Atrioventricular junctional parasystole with ventricular fusion beats due to complicating Wolff-Parkinson-White syndrome

We present a case of atrioventricular (AV) junctional parasystole manifesting with ventricular fusion beats due to the presence of an accessory AV conduction pathway. Ventricular fusion beats are usually impossible in AV junctional parasystole. In the reported case the ventricular fusion occurs because the ectopic AV junctional impulse is conducted through the His bundle, whereas the sinus impulse is conducted to the ventricles through the Kent bundle.     

The electrocardiographic diagnosis of intraventricular blocks coexisting with ventricular preexcitation

The electrocardiographic diagnosis of intraventricular conduction disturbances may be hindered by the coexistence of ventricular preexcitation. In fact, the premature depolarization of ventricular myocardium through an accessory pathway tends to conceal any electrocardiographic manifestation of a bundle-branch block. However, there are several conditions favoring the diagnosis of bundle-branch block associated with ventricular preexcitation: intermittency of ventricular preexcitation and/or bundle-branch block, fast atrioventricular (AV) nodal impulse propagation, slow conduction over the accessory pathway or between its ventricular insertion site and the remaining myocardium, and presence of atrioventricular junctional ectopic beats exposing the intraventricular conduction disturbance. This article reexamines the available data on preexcitation in patients with intraventricular blocks and presents clinical examples to emphasize the importance of a thorough examination of the electrocardiogram to attain the correct diagnosis of this association.     

Three types of atrioventricular reciprocating tachycardia using bilateral accessory pathways in a patient with Wolff-Parkinson-White syndrome

Electrophysiologic studies were performed on a patient with Wolff-Parkinson-White syndrome and recurrent supraventricular tachycardia. Bilateral accessory pathways capable of antegrade and retrograde conduction and three different types of atrioventricular (AV) reciprocating tachycardia were demonstrated. One type of narrow QRS tachycardia used the normal AV pathway for antegrade conduction and the left-sided accessory pathway for retrograde conduction. Two types of wide QRS tachycardia (one with right bundle branch block and one with left bundle branch block) used both accessory pathways for antegrade and retrograde conduction, respectively, and were independent of the normal AV pathway. The data showed that bilateral accessory pathways have different electrophysiologic properties and participate in three different types of AV reciprocating tachycardia.     

Wolff-Parkinson-White syndrome with orthodromic supraventricular tachycardia associated with a "hyper-conductor" atrio-ventricular node. A therapeutic challenge

One case of Wolff-Parkinson-White Syndrome with paroxysmal supraventricular tachycardia related to orthodromic atrioventricular reentry using an accessory pathway for retrograde conduction an a rapidly conducting AV node for anterograde conduction is present. The pharmacological therapy with Digoxin, Propranolol, Quinidine, Disopyramide and Propafenone was not effective. An electrophysiologic study showed a reciprocating tachycardia induced by spontaneous ventricular beats. Both the effective refractory period of the AV node and the anterograde effective refractory period of the accessory pathway were minor or equal to 220 msec which made the control of the arrhythmia difficult. Amiodarone was able to suppress the premature ventricular beats, depress conduction and prolong refractoriness in both, the AV node and accessory pathway to prevent recurrences of atrioventricular reentry. In this patient a false positive test with ajmaline was documented. The electrophysiologic study showed the association of Wolff-Parkinson-White Syndrome with an enhanced atrioventricular nodal-conduction and allowed the selection of an appropriate antiarrhythmic agent.     

