Accessory Atrioventricular Nodal Research Articles

A history of collaboration between electrophysiologists and arrhythmia surgeons.

Introduction: The notion that medically‐refractory arrhythmias might one day be amenable to interventional therapy slowly began to appear in the early 1960's. At that time, there were no “interventional electrophysiologists” or “arrhythmia surgeons” and there was little appreciation of the relationship between anatomy and electrophysiology outside the heart's specialized conduction system. Methods: In this review, we describe the evolution of collaboration between electrophysiologists and surgeons. Results: Although accessory atrio‐ventricular (AV) connections were first identified in 1893 and the Wolff‐Parkinson‐White (WPW) syndrome was described 37 years later (1930), it was another 37 years (1967) before those anatomic AV connections were proven to be responsible for the clinical syndrome. The success of the subsequent surgical procedures for the WPW syndrome, AV node reentry tachycardia, automatic atrial tachycardias, ischemic and non‐ischemic ventricular tachycardias and atrial fibrillation over the next two decades depended on a close, sometimes daily, collaboration between electrophysiologists and surgeons. In the past two decades, that tight collaboration was largely abandoned until the recent introduction of “hybrid procedures” for the treatment of atrial fibrillation. Conclusions: A retrospective assessment of the 50 years of interventional therapy for arrhythmias clearly demonstrates the clinical benefits of a close collaboration between electrophysiologists and arrhythmia surgeons, regardless of which one is actually performing the intervention.

Patient with Wolff-Parkinson-White syndrome with intermittent pre-excitation under subarachnoid block for urological surgery

Wolff-Parkinson-White (WPW) syndrome is one of the pre-excitation syndromes in which activation of an accessory atrioventricular (AV) conduction pathway leads to bypass the AV node and cause earlier ventricular activation than the normal pathway. We report a patient with intermittent WPW syndrome who repeatedly manifested pre-excitation after subarachnoid block.

Atrial tachycardia originating at the tricuspid annulus

We report a patient with re-entrant atrial tachycardia that originated at the inferolateral tricuspid annulus. Single atrial extra-stimulation reproducibly induced the atrial tachycardia with an inverse relationship between the coupling interval of extra-stimulation and the return cycle of the first tachycardia beat. A real-time three-dimensional electroanatomical mapping showed focal atrial activation spreading semi-radially from the tricuspid annulus. The tachycardia was successfully eliminated by radiofrequency ablation at the earliest atrial activation site, preceding by 27 ms the arbitrary determined onset of surface P wave. An accelerated atrial rhythm with similar P-wave morphology to that of the tachycardia was observed at the successful ablation site during radiofrequency application. The mechanism of this tachycardia seems to be due to re-entry originating in or around the possible accessory atrioventricular node without ventricular connection.

Radiofrequency catheter ablation of septal accessory pathways within the triangle of Koch: importance of energy titration testing other than the local electrogram characteristics for identifying the successful target site.

Radiofrequency (RF) catheter ablation of accessory atrioventricular (AV) connections in the proximity of His bundle or AV node is at high risk of developing complete heart block. A safe and effective protocol has not been well established. Nineteen consecutive patients with 19 septal accessory pathways within the triangle of Koch underwent a protocol with power-titrated RF energy testing to identify the target site for successful catheter ablation. At every potential target site preselected by local electrogram characteristics, RF energy was started at 5 W for 10 seconds, with an increment of 5 W (duration remained at 10 s) until maximally 30 W or the observation of transient interruption of accessory pathway conduction. By this stepwise RF energy testing, we successfully localized and ablated 18 (94.7%) of the 19 septal accessory pathways, 10 close to His bundle (zone I) and 8 away from it (zone II). The test-effective RF power was 20 W or less in 9 of all 11 septal accessory pathways in zone I, and 5 of the 8 in zone II (P = 0.68). Meanwhile, the final RF power for successful ablation was 30 W or less in 9 of the 10 zone I and 6 of the 8 zone II septal accessory pathways (P = 0.83). One patient with an accessory pathway in zone I was complicated with complete AV block after final ablation at 30 W. None of the local electrogram characteristics except continuous electrical activity during retrograde mapping was helpful in the prediction of ablation outcome. Careful RF energy titration testing could effectively help identify the target site for successful RF catheter ablation of septal accessory pathways within the triangle of Koch. The dependence on local electrogram manifestations could be frustrated by a low probability of success.

