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The present investigation evaluates the ability of several electrocardiographic (ECG) and electrophysiologic methods to identify multiple accessory pathways in 47 patients in whom the presence and sites of multiple accessory pathways were confirmed intraoperatively. To establish ECG features that suggested the presence of multiple accessory pathways in these patients, we initially studied the 12-lead ECG during maximal preexcitation in 101 patients with single accessory pathways. Distinctive 12-lead ECG patterns were noted for six defined anatomic areas around the right and left atrioventricular groove. Multiple preexcited QRS morphologies, each typical for a separate accessory pathway, and atypical preexcited QRS morphologies were recorded during atrial fibrillation in 31 of 47 (66%) patients with multiple accessory pathways. By comparison, the ECG during sinus rhythm and rapid atrial pacing identified 14 (32%) and 26 (55%) of the patients, respectively. In 12 (26%) patients in whom evidence for multiple accessory pathways was absent from endocardial mapping data, atrial fibrillation provided the diagnosis. In five (11%) patients, atrial fibrillation was the only method that demonstrated the presence of multiple accessory pathways. A combination of ECG findings during atrial fibrillation and rapid atrial pacing plus endocardial mapping data identified 43 (91%) of the patients with multiple accessory pathways. There were two unique fusion patterns on the 12-lead ECG that were characteristic of specific multiple accessory pathway combinations.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrical activation-guided laser photocoagulation was used intraoperatively to terminate ventricular tachycardia in patients with ischemic heart disease. During ventricular tachycardia, laser irradiation was delivered to mapped sites with local diastolic activation. In 30 long-term survivors, 85 ventricular tachycardia configurations were terminated by ablation; 72 (84.7%) were terminated by endocardial photocoagulation. Thirteen (15.3%) required epicardial photocoagulation; however, these 13 ventricular tachycardias occurred in 10 (33%) of the 30 patients. An aneurysm was present in 70% of patients with successful endocardial photocoagulation, but in only 10% of patients requiring epicardial photocoagulation for at least one ventricular tachycardia configuration; 90% of all patients requiring epicardial laser photocoagulation had no aneurysm and had either a right or a left circumflex coronary artery-related infarction. In this group, epicardial activation data were similar to those described for ventricular tachycardia with an "endocardial" origin and included 1) delayed potentials during sinus rhythm, 2) presystolic or pandiastolic activation sequences during ventricular tachycardia, and 3) regions of block near the presumed region of reentry during ventricular tachycardia. This study suggests that the critical anatomic substrates supporting reentry in postinfarction ventricular tachycardia may occur at intramural or epicardial sites, particularly in patients with right or circumflex coronary artery-related infarction and no aneurysm.

Between 1970 and July 1980, wide QRS tachycardia due to re-entry confined to the AV node with bystander involvement of an accessory atrioventricular pathway (AAV) was documented in three of 290 patients with the Wolff-Parkinson-White syndrome studied at Duke Medical Center. In each of the patients, at least one transition between wide and narrow QRS morphology was recorded without change in either the cycle length of tachycardia or the atrial activation sequence. Two of the three patients had a single left-sided AAV (lateral, postero-lateral) showing antegrade conduction only. The third patient had two right-sided AAVs (free wall, septal), each capable of bidirectional conduction. Initiation and termination of repetitive concealed conduction into the ventricular insert of an AAV appeared to be one mechanism determining bystander AAV participation. Documentation of the retrograde sequence of atrial activation during tachycardia, and examination of the effects of interpolated premature depolarizations from both the ventricle and mid-line atrium are the most helpful features in resolving the differential diagnosis of wide QRS tachycardia in patients with W-P-W syndrome.

In this paper we summarize our experience and report the characteristics of energy delivery in 23 patients who have undergone closed chest ablation of the normal atrioventricular (AV) conduction system for the treatment of refractory supraventricular arrhythmias. The induction of AV block was achieved by the synchronous delivery of electrical energy with a damped sinusoidal waveform utilizing a standard direct current defibrillator and a standard tripolar His bundle catheter. The procedure was well tolerated, though one patient experienced ventricular fibrillation, which was uneventfully converted with external paddles. Complete AV block was achieved in 20 of 23 patients and all were rendered arrhythmia free, though two still required antiarrhythmic drugs. A stable escape rhythm was seen in all patients with a cycle length of 1,294 +/- 243 ms. Creatine phosphokinase-MB was positive at low levels in 19 of 23 patients and cleared within 24 h. 99mTc pyrophosphate scans were faintly positive in only 2 of 22 patients. Left ventricular wall motion and ejection fractions were unchanged in 19 of 19 patients, two-dimensional echocardiography with microcavitation technique was unchanged in 12 of 12 patients, and a slight increase in pulmonary artery wedge pressure was seen in only 1 of 11 patients. Current, voltage, and their product (power) waveforms were recorded in 12 patients (12 recordings at a defibrillator setting of 200 J and 5 recordings at a defibrillator setting of 300 J) and revealed a complex voltage-current relationship due to changes occurring at the catheter electrode-tissue interface. At 200 J the peak values were 42.2 +/- 3.3 A, 2.16 +/- 0.11 kV, and 87.9 +/- 4.7 kW, while at 300 J the peak values were 58.2 +/- 2.8 A, 2.40 +/- 0.10 kV, and 134.4 +/- 6.7 kW, respectively. No instance of catheter disruption was seen, though "pitting" of the distal electrode (through which current passed) occurred in all but one catheter.

