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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.

Although electrophysiologic studies have been used to evaluate tachycardia and AV conduction for over 10 years, there are no data comparing measurements obtained on the same patient studied in two institutions. We compared the records of 27 patients who underwent electrophysiologic studies at two different institutions and one patient studied twice in the same institution by two different investigators. We sought to determine if basic intervals, observed tachycardia, and diagnoses were comparable. We found no significant difference between the reported sinus cycle length, atrial-His interval, and His-ventricular interval when the patients were evaluated as a group. However, there were important measurement differences between the two studies in individual patients. The cycle length of induced tachycardias having similar QRS morphology and AV relation was also similar for the group, but individual patients again demonstrated important differences between the two studies. The diagnosis of the tachycardia varied in four patients. This report suggests that intracardiac recordings and the diagnosis of observed tachycardias are comparable among institutions studying the same patient when the group results are compared. However, individual patients demonstrate important measurement differences between the two institutions.

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.

The demonstrable value of EP studies for any given diagnostic or therapeutic category, in the last analysis, is largely a function of the subjects studied. Extrapolations from published data (that generally reflect a highly select patient population) to an individual patient can be fraught with error. Considerations of sensitivity and specificity must be balanced against the important need for information in patients at risk from life-threatening arrhythmias. We must never forget, however, that the EP substrate for any arrhythmia is not, as one might wish, a "black box" that should be expected to respond in a reproducible fashion to stimulation. The substrate is dynamic and subject to modification by change in autonomic tone, stretch, blood flow, basal rate, pH, electrolytes, oxygenation, and exposure to perhaps as yet undiscovered humoral mediators. The challenge to the clinical electrophysiologist is therefore not to exaggerate his efforts in one direction (i.e. programmed stimulation) while disregarding the other variables mentioned. Nor should we be disappointed and discard this approach because our expectations of an oversimplified model of arrhythmia testing are not fulfilled. Thus, in addition to careful stratification of patients, baseline studies should perhaps be carried out with more deliberate consideration of autonomic tone (exercise, isoproterenol), stretch (volume, handgrip, afterload), stress (physical and psychological), local anesthetic used, and body position. Only in this way will the scientific basis for acute and chronic EP testing be firmly established.

The effect of digitalis in 21 patients with Wolff-Parkinson-White syndrome was anlayzed with respect to the ventricular response during atrial fibrillation and antegrade and retrograde refractory periods of accessory pathways. Digitalis shortened the cycle length of the most rapid ventricular response (shortest R-R) (i.e., increased the ventricle response) in 6/21 patients, increased the cycle length in 7/21 patients, had no effect on the cycle length in 5/21, and could not be determined in 3/21. Digitalis could be directly related to the onset of ventricle fibrillation resulting from atrial fibrillation in 9/21 patients. Each of these patients had shortest R-R intervals (220 msec or less) during atrial fibrillation in the control data. The results of this study indicate that no a priori prediction about the effect of digitalis on the antegrade conduction of accessory pathways can be made. By elective induction of atrial fibrillation it is possible to separate WPW patients into groups at high and low risk for developing ventricular fibrillation with the administration of digitalis.

During the electrophysiologic study of 435 patients referred for evaluation of Wolff-Parkinson-White syndrome, 42 (10%) had preexcited reciprocating tachycardia (defined as a macro-reentrant tachycardia that used an accessory atrioventricular [AV] pathway for antegrade conduction). The ages of the patients ranged from 9 to 67 years (27 +/- 14). Thirty-three were male patients, nine female, and eight had Ebstein's anomaly. Preexcited reciprocating tachycardia cycle length was 220 to 430 msec (294 +/- 42). Significant hemodynamic compromise in the laboratory directly related to preexcitated reciprocating tachycardia occurred in only one patient. However, in 10 patients a transformation to atrial fibrillation was seen after a spontaneously occurring premature atrial contraction. Only 17 of the 42 patients with preexcited reciprocating tachycardia during electrophysiologic study had the same tachycardia documented clinically. These 17 patients were more often younger with multiple accessory pathways and with no history of orthodromic reciprocating tachycardia when compared with 25 patients in whom preexcited reciprocating tachycardia could be induced only in the laboratory. Preexcited reciprocating tachycardia was induced in the laboratory in 22 of 374 (6%) patients with single accessory pathways and in 20 of 61 (33%) of those with multiple accessory pathways. In the 20 patients with multiple accessory pathways, the spectrum of reentrant circuits included fusion over two or more accessory pathways or fusion over both an accessory pathway and the AV node. In the 22 patients with a single accessory pathway and true antidromic reciprocating tachycardia, all but two episodes were at least 4 cm from the AV node. No patient with true antidromic reciprocating tachycardia had a posterior septal accessory AV pathway. Only in patients with multiple accessory pathways was the posterior septal accessory AV pathway used as the antegrade limb.