Posterior sinus node artery and accessory atrioventricular node artery arising by a common origin: A case report

Posterior sinus node artery and accessory atrioventricular node artery arising by a common origin: A case report

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.

Accessory pathway and atrioventricular node reentrant tachycardia in elderly patients: Clinical features, electrophysiologic characteristics and results of radiofrequency ablation

Objectives. This study was designed to evaluate the clinical features, electrophysiologic characteristics and results of radio-frequency ablation in elderly patients with accessory atrioventricular (AV) pathways or AV node reentrant tachycardia. Background. Radiofrequency ablation in elderly patients with paroxysmal supraventricular tachycardia has not been well described, and comparative study between elderly and younger patients is limited.Methods. Electrophysiologic studies and radiofrequency ablation were performed in 92 elderly patients (45 with an accessory pathway, 47 with AV node reentrant tachycardia).Results. The elderly patients had poorer electrophysiologic properties in accessory pathways and dual AV node pathways than those of younger patients. The success rate of radiofrequency ablation was similar in elderly and younger patients. However, elderly patients had more complications (14%) in left-sided accessory pathways.Conclusions. Radiofrequency ablation in elderly patients with supraventricular tachycardia was effective. However, it must be performed cautiously in those patients with left-sided accessory pathways.

Electrophysiologic Effects of Intravenous E-4031, a Novel Class III Antiarrhythmic Agent, in Patients with Supraventricular Tachyarrhythmias

The electrophysiologic effects of intravenous (i.v.) E-4031, a new class III antiarrhythmic drug, were evaluated in 15 patients with supraventricular tachyarrhythmias [11 men, 4 women; mean age 41 +/- 19 (SD) years]. Eleven patients had accessory atrioventricular (AV) pathways, and 4 patients with no accessory pathway had paroxysmal atrial fibrillation. Electrophysiologic studies were performed before and after E-4031 administration (loading infusion 9 micrograms/kg for 5 min + maintenance infusion 0.15 microgram/kg/min). QT and QTc intervals were significantly prolonged by E-4031 from 0.40 +/- 0.03 (mean +/- SD) to 0.46 +/- 0.03 s (p < 0.0001) and from 0.43 +/- 0.03 to 0.49 +/- 0.04 s (p < 0.0001), respectively. No effect was observed on RR interval, PR interval, QRS duration, or AH and HV intervals. The effective refractory periods (ERPs) of the right atrium and ventricle were significantly prolonged from 219 +/- 27 to 236 +/- 26 ms (p < 0.001) and from 230 +/- 12 to 249 +/- 11 ms (p < 0.001), respectively. The ERP of the AV node did not change significantly after E-4031 administration. In patients with ventricular preexcitation, E-4031 significantly prolonged the ERP of the antegrade accessory pathway conduction from 340 +/- 101 to 362 +/- 106 ms (p < 0.001), but not retrograde accessory pathway conduction. AV reentrant tachycardia was induced in 3 of 11 patients with an accessory pathway, and repetitive atrial firing was induced in 3 of 4 patients with paroxysmal atrial fibrillation. E-4031 could prevent repetitive atrial firing in only 1 patient and could not prevent induction of AV reentrant tachycardia.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrophysiologic Effects of Intravenous E-4031, a Novel Class III Antiarrhythmic Agent, in Patients with Supraventricular Tachyarrhythmias

