- Email: [email protected]
Termination of atrial reentrant tachycardias by using transesophageal atrial pacing
Journal of Electrocardiology Vol. 35 Supplement 2002
Termination of Atrial Reentrant Tachycardias By Using Transesophageal Atrial Pacing
Konrad Brockmeier, MD, Herbert E. Ulmer, MD, and Gabriele Hessling, MD
Abstract: Atrial reentrant tachycardia (ART) is not an uncommon complication in patients after surgery for congenital heart defects, particularly after extensive atrial procedures with sutures lines or baffeling maneuvers. Primary atrial flutter is a rare dysrhythmia in newborns. Two issues of ART or atrial flutter can be addressed by the esophageal approach: First, ART (often with 2:1 A-V conduction) may be difficult to detect on the surface ECG as the P waves usually do not show the typical flutter morphology or are hidden in the T wave. Recordings over the esophageal lead clearly determine the underlying rhythm. Second, termination of ART by pacing the atria can easily be performed by using an esophageal electrode. We performed 62 conversions of ART in 39 pts. (median age 12.5 years), among them 7 newborns with typical atrial flutter. The pacing algorithm started with 4 extrastimuli and pacing intervals 20 msec shorter than the atrial cycle length of tachycardia. Conversion was achieved in 50/62 (81%) cases; in 12 of 62 (19%) cases conversion was performed externally as the transesophageal approach was insufficient to restore sinus rhythm. Intravenous infusion of amiodarone prior to atrial pacing seems to be helpful in some patients for termination of ART. We recommend transesophageal atrial pacing as a first step of acute management of atrial flutter and other forms of ART in neonates, infants, and children because it is a minimal invasive procedure with high success rates. Key words: Atrial flutter, atrial reentrant tachycardia, Transesophageal atrial pacing, intervention, noninvasive electrophysiology.
Atrial reentrant tachycardias (ART) are potentially dangerous depending on atrial cycle length
and conduction to the ventricles (1). Even short bursts of tachycardia with fast ventricular rates, particularly in the presence of underlying heart disease, may create life-threatening hazards and therefore should be treated (2). In pediatric cardiology— contrasting to adult cardiology—ARTs are typically seen in patients after surgery for congenital heart defects and often related to scars, particularly after atrial procedures with atriotomy, large sutures lines, or baffeling maneuvers (3). Primary atrial flutter is a rare find-
From the Department of Pediatric Cardiology, University of Heidelberg, Heidelberg, Germany. Reprint requests: Konrad Brockmeier, MD, Department of Pedatric Cardiology, University Children’s Hospital of Heidelberg, INF 153, 69120 Heidelberg, Germany; e-mail: [email protected]. Copyright 2002, Elsevier Science (USA). All rights reserved. 0022-0736/02/350S-0023$35.00/0 doi:10.1054/jelc.2002.37174
159
160 Journal of Electrocardiology Vol. 35 Supplement 2002 ing and typically seen in otherwise healthy newborns (4). Some patients with scar related ART might present with typical atrial flutter as well as other forms of atrial reentrant tachycardias. The success rate of acute termination of ART by antiarrhythmic medication is low. Therefore, electroconversion of these tachycardias plays an important role in the acute management. Different approaches of electrical conversion are distinguished: 1) electroconversion by using an external defibrillator, 2) atrial overdrive pacing by using perioperatively placed epicardial pacing leads, and 3) transesophageal atrial pacing. Benson et al. (5) proposed an algorithm for ART termination using transesophageal leads. We present our data of acute ART management by the transesophageal approach using this algorithm.