Patients with accessory atrioventricular pathways that conduct only in the antegrade direction represent an unusual variant of the Wolff-Parkinson-White syndrome. This report describes such patients and compares them with patients with accessory pathways that demonstrate bidirectional conduction. Of 143 patients with single accessory pathways, seven demonstrated exclusive antegrade conduction (study group), 111 demonstrated bidirectional conduction (control group), and 25 demonstrated exclusive retrograde conduction. Study group patients were significantly older than patients in the control group (42 +/- 9.8 years and 31.4 +/- 13.9 years, respectively, p < 0.0001). Refractoriness and conduction characteristics of the accessory pathways in the antegrade direction in the study group were not different from those in the control group. Control group patients presented with atrioventricular reentrant tachycardia (58 of 111), atrial fibrillation (23 of 111), both of these arrhythmias (19 of 111), or no documented arrhythmia (11 of 111). Study group patients presented with only atrial fibrillation (six of seven). An accessory pathway with only antegrade conduction is a rare cause of symptoms in the Wolff-Parkinson-White syndrome. These patients are asymptomatic until atrial fibrillation develops as the patient ages. Despite the absence of retrograde conduction over the accessory pathway, its antegrade functional properties are similar to pathways that demonstrate bidirectional conduction.

A case of permanent junctional reciprocating tachycardia with post-mortem documentation of an accessory atrioventricular pathway as the substrate of the arrhythmia is reported. Tachycardia had lasted for 15 years and showed a retrograde P wave (P') and R-P' longer than P'-R interval. The tachycardia circuit utilized a concealed posterior septal accessory pathway as the retrograde limb. Because the arrhythmia was disabling and unresponsive to pharmacological treatment, the patient underwent closed chest ablation of the His bundle. After the procedure, no anterograde or retrograde conduction over the normal conduction system was observed; anterograde conduction over the anomalous pathway showed decremental properties. Because of previous myocardial infarction, the patient developed a ventricular aneurysm and died suddenly 5 months after His bundle ablation. Histological examination of the heart revealed a group of tiny fibromuscular bundles joining the lower rim of the coronary sinus outlet to the summit of the interventricular septums; the anomalous atrioventricular connection pursued a sinuous, tortuous path. The geometrical disposition of the accessory pathway may have been responsible for the decremental properties of conduction observed during life.

In this report, we have outlined our experiences with the direct surgical treatment of 16 patients with supraventricular tachyarrhythmias (SVTA). Re-entry supraventricular tachycardia (SVT) was demonstrated by the 4 patients who had retrograde-conducting Kent pathways. The SVT was corrected by the successful division of the Kent bundle in 3 and a partially successful His bundle division in one patient. The remaining 9 patients with re-entry, which included 6 with Kent pathways and WPW, all had His bundle section. The remaining 3 with His interruption had focal tachycardias associated with dysfunction of the atrioventricular (AV) node. Of the 13 His bundle interruptions, nine were successful, three resulted in questionable AV conduction, and one failed. Problems with suture ligation and cautery explained the failures. Cryothermia was the most successful procedure used. However, excision of that portion of the atrium containing the AV node shows promise of being satisfactory. The possibility is discussed of using measures much more precise and less destructive than His bundle interruption for SVTA.

