Accessory Accessory Atrioventricular Pathways Research Articles

Reversing the direction of paced ventricular and atrial wavefronts reveals an oblique course in accessory AV pathways and improves localization for catheter ablation.

The purpose of this study was to determine how often accessory atrioventricular (AV) pathways (AP) cross the AV groove obliquely. With an oblique course, the local ventriculoatrial (VA) interval at the site of earliest atrial activation (local-VA) and the local-AV interval at the site of earliest ventricular activation (local-AV) should vary by reversing the direction of the paced ventricular and atrial wavefronts, respectively. One hundred fourteen patients with a single AP were studied. Two ventricular and two atrial pacing sites on opposite sides of the AP were selected to reverse the direction of the ventricular and atrial wavefronts along the annulus. Reversing the ventricular wavefront increased local-VA by >/=15 ms in 91 of 106 (91%) patients. With the shorter local-VA, the ventricular potential overlapped the atrial potential along a 17.2+/-8.5-mm length of the annulus. No overlap occurred with the opposite wavefront. Reversing the atrial wavefront increased local-AV by >/=15 ms in 32 of 44 (73%) patients. With the shorter local-AV, the atrial potential overlapped the ventricular potential along an 11.9+/-8.9-mm length of the annulus. No overlap occurred with the opposite wavefront. Mapping during longer local-VA or local-AV identified an AP potential in 102 of 114 (89%) patients. Catheter ablation eliminated AP conduction in all 111 patients attempted (median, 1 radiofrequency application in 99 patients with an AP potential versus 4.5 applications without an AP potential). Reversing the direction of the paced ventricular or atrial wavefront reveals an oblique course in most APs and facilitates localization of the AP potential for catheter ablation.

Ventricular preexcitation in children and young adults: atrial myocarditis as a possible trigger of sudden death.

Sudden death (SD) in ventricular preexcitation (VP) syndrome is believed to be the result of atrial fibrillation with rapid ventricular response over the accessory pathway. Previous reports are anecdotal and often lack autopsy validation. Prevalence and clinicopathological features of VP were investigated in a series of 273 SDs in children and young adults (aged <or=35 years). Site of accessory atrioventricular (AV) connection was predicted by 12-lead ECG. Right and left AV ring together with the sinoatrial and AV septal junction were studied in serial histological sections. Ten patients (3.6%; male, mean age 24+/-7 years) had VP: 8 had Wolff-Parkinson-White (WPW) and 2 had Lown-Ganong-Levine (LGL) syndrome. Six patients had previous symptoms, and SD occurred at rest in all but 1. Pathological substrates of LGL consisted of AV-node hypoplasia and right-sided atrio-Hisian tract, respectively. In the 8 WPW patients, 10 total accessory AV pathways consisting of ordinary myocardium were found (7 left lateral, 2 right posterolateral, and 1 septal). These pathways were close to the endocardium (mean distance, 750+/-530 microm) and 310+/-190 microm thick. In 4 WPW patients (50%), isolated acute atrial myocarditis was found, which was polymorphous in 1 and lymphocytic in 3. VP accounted for 3.6% of SD in young people and was not preceded by warning symptoms in 40%. A left accessory pathway was the most frequent substrate, and its subendocardial location supports the feasibility of catheter ablation. Isolated atrial myocarditis may act as a trigger of paroxysmal atrial fibrillation that leads to SD.

Characteristic electrocardiographic features of manifest left anterior paraseptal accessory atrioventricular connection