Summary: The electrophysiologic effects of intravenous (i.v.) E-4031, a new class III antiarrhythmic drug, were evaluated in 15 patients with supraventricular tachyar-rhythmias [11 men, 4 women; mean age 41 ± 19 (SD) years]. Eleven patients had accessory atrioventricular (AV) pathways, and 4 patients with no accessory pathway had paroxysmal atrial fibrillation. Electrophysiologic studies were performed before and after E-4031 administration (loading infusion 9 μg/kg for 5 min + maintenance infusion 0.15 μg/kg/min). QT and QTc intervals were significantly prolonged by E-4031 from 0.40 ± 0.03 (mean ± SD) to 0.46 ± 0.03 s (p < 0.0001) and from 0.43 ± 0.03 to 0.49 ± 0.04 s (p < 0.0001), respectively. No effect was observed on RR interval, PR interval, QRS duration, or AH and HV intervals. The effective refractory periods (ERPs) of the right atrium and ventricle were significantly prolonged from 219 ± 27 to 236 ± 26 ms (p < 0.001) and from 230 ± 12 to 249 ± 11 ms (p < 0.001), respectively. The ERP of the AV node did not change significantly after E-4031 administration. In patients with ventricular preexcitation, E-4031 significantly prolonged the ERP of the antegrade accessory pathway conduction from 340 ± 101 to 362 ± 106 ms (p < 0.001), but not retrograde accessory pathway conduction. AV reentrant tachycardia was induced in 3 of 11 patients with an accessory pathway, and repetitive atrial firing was induced in 3 of 4 patients with paroxysmal atrial fibrillation. E-4031 could prevent repetitive atrial firing in only 1 patient and could not prevent induction of AV reentrant tachycardia. Blood pressure (BP) did not change significantly, and no undesirable side effects were associated with E-4031 administration. That E-4031 prolonged the ERP without affecting conduction time indicates that it possesses pure class III antiarrhythmic properties in patients with supraventricular tachyarrhythmias. Further evaluation of the therapeutic potential of this drug using the higher dosage may be needed.

Radiofrequency ablation of accessory pathways associated with congenital heart disease including heterotaxy syndrome

Congenital heart disease complicates the management of most accessory pathway-mediated tachycardias and also increases the challenge of radiofrequency ablation. Since 1990, radiofrequency ablation of accessory atrioventricular (AV) pathways has been attempted in 10 patients (age range 3.5 months to 30 years) with congenital heart disease: Ebstein's anomaly (n = 5), heterotaxy with AV discordance (n = 3), tetralogy of Fallot (n = 1) and total anomalous pulmonary venous return (n = 1). Eight patients had manifest Wotff-Parkinson-White syndrome and 2 had concealed pathways. Five patients had multiple pathways including 4 of the 5 with Ebstein's anomaly. Of 16 pathways total, 15 were associated with the tricuspid valve including all pathways in the patients with Ebstein's anomaly and heterotaxy. The His bundle area was identified in all patients and involved an anterior AV node in 2 of 3 with heterotaxy. Ablation was performed on the atrial side of the AV ring in all cases. No instance of AV block was encountered. Complete success was achieved in 6 patients including the 3 with heterotaxy. In 2 patients, manifest preexcitation was eliminated and clinical symptoms were greatly modified. The procedure was transiently successful in 1 patient who later had surgical interruption of the accessory pathway during tetralogy of Fallot repair. Ablation was unsuccessful in 1 patient. Thus, the overall success was 80%.

