Accessory Connections Research Articles

Primary treatment of supraventricular tachycardia in infants and children

The natural history and therapy of supraventricular tachycarida (SVT) in childhood vary according to the mechanism of tachycardia, emphasizing the importance of understanding the electrophysiologic diagnosis before recommending therapy. The most common types of SVT in childhood involve an accessory connection, atrioventricular nodal reentry tachycarida and, less frequently, primary atrial tachycardia. As the mechanisms vary according to age, long-term therapy should consider the mechanism of SVT, patient age and symptoms. In many cases no chronic therapy is necessary. This article summarizes the common mechanisms and treatment options of SVT in childhood.

Comparison of transesophageal and intracardiac electrophysiologic studies in characterization of supraventricular tachycardia in pediatric patients

This study sought to determine the accuracy of transesophageal electrophysiologic studies in diagnosing and characterizing various mechanisms of supraventricular tachycardia in pediatric patients. Transesophageal electrophysiologic studies are a relatively noninvasive means of characterizing supraventricular tachycardia. Although widely used, to our knowledge no data exist that directly compare information obtained from transesophageal electrophysiologic studies with that from intracardiac electrophysiologic studies. We reviewed the records of 57 pediatric patients undergoing both transesophageal and intracardiac electrophysiologic studies at our institution. The results of these studies were compared with respect to mechanism of tachycardia, localization of accessory atrioventricular (AV) connections (if present) and characterization of anterograde accessory connection conduction properties. Tachycardia mechanisms were concordant in 56 of 57 patients: orthodromic reciprocating tachycardia in 43, antidromic reciprocating tachycardia in 1, both orthodromic and antidromic tachycardia in 2, AV node reentrant tachycardia in 5, atrial reentrant tachycardia in 4 and ectopic atrial tachycardia in 2. Of 29 patients with orthodromic reciprocating tachycardia using a concealed accessory connection, transesophageal study predicted the accessory connection site through changes induced by transient bundle branch block in 12. By the Bland-Altman method in 14 patients with pre-excitation, the anterograde accessory connection effective refractory period determined by transesophageal study compared favorably with that determined by intracardiac study (mean difference 5.0 ms, limits of agreement -55 and 65 ms). Transesophageal electrophysiologic studies are a highly accurate means of diagnosing and characterizing various mechanisms of supraventricular tachycardia in pediatric patients.

Electrophysiological manifestations of the excitable gap of slow-fast AV nodal reentrant tachycardia demonstrated by single extrastimulation.

Although AV nodal reentrant tachycardia (AVNRT) is a well-known rhythm disorder, its anatomic substrate and electrophysiological mechanism remain to be defined. Previously, the description of the excitable gap (EG) of AVNRT was based on electrical stimulation performed from sites remote from the reentrant circuit. In the present study, we characterized the EG of AVNRT by atrial extrastimulation close to the putative reentrant circuit in the AV junction. In 16 patients (3 men, 13 women; mean age, 45 +/- 13 years) with inducible slow-fast AVNRT (mean cycle length, 353 +/- 52 ms), single extrastimuli with a 10-ms decrement in the premature coupling interval were delivered from the anterosuperior interatrial septum (fast pathway area) and the posteroinferior interatrial septum (slow pathway area) from late diastole until atrial refractoriness. An EG was considered present when resetting or termination of AVNRT was induced by single atrial extrastimulation. The study showed that the duration of the EG of AVNRT was wide, measuring 121 +/- 56 and 123 +/- 47 ms and occupying 33 +/- 11% and 34 +/- 9% of the tachycardia cycle length during single extrastimulation from the slow pathway area and the fast pathway area, respectively. The resetting pattern most commonly manifested as the sum of the coupling interval and the return cycle being less than a fully compensatory pause (two times the basic tachycardia cycle length). However, patterns equal to and greater than a fully compensatory pause were also observed. Of note, in 2 of the 16 patients, atrial extrastimulation from either the fast or slow pathway area also affected the preceding tachycardia cycle length (HH interval), indicating alteration of the anterograde input. In all patients, the curve derived from plotting the coupling interval of extrastimuli against the return cycle during resetting exhibited an "increasing" pattern. The mode of tachycardia termination usually occurred when the premature atrial impulse was orthodromically blocked in the anterograde slow pathway. The EG of slow-fast AVNRT is relatively wide, as demonstrated by single atrial extrastimulation from the interatrial septum near the AV junction. Overall, the electrophysiological manifestations of the EG of AVNRT are very similar to those described in AV reciprocating tachycardia incorporating an accessory connection. These findings lend further support to the notion that, in humans, AVNRT involves a reentrant mechanism with a wide excitable gap.

