Coexistence of functional Kent and Mahaim-type tracts in the pre-excitation syndrome. Demonstration by catheter techniques and epicardial mapping

Multiple Ablation Targets in Children: Multiple Accessory Pathways and Coexistent Arrhythmia

The coexistence of different mechanisms of arrhythmia and multiple accessory pathways (MAPs) leading to multiple ablation targets is rarely seen in children, and data regarding these patients in the literature are limited. Herein, we aimed to evaluate patients who required multiple ablation applications, focusing on different targets during the procedures in children, and evaluating the characteristics of coexistent arrhythmia and MAPs, and the results of these procedures in children. Ablation procedures conducted between March 2009 and December 2018 were evaluated retrospectively, and patients with MAPs and/or coexistent arrhythmia who had undergone ablation procedures were included in the study. Among the 1210 patients who underwent ablation procedures, 52 patients (26 male, 26 female) were ablated for multiple targets. Of the 456 patients with APs, 21 had MAPs (4.6%) and of the 1210 patients who underwent ablation procedures, 31 patients had coexistent arrhythmia (2.5%). The patients had a mean age of 12.24 ± 3.4 (4-18) years and mean body weight of 45.17 ± 14.12 (17-74) kg. A total of 110 APs or foci were identified as quaternary in one patient, while it was triple in four patients. The procedures were unsuccessful in six targets of six patients. Although recurrence was observed in four patients, none were ablated for MAPs. Two complications were encountered, comprising ST segment depression that developed in one patient with Wolf-Parkinson-White syndrome, atrioventricular nodal re-entry tachycardia, and a temporary atrioventricular block during atrioventricular nodal re-entrant tachycardia ablation. The overall success rate according to the pathway/foci number was 94.5% (104/110), with a recurrence rate of 4.5% (5/110), and a complication rate of 1.8% (2/110). The patient success, recurrence, and complication rates were 88.4% (46/52), 7.6% (4/52), and 3.8% (2/52), respectively. In conclusion, the incidence of multiple arrhythmogenic foci and MAPs were not as low as expected in children. A structured and stepwise approach is mandatory for the diagnosis of the different mechanisms of tachycardia, even after successful ablation procedures. The success, recurrence, and complication rates were comparable with those of patients who had a solitary arrhythmogenic focus or solitary AP.

New observation of electrocardiogram during sinus rhythm on the atriofascicular and decremental atrioventricular pathways/clinical perspective: [corrected] terminal QRS [corrected] complex slurring or notching

BACKGROUND

Atriofascicular and decremental atrioventricular pathways are variants of accessory pathways with anterograde decremental conduction properties. They result in typical wide Quantronic Resonance System (QRS) tachycardia of left bundle branch block morphology. Data on the sinus rhythm electrocardiographic characteristics are limited.

METHODS AND RESULTS

Thirty patients with accessory pathways of anterograde decremental conduction properties were studied retrospectively (10 atriofascicular pathways and 20 decremental atrioventricular pathways). All patients had a pre-excited atrioventricular tachycardia with anterograde conduction over anterograde decrementally conducting fiber. Eighteen patients fulfilled criteria of minimal pre-excitation during sinus rhythm before ablation. In 10 patients (33%), delta wave was absent, and the only abnormality was terminal QRS slurring or notching on the ECG. It was mainly in leads I, V5, and V6. After ablation, terminal QRS slurring or notching disappeared in all 10 patients. We also did a survey in a control group comprised of 200 subjects without structural heart disease who were matched for age and sex. Terminal QRS slurring or notching was found in 3%.

CONCLUSIONS

This study showed a high prevalence of terminal QRS slurring or notching in patients with atriofascicular or decremental atrioventricular pathways. It can be the sole manifestation of such accessory pathways during sinus rhythm, and disappearance of terminal slurring or notching can be the only hallmark of successful ablation visible on the surface ECG.

Right posterior atrioventricular ring: a location for different types of atrioventricular accessory connections

We present an unusual case of a 28-year-old female patient with recurrent episodes of tachycardias due to participation of two accessory connections located in the posterior tricuspid annulus. Both connections were of the atrioventricular type, the one with non decremental fast conducting properties at the right posteroseptal area, the other with node-like properties at the posterolateral tricuspid ring. Both pathways were successfully ablated transvenously with radiofrequency energy application at the same session. Implications about a common embryological origin of the two pathways as well as review of the literature for similar cases are presented.

Radiofrequency catheter ablation of two right Mahaïm-like accessory pathways in a patient with Ebstein's anomaly

A 17-year-old woman with Ebstein's anomaly and recurrent episodes of antidromic tachycardia with two distinct morphologies is described. The tachycardias were produced by two separate Mahaïm-like accessory pathways. These were localized by their activation potentials at the anterolateral ventricular margin of the tricuspid annulus and ablated in a single session using radiofrequency current.

