Accessory Atrioventricular 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.

Accessory pathway recording and ablation

Beginning in the mid-1970s, surgical ablation of accessory atrioventricular (AV) pathways (APs) was performed at a limited number of centers. The potential to target APs by catheter ablation became apparent in 1982, when Scheinman and coworkers introduced catheter ablation of the AV junction using high-energy direct current (DC) shocks from a defibrillator to produce AV block as palliative therapy for drug-resistant supraventricular tachyarrhythmias. Early attempts at DC shock ablation of APs were associated with some success,1 but the large area of barotrauma limited focused ablation and was associated with risk of cardiac perforation, AV block, and coronary artery injury.

Evolution of acute ST-segment elevation myocardial infarction in a patient with ventricular preexcitation

Wolff-Parkinson-White pattern is a relatively common electrocardiographic phenomenon caused by accessory atrioventricular (AV) conduction, which can make the diagnosis of acute myocardial infarction challenging. There is little existing literature regarding the interpretation of electrocardiograms in patients with accessory AV conduction pathways who present with acute myocardial infarction. We describe a case of electrocardiographic evolution of acute ST-segment elevation myocardial infarction in a patient with Wolff-Parkinson-White pattern, review pseudo-infarction patterns, and discuss proposed mechanisms for these repolarization abnormalities.

P waves in the electrocardiogram recording of tachycardia: 'You can run, but you cannot hide'

This editorial refers to ‘A new method of filtering T waves to detect hidden P waves in ECG signals’ by D. Goldwasser et al ., on page 1028. The history of the evolution of recording of cardiac electrical activities by electrocardiogram (ECG) is quite fascinating.1 The initial ECG recording systems used by Waller, Einthoven, and Lewis consisted of mercury capillary electrometers and string galvanometers that were cumbersome to use and provided limited information.1–3 In Waller's demonstration of the human ECG, only ventricular activities were recorded and the P waves were not discernible.1 Interestingly, even today there are situations where in the ECG recordings obtained with modern and sophisticated ECG machines the P waves may not be easily discernible. Interpretation of ECG recordings remains fundamental to the clinical investigation of cardiac arrhythmias. To confirm the diagnosis of ventricular tachycardia from the ECG tracing of a wide complex tachycardia would require accurate detection of the P waves to determine atrioventricular (AV) dissociation. Likewise, detection of the P waves, their morphological characteristics, axis, and timing relationships with the R waves would be important to confirm and further differentiate supraventricular tachycardias (SVTs) into AV nodal reentrant tachycardia (AVNRT), accessory bypass tract-mediated AV reentrant tachycardia (AVRT), atrial tachycardia, junctional ectopic tachycardia, or sinus tachycardia. However, simple as it sounds, the task of finding P waves let alone their characterization may be extremely difficult, if not impossible. In an approach to make a correct diagnosis of SVT recorded by 12-lead ECG, general criteria such as RP intervals, QRS alternans, pseudo-r′, pseudo-S-wave, etc. although frequently used, lack robustness in their sensitivity and specificity. Because the P waves are generated by the atrial chambers that have lower muscle mass, they are of lower amplitude when compared with the QRS complexes. As such, during SVT …

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.

Preexcitation unmasked after successful accessory atrioventricular connection ablation: What is the mechanism?

Case presentation A 19-year-old man with a history of palpitations and no underlying structural heart disease underwent electrophysiologic diagnostic evaluation for possible catheter ablation of the arrhythmogenic substrate responsible for the palpitations. Twelve-lead ECG showed ventricular preexcitation consistent with a left free-wall accessory atrioventricular (AV) connection (Figure 1A). Electrophysiologic study was performed using standard methodology with catheters in the right ventricular apex (RVA), high right atrium (HRA), His bundle, and coronary sinus. Basic intervals during sinus rhythm were as follows: PR interval 110 ms, AH interval 40 ms, HV interval 0 ms, and QRS duration 110 ms. Ventricular preexcitation was maximal during incremental atrial pacing (Figure 1B). Ventricular pacing showed nondecremental and eccentric retrograde ventriculoatrial (VA) conduction. HRA programmed stimulation induced a minimally preexcited AV reciprocating tachycardia with eccentric VA conduction (Figures 1B and 2A). Measurements of the tachycardia were as follows: AH interval 238 ms, HV interval 16 ms, and VA interval 151 ms. Retrograde conduction was due to a left free-wall accessory AV connection. However, during tachycardia, the HV interval was shorter than expected (Figure 2A). We performed radiofrequency catheter ablation of the left freewall accessory AV connection with subsequent VA dissociation during RVA pacing. After the successful ablation, a short HV interval and ventricular preexcitation of possible septal origin were apparent (Figures 1C and 2B). Atrial pacing showed rateependent prolongation of the AH interval with fixed HV nterval. Intravenous adenosine bolus showed blocked P aves with no change in degree of ventricular preexcitation.