Patients and Methods We performed 62 ART conversions in 39 patients. Patient age ranged from 1 day to 33.5 years (median 12.5 years). There were 7 newborns and one 6-year-old boy with primary typical (counterclockwise) atrial flutter. ART was seen postoperatively in 31 patients after palliation or correction of congenital heart defects. Patients had their first ART episode 1 day to 19 years after surgery (median 2 years); onset of tachycardia within the first 4 weeks postoperatively was found in 7 patients. Tachycardias were detected by fetal monitoring (ultrasound/echocardiogram), postoperative monitoring, subjective symptoms, or on routine postoperative ECG during follow-up. The heart defects and surgical procedures were atrial baffle operation (Mustard/Senning) for DTransposition of the Great Arteries (n⫽3), Fontan procedure and modifications for complex (functionally univentricular) congenital defects (n⫽4), or surgery for atrio-ventricular septal defects (n⫽5), Tetralogy of Fallot / double outlet right ventricle (n⫽4), ventricular septal defects (n⫽4), atrial septal defects (n⫽3), aortic stenosis (⫽2), pulmonary valve stenosis (n⫽3), Ebstein‘s anomaly of the tricuspid valve (n⫽1), congenitally corrected transposition of the great arteries (n⫽1), and mitral insufficiency (n⫽1). Transesophageal electrocardiogram (ECG) recording and atrial pacing was performed in the facilities of the catheter/electrophysiology laboratory or the intensive care unit, depending on the severity of clinical impairment. A DC cardioverter/ defibrillator and the usual equipment for resuscita-
tion were available. Age-dependent fasting conditions prior to the procedure were insured whenever the clinical presentation of the patient allowed an elective procedure. Moderate sedation and analgesia was performed stepwise with phenobarbital, midazolam, and morphin to avoid discomfort and anxiety. Additionally, local anesthesia of the mouth was applied. After placement of standard 12-lead surface electrodes, a flexible quadripolar transesophageal electrophysiology catheter (5F, 6F, or 7F Fiab) was introduced through the nares and positioned in the esophagus at the level of the left atrium. Electrode position was controlled without fluoroscopy using standardized insertion depth values according to body height and yielded maximal amplitude of the atrial signal on the display (5). For signal recording and filtering, a Cardioscript CU 12 (Schwarzer Medizintechnik, Germany) was used. Bipolar transesophageal ECG recording was performed using the proximal electrodes, and transesophageal pacing was performed using the distal electrodes respectively. Pacing was performed with a Medtronic 5328 stimulator (Medtronic Inst., Minneapolis, MN) using an impulse duration 9.9 ms and a stimulation amplitude of 24 to 28 mA. The pacing algorithm for termination of ART was performed as described: 1. Determination of the atrial cycle length (ACL) of tachycardia 2. Stimulation with 4 stimuli (ES) at an interval 20 ms shorter than ACL 3. Decremental steps of 10 ms down to a 120 ms interval 4. Increase number of ES by 2 up to 10 ES 5. Increase output from 24 mA to 28 mA Statistical Analysis All data were presented using ranges and medians. Comparison of group differences were made using one-way ANOVA test. A value of P ⬍.05 was considered statistically significant.
Results Overall, 50 of 62 (81%) tachycardia episodes were terminated successfully by transesophageal atrial pacing without complications. All episodes of primary typical atrial flutter were converted to sinus rhythm using the transesophageal approach. Spontaneous reinitiation of atrial flutter occurred in
Termination of Atrial Reentrant Tachycardias •
one of the newborns and was again successfully converted. Among the postoperative atrial reentrant tachycardias, typical atrial flutter on ECG was documented in 21 cases; 4 patients postoperatively showed both typical atrial flutter and atrial reentrant tachycardia with a different P-wave morphology. Atrial cycle length of tachycardia (ACL) ranged between 160 and 380 ms (median 235 ms) with 2:1 AV-conduction in 50 of 62 (81%) of the episodes. Various degrees of AV-conduction (1:1, 2:1, 3:1, 4:1) were found in 12 of 62 (19%). In 12 of 62 (19%) episodes, conversion was performed using an external cardioverter/defibrillator, as termination of ART could not be achieved by the transesophageal approach. The typical pacing protocol leading to conversion had 4 ES with 150 ms interval [median of 4 ES (max. 10 ES) with median of 150 ms (min. 120 ms)]. There was no statistical difference in atrial cycle length and the effective stimulation protocol between newborns with typical atrial flutter and patients with postoperative scar related ART. External DC conversion was performed under sedation with additional ketamin infusion when the transesophageal approach had failed to terminate ART. In 5 patients with ART, tachycardia could not be terminated immediately using the pacing algorithm. In 2 of these 5 patients, the algorithm was repeated after administration of 5 mg/kg intravenously amiodarone over 30 minutes and resulted in conversion of tachycardia. Another 2 of these patients had intermittent atrial fibrillation with subsequent reorganization to a macro-reentrant circuit of slower cycle length after pacing. After administration of amiodarone tachycardia could also be terminated by atrial pacing. In 1 patient with sustained atrial fibrillation induced by transesophageal pacing intravenous amiodarone did not change the rhythm. In this patient, external DC conversion was then performed which resulted in normal sinus rhythm. External DC conversion was also used in those episodes, with unsuccessful transesophageal pacing. However, the reason for not being effective in terminating ART by transesophageal pacing in 19% of the presented episodes could not be decided definitively. In some episodes, insufficient capture might have been responsible. No clear correlation was seen concerning age of the patient, size of the atria or type of underlying congenital heart defect.