A left free-wall, decrementally conducting, atrioventricular (Mahaim) fiber: diagnosis at electrophysiological study and radiofrequency catheter ablation guided by direct recording of a Mahaim potential

A 64-year-old female with Wolff-Parkinson-White syndrome and an ECG demonstrating a right posterolateral accessory pathway was referred for electrophysiological study. During electrophysiological testing two AV pathways were identified: a right posterolateral pathway that displayed conventional electrophysiological properties: and a left free-wall pathway that conducted only anterogradely and demonstrated decremental properties. Two separate wide complex tachycardias were induced that utilized the left free-wall pathway anterogradely and either the AV node or the right posterolateral accessory pathway retrogradely. A discrete electrical potential on the free wall of the mitral annulus was identified during tachycardia and was utilized to facilitate mapping and ablation.

Variants of preexcitation--specialized atriofascicular pathways, nodofascicular pathways, and fasciculoventricular pathways: electrophysiologic findings and target sites for radiofrequency catheter ablation

INTRODUCTION

In the present report, the electrophysiologic findings in patients with different types of variants of preexcitation, i.e., atriofascicular, nodofascicular, 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 atriofascicular 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 five 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 be 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 be 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.

CONCLUSION

The majority of patients with variants of the preexcitation syndrome present with specialized atriofascicular pathways that seem to originate from remnants of the specialized AV ring tissue. Nodofascicular and fasciculoventricular pathways exist and may give rise to preexcitation, although their functional role in participation of clinical arrhythmias still needs to be elucidated. In the present study, both a fasciculoventricular pathway and a nodofascicular pathway acted as a bystander.

Radiofrequency catheter ablation of Mahaim tachycardia by targeting Mahaim potentials at the tricuspid annulus

BACKGROUND

Reentrant tachycardias associated with Mahaim pathways are rare but potentially troublesome. Various electrophysiological substrates have been postulated and catheter ablation at several sites has been described.

OBJECTIVE

To assess the efficacy and feasibility of targeting discrete Mahaim potentials recorded on the tricuspid annulus for the delivery of radiofrequency energy in the treatment of Mahaim tachycardia.

PATIENTS

21 patients out of a consecutive series of 579 patients referred to one of three tertiary centres for catheter ablation of accessory pathways causing tachycardia. All had symptoms and presented with tachycardia of left bundle branch block configuration or had this induced at electrophysiological study. In all cases, the tachycardia was antidromic with anterograde conduction over a Mahaim pathway.

RESULTS

6 patients had additional tachycardia substrates (4 had accessory atrioventricular connections and 2 had dual atrioventricular nodal pathways and atrioventricular nodal reentry). After ablation of the additional pathways, Mahaim potentials were identified in 16 (76%) associated with early activation of the distal right bundle branch and radiofrequency energy at this site on the tricuspid annulus abolished Mahaim conduction in all 16 cases. In 2 patients there was early ventricular activation at the annulus without a Mahaim potential but radiofrequency energy abolished pre-excitation. In the remaining patients no potential could be found (1 patient), no tachycardia could be induced after ablation of an additional pathway (1 patient), or no Mahaim conduction was evident during the study (1 patient). During follow up (1-29 months (median 9 months)) all but 1 patient remained symptom free without medication.

CONCLUSIONS

Additional accessory pathways seem to be common in patients with Mahaim tachycardias. The identification of Mahaim potentials at the tricuspid annulus confirms that most of these pathways are in the right free wall and permits their successful ablation and the abolition of associated tachycardia.

Will C. Sealy, MD: the father of arrhythmia surgery--the story of the fisherman with a fast pulse

The development of clinical electrophysiology and arrhythmia surgery has a long and interesting history. On May 2, 1968, Dr. Will C. Sealy, with the electrophysiologists at Duke University, performed the first successful ablation of a pathway in a patient with Wolff-Parkinson-White syndrome using an epicardial approach. Thereafter, he and his colleagues developed improved endocardial techniques to ensure ablation of even multiple and complex anatomic pathways. From this work the impulse to perform these procedures spread worldwide, and a school of arrhythmia surgeons sprouted. For these and other accomplishments, Dr. Sealy clearly became the Father of Arrhythmia Surgery. The story is told herein.

Involvement of a nodofascicular connection in supraventricular tachycardia with VA dissociation

We present the case of a patient with episodes of supraventricular tachycardia and atrial dissociation that were terminated by either adenosine or verapamil. Involvement of an accessory pathway was shown by ventricular extrastimuli, elicited during His-bundle refractoriness, that interrupted the tachycardia or advanced the next His potential. The tachycardia circuit was demonstrated to be confined to the nodofascicular region based on the exclusion of surrounding tissues. Atrial activity, including that in the perinodal region, was totally dissociated during tachycardia. The lowest part of the circuit was determined to be located above the Hisian bifurcation, as multiple episodes with either a right or left bundle branch configuration during tachycardia did not modify the HH cycle. The ventricular septum summit was determined not to be involved, as no preexcitation was present during tachycardia or atrial pacing, and the right bundle branch was not part of the circuit. Radiofrequency current applied beneath the tricuspid valve at the His region successfully eliminated the nodofascicular connection with preservation of 1:1 AV conduction. The anatomical substrate underlying the abnormal connection may be either nodofasciculoventricular Mahaim fibers or a duality or dispersion of the nodo-Hisian conducting system.