Independent Ablation of Retrograde and Anterograde Accessory Connection Conduction at the Atrial and Ventricular Insertion Sites:

The impedance mismatch hypothesis has been proposed as one of the mechanisms responsible for accessory connection conduction block. We describe a case in which retrograde conduction across a posteroseptal accessory connection was ablated at the atrial insertion site in the coronary sinus os, whereas anterograde conduction was ablated at the ventricular insertion site in the left ventricle. The evidence supports the impedance mismatch concept as the cause of unidirectional conduction block and shows that the distal junction between the accessory connection and the myocardium is more vulnerable to ablation.

Catheter-induced mechanical conduction block of right-sided accessory fibers with Mahaim-type preexcitation to guide radiofrequency ablation.

Accessory pathways originating at the tricuspid annulus that exhibit decremental antegrade conduction properties (Mahaim-type preexcitation) are amenable to radiofrequency (RF) current catheter ablation. However, a reliable and reproducible strategy for mapping and ablation of these fibers is lacking. Eleven patients with preexcited atrioventricular tachycardia involving a decrementally conducting antegrade accessory pathway underwent complete electrophysiological evaluation and subsequent attempts at RF catheter ablation. Mechanical conduction block at the subannular level of the atrial input to the accessory fiber was induced by catheter manipulation in 8 patients, in 2 of them during atrial fibrillation. RF current was delivered, after resumption of preexcitation, to the site of mechanical block during atrial pacing (n = 6) or atrial fibrillation (n = 2) and eliminated the accessory pathway in all 8 patients. In another patient, mechanical block was not observed, but ablation of the atrial accessory fiber insertion was achieved at the subannular level during atrioventricular tachycardia. The anatomic site of ablation along the tricuspid annulus was anterolateral (n = 1), lateral (n = 3), or posterolateral (n = 5). Failures were encountered in the first patient of the series in whom ablation attempts were directed at the ventricular insertion of the accessory fiber and in a patient in whom ablation of the atrial insertion was attempted at the supraannular level. Recurrence of preexcitation within 12 hours was observed in 5 of 6 patients in whom ablation had been achieved during atrial pacing. Eventually successful repeat sessions were performed the following day using a simplified ablation approach. Thus, a median of 5 RF pulses (range, 1 to 26) per accessory fiber eliminated conduction in 9 (82%) of the 11 patients in 1.9 +/- 0.9 sessions. During a follow-up of 9.5 +/- 2.3 months, preexcitation recurred in 1 patient. The atrial origin of accessory connections with Mahaim-type preexcitation is apparently confined to the anterolateral-to-posterolateral region of the tricuspid annulus. Mechanical conduction block in the atrial input to the accessory fiber induced at the subannular level by catheter manipulation provides an optimal marker to locate the ablation site, even during atrial fibrillation. To expose early recurrence of antegrade accessory pathway conduction, intermittent atrial pacing in the 12 hours after ablation is advisable; in cases of recurrence, a repeat procedure can readily be performed using just the ablation catheter advanced to the target site at the tricuspid annulus.

Catheter ablation in children with supraventricular tachycardia mediated by accessory pathways—use of radiofrequency current as a first line of therapy

AbstractCatheter ablation of an accessory atrioventricular pathway using 500 kHz radiofrequency current was attempted in 53 children and young adolescents less than 16 years of age (mean 9.3±4.1 years) who were referred for treatment of symptomatic supraventricular tachycardia. Thirty children had the Wolff-Parkinson-White syndrome and 23 had tachyarrhythmias related to an accessory pathway conducting only in retrograde fashion. Of the latter, seven were found to have the permanent form of junctional reciprocating tachycardia, which had resulted in depressed left ventricular function in four. Ablation of left-sided accessory pathways was usually attempted utilizing an arterial approach to the annulus of the mitral valve, while the venous route to the atrial aspect of the tricuspid valvar annulus was chosen for right-sided accessory connections. To reduce invasiveness and the duration of the procedure, a technique with a solitary catheter was attempted in 20 children with the Wolff-Parkinson-White syndrome, regardless of the anatomical site of the accessory pathway. Ablation of 54 of 56 accessory connections was achieved in 51 patients (96% success) with a median of six applications of radiofrequency current. The sessions were completed within 3.4±2.2 hours, with a median exposure to radiation of 31.1 minutes. During a 10-month period of follow- up, no patient required antiarrhythmic medication, and 51 children (96%) were completely free of any symptoms related to arrhythmias. Left ventricular function returned to normal in the four children with tachycardia-induced cardiomyopathy. Except for a patient with an arterial thrombotic occlusion, no serious complications were encountered. Catheter ablation using radiofrequency current is a highly effective and safe curative approach for treating young patients with supraventricular tachycardias mediated by accessory pathways. The use of fewer catheters of smaller size is feasible and advisable in this cohort of patients.