Discussion The electrocardiogram of incisional or scar related atrial reentrant tachycardaias can sometimes be
Brockmeier et al. 161
rather challenging (Fig. 1). A sawtooth pattern on the ECG is the clue to differentiate typical atrial flutter from other forms of atrial reentrant tachycardias; this might be facilitated by increasing atrioventricular conduction and “demasking” P-waves by vagal maneuvers or intravenous injection of adenosine. Another hint to identify atrial macroreentrant tachycardia in the absence of typical flutter waves is an often inappropriately high heart rate in conjunction with an abnormal P-wave pattern with measurable periodic strength, possible changes of 2:1 to 3:1 AV conduction and T-wave morphology changes due to hidden P waves. Here the esophageal recording of atrial and ventricular depolarization is extremely useful in helping to clarify the underlying rhythm and offers the possibility of acute treatment (Fig. 2). New insights from invasive electrophysiologic studies and mapping techniques will offer a much clearer differentiation of ART as outlined in a recent paper from the Joint Expert Group from the Working Group of Arrhythmias of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology (6). In pediatric cardiology, ART is not an uncommon problem in the follow-up of surgically corrected or palliated children and young adults with congenital heart disease. In fact, atrial tachycardias other than typical atrial flutter, which are often due to scars and sutures in the right atrium, are the predominant form of ART seen in the postoperative pediatric population. These reentrant tachycardias are often complex in their spacial orientation and sometimes present with various forms of reentrant circuits—including typical atrial flutter (2). In 4 patients of our series of postoperative ART both typical flutter and other forms of atrial reentrant tachycardia with various cycle lengths occurred. Typical atrial flutter without congenital heart disease is rare in children, probably due to the smaller volume of the atria in comparison to adults. In our series (excluding newborn atrial flutter as a different entity with an excellent long-term prognosis) only one older patient showed typical atrial flutter without underlying congenital heart disease. After open-heart surgery the right atrium can enlarge as seen in patients after the Fontan operation, which predisposes to atrial macroreentrant tachycardias. Other predisposing factors include discontinuities of the atrial surface as a result of surgery, focal scarring, atrial fibrosis related to abnormal atrial wall stress and changes in atrial refractoriness associated with sinus node dysfunction and prolonged atrial activation (7).
162 Journal of Electrocardiology Vol. 35 Supplement 2002
Fig. 1. Example of an atrial reentrant tachycardia (with 2:1 AV conduction) in a patient after operation of an atrial septal defect with large residual right atrial and right ventricular cavities. The upper 3 rows represent a subset of the recorded surface ECG with a heart rate of 140 beats per minute. The last row represents a recording from the esophagus. In the esophageal lead one can clearly distinguish 2 types of signals with a 2:1 occurrence, one of them at the time of the QRS in the surface leads, one at the time of the P-wave signal in the third row, and one at T-wave onset-invisible in the surface ECG.