In patients with Wolff-Parkinson-White syndrome, observations during bundle branch block (BBB) in reciprocating tachycardia are of value in accessory pathway localization. Most importantly, an increase in the ventriculoatrial (VA) interval of greater than or equal to 35 ms has indicated an ipsilateral free wall location and excluded a septal location. The present study examined whether data collected in the presence of type I antiarrhythmic drugs retained localizing value. Review of retrospective data showed that observations in the drug-free state were precluded by the need to suppress atrial arrhythmia during electrophysiologic study in 20% of patients with Wolff-Parkinson-White syndrome who underwent preoperative workup. Prospectively, in 15 patients with left free wall or posteroseptal pathways, we observed transient left BBB during tachycardia before and after administration of procainamide, disopyramide or quinidine. Serum drug levels ranged from 4.6 to 6.9 mg/liter, except in 1 patient with a serum procainamide level of 18 mg/liter. Drugs increased the VA interval during narrow QRS tachycardia by 17% (p less than 0.01). However, the change in the VA interval with left BBB was not significantly affected. The baseline and drug values averaged 73 ms (range 39 to 94) and 70 ms (range 39 to 90), respectively, for left free wall pathways (n = 8), and 19 ms (range 0 to 28) and 21 ms (range 2 to 35), respectively, for posteroseptal pathways (n = 7). Among the latter, the interval increased less than 30 ms during left BBB except in the patient with the high serum procainamide level, in whom the increase was 35 ms. Thus, the VA interval change that accompanied left BBB remained of localizing value with moderate blood levels of type I drugs, and an increase greater than or equal to 35 ms indicated a left free wall rather than posteroseptal pathway.

To examine whether different septal pacing sites could be distinguished by their epicardial activation patterns, six to eight stimulating electrodes were placed throughout the septum in seven open chest dogs. Unipolar electrograms were obtained from 52 epicardial electrodes during pacing from each stimulating electrode and isochronous epicardial maps were constructed. The location of each stimulating electrode was found by dissection, and its distance from the overlying epicardium was measured. To allow comparison among epicardial maps, the septum was conceptually subdivided into nine regions to which stimulating electrodes were assigned. Epicardial activation patterns from the same region were similar and these patterns allowed the region containing a stimulating electrode to be identified in many cases. Three other variables were found to have additional localizing value. There were: 1) the time from the stimulus to epicardial breakthrough, 2) the duration of epicardial activation, and 3) the area of epicardium activated in the first 5 ms after epicardial breakthrough. For those stimulating electrodes that could not be localized by their epicardial activation patterns, the distance of the stimulating electrode beneath the epicardium was well fit from these three variables by multiple regression (correlation coefficient [r] = 0.97). Thus, using all the previous factors, localization of septal pacing sites was possible in the noninfarcted dog heart by epicardial mapping.

We describe the results of surgical dissection of multiple accessory pathways in two brothers. A significant family history of pre-excitation syndrome was present: two children died suddenly and at the autopsy of one of them an accessory atrioventricular connection was found. In the first patient the preoperative electrophysiologic study showed anterior septal and posterior septal accessory pathways, and enhanced conduction in the A-V node. The second patient had the following anomalous connections: enhanced conduction in the A-V node; anterior septal, posterior septal and right lateral accessory pathways; Mahaim fiber. Intraoperative mapping, performed during pacing from different sites at different cycle length, was used to define the atrial and ventricular insertions of the accessory pathways as well as to confirm the surgical success.