Transient entrainment and interruption of atrioventricular node tachycardia

The possibility of transiently entraining and interrupting the common type of atrioventricular (AV) node tachycardia (anterograde slow, retrograde fast AV node pathway) was studied using atrial and ventricular pacing in 18 patients with paroxysmal AV node tachycardia. Transient entrainment occurred in all patients. During atrial pacing, localized block in the AV node for one beat followed by anterograde conduction over the fast pathway was observed in three patients. During ventricular pacing, localized block for one beat followed by retrograde conduction over the slow pathway was not observed in any patient. Neither atrial nor ventricular fusion beats were observed during entrainment. These observations indicate in a way not previously shown that reentry involving two functionally dissociated pathways in the AV node is the underlying mechanism of paroxysmal AV node tachycardia. The inability to demonstrate atrial or ventricular fusion beats during entrainment suggests a true intranodal location of the reentrant circuit. Finally, the ability to transiently entrain intranodal tachycardia demonstrates that this electrophysiologic phenomenon is not exclusively limited to macroreentrant circuits.     

Variants of Preexcitation—Specialized Atriofascicular Pathways, Nodofascicular Pathways, and Fasciculoventricuiar Pathways:

Variants of Preexcitation. introduction: In the present report, the electrophysiiologic findings in patients with different types of variants of preeexcitwtion, i.e., atriofascicualr, nodofacicular, and fasciculoventricular fibers, and the results of radiofrequency catheter ablation using different target sites are described. Methods and Results: Twelve patients (mean age 36 ± 17 years) with variants of the preexcitation syndromes underwent electrophysiologic study and radiofrequency catheter ablation. The atrial origin of atriofascicular pathways remote from the normal AV node was assessed by application of late atrial extrastimuli that advanced (“reset”) the timing of the next QRS complex without anterograde penetration into the AV node. In patients with atriofacicular pathways, ablation of the accessory pathway or the retrograde fast AV node pathway was attempted. Ablation of the atriofascicular pathways was guided by a stimulus-delta wave interval mapping in the first live patients and by recording of atriofascicular pathway activation potentials in the next five patients. A nodofascicular pathway was suggested if VA dissociation occurred during tachycardia and if atrial extrastimuli failed to reset the tachycardia without anterograde penetration into the AV node. A fasciculoventricular connection was suggested if the proximal insertion of the accessory pathway was found to arise from the His bundle or bundle branches. The PR interval was expected within normal limits during sinus rhythm and the QRS complex to he slightly prolonged with a discrete slurring of the R wave, suggesting a small delta wave. Ten of the 12 patients had evidence for atriofascicular pathways and one patient each for a nodofascicular and fasciculoventricular pathway. In six patients, the atriofascicular pathways were successfully ablated, and in two patients, the retrograde fast AV node pathway. In one patient, a concealed right posteroseptal accessory AV pathway served as the retrograde limb and was successfully ablated. The nodofascicular pathway was shown to he a bystander during AV node reentrant tachycardia. After successful fast AV node pathway ablation resulting in marked PR prolongation, no preexcitation was present during sinus rhythm because of the proximal insertion of the nodofascicular pathway distal to the delay producing parts of the AV node. The proximal insertion of the fasciculoventricular pathway was suggested to arise distal to the AV node at the site of the penetrating AV bundle. The earliest ventricular activation at the His-bundle recording site indicated the ventricular insertion of this accessory connection into the ventricular summit. The fasciculoventricular connection gave rise to a fixed ventricular preexcitation and served as a bystander during orthodromic AV reentrant tachycardia incorporating a left-sided accessory AV pathway.     

Radiofrequency catheter ablation of two accessory pathways with different unidirectional conduction properties

Simultaneous occurrence of narrow and broad QRS complex tachycardias in patients with WPW syndrome usually indicates a macroreentry in an orthodromic atrioventricular reentry-tachycardia using the AV node as antegrade and the accessory pathway as retrograde conduction and vice versa in an antidromic circuit. We report on a 32-year-old woman with WPW syndrome presenting with both a narrow and a broad QRS complex tachycardia using two accessory pathways with different unidirectional conduction properties in combination of an exclusively antegrade conducting AV node. This case report describes conventional mapping techniques and ablation of this unusual entity of a WPW syndrome.     