The mechanism of terminating ART by transesophageal atrial pacing is rather similar to the classical overdrive pacing approach. Termination relies on the ability of the pacing impulses to penetrate the excitable gap within the reentrant circuit and capture, thus achieving a critical pacing rate and duration (8). The duration of rapid atrial pacing in the presented approach, however, is less aggressive than the classical approach with pacing times of up to 30 seconds. Usually 4-6 extrastimuli are sufficient to terminate tachycardia thereby causing less discomfort and pain. External DC conversion should be used as a therapeutic approach for termination of ART only when the esophageal approach fails or the patients is critically ill and requires immediate intervention. The use of an intravenous infusion of amiodarone prior to atrial pacing seems to be helpful in some patients for termination of ART; controlled data are yet lacking. The low median of effective atrial pacing intervals (150 ms) for ART termination seen in this investigation is explained by the typical conditions of the pediatric population with short atrial tachycardia cycle lengths. Using rapid atrial pacing in children is usually not a problem; if atrial fibrillation is induced, this is rarely sustained. Performed in the
appropriate environment, transesophageal pacing for termination of atrial flutter is a safe procedure in the hands of pediatric electrophysiologists. Long-term therapeutic aspects of recurrent ART in the pediatric population include revision of possible underlying morphological problems, which might be ameliorated by reoperation or intervention. Furthermore, oral antiarrhythmic medication is useful in some patients, but has its drawback with unwanted side effects and limited long-term success. Invasive radiofrequency catheter ablation techniques, recently introduced in pediatric cardiology, provide hope and the possibility for a definitive cure of ART in patients of this population (2). We—as others— think that transesophageal atrial pacing is a safe tool for the acute termination of ART with high success rates in the pediatric age group.
Limitations Patients with typical atrial flutter and postoperative atrial reentrant tachycardias form quite a heterogenous group of patients, although much has been learned about these forms of tachycardias in
Termination of Atrial Reentrant Tachycardias •
Brockmeier et al. 163
Fig. 2. Termination of the atrial tachycardia (in the same patient as in Figure 1) with 4 extrastimuli of 160 ms interval. Shortly thereafter normal sinus rhythm resulted.
pediatric patients by intracardiac electrophysiologic mapping studies (9). Despite methodological problems regarding this heterogeneity, a study about the acute management of both entities using the same transesophageal approach seems to be of clinical use. The main issue of this presentation was to show the feasibility of this minimal invasive approach for children of all ages with atrial reentrant tachycardias showing that short atrial pacing intervals are highly effective in acutely terminating these tachycardias.
References 1. Goodacre S, Irons R: Atrial arrhythmias. BMJ 324: 594, 2002 2. van Hare GF: Intra-atrial reentry tachycardia in pediatric patients. Prog Ped Cardiol 13:41, 2001 3. Saul P: Transesophageal atrial recording and pacing, in Walsh EP, Saul P, Triedman JK, (eds): Cardiac arrhythmias in children and young adults with congenital heart disease. Baltimore,MD, Lippincott Williams & Wilkins, 2001 p 33 4. Campbell RWF: Supraventricular tachycardia. In
5. 6. 7.
8.
9.
10.