Electrophysiologic properties of sotalol and d-sotalol. A current view.

Although discovered more than two decades ago, the clinical applications of sotalol are still a matter of debate. Together with amiodarone, sotalol is considered a prototype of a new class of antiarrhythmic agents characterized by repolarization-prolonging effects (class III). Lengthening of repolarization is associated with an increase in the effective refractory period of cardiac tissues. There is no change in the maximum rate of rise during phase 0, a finding that supports the lack of sotalol effect on the fast sodium channel. The electrophysiologic action of the drug in humans provides evidence for direct cardiac effects of sotalol in addition to beta blockade. The beta-blocking properties play a major role in the sinus-rate slowing and lengthening of the atrioventricular nodal conduction time observed after sotalol administration. However, the drug also prolongs refractoriness in atria, His-Purkinje tissue, ventricular muscle and accessory atrioventricular connections. These latter changes are absent or minimal with conventional beta blockers and are likely to reflect sotalol-induced prolongation of cardiac repolarization. They result in an increase in the QT interval, an effect that is dose-dependent and more marked during chronic therapy. The dextrorotatory isomer, d-sotalol, shares a similar electrophysiologic profile. Lengthening of repolarization in cardiac cells following d-sotalol is of the same magnitude as that produced by the levoisomer. This finding provides further evidence for a class III action of sotalol, as the dextroisomer is almost devoid of beta-blocking properties. In humans, the electrical effects of both drugs are similar. However, d-sotalol-induced changes in sinus rate and atrioventricular nodal conduction are modest.(ABSTRACT TRUNCATED AT 250 WORDS)

Delayed response to radiofrequency ablation of accessory connections.

This article summarizes delayed interruption in anomalous conduction through accessory connections following radiofrequency ablation attempts in three patients. The time course of the delayed interruption in accessory connection conduction suggests that such an effect is unlikely to occur after the first week following unsuccessful radiofrequency ablation.

Rhabdomyoma and Ventricular Preexcitation Syndrome

A description of two infants with ventricular preexcitation syndrome and supraventricular tachycardia associated with rhabdomyoma and review of the literature. A review of two patients who were seen between 1981 and 1986 in the cardiology department. Pediatric Heart Institute at St Christopher's Hospital for Children, Philadelphia, Pa. Two newborn female infants with ventricular preexcitation syndrome, supraventricular tachycardia, rhabdomyomatous tumor of the heart, and tuberous sclerosis are described. The first patient had unsuccessful partial resection of the rhabdomyomatous tumors obstructing the tricuspid valve and right ventricular cavity and died immediately after surgery. By histologic examination, no direct accessory connection was noted between the myocardial fibers of atria and ventricles through annulus fibrosus. By gross examination, the tumor extended from the right atrium through the tricuspid valve to the right ventricular cavity, suggestive of macroscopic accessory connection. The second patient presented with unsustained ventricular tachycardia and obstructive subaortic rhabdomyoma, requiring emergency surgery. One week later, reentrant supraventricular tachycardia developed and she required digoxin therapy for 15 months. Infants with rhabdomyomatous tumor of the heart and ventricular preexcitation syndrome may have microscopic or macroscopic accessory connections. Cardiac tumors like rhabdomyoma and oncocytic tumors should be suspected in infants with ventricular preexcitation syndrome or supraventricular tachycardia.

Complexities of Junctional Tachycardias

The atrioventricular junction is a compact area in which most of the known electrophysiologic substrates and mechanisms play a role in the genesis and maintenance of tachyarrhythmias. The purpose of this review is to summarize the data on normal atrioventricular junction anatomy and electrophysiologic function and correlate that information with surface electrocardiographic recordings, intracardiac electrophysiologic data, and interventional data from surgical and catheter techniques. Models of tachycardia mechanisms are proposed for typical and atypical atrioventricular nodal reentrant tachycardia, permanent junctional reciprocating tachycardia, and orthodromic supraventricular tachycardias utilizing "intermediate septal" accessory connections.

Propranolol Induced Electrical and Mechanical Alternans in Orthodromic Reciprocating Tachycardia

During an electrophysiological study in a patient with a concealed accessory connection, there was no evidence of electrical or mechanical alternans during tachycardia until propranolol was administered, but both forms of alternans developed with tachycardia of a slower rate following propranolol. Echocardiographic, arterial pressure, and electrocardiographic data obtained prior to and following propranolol administration are presented.