Manifest left anterior paraseptal accessory atrioventricular (AV) connections are extremely rare, and their associated electrocardiographic preexcitation pattern has not been well defined. In this report we give an account of the unique surface electrocardiographic (ECG) features exhibited by a patient with a documented left anterior paraseptal accessory AV pathway. Additionally, we show that this unique ECG pattern can be reproduced in patients lacking this pathway by ventricular pacing at this left anterior paraseptal location. A 28-year-old woman with a 10-year history of paroxysmal supraventricular tachycardia was referred for intracardiac electrophysiology study. A 12-lead ECG obtained during atrial-paced rhythm (Fig. 1, A) showed a frontal plane axis of +110 degrees and ventricular preexcitation with a P wave to A wave interval of 60 msec. The h waves were positive in leads II, III, and aVF and negative in lead V1. QRS complexes were isoelectric in lead V1, negative in leads V2 to V4, and positive in leads V5 to V6. With standard percutaneous techniques, intracardiac multipolar electrode catheters were placed in the high right atrium, right ventricular apex, His bundle region, and coronary sinus. To precisely localize the ventricular insertion of the accessory AV connection, a deflectable quadripolar catheter (2 mm interelectrode distance) was positioned along the ventricular side of the mitral annulus with the retrograde transaortic approach. During sinus rhythm with ventricular preexcitation evident, mapping of the mitra] annulus revealed earliest ventricular activation with the tip of the mapping catheter located at a left anterior paraseptal location (Fig. 2, A). During orthodromic AV reciprocating tachycardia, the earliest retrograde atria] activation was recorded at the same site (Fig. 2, B). Simultaneous activation

Atrial and accessory pathway activation direction in patients with orthodromic supraventricular tachycardia: Insights from vector mapping

Objectives. The purpose of this study was to utilize vector mapping to investigate atrial and accessory pathway activation direction during orthodromic supraventricular tachycardia.Background. Although advances have been made in the electrophysiologic evaluation and management of accessory pathways, our understanding of accessory pathway anatomy and physiology remains incomplete. Vector mapping has been validated as a method of studying local myocardial activation.Methods. In 28 patients with a left-sided or posteroseptal accessory atrioventricular (AV) pathway referred for ablation, atrial and accessory AV pathway activation direction was determined during ventricular pacing or orthodromic supraventricular tachycardia, or both, by summing three orthogonally oriented bipolar electrograms recorded from the coronary sinus to create three-dimensional vector loops. Atrial and accessory AV pathway activation direction was determined in all patients from the maximal amplitude vectors of the vector loops. Because of beat to beat variability in the directions of the vector loops, data from 8 of 28 patients could not be analyzed.Results. At 81 of 83 sites, atrial activation direction along the long axis of the coronary sinus corresponded with the direction suggested by activation time mapping. Activation direction along the anteroposterior and inferosuperior axes was variable, potentially due to variations in the level of the atrial insertion of the accessory AV pathway and in the depth or angling of pathway fibers in the AV fat pad. In eight patients, at least one recording was obtained at the site of an accessory AV pathway potential. Accessory AV pathway activation proceeded superiorly and to the right in seven of eight patients; in one patient with a posteroseptal pathway, accessory AV pathway activation proceeded superiorly and to the left.Conclusions. 1) Vector mapping is a useful technique for localizing accessory AV pathways; 2) left-sided accessory AV pathways angle from left to right as they traverse the AV groove; and 3) variable activation directions of the atrial myocardium adjacent to the coronary sinus suggest that accessory AV pathway insertion into the atrium differs from patient to patient.

Catheter ablation of accessory atrioventricular pathways in young patients: Use of long vascular sheaths, the transseptal approach and a retrograde left posterior parallel approach

Objectives. This study retrospectively assesses the technical aspects of the catheter techniques used to ablate 83 accessory atrioventricular (AV) pathways during 88 procedures in 71 pediatric and adult patients (median age 14 years, range 1 month to 55 years). A number of catheter approaches and techniques evolved that may have improved success and shortened procedure times.Background. Radiofrequency catheter ablation of accessory AV pathways can be highly successful. However, the technical difficulty of many of the procedures is masked by the success rate.Methods. Left free wall, right free wall and septal accessory pathways were ablated with a variety of approaches.Results. Left free wall pathways were ablated successfully by using a standard retrograde approach through the aortic valve in only 10 (24%) of 43 cases. The remaining 33 (76%) required an approach that was either retrograde through the mitral valve (2 of 33), transseptal (21 of 33) or retrograde where the catheter was advanced behind the posterior mitral leaflet at the point of mitral-aortic continuity, so that the catheter course was parallelrather than perpendicularto the mitral anulus (10 of 33). Nineteen of 20 septal pathways were ablated successfully by using either the parallel approach (2 of 29), a transseptal approach (2 of 19), ablation within the coronary sinus or one of its veins (8 of 19) or ablation on the atrial side of the tricuspid valve (7 of 19). Fifteen of 20 right free wall pathways were ablated successfully with a variety of approaches on both the atrial and the ventricular side of the tricuspid valve. Long vascular sheaths were judged to contribute directly to success in 33 (43%) of 77 pathways. The overall success rate has been 93% (77 of 83 pathways), with 100% success for left free wall (43 of 43), 75% for right free wall (15 of 20) and 95% for septal pathways (19 of 20).Conclusions. Thus, successful ablation of accessory AV pathways in a mixed group of pediatric and adult patients appears to benefit from a wide range of vascular and catheter approaches.