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

BACKGROUND

Accessory pathways originating at the tricuspid annulus that exhibit decremental antegrade conduction properties (Mahaim-type preexcitation) are amenable to radiofrequency (RF) current catheter ablation. However, a reliable and reproducible strategy for mapping and ablation of these fibers is lacking.

METHODS AND RESULTS

Eleven patients with preexcited atrioventricular tachycardia involving a decrementally conducting antegrade accessory pathway underwent complete electrophysiological evaluation and subsequent attempts at RF catheter ablation. Mechanical conduction block at the subannular level of the atrial input to the accessory fiber was induced by catheter manipulation in 8 patients, in 2 of them during atrial fibrillation. RF current was delivered, after resumption of preexcitation, to the site of mechanical block during atrial pacing (n = 6) or atrial fibrillation (n = 2) and eliminated the accessory pathway in all 8 patients. In another patient, mechanical block was not observed, but ablation of the atrial accessory fiber insertion was achieved at the subannular level during atrioventricular tachycardia. The anatomic site of ablation along the tricuspid annulus was anterolateral (n = 1), lateral (n = 3), or posterolateral (n = 5). Failures were encountered in the first patient of the series in whom ablation attempts were directed at the ventricular insertion of the accessory fiber and in a patient in whom ablation of the atrial insertion was attempted at the supraannular level. Recurrence of preexcitation within 12 hours was observed in 5 of 6 patients in whom ablation had been achieved during atrial pacing. Eventually successful repeat sessions were performed the following day using a simplified ablation approach. Thus, a median of 5 RF pulses (range, 1 to 26) per accessory fiber eliminated conduction in 9 (82%) of the 11 patients in 1.9 +/- 0.9 sessions. During a follow-up of 9.5 +/- 2.3 months, preexcitation recurred in 1 patient.

CONCLUSIONS

The atrial origin of accessory connections with Mahaim-type preexcitation is apparently confined to the anterolateral-to-posterolateral region of the tricuspid annulus. Mechanical conduction block in the atrial input to the accessory fiber induced at the subannular level by catheter manipulation provides an optimal marker to locate the ablation site, even during atrial fibrillation. To expose early recurrence of antegrade accessory pathway conduction, intermittent atrial pacing in the 12 hours after ablation is advisable; in cases of recurrence, a repeat procedure can readily be performed using just the ablation catheter advanced to the target site at the tricuspid annulus.

Radiofrequency catheter ablation of right atriofascicular (Mahaim) accessory pathways guided by accessory pathway activation potentials

BACKGROUND

Accessory pathways (APs) exhibiting "Mahaim fiber" physiology (antegrade conduction only, long conduction time, and decremental properties) often connect the lateral right atrium to the right bundle branch (right atriofascicular pathways). Potentials from these pathways have not been recorded previously. The purpose of this study was to determine whether AP activation potentials could be recorded from right atriofascicular APs and to determine whether these potentials could be used to localize a site for catheter ablation.

METHODS AND RESULTS

Of 26 consecutive patients referred for catheter ablation of an AP producing a preexcited (antidromic) atrioventricular (AV) reentrant tachycardia having a left bundle branch block pattern with short ventriculoatrial and long AV intervals, 23 (88.5%) were found to have a right atriofascicular AP. During antidromic AV reentrant tachycardia, (1) right atrial extrastimuli (that did not penetrant tachycardia, (1) right atrial extrastimuli (that did not penetrate the AV node) advanced the timing of the next QRS complex, indicating that the AP was connected to the right atrium; (2) earliest antegrade ventricular activation was recorded at the apical right ventricular free wall, and (3) ventricular activation was preceded by activation of the distal right bundle branch, indicating a fascicular insertion or a ventricular insertion close to the terminus of the right bundle branch. A single, discrete, high-frequency AP potential was recorded at the lateral, anterolateral, or posterolateral tricuspid annulus in 22 of the 23 patients 63 +/- 12 milliseconds after the local atrial potential and 83 +/- 23 milliseconds before the local ventricular potential during sinus rhythm. The AP potential was also recorded at sites along the right ventricular free wall between the tricuspid annulus and the site of earliest ventricular activation at the apical region. Programmed atrial stimulation and adenosine each produced prolongation of AP conduction time because of an increase in the A-AP interval and Wenckebach block proximal to the AP potential. Radiofrequency current applied at a site recording the AP potential (tricuspid annulus in 19 patients and right ventricular free wall in 3 patients) eliminated AP conduction in all 22 patients. Tachycardia has not recurred in any patient during 18 +/- 13 months of follow-up. AP conduction was absent in all 9 patients who had a follow-up electrophysiological study 3.8 +/- 1.7 months after ablation.

CONCLUSIONS

Right atriofascicular APs consist of two components. The proximal component is located at the lateral, anterolateral, or posterolateral tricuspid annulus, does not generate an AP potential recordable by catheter electrodes, and is responsible for the decremental conduction properties. The "distal" component extends from the tricuspid annulus to the distal right bundle branch at the apical right ventricular free wall and generates a large, high-frequency AP potential that accurately identifies a site for ablation.