Comparative effects of adenosine triphosphate on accessory pathway and atrioventricular nodal conduction

Adenosine triphosphate (ATP) has potent negative dromotropic effects on the atrioventricular (AV) node, but variable effects on accessory pathway conduction have been described. The effects of an intravenous bolus injection of 8 mg ATP on accessory pathway and AV nodal conduction were determined during electrophysiologic testing with controlled atrial and ventricular rates. AV conduction was monitored during atrial or ventricular pacing at a constant cycle length, 30 msec longer than the cycle length at which block occurred. During atrial pacing antegrade block after administration of ATP occurred in 1 of 30 (3.2%) patients with accessory pathway conduction and 12 of 13 (92%) patients with AV nodal conduction (p less than 0.001). During ventricular pacing only 5 of 26 (16%) patients had accessory pathways blocked, whereas 25 of 35 (71%) patients with AV nodal conduction had block (p less than 0.001). Thus, failure of ATP to produce ventriculoatrial block identified the presence of an accessory pathway with a sensitivity of 84%, specificity of 71%, and predictive value of 72%. There was no correlation between accessory pathway properties and the effects of ATP. The effects of ATP on the AV node were concordant with the effects of a combination of verapamil and propranolol in 21 of 23 patients, suggesting that this dose ATP is an equipotent AV nodal blocker with a short duration of action. Thus, although the effects of ATP on accessory pathways and the AV node differ, block in ventriculoatrial conduction after administration of ATP cannot be used as the sole criterion to distinguish the mechanism of conduction.     

An unusual accessory pathway: anteroseptal to ventricular outflow region connection

Accessory pathways are typically located along the left or right atrioventricular junction. Distinct ventricular pre-excitation patterns determined by surface electrocardiography can provide reasonable pathway localization prior to invasive mapping and catheter ablation. We report an accessory pathway producing an unusual electrocardiographic appearance suggestive of ventricular outflow region pre-excitation. Pacing maneuvers and standard intracardiac recordings confirmed an atrial insertion immediately adjacent to the atrioventricular (AV) node and supported a ventricular insertion at the outflow tract region well away from the AV junction. The elimination of pathway conduction was achieved with radiofrequency (RF) energy at the atrial insertion after successful ice mapping excluded AV block at the target site. This is the second such pathway observed at our institution over a 20-year period.     

Variant Preexcitation Syndrome: A True Nodoventricular Mahaim Fiber or an Accessory Atrioventricular Pathway with Decremental Properties?

WPW Variant. Introduction: The differentiation between a nodoventricular fiber and an accessory atrioventricular (AV) pathway with long conduction times and decremental properties could he very difficult even at detailed electrophysiologic study.
Methods and Results: A 20-year-old male with a history of a wide QRS tachycardia underwent electrophysiologic study. Baseline intervals were normal. There was evidence of dual AV pathways, and a sudden increase in AH interval was associated with the emergence of a delta wave. The atrio-delta interval showed a progressive prolongation. The preexcited QRS complex was typical of a posteroseptal pathway, and the earliest ventricular activation site was recorded at the posteroseptal region. Retrograde conduction was exclusively over the normal conduction system. During ventricular extrastimulation, a sudden increase in HA interval was associated with anterograde conduction over the accessory pathway. The intervals between the stimulus artifact and the onset of the delta wave during atrial pacing from two atrial sites (S-Delta) were compared with those between the retrograde atrial electrogram on the His channel and the onset of the delta wave during ventricular pacing (A2_HB-Delta). When pacing from the proximal coronary sinus, the shortest S-Delta interval did become shorter than the longest A2HK-Delta interval (155 vs 170 msec).
Conclusion: The finding that the S-Delta interval could become shorter than the A2_HB-Delta interval provides strong evidence that this accessory pathway was not connected to the AV node hut arose directly from the atrial tissue of the posteroseptal region.     

Concealed accessory pathway and dual AV conduction: drug-dependent reentrant tachycardia.