Non-invasive magnetocardiographic localization of ventricular pre-excitation in the Wolff-Parkinson-White syndrome using a realistic torso model.

This study was performed to evaluate the accuracy of magnetocardiography in non-invasive localization of the ventricular pre-excitation site in patients suffering from the Wolff-Parkinson-White (WPW) syndrome. Twelve WPW patients were studied, in whom the pre-excitation caused serious supraventricular arrhythmias refractory to drug therapy. Magnetocardiographic measurements were performed in a magnetically shielded room, and non-invasive localization was computed from preprocessed magnetic signals using a current dipole source in a realistically shaped digital torso. All patients underwent intra-operative multicatheter mapping and subsequent dissection of the accessory atrioventricular connection. The intra-operative localization results were marked on magnetic resonance images of the heart, where magnetocardiographic results were also superimposed to allow comparison. The average of the three-dimensional differences between the magnetocardiographic and the invasive results was 2.1 +/- 0.9 cm. In all cases, the computed localization result was in the same or adjacent anatomical region as the intra-operative result. The present results show that the magnetocardiographic method using a realistic torso model is capable of localizing pre-excitation sites with sufficient accuracy to provide extra information so that non-pharmacological therapeutic interventions can be applied.

Phase image analysis of anomalous ventricular activation in pediatric patients with preexcitation syndromes or ventricular tachycardia

This prospective study evaluated the accuracy of phase analysis of scintigraphic imaging in defining the site of earliest ventricular activation in pediatric patients with electrophysiologic disorders. Twenty patients (10.8 ± 5.5 years) with preexcitation ( n = 16) or ventricular tachycardia (VT) ( n = 4) were independently evaluated by phase image analysis and endocardial catheter mapping. The earliest phase angle (contraction), which was common to three scintigraphic imaging planes during preexcited sinus rhythm or VT, was compared with the earliest retrograde atrial activation during reciprocating tachycardia or the origin of VT, as defined by catheter mapping. Phase analysis of earliest contraction was concordant with catheter mapping of electrical activation in all 13 free-wall accessory connections and in three of four patients with VT. Inconclusive definition of activation occurred only in paraseptal accessory connections or VT. In conclusion, phase analysis accurately defines anomalous ventricular activation that is due to free-wall accessory connections or VT. In patients with complex anatomy or small size, phase analysis allows noninvasive localization of the anatomic substrates of tachycardia.

Preservation of atrioventricular nodal conduction during radiofrequency current catheter ablation of midseptal accessory pathways.

Septal accessory atrioventricular (AV) pathways may be located in close vicinity of the His bundle-AV nodal conduction system. Attempts at surgical or electrical interruption of these pathways may therefore result in impairment of normal AV conduction. This study focuses on a subset of septal pathways with an atrial insertion located inside the triangle of Koch. In this study, they were called "midseptal." Six patients with a midseptal accessory pathway (mean +/- SD age, 40 +/- 12 years; five with Wolff-Parkinson-White syndrome and one with a concealed accessory pathway) underwent attempts at ablation of their pathway using 500-kHz radiofrequency current applied to the atrial insertion of the accessory connection. Guided by the recording of accessory pathway activation potentials, the ablation catheter was positioned in all patients in an area bounded anteriorly by the tip electrode of the His bundle catheter and posteriorly by the coronary sinus ostium. All pathways were successfully ablated without the induction of complete heart block. First-degree AV conduction block occurred in one patient in whom a concealed accessory connection was located closer to the AV node than to the coronary sinus ostium. Radiofrequency current catheter ablation may be used effectively for midseptal accessory pathways and should be preferred in experienced centers as a safe alternative to surgical therapy.

Surgically created Wolff-Parkinson-White syndrome after fontan operation

The Wolff-Parkinson-White syndrome is caused by a congenital accessory connection between the atrium and ventricle. We describe a case of symptomatic Wolff-Parkinson-White syndrome that arose after a Björk modification of the Fontan operation. Invasive electrophysiologic and intraoperative mapping indicated that the surgically created atrioventricular connection was functioning as an accessory pathway. Surgical dissection and cryoablation abolished the symptoms and the preexcitation.