Catheter ablation of Mahaim fibers with preservation of atrioventricular nodal conduction

Three patients with refractory preexcited tachycardia implicating Mahaim fibers underwent attempted catheter ablation of the accessory pathway. In the absence of demonstrable retrograde conduction in Mahaim fibers, we located the accessory pathway ventricular insertion site using the criteria of concordance between paced and spontaneous QRS morphologies during pace-mapping and earliest onset of local electrogram relative to surface preexcited QRS. At this site, a QS-like pattern of unfiltered unipolar electrograms with steep downstroke was recorded. The optimal site appeared radiologically at the right ventricular anterior wall or the adjacent septum, 2-4 cm from the tricuspid anulus. Three to six 160-J shocks were delivered at this site using an anterior chest wall plate as anode. After fulguration, conduction through the Mahaim tract was absent. A right bundle branch block persisted in two patients. All patients remained free of preexcited tachycardia during 12-16 months of follow-up. Postablation electrophysiological assessment showed no preexcitation in any patient. No reciprocating tachycardia was inducible, even during isoproterenol infusion. Atrioventricular nodal conduction parameters were unchanged from baseline study. Catheter ablation of Mahaim fibers is an effective alternative method for the treatment of tachycardias that include the accessory pathway in the circuit.

Cryoablation of medically refractory nodoventricular tachycardia

Paroxysmal wide QRS tachycardia, based on a nodoventricular accessory connection, is an uncommon arrhythmia. In this report, the endocardial and epicardial mapping and cryoablation of a nodoventricular fiber, documented to participate in medically refractory tachycardia in an 11-year-old boy, are described. Epicardial cryothermia, applied at the earliest site of right ventricular activation, resulted in the abrupt termination of tachycardia. Endocardial cryothermia was subsequently applied in the perinodal region, the presumed site of origin of the nodoventricular fiber. No tachyarrhythmias were inducible postoperatively, and no antiarrhythmic treatment has been required during 18 months of follow-up. Based on precise anatomic localization of the nodoventricular connection, a definitive cure of associated tachyarrhythmias may be possible utilizing cryothermia, without the requirement for extensive intraoperative dissection.

Participation of a concealed nodoventricular fiber in the genesis of paroxysmal tachycardias

An unusual form of tachycardia circuit is described. The circuit incorporates a concealed nodoventricular fiber that conducts in a retrograde path, connects the atrioventricular node and the right ventricle, and also includes the distal portion of the atrioventricular node, the His-Purkinje system, and the ventricle. The study patient was first seen with paroxysmal tachycardias of normal QRS duration, complete right bundle branch block, and complete left bundle branch block. Electrophysiologic studies disclosed poor anterograde atrioventricular nodal conduction with a block proximal to His deflection that occurred at an atrial paced cycle length of 600 msec with no ventriculoatrial conduction. The tachycardias were inducible with two ventricular extrastimuli, had a His deflection that preceded each QRS complex and an HV interval identical to that during sinus rhythm, and revealed ventriculoatrial dissociation. Tachycardia with QRS patterns of right bundle branch block had a cycle 30 to 35 msec longer than tachycardias with either normal QRS duration or complete left bundle branch block. Tachycardias could be entrained by appropriate right ventricular pacing at rates slightly faster than the rate of tachycardia. Tachycardias could be terminated abruptly by an intravenous bolus of either adenosine triphosphate or verapamil.

The scintigraphic characteristics of ventricular pre-excitation through Mahaim fibers with the use of phase analysis

The phase image pattern of blood pool scintigrams was blindly assessed in 11 patients exhibiting conduction through Mahaim pathways, including 6 nodoventricular and 5 fasciculoventricular. These patterns were compared with the phase image findings in normal subjects, patients with left and right bundle branch block in the absence of pre-excitation and patients with pre-excitation through atrioventricular (AV) connections. In all patients with a Mahaim pathway, the site of earliest phase angle was septal or paraseptal. Phase progression was asymmetric and the pre-excited ventricle demonstrated the earliest mean ventricular phase angle in 10 of 11 patients. This pattern, and the associated ventricular phase difference, appeared to vary from that in normal subjects and in those with a septal AV connection, in whom phase progression is generally symmetric. Scintigraphic phase analysis provided localizing information and presented patterns consistent with Mahaim pathways. Although not able to differentiate among Mahaim pathway subtypes, these phase patterns differed from those in normal subjects, those with right and left lateral free wall pathways and most patients with a septal AV pathway. However, the phase pattern of patients with a Mahaim pathway may not differ from that of patients with a septal AV connection displaying an asymmetric pattern of phase progression, or those with left and right bundle branch block in the absence of pre-excitation. Objective, yet imperfect phase measurements supported these differences. Such image findings may complement the often complex electrophysiologic evaluation of patients presenting with pre-excitation.