Recent reports have suggested that an accessory bypass tract connecting the His bundle to the atrium (His-atrial fiber) may form the retrograde limb of "AV nodal" re-entry tachycardia (AVNRT). We studied 12 patients with AVNRT in whom the presence of an accessory atrioventricular fiber (Kent fiber) was excluded. We investigated the possibility of a His-atrial (H-A) fiber by examining the nature of retrograde conduction and by assessing the necessity of the atrium as a part of the re-entry pathway. Retrograde conduction through the AV node had characteristics similar to retrograde conduction over a Kent bundle; that is, retrograde conduction times were short and did not vary. With echo beats (Ae) evoked during antegrade refractory period determination early premature beats resulted in prolongation of the AH interval with no change in HAe interval. During AVNRT the A'H':H'A' ratios ranged from 2.0-8.0 (mean 4.0 +/- 1.8) and with changes in tachycardia cycle length the H'A' interval remained constant. During retrograde refractory period determination, delay occurred below the AV node without change in the H-A interval. Estimations of retrograde conduction times by all 3 methods were not significantly different (p greater than 0.2). The pattern of retrograde conduction suggests anatomical or functional specialized fibers as the retrograde limb of the tachycardia. The necessity of the atria as a part of the re-entry circuit was assessed by the introduction of atrial premature beats (APBs) in the region of the atrial septum during AVNRT in 10 patients. APBs pre-excited the atria by 40-140 ms without changing the cycle length of the tachycardia, providing strong evidence against the participation of an extranodal His-atrial fiber in AVNRT. In conclusion, retrograde conduction during AVNRT appears to take place over a functional or anatomical specialized fiber within the AV node and not over an extranodal H-A fiber.

A long pause after an abnormal heat during atrial fibrillation has been called a "compensatory pause" and has been used to identify premature ventricular complexes (PVCs) and to differentiate them from supraventricular beats with aberration. The diagnostic value of the compensatory pause is controversial and has not been tested systematically with programmed stimulation and intracardiac recordings. In this study we used these methods to determine if PVCs induced during atrial fibrillation were followed by compensatory pauses. Five patients were studied who had ECGs with a normal PR interval and a normal QRS duration and morphology during sinus rhythm. Atrial fibrillation was induced by rapid atrial pacing. PVCs were induced by coupling a ventricular extrastimulus to every eighth or tenth QRS complex during atrial fibrillation. The coupling interval of the PVC was changed in 10- or 20-msec increments until the entire cardiac cycle was scanned. The mean duration of recorded atrial fibrillation was 15.7 minutes. Fifty-seven to 163 PVCs were induced in each patient. The mean cycle after the induced PVC was calculated and compared with the mean control cycle. The mean cycle after the PVC was 107-136 msec longer than the mean control cycle (p < 0.001 in every patient). This study confirms the presence of a compensatory pause after stimulated PVCs in atrial fibrillation.

Transvenous atrial pacing via an electrode placed in the coronary sinus has become an increasingly frequent procedure during the past 10 years for both diagnosis and therapy of cardiac arrhythmias. The coronary sinus has five major venous tributaries, any one of which can be entered by a pacing catheter. A catheter in the middle cardiac vein can mimic the usual ventricular pacemaker position, while an electrode in the coronary sinus or in a persistent left superior vena cava may be mistaken for myocardial perforation. A persistent left superior vena cava may also be catheterized. This anomaly is associated with a tenfold increased incidence of congenital atrioventricular conduction abnormalities and, therefore, is surprisingly common in patients having coronary sinus pacers placed because of cardiac arrhythmias.

Data are reported on three patients with the permanent form of junctional reciprocating tachycardia, in whom conduction over a slow accessory pathway was observed after His bundle ablation. Tachycardia was almost incessant and showed a retrograde P wave (P') and RP' interval longer than P'R interval in all patients; during sinus rhythm, the PR interval was normal and there was no evidence of a delta wave. An accessory pathway with a long conduction time located in the posterior pyramidal space provided the retrograde limb of the reentry circuit. After His bundle ablation, the accessory pathway was capable of conducting in both anterograde and retrograde directions with decremental properties in all patients. Postmortem documentation of the accessory pathway was achieved in one patient. Serial sections revealed an accessory atrioventricular connection composed of ordinary myocardium joining the lower rim of the coronary sinus outlet to the uppermost ventricular muscle. This anomalous atrioventricular connection pursued a sinuous, tortuous path. As a result of changing cross-sectional area, such an accessory pathway might exhibit slow conduction, thus explaining its decremental characteristics.

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.

Postmortem examination of the heart was done in a case with disabling supraventricular tachyarrhythmia successfully treated by closed-chest ablation of the His bundle. A ventricular aneurysm developed as a result of a previous myocardial infarction, and death occurred suddenly five months after the procedure. Histologic studies of the atrioventricular (AV) junctional tissue demonstrated severe damage to the nearby AV node and penetrating His bundle. No damage to the branching His bundle or either bundle branch was observed.