We have studied 135 patients with the pre-excitation syndrome and have demonstrated evidence of multiple accessory pathways in 20 patients. Five patients had two distinct accessory atrioventricular (A-V) connections, associated with enhanced A-V node conduction in one patient. Twelve patients had a single accessory A-V connection associated with enhanced A-V conduction. In one of these there was an additional fasciculo-ventricular connection. One patient had an accessory A-V connection associated with a nodoventricular bundle. Two patients had fasciculo-ventricular connections combined with enhanced A-V conduction. The latter two patients had electrocardiograms suggestive of a complete accessory A-V connection. Patients with enhanced A-V conduction had shorter cycle lengths during reciprocating tachycardia, primarily because of a short A-H during the dysrhythmia, than those without such conduction. In addition, patients with enhanced A-V conduction demonstrated more rapid conduction from atrium to His bundle during induced atrial fibrillation and two developed life-threatening ventricular responses during atrial fibrillation. A nodo-ventricular pathway was documented to participate in reciprocating tachycardia in one patient. Surgery was undertaken in 13 patients. In 11, the intraoperative mapping studies confirmed the preoperative predictions. In two patients, the presence of a second accessory A-V connection was documented after ablation of one.

The acute and chronic electrophysiological effects of a cryolesion produced in the left ventricle were studied in six dogs. All dogs had frequent ventricular premature beats (VPB) and five of six dogs had ventricular tachycardia during the first 4 days after the cryolesion; only one of the six dogs continued to have VPBs after 1 week, and this dog had identical VPBs before the creation of the cryolesion. Neither control dog had VPBs. Two additional dogs underwent epicardial and transmural mapping studies immediately after production of a cryolesion. VPBs in these animals were shown to originate at the border of the cryolesion. Epicardial activation sequence during normal sinus rhythm was not altered by the chronic cryolesion. The border zone of the chronic cryolesion was sharply demarcated with normal potentials recorded outside of the lesion and "extrinsic" potentials recorded within.

Surgical techniques for the approach to and division of atrioventricular accessory pathways have been designed and perfected during the past 18 years. The standard method of exposure of a single left free wall accessory pathway is by a left atriotomy. All other single accessory pathways are exposed through a right atriotomy. Up to twenty percent of patients with Wolff-Parkinson-White (WPW) syndrome harbor multiple atrioventricular accessory pathways. In this subgroup, classic operative techniques, especially the methods of approach, must be combined or modified depending on the specific locations of the accessory pathways encountered. Eighteen of 90 patients operated on for WPW syndrome at Charlotte Memorial Hospital from August, 1983, through September, 1986, had multiple accessory pathways. Thirty-eight of thirty-nine pathways were successfully divided. One posterior septal accessory pathway reappeared 2 months postoperatively and was catheter ablated. The most frequent combination of atrioventricular accessory pathways included a right free wall and a posterior septal accessory pathway (10 patients). This combination is approached by a right atriotomy. The posterior septal space dissection is extended onto the right free wall area. Technically the most difficult combination includes a left free wall and a posterior septal accessory pathway (3 patients in the present series). Our preferred approach is begun with a right atriotomy for the posterior septal space dissection, followed by an atrial septotomy to expose the left free wall area. There are other methods, however, that may be advantageous depending on the exact locations of the accessory pathways encountered.

The permanent or recurring form of junctional reciprocating tachycardia (PJRT) is an incessant tachycardia that has characteristic clinical and electrophysiologic features of PJRT. Each patient demonstrated near-incessant reciprocating tachycardia with a 1:1 atrioventricular (AV) relationship and with a retrograde P wave (P') occurring closer to the succeeding QRS complexes (i.e., long RP'). With initiation of the tachycardia, there was no prolongation of the PR or AH interval. All patients had evidence of early retrograde atrial activation in their posterior atrial septa and this retrograde limb had properties of decremental conduction. Eight of the nine patients underwent elective surgical ablation of the retrograde limb of tachycardia, and in seven it was successful. Epicardial and endocardial atrial maps recorded during PJRT demonstrated that the site of earliest retrograde activation was in the posterior atrial septum near the coronary sinus orifice. The seven patients in whom surgery was successful left the hospital in sinus rhythm with antegrade conduction, and all are free of tachycardia during the mean follow-up period of 31 months (range 1 to 70 months). In the two remaining patients PJRT was controlled by interruption of the antegrade limb of the tachycardia, the AV node-His bundle. In one patient this was done under direct vision at surgery after an unsuccessful attempt at pathway dissection.(ABSTRACT TRUNCATED AT 250 WORDS)

Experience gained from interruption of 45 anterior and posterior septal Kent bundles has permitted the formulation of a safe surgical approach to the anterior and posterior divisions of the septal area. To clarify the surgical anatomy of this difficult region, the posterior space has been likened to a trihedral pyramid, toppled on its side, with the apex the right fibrous trigone, the right and left atria making two of its sides, and the muscular ventricular septum and the left ventricle or third side, the floor. The pyramidal space contains fat, the atrioventricular (AV) nodal artery, and coronary sinus. The anterior division extends from the right fibrous trigone anteriorly to the free wall. The right atrium is connected to the anulus fibrosus, which rests upon the muscular septum and infundibulum. The AV node and His bundle are protected from dissections in both divisions by the atrial septum and right fibrous trigone. The cases of 31 patients with posterior septal Kent bundles in whom interruption was attempted resulted in division in 20, forced His division in four, and failure in seven. Elective His interruption was done in three. Success occurred in the last 10. Three failures at interruption occurred in 14 anterior septal Kent bundles.