Transcatheter radiofrequency ablation

To describe our initial experience with transcatheter radiofrequency ablation, a useful new treatment for supraventricular tachyarrhythmias related to the presence of an accessory atrioventricular (AV) pathway or dual atrioventricular nodal pathways. One hundred and ten patients, including 77 with accessory pathways, 32 with dual atrioventricular (AV) nodal pathways and one with both, underwent electrophysiological studies and were treated with transcatheter radiofrequency ablation in a large metropolitan teaching hospital. Ninety-five patients (86%) were without evidence of accessory pathway conduction or inducible supraventricular tachycardia and were free of symptoms after a mean follow-up of 13 months (range, 3.0-51 months). Sixty-six of 79 accessory pathways (83.5%) were ablated including 42 of 46 left-sided (91%), 14 of 21 posteroseptal (66%), six of seven anteroseptal (86%), three of four right-sided and one of one midseptal pathways. Thirty-one patients with AV nodal reentry were successfully treated by ablation of either the slow (12 patients) or fast (19 patients) conducting AV nodal pathway. There was a progressive improvement in the success rate of the first procedure from 17% to 64% with the use of large-tip catheters and from 64% to 91% when a purpose-built radiofrequency generator was employed. Complications occurred in nine patients: cardiac tamponade (two patients); mild mitral regurgitation (four); subclavian vein thrombosis (one); transient cerebral ischaemic attack (one); and non-thrombocytic purpuric rash (one). These occurred predominantly during the early experience and were without long-term sequelae. Late in our experience, one patient developed complete atrioventricular block requiring permanent pacemaker implantation. In this institution, radiofrequency catheter ablation has been a safe and effective treatment strategy for patients with life-threatening or highly symptomatic supraventricular arrhythmias.

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.

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.

Efficacy of intravenous sotalol for suppressing inducibility of supraventricular tachycardias at rest and during isometric exercise

The efficacy of intravenous sotalol (1 mg/kg) for suppressing inducibility of supraventricular tachycardias (SVT) with different electrophysiologic mechanisms was studied in 30 consecutive patients referred for an electrophysiologic study because of paroxysmal SVT. Orthodromic SVT using accessory atrioventricular (AV) connection was inducible in 14 patients, AV nodal reentrant SVT in 8, and intraatrial SVT in 8 before administration of sotalol. Isometric handgrip exercise facilitated the inducibility of SVT in 8 patients who were noninducible at rest. After intravenous sotalol, 7 of 14 patients (50%) with orthodromic SVT, 8 of 8 (100%) with AV nodal reentrant SVT, and 8 of 8 (100%) with intraatrial reentrant SVT became noninducible into sustained SVT. Isometric exercise facilitated the inducibility of only 3 nonsustained SVT runs after sotalol infusion, and exercise did not reverse the prolongation of refractory periods of the atrium, AV node, accessory pathway and ventricle caused by sotalol. During a mean follow-up period of 18 ± 7 months, none of the 14 patients who remained noninducible into sustained SVT during the stress test after intravenous sotalol and tolerated long-term oral sotalol therapy had recurrence of symptomatic SVT. Thus, sotalol is efficacious for suppressing SVT with AV nodal or intraatrial reentrant mechanism, but less efficacious in patients with accessory AV pathway. The β-blocking and cellular antiarrhythmic effects of sotalol are not significantly reversed by exercise.

Study of P wave morphology in lead V 1 during supraventricular tachycardia for localizing the reentrant circuit

Paroxysmal supraventricular tachycardia (SVT) is a benign form of tachycardia that generally does not require costly evaluation. The purpose of this study was to describe a new sign permitting delineation of the mechanism of SVT by analysis of the P wave in lead V 1 and the left atrial electrogram, which may be registered by the esophageal electrode. Among 146 patients with SVT, 72 had a ventriculoatrial interval >70 msec. The P wave in lead V 1 during SVT was discernible in 69 of them. The precession of the left atrial electrogram on the P wave in lead V 1 was always associated with reentry through a left lateral (n = 37) or posteroseptal (n = 4) accessory atrioventricular (AV) connection. When the P wave in lead V 1 preceded or occurred simultaneously with the left atrial electrogram, reentry was through either the AV node or a right-sided accessory AV connection. On the other hand, although the P wave in lead V 1 was more frequently negative in reentry through a right-sided connection and positive in reentry through a left-sided connection, the polarity was not specific enough to identify the reentry. The precession of the left atrial electrogram recorded by the esophageal electrode on the P wave in lead V 1 during SVT was a specific criterion of reentry through a left accessory AV connection, and this technique could be useful for preliminary localization of the accessory connection before electrophysiologic study.