A case of ventricular aneurysm with refractory ventricular tachycardia is presented. Epicardial mapping was used to localize the site of earliest epicardial activity to the margin of the aneurysm, and subsequent resection of this area abolished the rhythm disturbance.

Catheter-induced conduction delay or block in the accessory atrioventricular pathway of four patients with the preexcitation syndrome was observed. Block in the accessory pathway occurred during routine catheter placement and lasted from 90 seconds--14 hours. All of the pathways were in locations readily accessible to catheter trauma, located in the right anterior septal/paraseptal area in three patients, and in the posterior septum near the orifice of the coronary sinus in the fourth. The location of the acessory pathway was confirmed at surgery by endocardial mapping in three of the four patients. The fourth patient did not undergo survey. These findings suggest the need for caution in performing and interpreting electrode catheter studies which are undertaken to document the presence of accessory pathways.

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.

Thirty-six accessory pathways of atrioventricular conduction of the Kent type were found in 17 patients in a series of 161 patients subjected to direct operation for arrhythmias caused by the pathways. Careful preoperative studies detected the multiple pathways in 11 patients. In four patients, the additional pathways were found at operation, and in two patients they were found after operation. The operation successfully interrupted 32 of the 36 pathways. Multiple pathways must be sought for in all patients who are operated upon for arrhythmias caused by accessory pathways.

Forty-seven consecutive patients with the Wolff-Parkinson-White syndrome due to posterior septal accessory pathways were operated on from August 3, 1983 to March 23, 1989. Seven of these patients had Ebstein's anomaly, another three coronary sinus aneurysms, one a persistent left superior vena cava, and five others complex multiple pathway combinations. Two additional patients required surgery following unsuccessful catheter ablation and one after failed surgery at another institution. Thus nineteen of forty-seven patients (40%) had additional difficulty factors which tend to complicate the operative dissection in this already complex anatomical area. The surgical anatomy of the posterior septal space as well as the essential operative principles and techniques are reviewed. Each of the frequently encountered additional difficulty factors is described with emphasis on the coronary sinus aneurysm, a recently recognized entity.

The study of transmural activation of the intact heart requires placement of multipolar needle electrodes through the wall of the beating heart. This report describes a method developed for constructing lightweight multipolar needles with 10-30 leads mounted 1 mm apart. The electrodes are constructed from readily available materials and no special equipment is required. The electrodes are well suited to the intraoperative mapping studies required to surgically correct arrhythmias.

Eight patients, aged 5 to 57 years, with uncontrolled symptomatic tachycardia for 2.5 to 41 years (mean 15) and significant left ventricular (LV) dysfunction in the absence of any other apparent underlying cardiac disease underwent evaluation. Incessant tachycardia was present for 0.5 to 6.0 years (mean 2.1) in 7 patients. One patient had an ectopic atrial tachycardia and 7 patients had an accessory atrioventricular pathway that participated in reciprocating tachycardia. Six patients underwent surgery; the ectopic focus was ablated in 1 patient and an accessory pathway was divided in 5 patients. One patient underwent open ablation of the His bundle and 1 patient underwent closed-chest ablation of the atrioventricular conduction system. Myocardial biopsy specimens were obtained from 5 patients, none of which yielded a specific diagnosis. Pretreatment radionuclide angiography demonstrated a mean ejection fraction (EF) of 19 +/- 9% (range 10 to 35%). Following tachycardia control a marked improvement in LV function was noted in 6 of 8 patients at rest and in 1 additional patient during exercise. The EF increased to 33 +/- 17% (range 16 to 56%) an average of 8 days after treatment and to 45 +/- 15% (range 22 to 67%) at late follow-up 3.5 +/- 40 months (mean 17) later (p less than 0.005). Seven patients remain asymptomatic 11 to 40 months (mean 22) after the corrective procedure and have resumed normal activities. These findings suggest that chronic uncontrolled tachycardia may result in significant LV dysfunction, which is reversible in some cases after control of the arrhythmia.

Giant sigmoid diverticula ("giant gas cysts," "giant sigmoid cysts") are an unusual complication of diverticulitis. We have recently seen two patients with such lesions, bringing the total number of reported cases to 48. Most patients are elderly and complain of abdominal pain or the presence of an abdominal mass. Air trapping by a ball-valve mechanism may be responsible for formation of the fibrous cysts. The gas-filled structures can usually be differentiated from other conditions by contrast studies. Excision of the cyst and adjacent colon with anastomosis can usually be accomplished safely under elective circumstances.