About 5-10% of patients after myocardial infarction experience sustained ventricular tachycardias. Drug therapy is successful only in 60% of these patients, so that a number of them is on a high risk of a sudden cardiac death. Indirect surgical approaches like myocardial revascularization, or aneurysm resection have proven to be ineffective in the treatment of these malignant tachycardias. By the development of electrophysiologic techniques a mechanism of the ventricular tachycardias could be identified as a micro-reentry at the border of myocardial infarction. On this base different direct surgical approaches were advocated by Guiraudon, proposing an encircling endocardial ventriculotomy and by Josephson and Harken recommending a subendocardial resection technique. The results of these direct procedures were much better than those of the prior indirect techniques. The mortality in this series was around 10% and there still was a postoperative recurrence of the tachycardia in about 20-30%. Our group started a study in which a Nd:YAG laser was used to photocoagulate areas of myocardium responsible for the initiation of ventricular tachycardia. By its deeper penetration depth the Nd:YAG laser was preferrable to other laser systems like CO2 and Argon-laser. In contrast to cryothermy the Nd:YAG showed three special advantages: First, it was more effective in the normothermic myocardium, it showed not peripheral zone of temporary myocardial injury, potentially causing late failures, and third equal ablation of tissue could be achieved in much shorter time. Patients were considered operative candidates when drug therapy failed. Preoperative investigations included formal cardiac catheterization and an electrophysiologic testing with induction and mapping of the ventricular tachycardia.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Surgical treatment of arrhythmias is often more expeditious and more cost-effective in the long run than pharmacologic therapy. In the past, surgical treatment of arrhythmias has been reserved for patients with disabling paroxysmal or incessant tachycardia refractory to medical management, severe life-threatening arrhythmia or aborted episodes of sudden death. However, tachyarrhythmias that are refractory to pharmacologic therapy because of drug inefficacy, noncompliance or limiting side effects are not uncommon. Although nonpharmacologic treatment of arrhythmias carries with it a one-time period of higher risk (i.e., when the patient undergoes surgery), it is curative and often preferable to the uncertainty and possibly higher cumulative risk associated with medical management.

The correlation of histologic and electrophysiologic findings in dogs undergoing transvenous ablation of atrioventricular (AV) conduction has not been described. The creation of complete AV block in 10 dogs was attempted by delivering a direct-current shock transvenously through a standard tripolar electrode catheter. The catheter was positioned to record the largest unipolar atrial and His bundle electrograms. A 280 J shock was delivered to the recording electrode by a standard cardioversion unit. After 1 shock, all dogs were in complete AV block refractory to isoproterenol (1 to 4 micrograms/min) and atropine (0.5 to 2.0 mg). Four weeks later, 5 dogs remained in complete AV block, 1 had first-degree block, and 4 had resumed normal AV conduction. Each dog with complete heart block had histologic evidence of severe damage to the AV node, His bundle, or both. On gross examination, these dogs were found to have discrete scars at the base of the septal leaflet of the tricuspid valve. Of the 5 dogs that had resumption of AV conduction, only 1 had histologic evidence of significant damage to the AV conduction system. That animal manifested a marked increase in the P-R interval (100 to 210 ms). Although temporary heart block occurred in each animal, chronic interruption of AV conduction was more difficult. Catheter location, atrial and His bundle electrogram relations, and the electrode used for delivery of energy were factors determining the effectiveness of this technique.

An unusual patient with Ebstein's anomaly of the tricuspid valve and the Wolff-Parkinson-White syndrome is presented. Ventricular pre-excitation related to conduction over both a right posterior Kent bundle and Mahaim fibers coursing from the atrioventricular node to the right ventricle. Two types of supraventricular tachycardia were demonstrable. These were due to re-entry involving antegrade conduction over either the normal or Mahaim paths, and retrograde retrograde conduction via the Kent bundle. Surgical division of the Kent bundle has abolished the clinically debilitating arrhythmias.

Cardiac mapping during sinus rhythm and during spontaneous or induced ventricular arrhythmias is a promising technique that offers a variety of potential strategies to improve our ability to locate abnormal areas in the heart that are the seat of arrhythmias. If surgical procedures are to become more limited in scope in an attempt to salvage myocardium, mapping will need to be used to a greater extent. However, it remains to be established which mapping technique will prove most sensitive and specific in detecting sites of arrhythmia, and whether the localizing method used allows a more directed surgical intervention to be successful.