Wren C, Campbell RWF, (eds): Paediatric cardiac arrhythmias. Oxford University Press 1996, p 94-126 Benson DW: Transesophageal pacing for conversion of atrial flutter. Pract Cardiol 16:1990 Benson DW: Transesophageal electrocardiography and cardiac pacing: State of the art. Circulation 75:86, 1987 Saoudi N, Cosio F, Waldo A, et al: Classification of atrial flutter and regular atrial tachycardiac according to electrophysiologic mechanism and anatomic bases: A statement of the joint expert group from the working group of arrhythmias of the european society of cardiology and the north american society of pacing and electrophysiology. J Cardiovasc Electrophysiol 12:852, 2001 Kurer CC, Tanner CS, Vetter VL: Electrophysiologic findings after Fontan repair of functional single ventricle. J Am Coll Cardiol 17:174, 1991 Watson R, Josephson M: Atrial flutter. I. Electrophysiologic substrate and modes of initiation and termination. Am J Cardiol 45:732, 1990 Triedman JK, Jenkins KJ, Colan ST, et al: Intra-atrial reentrant tachycardia after palliation of congenital heart disease: Characterization of multiple macroreentrant circuits using fluoroscopically based threedimensional endocardial mapping. J Cardiovasc Electrophysiol 8:259, 1997
Termination of Atrial Reentrant Tachycardias By Using Transesophageal Atrial Pacing
Konrad Brockmeier, MD, Herbert E. Ulmer, MD, and Gabriele Hessling, MD
Abstract: Atrial reentrant tachycardia (ART) is not an uncommon complication in patients after surgery for congenital heart defects, particularly after extensive atrial procedures with sutures lines or baffeling maneuvers. Primary atrial flutter is a rare dysrhythmia in newborns. Two issues of ART or atrial flutter can be addressed by the esophageal approach: First, ART (often with 2:1 A-V conduction) may be difficult to detect on the surface ECG as the P waves usually do not show the typical flutter morphology or are hidden in the T wave. Recordings over the esophageal lead clearly determine the underlying rhythm. Second, termination of ART by pacing the atria can easily be performed by using an esophageal electrode. We performed 62 conversions of ART in 39 pts. (median age 12.5 years), among them 7 newborns with typical atrial flutter. The pacing algorithm started with 4 extrastimuli and pacing intervals 20 msec shorter than the atrial cycle length of tachycardia. Conversion was achieved in 50/62 (81%) cases; in 12 of 62 (19%) cases conversion was performed externally as the transesophageal approach was insufficient to restore sinus rhythm. Intravenous infusion of amiodarone prior to atrial pacing seems to be helpful in some patients for termination of ART. We recommend transesophageal atrial pacing as a first step of acute management of atrial flutter and other forms of ART in neonates, infants, and children because it is a minimal invasive procedure with high success rates. Key words: Atrial flutter, atrial reentrant tachycardia, Transesophageal atrial pacing, intervention, noninvasive electrophysiology.
Atrial reentrant tachycardias (ART) are potentially dangerous depending on atrial cycle length
and conduction to the ventricles (1). Even short bursts of tachycardia with fast ventricular rates, particularly in the presence of underlying heart disease, may create life-threatening hazards and therefore should be treated (2). In pediatric cardiology— contrasting to adult cardiology—ARTs are typically seen in patients after surgery for congenital heart defects and often related to scars, particularly after atrial procedures with atriotomy, large sutures lines, or baffeling maneuvers (3). Primary atrial flutter is a rare find-
From the Department of Pediatric Cardiology, University of Heidelberg, Heidelberg, Germany. Reprint requests: Konrad Brockmeier, MD, Department of Pedatric Cardiology, University Children’s Hospital of Heidelberg, INF 153, 69120 Heidelberg, Germany; e-mail: [email protected]. Copyright 2002, Elsevier Science (USA). All rights reserved. 0022-0736/02/350S-0023$35.00/0 doi:10.1054/jelc.2002.37174
159
160 Journal of Electrocardiology Vol. 35 Supplement 2002 ing and typically seen in otherwise healthy newborns (4). Some patients with scar related ART might present with typical atrial flutter as well as other forms of atrial reentrant tachycardias. The success rate of acute termination of ART by antiarrhythmic medication is low. Therefore, electroconversion of these tachycardias plays an important role in the acute management. Different approaches of electrical conversion are distinguished: 1) electroconversion by using an external defibrillator, 2) atrial overdrive pacing by using perioperatively placed epicardial pacing leads, and 3) transesophageal atrial pacing. Benson et al. (5) proposed an algorithm for ART termination using transesophageal leads. We present our data of acute ART management by the transesophageal approach using this algorithm.