Determinants of the ventricular rate during atrial fibrillation

Determinants of the ventricular cycle length during atrial fibrillation were examined in 52 patients. Thirty-three patients had structural heart disease and none had an accessory atrioventricular (AV) connection. The AV node effective and functional refractory periods, the shortest atrial pacing cycle length associated with 1:1 conduction, the AV node conduction time and indexes of concealed conduction in the AV node were measured in the baseline state (36 patients) and after modification of sympathetic tone by infusion of isoproterenol or propranolol (8 patients each). Atrial fibrillation was then induced with rapid atrial pacing, and the mean, shortest and longest ventricular cycle lengths were measured.Variables that correlated most strongly with the mean RR interval during atrial fibrillation were the AV node effective refractory period (r = 0.93; p < 0.001), AV node functional refractory period (r = 0.87; p < 0.001) and shortest atrial pacing cycle length associated with 1:1 conduction (r = 0.91; p < 0.001). The AH interval during sinus rhythm (r = 0.74; p < 0.001) and during atrial pacing at the shortest cycle length with 1:1 conduction (r = 0.52; p < 0.001) had weaker correlations. Measures of concealed conduction did not improve the prediction of the mean or longest ventricular cycle length during atrial fibrillation.In conclusion, the refractory periods and conductivity of the AV node are the best indicators of the potential of the node to transmit atrial impulses to the ventricles during atrial fibrillation. The degree of concealed conduction in the AV node is a less important determinant of the mean ventricular rate during atrial fibrillation.

Follow-up evaluation of infant paroxysmal atrial tachycardia: transesophageal study.

We report results of follow-up transesophageal electrophysiologic studies in 35 infants seven to 27 months old (mean, 12 months) in whom paroxysmal atrial tachycardia (PAT) using an accessory atrioventricular (AV) connection had been previously evaluated by transesophageal study in the first 2 months (mean, 14 days) of life. No infants were receiving antiarrhythmic drug therapy at the time of follow-up study. To evaluate AV conduction and initiate PAT, a standard transesophageal pacing protocol was used: single extrastimuli in sinus rhythm, incremental pacing to second-degree AV block, and burst pacing at cycle lengths near those resulting in second-degree AV block. If PAT was not initiated during the baseline period, the protocol was repeated during the infusion of isoproterenol and after administration of atropine. At follow-up study, PAT was reinitiated in 24 of 35 (68%) infants, six of whom had exhibited recent spontaneous recurrence of PAT. AV nodal function did not differ in those with and those without inducible PAT. However, when initial and follow-up studies were compared, changes in antegrade conduction of the accessory AV connection were observed, since only five of 10 infants with preexcitation at initial study continued to exhibit preexcitation at follow-up study (1/5 infants only after isoproterenol). Additionally, changes in retrograde conduction of the accessory AV connection were observed; the ventriculoatrial interval in PAT induced at follow-up study increased by 20 to 40 msec in eight of 24 infants and by 50 to 80 msec in five of 24 infants compared with the interval at initial study.(ABSTRACT TRUNCATED AT 250 WORDS)

Spontaneous termination of reciprocating tachycardia owing to interaction of dual atrioventricular nodal pathways in patients with an accessory pathway

Retrospective analysis of the electrophysiologic recordings from 125 consecutive patients with reciprocating tachycardia involving an accessory atrioventricular (AV) pathway suggested, by the mode of spontaneous termination of reciprocating tachycardia, the coexistence of dual AV nodal pathways in 7 patients. Three different modes of spontaneous tachycardia termination were observed. In 2 patients with antidromic tachycardia, termination was a result of AV nodal reentry, preceded by a decrease in retrograde AV nodal conduction. In 3 other patients with antidromic tachycardia, termination occurred after a sudden switch from a slow to a fast AV nodal pathway, leading to conduction block in either the accessory pathway or the His-Purkinje system. In 2 patients with orthodromic tachycardia, termination was caused by a sudden change of anterograde conduction from a fast to a slow AV nodal pathway, eliciting an AV nodal echo beat. The interaction of dual AV nodal pathways within the reentry circuit incorporating the accessory pathway always inhibited sustained reciprocating tachycardia.