Clinical characteristics and electrophysiologic properties of atrioventricular accessory pathways: Importance of the accessory pathway location

Objectives. This study was designed to assess the influence of accessory atrioventricular (AV) pathway location on the clinical and electrophysiologic characteristics of 384 consecutive symptomatic patients having a single accessory pathway.Methods. Four locations were studied: left free wall (n = 270), posteroseptai (n = 52), anteroseptal (n = 29) and right free wall (n = 33). Ten clinical variables and 12 electrophysiologic variables were analyzed, including the effective refractory period of the accessory pathway and the different clinically occurring and inducible arrhythmias.Results. Only two clinical findings were associated with accessory pathway location: 1) later age at onset of symptoms in the left free wall versus other accessory pathway locations (24 ± 12 vs. 20 ± 11 years, p = 0.02), and 2) later age at the time of electrophysiologic study in the left free wall accessory pathway location (36 ± 13 vs. 32 ± 11 years, p = 0.01).Six electrophysiologic variables showed a correlation with the accessory pathway location: 1) retrograde conduction only was found less frequently in right free wall (9%) and anteroseptal (10%) than in left free wall (26%) and posteroseptal (29%) accessory pathway locations (p = 0.05); 2) the retrograde effective refractory period of the accessory pathway was shorter in anteroseptal (253 ± 52 ms) and left free wall (270 ± 72 ms) as compared with right free wall (296 ± 101 ms) and posteroseptal (301 ± 76 ms) locations (p = 0.05); 3) retrograde decremental conduction over the accessory pathway was present in the posteroseptal (17%) and left free wall (3%) but absent in the other locations (p < 0.001); 4) anterograde decremental conduction was only seen in the right free wall location (12%) (p < 0.001); 5) orthodromic reentrant tachycardia was induced less frequently in the right free wall than in other locations (70% vs. 93%, p < 0.001); and 6) inducibility of atrial fibrillation was greater in anteroseptal (62%) than in right free wall (21%), left free wall (44%) and posteroseptal (36%) locations (p = 0.01).Conclusions. The location of the accessory AV pathway is associated with specific electrophysiologic characteristics.

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.

Localization and radiofrequency catheter ablation of accessory AV pathways in Wolff-Parkinson-White syndrome.

Direct catheter recordings of accessory pathway activation were utilized to localize accessory atrioventricular (AV) pathways for radiofrequency catheter ablation in 187 patients with Wolff-ParkinsonWhite syndrome. Closely spaced bipolar catheter electrodes (1.5-2.5 mm center-to-center) were positioned perpendicular to the mitral anulus (orthogonal electrodes placed circumferentially around the catheter) and the tricuspid anulus (conventional ring electrodes), and recordings were obtained at low gain « 1 cm/mV). The small recording range of the close bipolar electrodes minimized the recording of distant atrial or ventricular potentials occurring simultaneously with accessory pathway activation and enabled differentiation of accessory pathway activation potentials from local atrial and ventricular potentials. For ablation, a special large tip electrode (7F, 4 mm long, 27 mrrr' surface area) was positioned against the mitral or tricuspid anulus at a site guided by direct recordings of accessory pathway activation. The large tip electrode was positioned either beneath or above the leaflet, and radiofrequency current (power approximately 30 watts) was delivered for approximately 45 seconds to the large tip electrode using a large skin lead for the return electrode .