The report relates experience with six patients with Kent bundles, five of whom had the Wolff-Parkinson-White syndrome, operated upon for tachyarrhythmias caused by the presence of the pathway. It was successfully divided in four patients, its antegrade conduction capacity interrupted in one, and a failure occurred in the sixth patient. In the three patients who had a Kent bundle with a short effective refractory period for antegrade conduction, the life-endangering potential of the Kent pathway was corrected. To emphasize the complexities of the tachyarrhythmias in Ebstein's anomaly, two patients have mild but controllable postoperative supraventricular tachyarrhythmias (SVT) due to a Mahaim pathway. The surgical problems encountered in these patients are reviewed.

In 34 successive patients with Wolff-Parkinson-White syndrome premature beats were induced from the right ventricular apex during reciprocating tachycardia (RT) at progressively shorter coupling intervals. The presence of an accessory pathway was confirmed by a reduction in the atrial cycle length (A-A interval) during which the premature ventricular beat was introduced. This retrograde preexcitation occurred at a time when the His-AV node pathway was refractory; i.e. there was premature activation of the atria over a pathway other than the His-AV node. 3 patients were excluded because of unsatisfactory or unstable H-H intervals. In the remaining 31 patients with constant preceding H-H intervals, the A-A interval shortened; (a) 35-65 msec in 4 patients with right-sided pathways and normal conduction during RT and by 110 msec in a 5th patient with a right-sided pathway, in whom bundle branch block aberration persisted during RT, (b) 45 msec in the single patient with both a right-sided and a septal accessory pathway, (c) 35-65 msec in 5 patients with septal pathways, and (d) 15-35 msec in only 4/20 patients with left-sided pathways and normal conduction during RT. Left-sided ventricular premature beats were introduced in 5 patients with left-sided pathways and normal conduction in RT. In 4/5, left-sided premature beats shortened the A-A interval 40-75 msec whereas right-sided premature beats at the same coupling interval failed to do so. In the fifth case, the left-sided premature resulted in a 65 msec abbreviation of the A-A interval compared to 30 msec from the right ventricular outflow tract and 15 msec from the right ventricular apex. In 5 patients with left-sided pathways, right ventricular premature beats were introduced during RT with left bundle branch block aberration, and shortened the A-A interval 30-50 msec in all of these, whereas right-sided premature beats in 4 of the 5 during normal conduction failed to do so. This technique is useful to confirm the participation of accessory pathways in reciprocating tachycardias associated with the preexcitation syndromes, and emphasizes the importance of the site of stimulation used relative to the location of the accessory pathway. Because of the possibility of multiple accessory pathways, stimulation of the left ventricle should be performed in patients undergoing surgery for preexcitation unless the left ventricle is already inplicated by right-sided studies.

The Wolff-Parkinson-White syndrome is an uncommon cardiac disorder due to the presence of an accessory atrioventricular pathway resulting in ventricular pre-excitation and supraventricular tachycardias. The recognition of the Wolff-Parkinson-White syndrome is important because of the potential for the development of extremely rapid ventricular rates during atrial fibrillation that may lead to ventricular fibrillation and sudden death. The diagnosis of the Wolff-Parkinson-White syndrome is obvious when classic delta waves and short P-R intervals are present, but the electrocardiographic manifestations of the syndrome may be subtle and vary considerably from patient to patient. Certain commonly used antiarrhythmic medications may be useful for the treatment of reciprocating tachycardia in these patients and yet prove to be ineffective--or even deleterious--in preventing excessively rapid conduction to the ventricles during atrial fibrillation. An appreciation of the functional properties of the accessory pathways in the Wolff-Parkinson-White syndrome and how they are affected by pharmacologic agents should result in improved recognition of this entity and more effective medical management of patients with a risk of sudden death.

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.

6 patients with reentrant supraventricular tachycardia were studied using the atrial extra-stimulus (S1-S2) technique. 3 patients had smooth curves of H1-H2 intervals plotted against A1-A2 intervals, and echoes occurred only in the relative refractory period of the AV node. These patients met traditional criteria for reentry within the AV node, but all 3 were found to have accessory pathways which functioned only in the retrograde direction. 3 other patients had discontinuous curves of H1-H2 intervals plotted against A1-A2 intervals, and the echo zone was confined to coupling intervals producing the longer of the two observed AV node responses. Accessory pathways could not be demonstrated in these latter 3 patients. In patients with accessory pathways the effect of changing atrial pacing site on the echo zone was studied. Pacing at a site remote from the accessory pathway shifted the echo zone to shorter coupling intervals. Some patients previously thought to have reentry within the AV node may have had accessory pathways which conducted only in the retrograde direction. The prevalence of this syndrome is unknown but is important because ablation of the accessory pathway is curative.

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.