Patients and Methods We performed 62 ART conversions in 39 patients. Patient age ranged from 1 day to 33.5 years (median 12.5 years). There were 7 newborns and one 6-year-old boy with primary typical (counterclockwise) atrial flutter. ART was seen postoperatively in 31 patients after palliation or correction of congenital heart defects. Patients had their first ART episode 1 day to 19 years after surgery (median 2 years); onset of tachycardia within the first 4 weeks postoperatively was found in 7 patients. Tachycardias were detected by fetal monitoring (ultrasound/echocardiogram), postoperative monitoring, subjective symptoms, or on routine postoperative ECG during follow-up. The heart defects and surgical procedures were atrial baffle operation (Mustard/Senning) for DTransposition of the Great Arteries (n⫽3), Fontan procedure and modifications for complex (functionally univentricular) congenital defects (n⫽4), or surgery for atrio-ventricular septal defects (n⫽5), Tetralogy of Fallot / double outlet right ventricle (n⫽4), ventricular septal defects (n⫽4), atrial septal defects (n⫽3), aortic stenosis (⫽2), pulmonary valve stenosis (n⫽3), Ebstein‘s anomaly of the tricuspid valve (n⫽1), congenitally corrected transposition of the great arteries (n⫽1), and mitral insufficiency (n⫽1). Transesophageal electrocardiogram (ECG) recording and atrial pacing was performed in the facilities of the catheter/electrophysiology laboratory or the intensive care unit, depending on the severity of clinical impairment. A DC cardioverter/ defibrillator and the usual equipment for resuscita-
tion were available. Age-dependent fasting conditions prior to the procedure were insured whenever the clinical presentation of the patient allowed an elective procedure. Moderate sedation and analgesia was performed stepwise with phenobarbital, midazolam, and morphin to avoid discomfort and anxiety. Additionally, local anesthesia of the mouth was applied. After placement of standard 12-lead surface electrodes, a flexible quadripolar transesophageal electrophysiology catheter (5F, 6F, or 7F Fiab) was introduced through the nares and positioned in the esophagus at the level of the left atrium. Electrode position was controlled without fluoroscopy using standardized insertion depth values according to body height and yielded maximal amplitude of the atrial signal on the display (5). For signal recording and filtering, a Cardioscript CU 12 (Schwarzer Medizintechnik, Germany) was used. Bipolar transesophageal ECG recording was performed using the proximal electrodes, and transesophageal pacing was performed using the distal electrodes respectively. Pacing was performed with a Medtronic 5328 stimulator (Medtronic Inst., Minneapolis, MN) using an impulse duration 9.9 ms and a stimulation amplitude of 24 to 28 mA. The pacing algorithm for termination of ART was performed as described: 1. Determination of the atrial cycle length (ACL) of tachycardia 2. Stimulation with 4 stimuli (ES) at an interval 20 ms shorter than ACL 3. Decremental steps of 10 ms down to a 120 ms interval 4. Increase number of ES by 2 up to 10 ES 5. Increase output from 24 mA to 28 mA Statistical Analysis All data were presented using ranges and medians. Comparison of group differences were made using one-way ANOVA test. A value of P ⬍.05 was considered statistically significant.
Results Overall, 50 of 62 (81%) tachycardia episodes were terminated successfully by transesophageal atrial pacing without complications. All episodes of primary typical atrial flutter were converted to sinus rhythm using the transesophageal approach. Spontaneous reinitiation of atrial flutter occurred in
Termination of Atrial Reentrant Tachycardias •
one of the newborns and was again successfully converted. Among the postoperative atrial reentrant tachycardias, typical atrial flutter on ECG was documented in 21 cases; 4 patients postoperatively showed both typical atrial flutter and atrial reentrant tachycardia with a different P-wave morphology. Atrial cycle length of tachycardia (ACL) ranged between 160 and 380 ms (median 235 ms) with 2:1 AV-conduction in 50 of 62 (81%) of the episodes. Various degrees of AV-conduction (1:1, 2:1, 3:1, 4:1) were found in 12 of 62 (19%). In 12 of 62 (19%) episodes, conversion was performed using an external cardioverter/defibrillator, as termination of ART could not be achieved by the transesophageal approach. The typical pacing protocol leading to conversion had 4 ES with 150 ms interval [median of 4 ES (max. 10 ES) with median of 150 ms (min. 120 ms)]. There was no statistical difference in atrial cycle length and the effective stimulation protocol between newborns with typical atrial flutter and patients with postoperative scar related ART. External DC conversion was performed under sedation with additional ketamin infusion when the transesophageal approach had failed to terminate ART. In 5 patients with ART, tachycardia could not be terminated immediately using the pacing algorithm. In 2 of these 5 patients, the algorithm was repeated after administration of 5 mg/kg intravenously amiodarone over 30 minutes and resulted in conversion of tachycardia. Another 2 of these patients had intermittent atrial fibrillation with subsequent reorganization to a macro-reentrant circuit of slower cycle length after pacing. After administration of amiodarone tachycardia could also be terminated by atrial pacing. In 1 patient with sustained atrial fibrillation induced by transesophageal pacing intravenous amiodarone did not change the rhythm. In this patient, external DC conversion was then performed which resulted in normal sinus rhythm. External DC conversion was also used in those episodes, with unsuccessful transesophageal pacing. However, the reason for not being effective in terminating ART by transesophageal pacing in 19% of the presented episodes could not be decided definitively. In some episodes, insufficient capture might have been responsible. No clear correlation was seen concerning age of the patient, size of the atria or type of underlying congenital heart defect.