Supraventricular tachyarrhythmias: drug therapy versus catheter ablation.

Until recently, the only options available for treatment of supraventricular arrhythmias involved the use of drug therapy or cardiac surgery. However, over the past several years with the introduction of radiofrequency energy sources as well as steerable catheters, the clinician has a variety of additional nonpharmacologic options. This article reviews the use of pharmacologic therapy versus catheter ablation for the treatment of reentrant supraventricular arrhythmias, involving the atrioventricular junction and/or accessory atrioventricular connection, as well as arrhythmias emanating from the atria such as atrial fibrillation, atrial flutter, and atrial tachycardia.

Para-Hisian pacing: Useful clinical technique to differentiate retrograde conduction between accessory atrioventricular pathways and atrioventricular nodal pathways

Para-Hisian pacing is a useful tool to differentiate between retrograde conduction over an accessory pathway and retrograde conduction over the fast or slow atrioventricular (AV) nodal pathways. 1-3 Para-Hisian pacing uses right ventricular (RV) pacing close to the His bundle or proximal right bundle branch (RBB). As the position of the ventricular pacing catheter changes subtly during respiration (or by changing pacing output), the pacing stimulus changes capture among (1) basal anteroseptal RV plus His bundle or proximal RBB (His bundle-RBB capture); (2) capture of basal anteroseptal RV alone; and (3) His bundle-RBB capture alone. These changes in pacing capture result in abrupt changes in the timing of His bundle activation relative to the timing of ventricular activation. The presence or absence of a change in atrial activation sequence, stimulus-atrial (SA) intervals, and His bundle-atrial (HA) interval identifies whether retrograde conduction is dependent on ventricular activation (retrograde conduction over an accessory pathway) or His bundle activation (retrograde conduction over the AV node) or both (accessory pathway and AV node; Figures 1 and 2). The loss of His bundle-RBB capture is usually identified by the widening of the QRS complex, indicating that some of the ventricular myocardium (farthest from the RV basal septal pacing site) is activated by the His-Purkinje system during both RV and His bundle-RBB capture. Our preferred approach is to position the RV pacing catheter toward the RV outflow tract, 1‐2 cm superior to the His bundle catheter. While pacing at moderate output (5‐10 mA and 2 ms pulse width), the RV catheter is slowly withdrawn toward the His bundle catheter (proximal RBB) until intermittent His bundle-RBB capture occurs because of changes in catheter position during respiration. As the pacing catheter is moved closer to the His bundle, the ventricular potential in the His bundle electrogram becomes earlier and the retrograde His bundle potential becomes later, providing greater separation between the local ventricular and His bundle potentials. The use of closely spaced electrodes (1 mm edge-to-edge) on the His bundle catheter shortens the duration of the local ventricular potential in the His bundle electrogram, preventing the masking of the His bundle potential by the local ventricular potential. Closely spaced electrodes on the pacing catheter may provide a smaller pacing field, facilitating intermittent loss of His bundle-RBB capture with small changes in catheter position during respiration. A deflectable RV pacing catheter is positioned more easily for para-Hisian pacing and subsequent positioning of the pacing catheter close to the location of an accessory pathway (Figure 3A). In patients with proximal RBB block (such as resulting from previous ablation), His bundle-RBB capture requires pacing proximal to the RBB block site and may not be achieved from the RV. Other approaches include changing pacing output to achieve intermittent His bundle-RBB capture and use of the distal electrodes on the His bundle catheter for pacing. 4

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.

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.

Electrophysiologic characteristics, electropharmacologic responses and radiofrequency ablation in patients with decremental accessory pathway

Objectives. This study sought to characterize the functional properties of decremental accessory atrioventricular (AV) pathways and to investigate their pharmacologic responses.Background. Although decremental AV pathways associated with incessant reciprocating tachycardia have been studied extensively, information about the electrophysiologic characteristics and pharmacologic responses of anterograde and retrograde decremental AV pathways is limited.Methods. Of 759 consecutive patients with accessory pathway-mediated tachyarrhythmia, 74 with decremental AV pathways were investigated (mean age 43 ± 18 years). After baseline electrophysiologic study, the serial drugs adenosine, verapamil and procainamide were tested during atrial and ventricular pacing. Finally, radiofrequency catheter ablation was performed.Results. Five patients had anterograde decremental conduction over the accessory pathway but had no retrograde conduction. Of the 64 patients with retrograde decremental conduction over the accessory pathway, anterograde conduction over the pathway was absent in 41 (64%), intermittent in 5 (8%) and nondecremental in 18 (28%). In the remaining five patients, anterograde and retrograde decremental conduction over the same pathway was found. The anterograde and retrograde conduction properties and extent of decrement did not differ between anterograde and retrograde decremental pathways. Posteroseptal pathways had the highest incidences of anterograde and retrograde decremental conduction. Intravenous adenosine, procainamide and verapamil caused conduction delay or block, or both, in 10 of 10, 10 of 10 and 4 of 10 of the anterograde and 20 of 20, 20 of 20 and 8 of 20 of the retrograde decremental pathways, respectively. All patients had successful ablation of the decremental pathways without complications. During the follow-up period of 31 ± 19 months, only one patient experienced recurrence.Conclusions. Decremental accessory pathways usually had functionally distinct conduction characteristics in the anterograde and retrograde directions. Their pharmacologic responses suggested the heterogeneous mechanisms of decremental conduction.