Intermittent preexcitation, block in the accessory pathway after intravenous injection of ajmaline or procainamide, and block in the accessory pathway during exercise usually exclude a short antegrade refractory period of an accessory pathway in patients with the Wolff-Parkinson-White syndrome. This report describes three patients with these findings suggestive of a relatively long antegrade effective refractory period of the accessory pathway in whom life-threatening ventricular response occurred during atrial fibrillation. In the first patient with a pattern of intermittent preexcitation, rapid ventricular response with wide QRS was present during atrial fibrillation. In the second patient in whom preexcitation disappeared after intravenous injection of ajmaline or procainamide as well as during exercise testing, atrial pacing showed 1:1 conduction over the accessory pathway at a cycle length of 220 msec and the shortest R-R interval during induced atrial fibrillation was 190 msec. The third patient, with no evidence of preexcitation during sinus rhythm, presented antidromic reciprocating tachycardia and atrial fibrillation with life-threatening ventricular response, the minimal R-R interval being 220 msec. Noninvasive tests in the preexcitation syndrome lack sufficient prognostic sensitivity. The evaluation of ventricular response during induced atrial fibrillation represents the most reliable means of identifying such patients at risk.

Electrophysiological characteristics of atrioventricular (A-V) conduction and refractoriness were examined in 12 patients with Lown-Ganong-Levine (LGL) syndrome referred for assessment of the following arrhythmias: (group I) regular narrow QRS tachycardia 6/12 (50%), (group II) atrial fibrillation (AF) 2/12 (17%), group III) ventricular tachycardia (VT) 4/12 (33%). A-V node refractory periods were shorter, and enhanced A-V conduction more frequent (7/12, 58% vs 7/28, 25%) in LGL patients compared to similar studies in 28 normal controls. During laboratory study reciprocating tachycardia (RT) due to re-entry within the A-V node occurred in 4/12 (33%) LGL patients, and exhibited a shorter cycle length (294 +/- 60.4 msec) than did the same arrhythmia in 11/28 (39%) controls 372 +/- 51.8 msec, P less than 0.05). Similarly, RT utilizing a concealed accessory pathway had a shorter cycle length (228 +/- 3.5 msec) in 2/12 (17%) LGL patients than in 11/28 (39%) controls (314 +/- 24.3 msec, P less than 0.001). In AF, the shortest R-R intervals in 4/12 (33%) LGL patients (2 group I, 2 group II) were shorter than in 15/28 (54%) control patients (254 +/- 42.2 msec vs 325 +/- 64.2 msec, P less than 0.05). The mean R-R internvals did not differ significantly (LGL 372 +/- 89 msec vs control 428 +/- 82.6 msec). This study suggests that the characteristics of A-V conduction and refractoriness may permit development of more rapid heart rates during certain arrhythymias in LGL patients compared to normal controls. Furthermore, the occurrence of VT in patients with LGL sydrome indicates that symptomatic arrhythmias require specific diagnosis.

Records from patients with the Wolff-Parkinson-White syndrome were reviewed with particular emphasis on the occurrence of bundle-branch block aberration during reciprocating tachycardia and the significance of this observation with respect to accessory pathway location. Increase by greater than 25 ms in the ventriculoatrial interval during reciprocating tachycardia with bundle-branch block, when compared to reciprocating tachycardia with normal intraventricular conduction, occurred only with right or left free wall accessory pathways. No patient with a septal accessory pathway proven by epicardial mapping showed a ventriculoatrial interval prolongation greater than 20 ms during bundle-branch block aberration. Measurement of ventriculo-atrial interval during bundle-branch block abe-ration also helped to diagnose accessory pathways AH and HV intervals as well as ventriculo-atrial times, may give midleading information. In one patient increase in cycle length during left bundle-branch block was the result of prolonged HV interval rather than prolonged ventriculo-atrial interval. In another patient cycle length remained the same during bundle-branch block while the ventriculo-atrial interval increased by an increment identical to the decrease in AH interval.

We present a patient with Wolff-Parkinson-White syndrome who died of a myocardial infarction 19 months after clinical electrophysiologic studies. These studies suggested the presence of a left atrioventricular accessory pathway that sustained conduction well in the retrograde direction but only intermittently in the antegrade direction. Postmortem examination of the heart revealed three accessory atrioventricular pathways in proximity to each other in the posterolateral atrioventricular region. One pathway showed complete fibrosis and two showed patchy fibrosis. The fibrosis suggests an anatomic basis for the impaired antegrade conduction observed in life.