Discussion The electrocardiogram of incisional or scar related atrial reentrant tachycardaias can sometimes be
Brockmeier et al. 161
rather challenging (Fig. 1). A sawtooth pattern on the ECG is the clue to differentiate typical atrial flutter from other forms of atrial reentrant tachycardias; this might be facilitated by increasing atrioventricular conduction and “demasking” P-waves by vagal maneuvers or intravenous injection of adenosine. Another hint to identify atrial macroreentrant tachycardia in the absence of typical flutter waves is an often inappropriately high heart rate in conjunction with an abnormal P-wave pattern with measurable periodic strength, possible changes of 2:1 to 3:1 AV conduction and T-wave morphology changes due to hidden P waves. Here the esophageal recording of atrial and ventricular depolarization is extremely useful in helping to clarify the underlying rhythm and offers the possibility of acute treatment (Fig. 2). New insights from invasive electrophysiologic studies and mapping techniques will offer a much clearer differentiation of ART as outlined in a recent paper from the Joint Expert Group from the Working Group of Arrhythmias of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology (6). In pediatric cardiology, ART is not an uncommon problem in the follow-up of surgically corrected or palliated children and young adults with congenital heart disease. In fact, atrial tachycardias other than typical atrial flutter, which are often due to scars and sutures in the right atrium, are the predominant form of ART seen in the postoperative pediatric population. These reentrant tachycardias are often complex in their spacial orientation and sometimes present with various forms of reentrant circuits—including typical atrial flutter (2). In 4 patients of our series of postoperative ART both typical flutter and other forms of atrial reentrant tachycardia with various cycle lengths occurred. Typical atrial flutter without congenital heart disease is rare in children, probably due to the smaller volume of the atria in comparison to adults. In our series (excluding newborn atrial flutter as a different entity with an excellent long-term prognosis) only one older patient showed typical atrial flutter without underlying congenital heart disease. After open-heart surgery the right atrium can enlarge as seen in patients after the Fontan operation, which predisposes to atrial macroreentrant tachycardias. Other predisposing factors include discontinuities of the atrial surface as a result of surgery, focal scarring, atrial fibrosis related to abnormal atrial wall stress and changes in atrial refractoriness associated with sinus node dysfunction and prolonged atrial activation (7).
162 Journal of Electrocardiology Vol. 35 Supplement 2002
Fig. 1. Example of an atrial reentrant tachycardia (with 2:1 AV conduction) in a patient after operation of an atrial septal defect with large residual right atrial and right ventricular cavities. The upper 3 rows represent a subset of the recorded surface ECG with a heart rate of 140 beats per minute. The last row represents a recording from the esophagus. In the esophageal lead one can clearly distinguish 2 types of signals with a 2:1 occurrence, one of them at the time of the QRS in the surface leads, one at the time of the P-wave signal in the third row, and one at T-wave onset-invisible in the surface ECG.
