofrequency transcatheter AV nodal modification attempts (primarily in adult patients) targeted the fast pathway of the AV node and were associated with a risk for development of complete heart block of 5 %
to 10 % , thus discouraging its use in the pediatric population. With the advent of slow-pathway ablation/modification, this risk has been considerably reduced. Nevertheless, reported experience with catheter modification of the AV node in the pediatric age group is sparse. Hence it is difficult to define the role of radiofrequency catheter modification of the AV node as a primary treatment modality in these patients. We therefore report our experience in a series of consecutive patients with transcatheter modification of the AV node.
From the Electrophysiology Laboratory, Milwaukee Samaritan Medical Center, and St. Luke’s Medical Wisconsin-Milwaukee Clinical Campus.
4, and syncope in 1. In 18 patients supraventricular tachycardia had been documented electrocardiographically either during visits to the emergency department (12 patients) or during ambulatory monitoring (6). In the remaining patients, although the symptomswere suggestive, rhythm documentation wasunavailable and AV nodal reentrant tachycardia wasdiagnosedduring an electrophys-
Received
for publication
Oct. 4, 1993;
accepted
Dhala, Pkwy.
Health Science Building East, Milwaukee, WI 53215-3660.
Reprint requests: West Kinnickinnic
Anwer River
Copyright @ 1994 0002.8703/94/$3.00
by Mosby-Year + 0 4/l/68140
MD, #470,
Book,
Inc.
Feb.
Heart Institute of Sinai Center, University of 7, 1994. 2901
METHODS Patients.
From June 1990to June 1993,21 consecutive patients with a mean age of 14.9 + 3.65 years (range 5 to 18 years) underwent AV nodal modification for treatment of AV nodal reentrant tachycardia. All patients had symptoms, the worst being uncomfortable palpitations in 6 patients, dizzinessor presyncopein 10, shortness of breath in
903
904
Dhala
et al.
Table I. Clinical dergoing
AVN
American
characteristics modification
of pediatric
No. of patients Age (~4 Mean + SD Range Sex Men Women Duration of symptoms (yr) Mean f SD Range Structural heart disease Worst symptoms Palpitations Dizziness/presyncope Shortness of breath Syncope No. of medications tried 0
patients
un-
14.9 k 3.6 5-18 14 I 2.5 f 2.4 0.25 to 11 None 6 10 4 1 5 11 5
1 2
*Hemothorax,
iologic study. The meanduration of symptomswas2.5 f 2.4
years, range 2 months to 11 years. Of the 16 patients who had previously received ant&rhythmic therapy, catheter ablation wasdone either for inadequate symptom control (12 patients) or side effects (4). The clinical features of these patients are summarized in Table I. Ablative procedure. At the time of the planned catheter ablation procedure, all patients underwent a baseline electrophysiologic evaluation in the drug-free state. The ablative procedure wasperformed with general anesthesia in 18patients and intravenous midazolamhydrochloride in three patients who were older and able to cooperate. Electrode catheters were positioned in the high right atrium acrossthe tricuspid valve for His bundle recordings, coronary sinus, and right
ventricular
apex. The
stimulation
protocol consisted of atrial and ventricular incremental pacing
and extrastimulation.
When
AV nodal
reentrant
tachycardia could not be induced or sustainedat baseline, an infusion
of isoproterenol
at 0.5 pg/min
was started
and
incremented until sustained tachycardia was inducible. The maximum
isoproterenol
dosage required
was 2 rg/min.
In patients requiring isoproterenol administration, all electrophysiologicparameterswereremeasuredboth before and after ablation. Intravenous heparin wasadministered at an initial
dose of 2000 U at the onset of the procedure;
subsequently 1000U were given hourly for the duration of the procedure. Radiofrequency current was delivered between the distal electrode of a 7F deflectable quadripolar catheter with a 4 mm bulbous-tip electrode and an external adhesive patch electrode placed below the right scapula. Slow-pathway modification was performed with a stepwise anatomic approach, as previously described from our laboratory.4 In this approach the part of the tricuspid annulus in relation to the septal leaflet of the tricuspid
valve (baseof the triangle of Koch) is divided into six regions labeled
Pl, P2, Ml,
Table II. Ablation sessiondata and follow-up No. of lesions Mean +- SD Range Successful ablation site PI P2 Ml M2 Fluoroscopic time (mm) Mean -t SD Range Success Redo Complications* Atrioventricular block Length of follow-up (mo) Mean + SD Range
21
M2, Al, and A2, with Pl being
November 1994 Heart Journal
6.8 * 5.3 1-18
36.1 3~ 22 8-85 21(100%)
1 1 0 15 of: 9.06 5-37
1 patient.