Atriofascicular connection or a nodoventricular Mahaim fiber? Electrophysiologic elucidation of the pathway and associated reentrant circuit

Accessory pathways showing decremental properties and inserting into the right ventricle have been frequently described as "nodoventricular" or Mahaim pathways. However, conclusive evidence for a nodal origination of such pathways is lacking. The patient in this study had characteristics typical of such a pathway. Antegradely, the pathway showed decremental, nodelike conduction properties. With the aid of right bundle branch recordings, the pathway was demonstrated to insert directly into the right bundle branch. Atrioventricular reciprocating tachycardia could be readily initiated by atrial or ventricular pacing. The QRS morphology was normal during sinus rhythm and demonstrated a left bundle branch block pattern with normal axis during tachycardia. The reentrant circuit involved antegrade conduction over the accessory pathway and retrograde conduction via the bundle branches, His bundle, and the atrioventricular node. More significantly, late atrial stimuli delivered during tachycardia could preexcite the ventricle via the accessory pathway despite their inability to enter the atrioventricular node. Thus, the upper "turn around" of the reentrant circuit involved atrial tissue and the accessory pathway originated directly from the right atrium independent of the atrioventricular node. In view of these new findings and other recent observations during surgical resection of similar pathways, a reassessment of previous descriptions of "nodoventricular" fibers may be necessary. Many of these pathways may actually represent atriofascicular or atrioventricular connections with decremental properties.

Coexistent Mahaim and Kent accessory connections: diagnostic and therapeutic implications

Six patients with coexistent Mahaim and Kent accessory connections are described. Two had left nodoventricular Mahaim connections, the first reported cases demonstrating these findings. In neither were the left-sided Mahaim connections components of a tachycardia and their presence was incidental. In two of four with nodoventricular connections, associated atrioventricular (AV) node conduction and coexistent posteroseptal accessory pathways were found. One of these had the unusual finding of a right-sided Mahaim connection arising from a "fast" AV node pathway. In only one patient did the tachycardia incorporate the Mahaim connection. In this patient, anterograde conduction during tachycardia occurred over a right nodoventricular connection whereas retrograde conduction occurred through a concealed right free wall Kent connection. Two patients had fasciculoventricular connections that were associated with either septal (one patient) or left free wall (one patient) Kent connections. The latter also had evidence of enhanced AV node conduction. This report is unique in that it describes in detail two patients with left nodoventricular connections (Mahaim) inserting in or near the left posterior fascicle. Combined Kent and Mahaim connections, present in the six patients, appear to occur in approximately 5% of patients with the Wolff-Parkinson-White syndrome. Precise identification of bypass connections critical for reentrant circuits is essential for intelligent application of treatment options.

The long R-P' tachycardias

The family of tachycardias that are called long R-P' tachycardias represent a unique group of tachycardias which have been notably refractory to pharmacologic therapy in the past. On the surface electrocardiogram, the rhythms may be indistinguishable. It is only with careful electrophysiological evaluation in many cases that these rhythms can be sorted out. The differential diagnosis in these rhythms is important because with incessant tachycardia, ventricular dysfunction may be produced. In many of the instances of long R-P' tachycardias definitive and directed ablation of the tachycardia can be accomplished. New techniques involving catheter ablation and super-selective surgical dissection are now present which makes ablation of these tachycardias possible.

An electrocardiogram database incorporated into the hospital information system

A database system was developed for storing and retrieving electrocardiogram (ECG) interpretations made by the Bonner program. One ECG record consists of the patient identification information, measurement matrix, and interpretive statements made by the program and by the reviewing cardiologist. The logical structure of the database is 3-level hierarchy. An ECG record is automatically inserted into the database when an ECG signal is analysed by the program. Stored ECG records can easily be retrieved using any parameter and qualifier for review, research and education. The physician can gather statistics on the parameters and qualifiers of the extracted ECG records using statistical program packages (BDMP, SCSS) and a decision support system (AS). Since the database management system is DL/I, the newly developed system can be transferred to various computers, and the relationships between the ECG findings and clinical records stored in the DL/I form can easily be studied.

Wide QRS supraventricular tachycardia due to coexisting Mahaim and Kent pathways

In two patients with Wolff-Parkinson-White syndrome, we observed the unusual coexistence of functional Mahaim and accessory atrioventricular pathways. In the first patient, three types of reciprocating tachycardia were demonstrable: (1) anterograde conduction over the atrioventricular (AV) node with right bundle branch block (RBBB) and retrograde conduction via a right-sided atrioventricular accessory pathway; (2) anterograde conduction through the AV node with RBBB and retrograde conduction via two (right-sided and septal) anomalous pathways; and (3) anterograde conduction through nodoventricular fibers and retrograde conduction over a right-sided accessory pathway. In the second patient the reentry circuit was comprised of AV node fasciculoventricular fiber in an anterograde direction and a right-sided accessory pathway in a retrograde direction. We believe this to be the first report of triple accessory pathways, consisting of two atrioventricular and one nodoventricular connection, demonstrated by intracardiac electrophysiologic study.