A cryosurgical instrument was used to ablate atrioventricular conduction. The procedure was carried out in 20 dogs and subsequently in three patients with drug resistant, life-threatening supraventricular tachycardias. In patients, the cryosurgical unit lowered the temperature of the His bundle area to 0 degrees C, effecting complete but reversible heart block. Rewarming resulted in resumption of normal atrioventricular conduction. The His bundle region then was cooled to -60 degrees C; complete heart block was produced with two or more 90-120 second freezes. Postoperative evaluations revealed persistent atrioventricular conduction block. The lesion showed no tendency to rupture, form aneurysm, or interfere with valvular function. In the clinical cases, postoperative studies demonstrated a stable pacemaker arising proximal to the branching portion of the His bundle. A potential application of the cryosurgical technique might be ablation of sites of dysrhythmia (i.e., ectopic foci, re-entry circuits, accessory pathways).

Forty-two patients with life-threatening or disabling atrial arrhythmias are discussed. Fifteen had Kent bundles as the basis for the reentry tachycardia, while 27 had arrhythmias that originated in or above the atrioventricular (AV) node. Nineteen of the latter had an AV node that conducted atrial impulses rapidly to the ventricle. These patients were classified as having enhanced conduction through the AV node, a diagnosis based on clinical and electrophysiological studies. Initially, the technique employed for His bundle interruption was, either separate or in combination, blind suture, electrocauterization, and incision of the septal portion of the right atrium. The technique later adopted was sharp division of the atrial septum at its attachment to the right fibrous trigone. Cryothermia was used in 31 patients. There were four failures. In the group in whom sharp division was used. there were two failures among 11 patients. Two patients, however, had to have a second operation. Following AV node-His bundle interruption, a junctional rhythm resulted and a pacemaker was always installed. Our studies indicate that interruption of atrial to ventricular conduction is a satisfactory operation for atrial arrhythmias that are disabling or life threatening and that are refractory to vigorous medical therapy. Cryothermic ablation is the preferable technique. However, if this is not successful, then division is required of the AV nod-His bundle junction by interruption of the insertion of the atrial septum into the right fibrous trigone.

Patterns of ventriculoatrial conduction have been used to distinguish retrograde conduction over an accessory atrioventricular pathway from that over the normal atrioventricular conduction system. Ventriculoatrial conduction at a constant interval during incremental ventricular pacing and during progressive prematurity of ventricular extrastimuli has been considered characteristic of conduction over an accessory pathway. We describe three patients with the Wolff-Parkinson-White syndrome who had progressive or sudden increments in ventriculoatrial conduction over an accessory pathway during fixed-rate ventricular pacing or during introduction of ventricular extrastimuli. Such properties have been considered characteristic of conduction over the normal atrioventricular conduction system. We conclude that retrograde conduction over accessory pathways may resemble conduction over the normal atrioventricular conduction system.

This report relates the surgical experience with 79 patients with arrhythmias who had 82 left free wall accessory pathways of atrioventricular conduction of the Kent type. The current operation for the interruption of the pathway consists of two steps. First, the localization of the pathway is done by mapping the epicardial excitation sequence of the atria and the ventricles. This is followed by a set group of maneuvers needed to divide the pathway, which is not visible or palpable. First, an endocardial atrial incision is made just above the anulus fibrosus extending 1.5 to 2.0 cm on each side of the pathway's crossing point. Then, a wide separation of the coronary sulcus fat from the atria and ventricles is done. Finally, superficial fibers of the ventricular myocardium are separated from the anulus fibrosus. The surgical problems such as the possible coronary sinus origin of a pathway and the proximity of pathways to the left fibrous trigone are discussed, both from the electrophysiological and the surgical standpoints. The overall success rate for interruption of left free wall pathways has been 90% with no failure in the last 34 patients.

The effect of atrial pacing and recording site and ventricular pacing site on assessment of conduction over the accessory pathway (AP) was examined in a group of patients with the Wolff-Parkinson-White syndrome. The importance of initial localization of the AP by recording the sequence of retrograde atrial activation during circus movement tachycardia is demonstrated. Inability to record or pace near the AP may lead to significant errors in the assessment of the antegrade and retograde conduction properties of the AP. During ventricular pacing, retrograde atrial fusion was consistently demonstrated with laterally located APs.

A case of the permanent form of junctional reciprocating tachycardia studied by endocardial and epicardial mapping is presented. The ability of the retrograde impulse to penetrate the atrium in 2 different areas, one near the region of the recorded His potential and the other near the orifice of the coronary sinus, is demonstrated. Retrograde conduction persisted after the surgical creation of complete antegrade heart block suggesting the existence of an accessory ventriculo-atrial connection. The decremental properties of retrograde conduction observed suggest that an accessory ventriculo-artrial nodal structure may be the underlying substrate of this arrhythmia.