Electrophysiological studies were performed in a patient with paroxysmal supraventricular tachycardia and a normal surface ECG at the time of the study. Premature atrial stimulation revealed dual AV conduction and an echo zone during AV conduction over the fast and the slow pathway. The prolongation of the AV conduction time by a calcium antagonist, Ro 11-1781, permitted the induction of tachycardias via both pathways. Premature ventricular stimulation yielded constant VA conduction times with activation of the low right atrium before the high right atrium before the left atrium. During the tachycardia, premature right ventricular beats conducted to the atrium at a time when the AV node and the His bundle would be refractory. The study suggests the simultaneous occurrence of an occult accessory bundle connecting the right ventricle to the right atrium and dual AV conduction.     

Spectrum of regular tachycardias with wide QRS complexes in patients with accessory atrioventricular pathways

Reciprocating tachycardia and atrial flutter or fibrillation are the rhythm disorders most frequently documented in patients with accessory atrioventricular (A-V) pathways. Reciprocating tachycardia typically results in a regular tachycardia (140 to 250/min) with a normal QRS pattern, although on occasion bundle branch block aberration occurs. Atrial flutter or fibrillation may result in an irregular ventricular response, with the QRS configuration being normal or exhibiting bundle branch block or various degrees of ventricular preexcitation, or both. Although much less common than either reciprocating tachycardia or atrial flutter/fibrillation, regular tachycardias with a wide QRS complex suggestive of ventricular preexcitation are observed in patients with accessory pathways. Excluding functional or preexisting bundle branch block, several arrhythmias may cause these electrocardiographic findings which may mimic those of ventricular tachycardia.In the present study a variety of arrhythmias that resulted in tachycardias with a wide QRS complex were examined in 163 patients with accessory pathways who underwent clinical electrophysiologic study for evaluation of recurrent tachyarrhythmias. Twenty-six patients (15 percent) manifested a regular tachycardia with a wide QRS complex suggesting ventricular preexcitation. Atrial flutter with 1:1 anterograde conduction over an accessory pathway (15 of 26 patients, 58 percent) was the most frequent arrhythmia and was usually associated with a heart rate of 240/min or greater (12 of 15 patients). Reciprocating tachycardia with conduction in the anterograde direction over an accessory pathway (antidromic reciprocating tachycardia) occurred in 7 of 26 patients (27 percent), and resulted in a slower ventricular rate than atrial flutter (217 ± 22 versus 262 ± 42, P < 0.01). Other arrhythmias included reciprocating tachycardia with reentry utilizing a fasciculoventricular or nodoventricular connection (two patients, 8 percent), reciprocating tachycardia with reentry in the atrium or A-V node and anterograde accessory pathway conduction (one patient, 4 percent) and ventricular tachycardia (one patient, 4 percent).In this study the clinical electrophysiologic diagnostic features of several arrhythmias which cause tachycardias with a wide QRS compex suggesting ventricular preexcitation are outlined. It is apparent that definitive arrhythmia diagnosis during these tachycardias is often complex and usually requires careful study using intracardiac electrode catheter techniques.     

Radiofrequency catheter ablation of two accessory pathways with different unidirectional conduction properties

Summary Simultaneous occurrence of narrow and broad QRS complex tachycardias in patients with WPW syndrome usually indicates a macroreentry in an orthodromic atrioventricular reentry-tachycardia using the AV node as antegrade and the accessory pathway as retrograde conduction and vice versa in an antidromic circuit. We report on a 32-year-old woman with WPW syndrome presenting with both a narrow and a broad QRS complex tachycardia using two accessory pathways with different unidirectional conduction properties in combination of an exclusively antegrade conducting AV node. This case report describes conventional mapping techniques and ablation of this unusual entity of a WPW syndrome.     