Surface electrocardiographic clues suggesting presence of a nodofascicular Mahaim fiber

Standard electrocardiograms from 87 consecutive patients with tachycardia of left bundle branch block configuration were analyzed retrospectively for features that might be characteristic of tachycardia utilizing a nodofascicular Mahaim fiber. The study group consisted of 13 patients with nodofascicular tachycardia, 34 with supraventricular tachycardia and aberrant conduction over the His-Purkinje system, 22 with ventricular tachycardia and 18 with antidromic tachycardia utilizing a right-sided accessory atrioventricular pathway. Six variables present during tachycardia of left bundle branch block configuration were predictive of a nodofascicular fiber: cycle length between 220 and 450 ms, QRS axis of 0 to -75 degrees, QRS duration 0.15 second or less, R wave in lead I, rS wave in precordial lead V1 and a precordial transition from a negative to a positive QRS complex after lead V4. All six criteria were present in 16 of the 87 patients. No patient with ventricular tachycardia satisfied these criteria, whereas 3 of 34 with supraventricular tachycardia, 1 of 18 with antidromic tachycardia and 12 of 13 with tachycardia using a nodofascicular fiber did. It is concluded that analysis of the surface electrocardiogram during tachycardia may suggest the presence of a nodofascicular fiber.

Dual accessory nodoventricular pathways: role in paroxysmal wide QRS reciprocating tachycardia

Clinical electrophysiological study in an otherwise healthy 21-year-old male with paroxysmal wide QRS tachycardia (cycle length 300 ms, heart rate 200/min) suggested the presence of two nodoventricular (NV) bypass connections. The first NV connection pre-excited the base of the interventricular septum (NVs), as evidenced by a short HV interval during sinus rhythm (15-20 ms), with local ventricular activation occurring earlier at the septal base than at either the right ventricular apex or the base of the left ventricle. The second NV connection appeared to connect the AV junction with the right ventricle (NVRV). Intracardiac recordings from a portion of the right-bundle branch of the interventricular conduction system demonstrated right ventricular pre-excitation by NVRV during both atrial pacing and reciprocating tachycardia. The latter finding supported participation of NVRV in the tachycardia. Further, following exclusion of atrial participation in the arrhythmia, premature depolarization of the right ventricle and interventricular septum appeared to advance the tachycardia without altering the timing of His bundle depolarization, implicating NVS in the retrograde limb of a re-entry circuit. Consequently, this study demonstrated the presence of two NV connections and provided further support to the concept that NV accessory bypass connections may comprise portions of a re-entry pathway during reciprocating tachycardia in man.

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 in 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.

Mechanisms of regular, wide QRS tachycardia in infants and children

A regular wide QRS tachycardia was electrocardiographically documented in 32 patients aged 1 month to 18 years. The mechanisms of the tachycardia were evaluated using standard multicatheter electrophysiologic techniques. These mechanisms included (1) orthodromic reciprocating tachycardia with bundle branch aberration (seven patients), (2) antidromic reciprocating tachycardia using single (three patients), or multiple (three patients) atrioventricular connections (Kent bundles), (3) atrial flutter with ventricular preexcitation over accessory connections (eight patients), (4) reciprocating tachycardia using a nodoventricular connection (Mahaim fiber) (five patients), and (5) ventricular tachycardia (six patients). Regular side QRS tachycardias are not rare in pediatric patients. Their mechanisms can be quite complex, and electrocardiographic analysis with respect to QRS configuration, heart rate, or the presence or absence of ventriculoatrial dissociation is not sufficient for diagnostic purposes. Our results show that considerable understanding of the mechanism of regular, wide QRS tachycardias can be obtained by multicatheter electrophysiologic study. Understanding the mechanism is essential in order to make rational use of available therapeutic options.

The electrophysiologic basis and management of symptomatic recurrent tachycardia in patients with Ebstein's anomaly of the tricuspid valve

Twenty-two patients with Ebstein's anomaly were evaluated because of recurrent tachycardia. A total of 30 accessory pathways were present in 21 of the 22 patients. Twenty-six accessory pathways were of the atrioventricular (A-V) type while four were Mahaim fibers. Multiple accessory pathways were present in eight patients. Twenty-five of the 26 accessory A-V pathways were right-sided, either in the posterior septum (12 pathways) or the posterolateral free wall (13 pathways); one patient with corrected transposition of the great arteries had a left-sided accessory A-V pathway in a lateral free wall location. Patients with accessory A-V pathways had a long minimal ventriculoatrial (V-A) conduction time during reciprocating tachycardia (192 +/- 47 ms) and usually showed a persistent complete or incomplete right bundle branch block morphology. At surgery, preexcitation was invariably localized to the atrialized ventricle. The long V-A conduction time during reciprocating tachycardia appeared to consist of late activation of the local ventricle in the region of the accessory pathway with a further delay occurring before excitation of adjacent atrium presumably due to conduction over the accessory pathway. Accessory A-V pathways were successfully sectioned with no deaths in 13 of 15 patients. On the basis of these data, certain electrocardiographic findings encountered in the study of patients with recurrent tachycardia should point to the possibility of associated Ebstein's anomaly: morphology of the surface electrocardiogram suggesting preexcitation of the right posterior septum or right posterolateral free wall as well as the combination during reciprocating tachycardia of a long V-A interval and right bundle branch block.