Electrophysiologic properties of flecainide acetate

Preliminary clinical experience indicates that flecainide is a useful antiarrhythmic agent for the suppression of spontaneous ventricular arrhythmias. The drug also exerts marked effects on accessory atrioventricular (AV) pathway and retrograde fast AV nodal pathway refractoriness, and therefore may be effective in treatment and prevention of reentrant supraventricular tachycardias. Electrophysiologic studies indicate that flecainide slows atrial, AV nodal, His-Purkinje and intraventricular conduction and, to a far lesser degree, prolongs refractory periods in these tissues. The effect of the drug in slowing conduction within the His-Purkinje system is particularly marked and is commonly associated with prolongation of the HV interval beyond the normal range. Flecainide causes a small but significant increase in the QT interval duration, which results largely from prolongation of the QRS interval. Significant prolongation of the sinus node recovery time has been observed in patients with preexisting sinus node dysfunction. Available electrophysiologic data suggest that flecainide should not be administered to patients with advanced disease of the His-Purkinje system or sinus node. The safety of the drug in patients with mild to moderate abnormalities of His-Purkinje conduction or sinus node function awaits further study.

Cardiac electrophysiologic effects of flecainide acetate for paroxysmal reentrant junctional tachycardias

Intravenous flecainide acetate was administered to 33 patients undergoing routine electrophysiologic study: 18 patients had a direct accessory atrioventricular (AV) pathway and 15 patients had functional longitudinal A-H dissociation (dual A-H pathways). Flecainide was given to 14 patients during sustained AV reentrant tachycardia and to 9 patients during sustained intra-AV nodal reentrant tachycardia. AV reentrant tachycardia was successfully terminated in 12 of 14 patients. Tachycardia termination was due to retrograde accessory pathway block in 11 patients and AV nodal block in 1. During flecainide administration, tachycardia cycle lengths increased (327 +/- 55 to 426 +/- 84 ms) principally because of retrograde conduction delay in the accessory pathway (127 +/- 34 to 197 +/- 67 ms). After flecainide administration, tachycardia reinitiation was not possible in 6 patients. In all 18 patients with accessory AV pathway conduction, flecainide significantly increased both anterograde and retrograde accessory pathway effective refractory periods, with anterograde accessory pathway block in 3 patients and retrograde accessory pathway block in 8. Intra-AV nodal reentrant tachycardia was successfully terminated in 8 of 9 patients. Tachycardia termination was due to retrograde "fast" A-H pathway block in 7 patients and anterograde "slow" A-H pathway block in 1 patient. During flecainide administration, tachycardia cycle lengths increased (326 +/- 50 to 433 +/- 64 ms) due to both anterograde, A-H and H-V (AV 242 +/- 97 to 343 +/- 75 ms), and retrograde, earliest ventricular to earliest atrial (51 +/- 14 to 70 +/- 23 ms) conduction delay. After flecainide administration, reinitiation of intra-AV nodal reentrant tachycardia was not possible in 4 patients. In all 15 patients with dual A-H pathways, flecainide selectively prolonged the retrograde effective refractory period of the fast A-H pathway, having little effect on anterograde fast A-H pathway refractoriness or on anterograde and retrograde slow A-H pathway refractoriness. Anterograde fast A-H pathway block occurred in 1 patient and retrograde fast A-H pathway block occurred in 6 patients. No serious adverse effects were encountered during the study. Flecainide acetate is an effective agent for the acute termination of both orthodromic AV and intra-AV nodal reentrant tachycardias. This antiarrhythmic action appears to be mediated through a predominant effect on either accessory AV pathway or retrograde fast A-H pathway refractoriness.