The mechanism of terminating ART by transesophageal atrial pacing is rather similar to the classical overdrive pacing approach. Termination relies on the ability of the pacing impulses to penetrate the excitable gap within the reentrant circuit and capture, thus achieving a critical pacing rate and duration (8). The duration of rapid atrial pacing in the presented approach, however, is less aggressive than the classical approach with pacing times of up to 30 seconds. Usually 4-6 extrastimuli are sufficient to terminate tachycardia thereby causing less discomfort and pain. External DC conversion should be used as a therapeutic approach for termination of ART only when the esophageal approach fails or the patients is critically ill and requires immediate intervention. The use of an intravenous infusion of amiodarone prior to atrial pacing seems to be helpful in some patients for termination of ART; controlled data are yet lacking. The low median of effective atrial pacing intervals (150 ms) for ART termination seen in this investigation is explained by the typical conditions of the pediatric population with short atrial tachycardia cycle lengths. Using rapid atrial pacing in children is usually not a problem; if atrial fibrillation is induced, this is rarely sustained. Performed in the
appropriate environment, transesophageal pacing for termination of atrial flutter is a safe procedure in the hands of pediatric electrophysiologists. Long-term therapeutic aspects of recurrent ART in the pediatric population include revision of possible underlying morphological problems, which might be ameliorated by reoperation or intervention. Furthermore, oral antiarrhythmic medication is useful in some patients, but has its drawback with unwanted side effects and limited long-term success. Invasive radiofrequency catheter ablation techniques, recently introduced in pediatric cardiology, provide hope and the possibility for a definitive cure of ART in patients of this population (2). We—as others— think that transesophageal atrial pacing is a safe tool for the acute termination of ART with high success rates in the pediatric age group.
Limitations Patients with typical atrial flutter and postoperative atrial reentrant tachycardias form quite a heterogenous group of patients, although much has been learned about these forms of tachycardias in
Termination of Atrial Reentrant Tachycardias •
Brockmeier et al. 163
Fig. 2. Termination of the atrial tachycardia (in the same patient as in Figure 1) with 4 extrastimuli of 160 ms interval. Shortly thereafter normal sinus rhythm resulted.
pediatric patients by intracardiac electrophysiologic mapping studies (9). Despite methodological problems regarding this heterogeneity, a study about the acute management of both entities using the same transesophageal approach seems to be of clinical use. The main issue of this presentation was to show the feasibility of this minimal invasive approach for children of all ages with atrial reentrant tachycardias showing that short atrial pacing intervals are highly effective in acutely terminating these tachycardias.
References 1. Goodacre S, Irons R: Atrial arrhythmias. BMJ 324: 594, 2002 2. van Hare GF: Intra-atrial reentry tachycardia in pediatric patients. Prog Ped Cardiol 13:41, 2001 3. Saul P: Transesophageal atrial recording and pacing, in Walsh EP, Saul P, Triedman JK, (eds): Cardiac arrhythmias in children and young adults with congenital heart disease. Baltimore,MD, Lippincott Williams & Wilkins, 2001 p 33 4. Campbell RWF: Supraventricular tachycardia. In
5. 6. 7.
8.
9.
10.
Wren C, Campbell RWF, (eds): Paediatric cardiac arrhythmias. Oxford University Press 1996, p 94-126 Benson DW: Transesophageal pacing for conversion of atrial flutter. Pract Cardiol 16:1990 Benson DW: Transesophageal electrocardiography and cardiac pacing: State of the art. Circulation 75:86, 1987 Saoudi N, Cosio F, Waldo A, et al: Classification of atrial flutter and regular atrial tachycardiac according to electrophysiologic mechanism and anatomic bases: A statement of the joint expert group from the working group of arrhythmias of the european society of cardiology and the north american society of pacing and electrophysiology. J Cardiovasc Electrophysiol 12:852, 2001 Kurer CC, Tanner CS, Vetter VL: Electrophysiologic findings after Fontan repair of functional single ventricle. J Am Coll Cardiol 17:174, 1991 Watson R, Josephson M: Atrial flutter. I. Electrophysiologic substrate and modes of initiation and termination. Am J Cardiol 45:732, 1990 Triedman JK, Jenkins KJ, Colan ST, et al: Intra-atrial reentrant tachycardia after palliation of congenital heart disease: Characterization of multiple macroreentrant circuits using fluoroscopically based threedimensional endocardial mapping. J Cardiovasc Electrophysiol 8:259, 1997