Malignant ventricular arrhythmia in the Wolff-Parkinson-White syndrome during amiodarone treatment

The ventricular rate during rapid atrial rhythms is related in Wolff-Parkinson-White (WPW) syndrome to antegrade effective refractory period of the accessory pathways. Among the many antiarrhythmic drugs available, amiodarone is most commonly used for its large therapeutic window and very long half-life. We report a case of cardiac pre-excitation syndrome in a young male patient in whom amiodarone therapy (3000 mg/weekly) was instituted to modify the dangerous ventricular response during atrial fibrillation (shortest R-R interval 190 ms, ventricular rate 210 beats/min). Four months later, starting pharmacological treatment, a new electrophysiological study documented a malignant ventricular arrhythmia: during atrial fibrillation the minimum R-R interval was 160 ms and the ventricular rate 280 beats/min. Finally, the possible mechanism of paradoxical effect observed in our patient is hypothesized. Amiodarone could favor conduction over the accessory pathways by slowing or blocking conduction into the atrioventricular node and decreasing concealed retrograde conduction into the accessory bypass tract by normally conducted beats.     

Electrocardiographic body surface potential mapping in the Wolff-Parkinson-White syndrome. Noninvasive determination of the ventricular insertion sites of accessory atrioventricular connections

BACKGROUND. A reliable, noninvasive procedure to determine the location of accessory atrioventricular connections in patients with Wolff-Parkinson-White syndrome would add an important diagnostic tool to the clinical armamentarium. METHODS AND RESULTS. Body surface potential mapping (BSPM) using 180 electrodes in various-sized vests and displayed as a calibrated color map was used to determine the ventricular insertion site of the accessory atrioventricular (AV) connections in 34 patients with Wolff-Parkinson-White syndrome. Attempts were made to determine the 17 ventricular insertion sites described by Guiraudon et al. All 34 patients had an electrophysiologic study (EPS) at cardiac catheterization, and 18 had surgery so the ventricular insertion sites could be accurately located using EPS at surgery. A number of physiologic observations were also made with BSPM. CONCLUSIONS. The following conclusions were drawn: 1) BSPM using QRS analysis accurately predicts the ventricular insertion site of accessory AV connections in the presence of a delta wave in the electrocardiogram; 2) the ventricular insertion sites of accessory AV connections determined by BSPM and by EPS at surgery were identical or within one mapping site (1.5 cm or less) in all but four of 18 cases; three of the four exceptions had more than one accessory AV connection, and the other had a very broad ventricular insertion; 3) BSPM and EPS locations of the accessory AV connections correlated very well in the 34 cases despite the fact that BSPM determines the ventricular insertion site and EPS determines the atrial insertion site of the accessory AV connection; 4) as suggested by the three cases of multiple accessory AV connections, EPS and BSPM may be complementary since BSPM identified one pathway and EPS identified the other (in the case with a broad ventricular insertion, BSPM and EPS demonstrated different proportions of that insertion); 5) BSPM using ST-T analysis is very much less accurate in predicting the ventricular insertion site of accessory AV connections unless there is marked preexcitation; 6) standard electrocardiography using the Gallagher grid methodology (but with no attempt at stimulating maximal preexcitation) was not as accurate as QRS analysis of BSPM in predicting the ventricular insertion site of the accessory AV connection; however, exact comparison is hampered by the different number and size of the Gallagher and Guiraudon insertion sites; 7) BSPM using QRS analysis appears to be very accurate in predicting right ventricular versus left ventricular posteroseptal accessory AV connections; 8) typical epicardial right ventricular breakthrough, indicative of conduction via the specialized AV conduction system, occurs in all patients with left ventricular free wall accessory AV connections; 9) epicardial right ventricular breakthrough was not observed in cases with right ventricular free wall or anteroseptal accessory AV connections; 10) epicardial right ventricular breakthrough can occur in the presence of posteroseptal accessory AV connections, whether right or left ventricular; and 11) the delay in epicardial right ventricular breakthrough in cases with left ventricular insertion may provide a marker to estimate the degree of ventricular preexcitation.     