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

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.

Successful and unsuccessful sites of radiofrequency catheter ablation of accessory atrioventricular connections

Local electrograms from 47 consecutive patients who underwent successful radiofrequency catheter ablation of 49 accessory atrioventricular (AV) connections were analyzed. One hundred twenty-two local electrograms were recorded at 27 successful and 95 unsuccessful sites immediately before radiofrequency catheter ablation of 27 manifest accessory AV connections during preexcited sinus rhythm or atrial pacing. Continuous electric activity was found in 96% of successful sites versus 71% of unsuccessful sites ( p < 0.01). Possible accessory pathway (AP) potentials were present only in 15% of successful and 2% of unsuccessful sites, respectively ( p < 0.05). All measured time intervals were significantly shorter for successful sites as compared to unsuccessful sites of ablation of manifest accessory AV connections. Unipolar electrograms from the tip of the ablation catheter of each successful and unsuccessful ablation site were available for the last 16 patients with manifest accessory AV connections. A PQS pattern of the unipolar electrogram was associated with a higher success rate, whereas a PrS pattern never resulted in successful ablation of an accessory AV connection. Multivariate logistic regression analysis of the local electrogram characteristics of rapidly conducting, concealed accessory AV connections revealed the interval between the onset of the local ventricular and atrial electrogram (VoAo interval) as the only independent variable associated with successful sites for radiofrequency catheter ablation. The only study patient with a slowly conducting, concealed accessory AV connection underwent successful ablation with the first lesion of radiofrequency energy at the site with the shortest VoAo interval. We conclude that (1) the shortest local AV intervals and local ventricular electrograms preceding the earliest onset of the delta wave in any surface lead are predictive of successful ablation of manifest accessory AV connections; (2) the shortest local VA intervals during orthodromic AV reentry tachycardia or right ventricular pacing are predictive of successful ablation of concealed accessory AV connections; and (3) unipolar recordings from the tip of the ablation catheter should be recorded routinely during mapping of manifest accessory AV connections to identify appropriate target sites for radiofrequency energy applications.

Memory T waves after radiofrequency catheter ablation of accessory atrioventricular connections in wolff-parkinson-white syndrome

Generalized, extensive electrical repolarization abnormalities, represented by negative or abnormally peaked T waves, are frequently observed after radiofrequency catheter ablation of overt accessory atrioventricular (AV) connections in Wolff-Parkinson-White (WPW) syndrome. Two mechanisms have been proposed to explain these changes: subendocardial injury, secondary to the application of radiofrequency lesions, and memory T waves. The purpose of this study is to evaluate the electrocardiographic (ECG) changes in patients with overt and concealed accessory AV connections after ablation. Fifty-one patients with accessory AV connections who underwent successful radiofrequency ablation were included in the study. Twenty-four patients with clear, manifest, and permanent preexcitation (group 1) were compared with 27 patients with concealed accessory AV connections (group 2). Electrocardiograms were obtained in all patients before ablation, shortly after ablation (within 4 hours), and late after ablation (6 weeks). The frontal and horizontal QRS-T angles in the ECGs, number of lesions, total Joules applied, total peak creatine kinase, and total peak creatine kinase-MB units were compared in both groups. Of the 24 patients with overt accessory AV connections, 23 (95.8%) demonstrated repolarization abnormalities in the ECG shortly after the procedure that reverted almost completely at 6 weeks. Of the 27 patients with concealed accessory AV connections, only 2 (7.4%) demonstrated repolarization abnormalities after the ablation ( P < .0001). The persistence of an abnormal QRS-T angle immediately after ablation in patients with overt accessory AV connections is caused by an abnormality in the T wave axis, opposite to the direction of the normal QRS axis. This phenomenon is an indicator of memory T waves (pseudo-primary T wave change), and after radiofrequency ablation does not correlate with myocardial damage. This is a transitory and benign phenomenon and should reverse after approximately 6 weeks. Patients with suspected ischemia should be evaluated by a method more specific than the ECG.

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)

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.

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.

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.