A six-year-old girl with syncope in association with atrial flutter-fibrillation and ventricular tachycardia produced by exercise or emotion is presented. The tachycardias could be reproduced by low-dose isoproterenol infusion and were blocked by high dose propranolol therapy. Catecholamine-induced tachyarrhythmias should be suspected in children with unexplained syncope in association with exercise or emotion.

A 10-month-old infant with multiple muscular ventricular septal defects, congestive heart failure, Wolff-Parkinson-White syndrome, and supraventricular tachycardia is presented. The site of ventricular pre-excitation was predicted by analysis of ST-T wave isopotential body surface maps to be in the posterior free wall of the right ventricle. The site was confirmed by epicardial mapping of the ventricles during surgery. The pathyway was cryoblated and the ventricular defects were closed. The patient has been free of pre-excitation and supraventricular tachycardia for over two years since surgery.

The effects of exercise and isoproterenol on atrial fibrillation (AF) were studied in 17 patients with Wolff-Parkinson-White syndrome (WPW) to assess the risk of developing a rapid ventricular response. Mean cycle length (R-R interval) and shortest R-R interval between both preexcited and nonpreexcited QRS complexes were recorded, as well as the percentage of preexcited complexes during control periods, during bicycle exercise, and during isoproterenol infusion. Exercise resulted in significantly shorter mean cycle length and the shortest R-R interval between nonpreexcited complexes. Exercise also resulted in a significantly lower percentage of preexcited complexes during AF, but had no effect on the R-R intervals between preexcited complexes. Isoproterenol had a variable effect on the percentage of preexcited QRS complexes, but resulted in significant shortening of mean cycle length and the shortest R-R interval between both normal and preexcited complexes. With isoproterenol, 12 of 17 patients had shortest preexcited R-R intervals less than or equal to 215 ms, compared with 6 of 17 in the control state. Isoproterenol infusion increased the rate of conduction over the accessory pathway during AF and allowed better assessment of the risk of excessively rapid rates occurring during AF. Exercise is not an adequate test for this purpose.

Thirty-three patients with Wolff-Parkinson-White syndrome were studied electrophysiologically before and after administration of intravenous procainamide and oral quinidine sulfate. Procainamide prolonged the shortest R-R (SRR) interval between two consecutive pre-excited beats during atrial fibrillation 20-70 msec in 15 of 21 patients with no change observed in 6 of 21 patients. Quinidine sulfate prolonged the SRR 20-170 msec in all 16. In 14 of 18 patients where procainamide and quinidine were comparable, quinidine prolonged the SRR 30-100 msec more than procainamide.

The development of the procedure for interruption of a Kent bundle for the correction of the tachyarrhythmias associated with the Wolff-Parkinson-White syndrome has been hampered by the lack of anatomic descriptions of the pathways. Only 21 descriptions are given in enough detail for guidance to the surgeon. Our experience with our first 100 patients operated upon for serious dysrhythmias associated with Kent bundles has supplemented this information. In our first 40 patients the Kent was divided in 22 of 39, one having elective and four having forced interruption of the His bundle, with success in 28. In the next 60 the Kent was divided in 52 of 59 attempts, one had elective and three had forced His bundle interruption, and the success rate was 56 of 60 patients. This increased success occurred because we learned the following: (1) The anomalous pathways are best approached through the atrium and can be for out in the fat, even subepicardial in the coronary sulcus or adjacent to the anulus. (2) Interruption should be started with an incision made just above the anulus fibrosus. (3) Posterior septal pathways can be adjacent to the His bundle or in the septum from this point posteriorly to the crux. (4) Anterior septal pathways can be divided and the His bundle protected. The details for the approach to the right and left free wall, posterior septal, and anterior septal pathways will be given. The approach to all pathways is now safe enough to allow the surgeon to offer this operation to patients with life-threatening tachyarrhythmias as well as the ones with rhythm disturbances that are either burdensome or impossible to treat medically.