Epicardial mapping in patients with "nodoventricular" accessory pathways

Some patients with electrophysiologic features suggesting nodoventricular fibers have been shown to have right parietal atrioventricular (AV) accessory pathways with decremental conduction properties intraoperatively. The experience with 11 patients (7 women and 4 men, mean age +/- standard deviation 25 +/- 5 years) who had electrophysiologic features consistent with a nodoventricular pathway and who underwent operative correction was reviewed. At electrophysiologic study, all patients had absent or minimal preexcitation in sinus rhythm. During atrial pacing and extrastimulus testing, maximal preexcitation with left bundle branch block morphology developed and the AH and AV intervals progressively prolonged. Preexcited tachycardia was initiated in all patients (AV reentrant tachycardia in 10 patients and AV node reentrant tachycardia in 1 patient). At operation all patients had a right parietal accessory pathway demonstrated. Intraoperative mapping demonstrated the earliest site of ventricular activation during anterograde preexcitation to be at the midanterior right ventricle, consistent with insertion of these pathways into the right bundle branch system, in 7 patients. The ventricular insertion was at the AV groove in 4 patients, in keeping with the typical Wolff-Parkinson-White syndrome. Retrograde conduction over the pathway was not demonstrated in any patient. Two patients had evidence of a second accessory AV pathway in the left paraseptal region. Operative AV node ablation was electively performed in 2 patients without affecting preexcitation in either case. In 1 of these patients, accessory pathway conduction was temporarily abolished by ice mapping in the right anterolateral AV groove.(ABSTRACT TRUNCATED AT 250 WORDS)     

The differences in atrioventricular conduction of premature beats in young and adult goats.

Atrioventricular (AV) conduction was studied in anesthetized, open-chest, 1-35-day-old goats. Atrial, bundle of His, and ventricular bipolar electrograms were recorded, and the functional refractory periods of the AV conduction system and the ventricles were determined. Supraventricular premature excitation invaded the ventricles during their vulnerable period. This AV conduction property is different from that of the adult goat heart; thus, the existence of a lateral accessory bypass tract was investigated. Electrocardiographic leads I, aVF, and V10 revealed no delta waves indicative of ventricular preexcitation. Bundle of His electrograms showed that: (1) bundle of His excitation always preceded the onset of ventricular depolarization, (2) no shortening occurred in the bundle of His to ventricular activation time following early atrial premature beats, and (3) the functional refractory period of the AV node was less than that of the ventricle. The ventricular epicardial excitation sequence indicated no involvement of a lateral bypass tract in the AV conduction of basic or premature beats. Interruption of the bundle of His caused complete AV block. Therefore, no functional lateral accessory bypass tracts are present in the young goat heart, and the AV node and the ventricular specialized conduction system of the young goat are capable of conducting premature atrial excitation to the ventricles within plus or minus 10 msec of the expiration of the ventricular functional refractory period.     

Electrocardiogram during tachycardia in patients with anterograde conduction over a Mahaim fiber: old criteria revisited.

OBJECTIVES: The aim of this study was to prospectively evaluate the sensitivity, specificity, and positive and negative predictive values of previously described ECG criteria to identify preexcited tachycardia due to decrementally conducting accessory pathways (QRS axis between 0 and -75 degrees , QRS width < or = 0.15 seconds, an R wave in lead I, an rS pattern in lead V(1), RS > 1 QRS transition > V(4), and cycle length between 220 and 450 ms). BACKGROUND: Preexcited tachycardia associated with decrementally conducting right-sided accessory pathways usually shows a rather "narrow" QRS complex and can be difficult to differentiate from supraventricular tachycardia (SVT) with left bundle branch block (LBBB) aberrant conduction. METHODS: We analyzed three groups of patients: 32 patients with an atriofascicular pathway (group I); 8 patients with long (n = 3) or short (n = 5) decrementally conducting right-sided AV pathway (group II); and a control group that consisted of 35 patients with SVT and LBBB (group III). RESULTS: Presence of all six criteria had 87.5% sensitivity in group I and a 0% sensitivity in group II. There were four false negatives in group I. The negative predictive value was 82.5%, with six false positives in group III (five patients with an aberrant LBBB-shaped tachycardia with ventriculoatrial conduction over an accessory AV pathway). The criterion cycle length was not helpful. CONCLUSIONS: Criteria for identifying a tachycardia with anterograde conduction over a Mahaim fiber are helpful only in atriofascicular pathways, with a sensitivity of 87.5% and a negative predictive value of 82.5%. The major cause of false positives was a tachycardia with aberrant LBBB conduction and ventriculoatrial conduction over an accessory AV pathway.     