His-ventricular dissociation in a patient with reciprocating tachycardia and a nodoventricular bypass tract

A patient with recurrent bouts of atrial fibrillation and wide-complex regular tachycardia underwent electrophysiologic studies. Premature atrial stimulation or atrial pacing during sinus rhythm resulted in gradual lengthening of the PR and AH intervals, narrowing of the HV interval and progressive preexcitation with a left bundle branch block and left-axis contour. Induction of tachycardia was dependent on critical delay in the atrioventricular interval and was associated with attainment of a maximal preexcitation pattern. During tachycardia, the ventriculoatrial interval was constant, whereas the interval from His bundle deflection to the ventricular complex was variable. We postulate that the tachycardia circuit involved reciprocation within the atrioventricular node and that a nodoventricular bypass tract was present in close anatomic or functional association with the slow atrioventricular nodal pathway. Our data suggest that both the nodoventricular bypass tract and the His-Purkinje system may be passive "bystanders" rather than essential components of the tachycardia circuit. In addition, although HV dissociation usually implies ventricular tachycardia, this case demonstrates that HV dissociation during wide-complex regular tachyarrhythmia is not diagnostic of ventricular tachycardia.

Role of Mahaim fibers in cardiac arrhythmias in man

Twelve patients with evidence of Mahaim fibers are reported, six with nodoventricular (NV) fibers and six with fasciculoventricular (FV) fibers. All patients with NV fibers had left bundle branch block morphology, and a sustained reentrant tachycardia with this morphology was proved in each case. In three of the six, ventriculoatrial dissociation occurred during tachycardia. We postulate that the mechanism of this tachycardia is a macroreentry circuit using the NV fiber for the antegrade limb and the His-Purkinje system with a portion of the atrioventricular node for the retrograde limb. ECGs of patients with FV fibers were varied, suggesting a functional relation to the right or left side of the septum. No direct relationship of FV fibers to observed arrhythmias could be found.

Atrial and His bundle stimulation with an accessory nodo-ventricular connection

A 39-year-old man with a history of frequent paroxysmal tachycardias for 27 years was referred for electrophysiology study. His resting electrocardiogram showed left bundle branch block, which persisted during paroxysmal tachycardia. Electrophysiology study demonstrated the presence of a right-sided accessory nodo-ventricular connection. The case is of particular importance as it illustrates the diagnostic value of QRS normalization with left atrial pacing and the therapeutic use of rapid His bundle pacing to terminate the tachycardia.

Surgery for life-threatening ventricular tachyarrhythmias

Among 203 left ventricular aneurysmectomies performed since 1970, the operative mortality rate was 18.7 percent. In 49 patients (24 percent), left ventricular aneurysmectomy was performed for refractory life-threatening ventricular arrhythmias. Eight additional patients had coronary bypass grafting without ventricular aneurysmectomy. One of these patients had bypass grafting followed later by ventricular aneurysmectomy. All 56 patients had underlying coronary artery disease. The operative mortality rate was 19.6 percent. In patients with a recent myocardial infarction, the rate was 60 percent, whereas it was 11 percent in patients with a remote myocardial infarction. Other high risk variables in these patients included coronary bypass grafting without myocardial resection, and an elevated left ventricular end-diastolic pressure. The late mortality rate was 17.9 percent, but only one of these deaths was sudden and unexpected. The 35 long-term survivors have been followed up for a mean of 40.7 months (range 7 to 92 months). Of these, 20 remain on antiarrhythmic medications for palpitation or documented ventricular premature complexes, whereas 15 are free of detectable rhythm disturbances and do not require antiarrhythmic agents. Only 4 of 35 (11 percent) have had recurrent documented ventricular tachycardia. Left ventricular aneurysmectomy may be performed for refractory ventricular tachyarrhythmias with an acceptable operative mortality, particularly if the patient has survived longer than 6 weeks after myocardial infarction. Although epicardial mapping techniques may be useful in localizing the reentrant pathway of the ventricular tachycardia, ventricular aneurysmectomy without mapping techniques produces a satisfactory clinical result in the vast majority of long-term survivors.

Multiple reentrant tachycardias due to retrograde conduction of dual atrioventricular bundles with atrioventricular nodal-like properties

A patient is presented who had two paroxysmal supraventricular tachycardias, one slow and incessant and the other fast. Both paroxysmal tachycardias appeared to be atrioventricular (A-V) reentrant, with anterograde conduction by way of a normal A-V pathway. Two pathways conducting in retrograde manner were demonstrated, characterized by different conduction times (fast and slow), identical abnormal atrial activation sequence and A-V nodal-like properties (retrograde Wenckebach periodicity with rapid ventricular pacing, and depression with ouabain and propranolol). Thus, there appeared to be two anomalous A-V bundles with nodal-like properties conducting in retrograde fashion. Whether the paroxysmal tachycardia was fast or slow depended on which of these pathways was utilized. Spontaneous cure of incessant paroxysmal tachycardia was observed and coincided with unexplained total loss of ability for ventriculoatrial conduction.