Successful transvenous catheter ablation of accessory pathway (AP) in a patient (pt) with the permanent form of junctional reciprocating tachycardia is reported. A concealed AP with long conduction time comprised the retrograde limb of tachycardia circuit. The atrial end of the AP was near the coronary sinus (CS) orifice. Catheter ablative technique was performed after assessment of its feasibility and safety by using a canine model. During an electrophysiologic study CS mapping was obtained; the earliest retrograde activity was recorded 1-2 cm inside the orifice of the CS. Two unipolar shocks of 120 J were delivered on the sites exhibiting the earliest retrograde atrial activity. After the procedure, the AP was no longer conducting in both anterograde and retrograde direction. During a follow-up period of 13 months, the pt remained free of tachycardia on no antiarrhythmic medication.

This report describes a catheter technique for ablating the His bundle and its application in nine patients with recurrent supraventricular tachycardia that was unresponsive to medical management. A tripolar electrode catheter was positioned in the region of the His bundle, and the electrode recording a large unipolar His-bundle potential was identified. In the first patient, two shocks of 25 and 50 J, respectively, were delivered by a standard cardioversion unit to the catheter electrode, resulting in an intra-His-bundle conduction defect. Subsequent delivery of 300 J resulted in complete heart block. In the next eight patients, an initial shock of 200 J was used. The His bundle was ablated by this single shock in six of these patients and by an additional shock of 300 J in one. In the remaining patient, conduction in the atrioventricular node was modified, resulting in alternating first and second-degree atrioventricular block. A stable escape rhythm was preserved in all patients. The procedure was well tolerated, without complications, and all patients have remained free of arrhythmia, without medication, for follow-up periods of two to six months.

Reciprocating tachycardias due to reentry either within the atrioventricular (AV) node or using an accessory AV pathway are a common cause of paroxysmal supraventricular tachycardia in humans. Unfortunately, although of potential therapeutic value, differentiation of these forms of reciprocating tachycardia may be difficult and require detailed electrophysiologic study. To develop diagnostic criteria that permit exclusion of participation of an accessory AV pathway in reciprocating tachycardia without extensive laboratory testing, results of electrophysiologic studies were examined in 50 patients with Wolff-Parkinson-White syndrome, 15 patients with accessory AV pathways that conducted only in the ventriculoatrial direction, and 15 patients with reentry within the AV node. The interval between onset of ventricular activation and both earliest recorded atrial activity (V-Amin) and high lateral right atrial electrogram (V-HRA) was measured during tachycardia. A V-Amin of 61 ms or less or V-HRA of 95 ms or less did not occur in patients with accessory AV pathways, but occurred frequently (12 of 15 and seven or eight, respectively) in patients with reentry within the AV node. Therefore, in patients with paroxysmal reciprocating tachycardias, V-A interval measurements provide a screening test capable of excluding participation of an accessory AV pathway.

A case of permanent junctional reciprocating tachycardia in a 36-year-old woman successfully treated with closed-chest interruption of the His bundle is reported. Tachycardia had lasted for 14 years and showed a retrograde P wave (P') and RP' longer than PR' interval. The tachycardia used an anomalous pathway with a long conduction time in the retrograde direction. The atrial end of the anomalous pathway was located near the coronary sinus orifice. His ablation was accomplished by delivering a direct-current shock from a cardioversion unit to the nodal-His zone by means of a conventional electrode catheter percutaneously introduced via the femoral vein. Two shocks were necessary to obtain the desired results. After the procedure, complete atrioventricular block below the His bundle was induced, while antegrade conduction was assured through the anomalous pathway that showed decremental properties. During 7 months of follow-up, stable sinus rhythm with a long PR interval has been observed; the patient has remained free from tachycardia. Furthermore, she is not pacemaker-dependent and requires no cardioactive medication. This case demonstrates the therapeutic value of closed-chest ablation of the His bundle in a patient with permanent junctional reciprocating tachycardia, as well as demonstrating for the first time that the underlying accessory pathway is capable, in some instances, of antegrade conduction.

We used a cryosurgical technique to ablate the atrioventricular (AV) node-His bundle in twenty-two selected patients with disabling supraventricular tachyarrhythmias unresponsive to medical management. Successful AV block was achieved in seventeen. There was no intraoperative mortality and significant surgical complications were not encountered. Electrophysiologic studies performed 7-10 days after surgery revealed that the subsidiary pacemaker had a narrow QRS complex morphology and a mean cycle length of 1244 msec. Isoproterenol (1-4 microgram/min i.v.) significantly increased (p less than 0.01) the rate of the subsidiary pacemaker (mean maximum response 1008.3 msec); atropine (2 mg i.v.) had no effect on its rate. The cycle length of the subsidiary pacemaker during long-term follow-up (mean 14.8 months) showed a small but significant (p = 0.024) increase (mean cycle length 1430 msec). Treadmill exercise in seven patients did not result in the subsidiary pacemaker exceeding the rate of the implanted demand pacemaker set at 70 beats/min. The properties of the subsidiary pacemaker suggest an intra-Hisian site of impulse formation.