Slow pathway ablation in children with documented reentrant supraventricular tachycardia not inducible during invasive electrophysiologic study

Radiofrequency catheter ablation (RFA) has become the procedure of choice for permanent therapy of atrioventricular nodal reentrant tachycardia (AVNRT). This report presents our experience with atrio-ventricular node (AVN) modification in patients with documented narrow complex reentrant SVT, but no evidence for an accessory pathway, and no inducible tachyarrhythmia during invasive electrophysiology (EP) study. METHODS: The study population consists of nine children, age range 6-13 years (median 9) with previously documented SVT who had no tachyarrhythmia inducible during EP study (at baseline and following isoprenaline infusion). Eight of the 9 EP studies were performed under general anesthesia, and one under conscious sedation. An accessory pathway was excluded in all patients by appropriate atrial and ventricular extrastimulus pacing techniques. Eight of the nine patients had dual AV nodal physiology, and one had single AV nodal echo beats. The slow AV nodal pathway was empirically ablated, by applying RF lesions in the right inferoseptal AV groove, achieving catheter tip temperature of 50 degrees C. The appearance of an accelerated junctional rhythm during RF application was deemed to denote a successful application site. AV conduction during RF application was confirmed by incremental atrial pacing. The catheter position, and its relation to the compact AV node was constantly monitored using the LocaLisa navigation system. The end-point was absence of dual AVN physiology, and/or AV nodal echo beats. RESULTS: Successful slow pathway ablation was achieved in all patients. One patient appeared to have two separate slow pathways with different locations and two AH-jumps, which were both successfully ablated. None of the patients had evidence of temporary or permanent AV block at follow-up (median duration 9 months, range 4 to 36 months); none has had recurrence of symptoms or documented tachyarrhythmia. CONCLUSIONS: In children with structurally normal hearts, a previously documented SVT, absence of an accessory pathway and noninducibility of SVT during EP study, empirical slow pathway ablation appears to be justified.     

Quintuple pathways participating in three distinct types of atrioventricular reciprocating tachycardia in a patient with Wolff-Parkinson-White syndrome

Electrophysiologic studies were performed in a patient with recurrent supraventricular tachyarrhythmias. Sinus and paced atrial beats had QRS complexes characteristic of atrioventricular (A-V) conduction through a manifest left lateral accessory pathway (Wolff-Parkinson-White syndrome, type A). Three distinct types of A-V reciprocating tachycardia and three different modes of retrograde atrial activation were demonstrated. Type 1 tachycardia involved the slow A-V nodal pathway and a second (left lateral or left paraseptal) accessory A-V pathway capable of retrograde conduction only. Type 2 tachycardia was of the slow-fast A-V nodal pathway type. Type 3 tachycardia involved a heretofore undescribed circuit in that retrograde conduction occurred through an accessory A-V pathway with long retrograde conduction times and anterograde conduction through both the manifest left lateral accessory A-V pathway and fast A-V nodal pathway. Premature ventricular beats delivered late in the cycle of this tachycardia advanced (but did not change) the retrograde atrial activity without affecting the timing of the corresponding anterograde H deflection. In summary, this patient had five (three accessory and two intranodal) pathways participating in three different types of A-V reciprocating tachycardia; the recurrence of these were prevented with oral amiodarone therapy.