Ebstein's anomaly in association with anomalous nodoventricular conduction. Pre-operative and intra-operative electrophysiological studies

A 13 year old girl with Ebstein's anomaly was investigated for refractory paroxysmal tachycardias and ventricular pre-excitation. Intracardiac electrophysiological studies demonstrated that ventricular pre-excitation was due to conduction in an anomalous nodo-ventricular pathway. Tachycardia occurred as a result of re-entry within the A-V node with pre-excitation during tachycardia due to conduction in the nodo-ventricular pathway. These tachycardias were controlled initially by medical therapy but because of increasing frequency of attacks, occasionally requiring D.C. conversion, further electrophysiological studies and epicardial mapping were undertaken. The epicardial surface of the right ventricle and right atrium were mapped during tachycardia. The results of the studies confirmed that a direct anomalous atrio-ventricular pathway was not present and that re-entrant tachycardia did not involve an accessory pathway of this type. A rapid atrial pacing system was implanted and paroxysmal tachycardias have been successfully controlled.

Mahaim conduction producing left axis deviation and normal QRS

An unusual patient is described in whom electrophysiological studies strongly suggest the occurrence of Mahaim conduction. The patient whose electrocardiogram previously showed a left anterior hemiblock pattern then developed advanced atrioventricular (AV) block (AH block). Beats conducted through the atrioventricular node always had a short HV interval (20 ms) and QRS complexes of left anterior hemiblock pattern. Junctional escape beats always had a normal HV interval (50 ms) with normal intraventricular conduction. His bundle pacing showed the StV interval and QRS contour of escape beats. These findings suggest the existence of an accessory pathway (Mahaim fibres) passing from the area of block, presumably the uppermost portion of the His bundle, to the posteroinferior division of the left bundle-branch. The surface electrocardiogram did not show the characteristic delta wave of the Wolff-Parkinson-White syndrome. Our observations suggest that patients in whom there is conduction along Mahaim fibres may show only the pattern of intraventricular conduction defect without a delta wave.

Re-entry via Mahaim fibres as a possible basis for tachycardia

Paroxysmal tachycardia with widened QRS complexes was recorded in a 21-year-old man. In sinus rhythm there was no evidence of pre-excitation. His bundle studies revealed an abnormally short HV interval of 30 ms. Premature atrial stimuli produced an increased PR interval. At short coupling intervals the His bundle activity became incorporated within the QRS complex. Concurrently, a left bundle-branch block pattern appeared identical to that seen during tachycardia. Closely coupled ventricular extrastimuli initiated a tachycardia identical to the initial episode. A re-entry mechanism via anterograde Mahaim fibres and retrograde His bundle -AV node pathway is postulated.

Epicardial mapping in the Wolff-Parkinson-White syndrome

Epicardial mapping provides a method for defining antegrade and retrograde sites of pre-excitation. It is best undertaken only after a careful, detailed preoperative electrophysiological study has been performed. The potential pitfalls of the technique are many and technical expertise must be constantly available to maintain a functioning system. For these reasons, it is not likely to lend itself to widespread application. The same techniques can be applied to localization of the site of origin of atrial or ventricular dysrhythmias, localization of myocardial ischemia and infarction, as well as to differentiate between epicardial delays due to conduction delay and those caused by intramural myocardial delay.

The preexcitation syndromes

Current methodology permits one to define the functional basis of the preexcitation syndromes with reasonable certainty and to develop a rationale for instituting trials of medical therapy. Future studies will hopefully result in a more exact definition of the anatomic substrates of preexcitation and their relationship to the pathophysiology of the associated syndromes. New antiarrhythmic agents must also be developed to add to the relatively small number of available drugs. Important questions still remain. Should asymptomatic patients with preexcitation be studied? If found to demonstrate potential for malignant arrhythmias, should they be treated prophylactically? The answers to these questions will require study and long-term follow-up of nonhospital referral patients. Surgery offers a feasible therapeutic alternative for patients with life-threatening or disabling arrhythmias but demands a team equipped to perform precise preoperative and intraoperative mapping studies to define the type and location of underlying anatomic substrates.

Functional properties of mahaim fibers

Electrophysiological studies were performed in a patient with a short P-R interval and a small delta wave. The findings suggest that ventricular pre-excitation resulted from an infranodal bypass (Mahaim type). As the functional properties of the pathway were evaluated, impaired conductivity (suggested by rather long refractory periods) became apparent at frequency stress. The pathway could easily be blocked by Ajmaline. This demonstrated an unexpected early diastolic improvement in conductivity; i.e. a supernormal phase of conduction. Due to this supernormal phase, Mahaim-fiber conduction was present when block in the anterior division of the left bundle branch, or even trifascicular block occurred. Thus the effects of exclusive Mahaim-fiber conduction on ventricular activation were documented.