Table Ill. Electrophysiologic characteristics before and after ablation
1:l AV 1:l VA
308.9 312.8
Tachycardia cycle length
312.5 f 62.9
AV, Atrioventricular duction.
+ 59.9 + 81.4
conduction;
p Value
After
Before 317.8 318.2
f 61.8 + 122.6
NS NS
-
NS, not signifkmt;
VA, ventricular
con-
most posteroinferior and A2 most anterosuperior (Fig. 1). For slow-pathway ablation, the ablating catheter was initially placed in the Pl location. An annular position was confirmed by electrograms that showed a small atrial deflection and a larger ventricular deflection, with an AV electrogram ratio of 0.1 to 0.5. After application of radiofrequency energy (30 to 35W for 40 to 65 seconds)attempts were made to induce AV nodal reentrant tachycardia. If tachycardia was still inducible, the tip of the catheter was repositioned in an anterior-superior manner progressing from Pl to Ml
location.
After
application
of each lesion,
attempts were made to induce tachycardia. The endpoint of the procedure was noninducibility of the tachycardia. Atrial and ventricular pacing protocols had appeared at 30 minutes, both at baselineand after isoproterenol infusion in all patients,
and 24 to 48 hours after ablation.
Pa-
tients underwent two-dimensionalechocardiography/Doppler studies 24 to 48 hours after the procedure.
RESULTS Twenty patients had inducible sustained AV nodal reentrant tachycardia of the common variety (mean cycle length 312.5 + 62.9 msec; range 240 to 460
Volume 128, Number 5 American Heart Journal
B Septal cusp of Tricuspid Valve
/
1-ricuspid Valve
Fig. 1. Anatomic location of slow pathway ablation sites in right anterior oblique projection (A). Tricuspid annulus along septal leaflet of tricuspid valve extending from coronary sinus ostium to most proximal His bundle recording site is divided into three zones: posterior (P), medial 00, and anterior (A). Each zone is further subdivided into two sites (PI, Ps; Ml, Ms; Al, As). For slow pathway ablation, only the posterior and medial sites are targeted. 8, Location of successful ablation sites in study group.
msec) induced either at baseline (16 patients) or after isoproterenol infusion (5). Two of these patients also had inducible uncommon AV nodal reentrant t,achycardia, and one patient had only the uncommon variety induced. Atrioventricular conduction characteristics before and after ablation are summarized in Table II. The ablation session data are summarized in Table III. The successful ablation sites were Pl in 4 patients, P2 in 9, Ml in 5, and M2 in 4. The mean cumulative fluoroscopy time per patient (22 procedures in 21 patients) was 36.19 + 22 min, range 8 to 85 min, median 30 min. Total number of lesions delivered were 6.8 f 5.3, range 1 to 18, median 6. Noninducibility of AV nodal reentrant tachycardia was obtained in all patients. However, single AV nodal ethos remained inducible in 5 patients with the atria1 extrastimulus technique (Fig. 2). In 4 of these patients, at the same or longer coupling interval of the extrastimulus, the conduction time via the slow pathway as measured by the As to HZ or Hi to Hz interval of the AV nodal echo beat after ablation was longer than that before ablation by 40 to 140 msec, mean 90 msec. In the fifth patient these intervals remained unchanged after ablation. No recurrence of symptoms was seen in any of these patients.