Doppler detection of valvular regurgitation after radiofrequency ablation of accessory connections

Radiofrequency current was used recently to ablate accessory connections in patients with supraventricular tachycardia. 1–5 After locating the accessory connection by electrophysiologic mapping, ablation is achieved by positioning a 7Fr catheter (with 4 mm electrode at distal tip) within the ipsilateral cardiac chamber and adjacent to the accessory connection. Radiofrequency current is then delivered at the point of earliest electrical activation along the atrioventricular valve annulus. For a left-sided accessory connection, the catheter is usually passed retrograde across the aortic valve into the left ventricle and under the posterior mitral valve leaflet. For a right-sided accessory connection, the catheter is passed anterograde into the right atrium or ventricle. 1–5 Systematic evaluation of the effects of this technique on the function of all cardiac valves has not been reported. This study evaluates the effects of catheter manipulation and radiofrequency current delivery on valve competence.

Radiofrequency Current for Catheter Ablation of Accessory Atrioventricular Connections in Children and Adolescents. Emphasis on the Single-Catheter Technique

Catheter ablation of an accessory atrioventricular connection using 500-kHz radiofrequency current was attempted in 10 children and adolescents aged between 6 and 15 years (mean 10.5 years). Six children had the Wolff-Parkinson-White syndrome and four had tachyarrhythmias related to a retrograde-only conducting ("concealed") accessory connection. No child had associated structural heart disease. Symptoms ranged from disabling palpitations to episodes of syncope (three patients) and cardiac arrest (one patient). Ablation was attempted from the left ventricle in all children; in one child, ablation of a second, right-sided pathway was attempted via a right atrial approach. Ten of the 11 accessory connections were interrupted successfully. A single complication was encountered in a 10-year-old girl in whom the procedure had to be terminated because a thrombotic occlusion of the right internal iliac artery had evolved. A simplification of the ablation procedure associated with reduced procedure duration and radiation exposure time was achieved in three children with the Wolff-Parkinson-White syndrome and a left free-wall accessory pathway when a single catheter placed in the left ventricle was used for pathway localization as well as ablation. It is concluded that catheter ablation using radiofrequency current is effective and safe and may supersede surgery as the curative treatment for children with serious symptoms mediated by an accessory atrioventricular connection.

Supraventricular tachycardia mechanisms and their age distribution in pediatric patients

To better define the natural history of supraventricular tachycardia (SVT) in young patients, age distribution of SVT mechanisms was examined in 137 infants, children and adolescents. Patients with a history of cardiac surgery or neuromuscular diseases were excluded. An electrophysiologic study was performed in each patient: transesophageal (110 patients) or transvenous (14 patients) or both (13 patients). Mechanisms were classified as SVT using accessory atrioventricular (AV) connection (SVT using accessory connection, including orthodromic and antidromic reciprocating tachycardia), primary atrial tachycardia (including chaotic, automatic and reentrant atrial tachycardia), and tachycardia due to reentry within the AV node. SVT using accessory connection occurred in 100 of 137 patients (73%) and was the most prevalent mechanism. Primary atrial tachycardia and reentry within the AV node were present in 19 of 137 (14%) and 18 of 137 (13%) patients, respectively. Using a multinomial logit model, relative probabilities for tachycardia mechanisms for 5 age groups — prenatal, <1, 1 to 5, 6 to 10 and >10 years — were determined. Primary atrial tachycardia (11 to 16%) and SVT using accessory connection (58 to 84%) appeared throughout infancy, childhood and adolescence. On the other hand, tachycardia due to reentry within the AV node (0 to 31%) rarely appeared before age 2 years. Mechanisms of SVT appear to have age-dependent distributions. SVT using accessory connection is the most common mechanism in young patients. We speculate that the propensity to tachycardia due to reentry within the AV node occurs during postnatal development.

Arrhythmias in childhood: an update

Atrioventricular re-entry tachycardia is the typical regular narrow QRS complex tachycardia seen in neonatal life and is due to an accessory connection between ventricle and atrium. Such a tachycardia may or may not be associated with the classical findings of Wolff-Parkinson-White syndrome i.e. a short PR interval and a delta wave in sinus rhythm. This tachycardia is the commonest seen in childhood particularly in young infants. Despite the lack of pre-

Atrial flutter in the fetus and young infant: an association with accessory connections.

To highlight the association between atrial flutter and accessory connections in the fetus and young infant. A retrospective review from January 1985 to January 1990. Fetuses, neonates, and young infants with atrial flutter. Four fetuses and five infants presented with atrial flutter. In two fetuses and one infant sinus rhythm returned spontaneously. The other six required cardioversion. Three of them developed orthodromic atrioventricular re-entry tachycardia and each had evidence of an accessory connection. Because atrial flutter in the fetus and neonate is rare, the high incidence of accessory connections in this group points to a possible aetiology of "idiopathic" atrial flutter in this age group.