Past legislation related to children and families has been used to improve services to specific target groups of children and families in need (i.e., poor, handicapped, etc.) Current legislation, notably Public Law 94-142, the Education for All Handicapped Children Act, and Public Law 99-457 (Part H), Services for Infants and Toddlers with Handicapping Conditions, also includes elements of mandated reform of certain professional practices (i.e., inclusion of parents in planning and requirements for multidisciplinary cooperation). Such a mandate has the effect of putting into practice changes that many professionals have said were needed but were unable to achieve, but it also makes the implementation of these policies more difficult.

'Dual atrioventricular nodal pathways" were found in five patients who also had the Wolff-Parkinson-White syndrome. All five patients had a re-entrant tachycardia that used the atrioventricular node for conduction in the anterograde direction and an accessory atrioventricular pathway for conduction in the retrograde direction. One of the patients also had a re-entrant tachycardia that originated within the atrium or the atrioventricular node. Dual atrioventricular nodal pathways were identified in three of the five patients during their first electrophysiological study because the effective refractory period of the accessory atrioventricular pathway in the anterograde direction was longer than the effective refractory period of the fast atrioventricular nodal pathway. In the other two patients the dual atrioventricular nodal pathways were found only after operative division of an accessory atrioventricular pathway. Re-entrant tachycardia that uses an accessory pathway may be cured by operative division of the accessory pathway. Tachycardia resulting from re-entry within the atrioventricular node cannot be cured by an operation unless the normal conduction system is divided and a permanent pacemaker implanted. These five patients indicate the importance of determining the aetiology of tachycardia by studying the tachycardia itself and not only the type of atrioventricular conduction present.

This paper includes some of the latest discussions regarding educational programming for autistic children. Until the last decade, special educators have not been either effective or optimistic regarding the prognosis for such children. Recent educational developments with such techniques as behavior modification, the behaviorally engineered classroom, and early identification of the condition have caused increased interest in the possible contributions of educators to the puzzling syndrome. The various alternative treatment possibilities will be presented together with an evaluation of the effectiveness of such programs to date.

The epicardial activation sequence of 34 patients with the Wolff-Parkinson-White syndrome was determined. Epicardial pre-excitation occurred at a spectrum of sites over either the free wall of the left or right ventricle or in a paraseptal region, always adjacent to the atrioventricular rings. The site of pre-excitation was related to the spatial position of the 10 msec vector of the vectorcardiogram (VCG) in 15 patients and the 20 msec vector of the electrocardiogram (ECG) in 29 patients with a single accessory pathway. All patients whose 20 msec vector (ECG) was directed to the right had accessory pathways which caused epicardial breakthrough over the free wall of the left ventricle. When the 20 msec vector (ECG) was to the left and inferior, epicardial pre-excitation was over either the right ventricular free wall or in the region of the pulmonary outflow tract. Superior location of the initial forces, especially the 10 msec vector (VCG), strongly suggested the presence of a septal bypass tract. The polarity of the delta wave and maximum QRS forces in precordial lead V1 were discordant in a significant number of patients, pointing to probable shortcomings of a classification based upon the latter.

Physiological studies of the type we have described, when performed in patients with the WPW syndrome, can yield diagnostic information regarding the mechanism of arrhythmia, demonstrate functional properties of therapeutic import, facilitate therapeutic decision-making about drug regimens and presumptively localize the site of pre-excitation as a basis for possible surgical intervention. Based on our experience, we feel that in selected patients, surgical correction of the WPW syndrome is entirely feasible, and can be accomplished in the majority of patients in whom free wall A-V connections are present. The continuing challenge of identification and correction of septal accessory pathways directs our present work with the WPW syndrome.

Myopotential signals were recorded from atrial and ventricular leads during isometric exercise in 25 patients who had chronically implanted dual chamber pacemakers using the electrogram telemetry capability of the pacemakers. Average electrogram amplitude on the atrial channel was 0.92 mV (range 0.3 to 1.9) and on the ventricular channel was 0.98 mV (range 0.3 to 2.2); the difference was not significant. There was a strong correlation (R = 0.82) between the amplitude of myopotentials on the atrial and ventricular leads for individual patients. Myopotential sensing caused ventricular output inhibition in two patients (8%) and ventricular tracking in sixteen patients (64%). Pacemaker reprogramming abolished ventricular myopotential inhibition in all patients and stopped ventricular myopotential tracking in seven patients. We conclude that myopotentials can be analyzed and their effects ameliorated by a multiprogrammable pacemaker with electrogram telemetry capability.