Complications. Immediately after the procedure, one patient had right-sided chest pain and was found to have a hemothorax probably caused by internal jugular vein cannulation. The hemothorax was treated with percutaneous thoracocentesis without need for blood transfusion. No patient had transient or permanent AV block. Follow-up. Twenty of 21 patients had no inducible tachycardia at the predischarge electrophysiologic evaluation. The patient who had inducible AV nodal reentrant tachycardia underwent a second ablation procedure immediately after the electrophysiologic study and has remained without symptoms for > 1 year of follow-up. All patients also underwent a predischarge two-dimensional echocardiogram with Doppler and color flow imaging to assess catheterinduced trauma. No patient had pericardial effusion, intracardiac thrombi, or structural abnormality of the tricuspid valve. Trace tricuspid regurgitation by Doppler color flow imaging was seen in nine patients and mild tricuspid regurgitation in one patient. Preprocedure echocardiograms with color flow imaging were available for comparison in only a few patients. However, the degree of tricuspid regurgitation seen in these patients was believed to be within the range of tricuspid insufficiency seen in normal subjects with
906
Dhulu et al.
American
A
A
A
November 1994 Heart Journal
IL
CSPI csp,+Jn-+q--
csp
HB&@, ACP : ACd e
‘!
-
.
-lqp/..-
H1-HP=
440
Fig. 2. Induction of commonAV nodal reentrant tachycardia, electrogramsat successfulablation site, and persistenceof single AV node echo after radiofrequency modification of AV node. Tracings from top to bottom are surface ECG leads (I, II, V), proximal and distal coronary sinus records (CSP and CSd, His bundle recording (HP), and time line CT). In 6, AC, and ACd are obtained from deflectable mapping catheter capable of delivering radiofrequency energy. A, Programmed atria1 stimulation at drive cycle of 400 msecand premature coupling interval of 240 msecinitiates commonAV nodal reentrant tachycardia. Note HI, Ha interval of tachycardia initiating beat is 360 msec.B, After delivery of radiofrequency energy, AV nodal reentrant tachycardia wasno longer inducible. However, it may be appreciated that when a drive cycle (400msec)and coupling interval (240 msec)similar to that shown in A are used,only oneAV node echo is induced with longer Hi, Hs interval of 460 msec.
this imaging modality.5 All but two of the patients were discharged within 36 hours of admission. Over a mean follow-up of 15 -+ 9.96 months (range 5 to 37 months), recurrence of symptoms was noted in one patient. All other patients remain symptom free, expressed satisfaction with the procedure and improvement in lifestyle, and would recommend the procedure to others with similar problems. DISCUSSION
This study demonstrates modification of the AV node nodal reentrant tachycardia cedure-related complications lation.
the efficacy of catheter in the treatment of AV with a low risk for proin the pediatric popu-
The approaches used for AV nodal modification in this study reflect an evolution in the method of this procedure.6l 7 In the early experience with AV nodal modification, the fast pathway was targeted. Because the catheter access to fast-pathway ablation is close to the region of the compact AV node, this approach is associated with an increased risk of AV block. With a catheter-ablation approach to the AV node, which involved modification of conduction through the slow pathway alone, preservation of antegrade AV nodal conduction was seen in all patients. However, unlike fast-pathway ablation, where abolition of retrograde conduction via the fast pathway is used to determine successful fast pathway ablation, endpoints for slowpathway ablation are less clear. The current under-
Volume American
128,
Number 5 Heart Journal
standing of AV nodal physiologic mechanisms suggests the existence of multiple antegrade and retrograde fast and slow AV nodal pathways8 We have therefore used noninducibility of tachycardia rather than abolition of dual physiologic mechanisms as the endpoint of the procedure. Even inducibility of single AV nodal echoes does not necessarily indicate that the tachycardia circuit has not been interrupted, because this may merely indicate the presence of a slow pathway (other than that used during sustained tachycardia) that is incapable of sustaining tachycardia. Aggressive attempts to ablate these persistent single AV nodal echoes prolongs procedure t,ime and may result in damage to the compact AV node with resultant AV block. During the period of follow-up in the present series, recurrence of