Electrophysiological Demonstration of Anterograde Concealed Conduction in Accessory Atrioventricular Pathways Capable Only of Retrograde Conduction

Anterograde concealed conduction into the concealed accessory atrioventricular (AV) pathway has been postulated to be one of the factors preventing the reciprocating process via the accessory pathway in patients with the concealed Wolff-Parkinson-White(WPW) syndrome but its presence has not been documented. To demonstrate the occurrence of anterograde concealment, 12 patients with the concealed WPW syndrome were selected for study. A pacing protocol was designed in which the retrograde conduction of the ventricular extrastimulus over the accessory pathway was assessed during ventricular pacing alone (conventional method) and during the AV simultaneous pacing (simultaneous method); the results were then compared. When the high right atrium was simultaneously paced, the effective refractory period of the concealed accessory pathway shortened as compared with the conventional method in five of 12 patients (from 341.7 +/- 110.8 to 312.5 +/- 108.2 msec, n = 12), whereas, it decreased in all patients studied when the coronary sinus near the accessory pathway was simultaneously paced (from 375.7 +/- 135.0 to 287.1 +/- 116.1 msec, n = 7). These results demonstrate that the AV simultaneous pacing frequently shortens the refractoriness of the concealed accessory AV pathway and such facilitation seems to be well explained by the probable anterograde concealment in it and peeling back of the refractory barrier.

Frequency, diagnosis and clinical characteristics of patients with multiple accessory atrioventricular pathways

Multiple accessory atrioventricular (AV) pathways were documented in 52 of 388 patients (13%) who underwent detailed electrophysiologic evaluation. Multiple AV pathways were identified during intraoperative mapping or electrophysiologic study by (1) different patterns of ventricular preexcitation during atrial fibrillation, flutter or atrial pacing with different delta-wave morphologic and ventricular activation patterns; (2) different sites of atrial activation during right ventricular pacing or orthodromic reciprocating tachycardia; or (3) preexcited reciprocating tachycardia using a second pathway as the retrograde limb of the tachycardia. A logistic model was used to determine which clinical, electrocardiographic and electrophysiologic variables were associated with multiple AV pathways. Right free-wall and posteroseptal accessory AV pathways were more common in patients with multiple AV pathways and were frequently associated. Multivariate logistic regression identified Ebstein's anomaly, and a history of preexcited reciprocating tachycardia as significant variables (p < 0.0001). Pathway location was not subjected to statistical analysis because of confounding variables.

Clinical efficacy and electrophysiologic effects of intravenous and oral encainide in patients with accessory atrioventricular pathways and supraventricular arrhythmias

The electrophysiologic effects and clinical efficacy of intravenous (i.v.) and oral encainide were studied in 13 patients with accessory atrioventricular (AV) pathways (7 overt, 1 intermittent and 5 concealed) and drug-resistant Supraventricular arrhythmias (5 paroxysmal atrial fibrillation, 1 atrial tachycardia and 7 with orthodromic circus movement tachycardia). Previously, therapy had failed with a mean of 3 conventional antiarrhythmic agents. In 5 patients, amiodarone administration had also been unsuccessful. All patients underwent programmed electrical stimulation of the heart before and after 1.5 mg/kg of i.v. encainide. Seven patients were restudied during oral encainide therapy (mean 155.8 ± 54.2 mg/ day) 3 days to 6 weeks (average 21 days) later. Anterograde conduction over the accessory AV pathway blocked in 4 of 7 patients after i.v. encainide. Oral encainide blocked anterograde conduction over the accessory pathway or prolonged the refractory period of the accessory pathway in 3 of 4 patients. This change in anterograde conduction was independent of the predrug value for the anterograde refractory period of the accessory AV pathway. Intravenous and oral encainide had minimal effects on retrograde conduction over the accessory AV pathway. The clinical effect of oral encainide was studied in 12 patients. Four patients responded to oral encainide and have been free of arrhythmia or side effects for 2 to 20 months (average 10.5). Encainide failed to prevent the clinical arrhythmia in 2 patients. In 4 patients with atrial arrhythmias, circus movement tachycardia developed during oral encainide therapy. In 1 patient the frequency of circus movement tachycardia increased with oral encainide treatment. Five of the previous 7 patients also suffered from central nervous system side effects, and in 1 patient serious central nervous system effects led to withdrawal of encainide. In conclusion, encainide has a marked effect on anterograde conduction and a minimal effect on retrograde conduction over the accessory AV pathway. Oral encainide was effective in controlling Supraventricular arrhythmia in 4 of 12 of this selected group of patients with accessory AV pathways. Failure to control the initial arrhythmia, facilitation of circus movement tachycardia and central nervous system side effects led to discontinuation of oral encainide in the other patients.

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.