tachycardia was seen in only one patient; no patient had heart block. The other major concern is the long-term consequences of radiation exposure. The typical radiation exposure times seen in this study are comparable to those of other radiographic imaging procedures which have been shown to be associated with low risk of development of malignancies.g We have had a reduction in fluoroscopy time with increasing experience, and improvements in x-ray equipment and catheter design are expected to shorten radiation times even further. The severity of symptoms in AV nodal reentrant tachycardia may range from occasional, brief, selflimited episodes where no treatment is warranted to symptoms that are frequent or severe enough to affect their lifestyles and therefore require therapeutic intervention. When such intervention is required, radiofrequency catheter ablation compares favorably with the other available treatment options for AV nodal reentrant tachycardia. Pharmacologic therapy may be associated with noncompliance, inefficacy, intolerable side effects, or with the potential for lifethreatening proarrhythmia.‘O Furthermore, drug effects may be reversed during periods of increased sympathetic tone such as during the physical activity expected in this young population.lr Surgical treatment requires cardiopulmonary bypass with its attendant morbidity. Cost-benefit analysis also appears to favor catheter ablation over the other treatment modalities.r2
In conclusion, radiofrequency catheter ablation of the slow pathway of the AV node can be performed safely in the pediatric population with low risk for immediate and long-term complications; in patients with AV nodal reentrant tachycardia requiring therapeutic intervention, it could be considered as a primary treatment modality. REFERENCES 1. Saul JP, H&e JE, Wang DE, Weber AT, Rhodes LA, Lock JE, Walsh EP. Catheter ablation of accassory atrioventricular pathways in young patients: use of long vascular sheaths, the transseptal approach and a retrograde left posterior parallel approach. J Am Call Cardiol 1993; 21:571-83. 2. Van Hare GF, Lesh MD, Scheinman M, Langberg JJ. Percutaneous radiofrequency catheter ablation for supraventricular arrhythmias in children. J Am CoU Cardiol 1991;17:1613-20. 3. Ko JK, Deal BJ, Strasburger JF, Benson DW, Donovan M. Supraventricular tachycardia mechanisms and their age distribution in pediatric patients. Am J Cardiol 1992;69:1028-32. 4. Huang SK, Bharati S, Graham AR, Lev M, Marcus FI, Ode11 RC. Closed-chest catheter desiccation of the atrioventricular junction using radiofrequency energy: a new method of catheter ablation. d Am Co11 Cardiol 1987;9:349-58. 5. Yoshida K, Yoshikawa J, Shakudo M, et al. Color Doppler evaluation of valvular regurgitation in normal subjects. Circulation 1988,78:840-7. 6. Lee MA, Morady F, Kadish A, Schamp DJ, Chin MKC, Scheinman MM, Griffin JC, Lash MD, Peterson D, Goldberger J, Calkins H, deBuitleir M, Kou WH, Rosenheck S, Sousa J, Langberg JJ. Catheter modification of the atrioventricular junction with radiofrequency energy for control of atrioventricular nodal reentry tachycardia. Circulation 1991;83:82735. 7. Jazayeri MR, Hempe S, Sra J, Dhala A, Blanck Z, Deshpande S, Avitall B, Krum D, Gilbert C, Akhtar M. Selective transcatheter ablation of the fast and slow pathways using radiofrequency energy in patients with atrioventricular nodal reentrant tachycardia. Circulation 1992;85:131828. 8. Jazayeri M, Sra J, Deshpande S, Blanck Z, Dhala A, Krum D, Avitall B, Akhtar M. Electrophysiologic spectrum of atrioventricular nodal behavior in patients with atrioventricular nodal reentrant tachycardia undergoing selective fast or slow pathway ablation. J Cardiovasc Electrophysiology 1993;4:99-111. 9. Lindsay BD, Eichlins JO, Ambos, Cain ME. Radiation exposure to patients and medical personnel during radiofrequency catheter ablation for supraventricular tachycardia. Am J Cardiol 1992;70:218-23. 10. Ruskin JN, McGovern B, Garan H, DiMarco JP, Kelly E. Antiarrhythmic drugs: a possible cause of out-of-hospital cardiac arrest. N Engl J Med 1983;309:1302-6. 11. Akhtar M, Niasi I, Naccarelli G, Tchou P, Rinkenberger R, Dougherty A, Jazayeri M. Role of adrenergic stimulation by isoproterenol in reversal of effects of encainide in supraventricular tachycardia. Am J Cardiol 1988;62:45L. 12. Kalbfleisch SJ, Calkiis H, Langberg J, El-Atassi R, Leon A. Borganelli M, Morady F. Comparison of the cost of radiofrequency catheter modification of the atrioventricular node and medical therapy for drug-refractory atrioventricular node reentrant tachycardia. J Am Co11 Cardiol 1992:19:1583-7.