'Incessant' tachycardias in Wolff-Parkinson-White syndrome. II: Role of atypical cycle length dependency and nodal-his escape beats in initiating reciprocating tachycardias

Iatrogenically induced intractable atrioventricular reentrant tachycardia after verapamil and catheter ablation in a patient with Wolff-Parkinson-White syndrome and idiopathic dilated cardiomyopathy

In a patient with WPW syndrome and idiopathic dilated cardiomyopathy, intractable atrioventricular reentrant tachycardia (AVRT) was iatrogenically induced. QRS without preexcitation, caused by junctional escape beats after verapamil or unidirectional antegrade block of accessory pathway after catheter ablation, established frequent AVRT attack.

Bursting behavior during fixed-delay stimulation of spontaneously beating chick heart cell aggregates

Spontaneously beating embryonic chick atrial heart cell aggregates were stimulated with depolarizing current pulses delivered at a fixed delay after each action potential. This preparation is an experimental model of a reentrant tachycardia. During fixed-delay stimulation, bursting behavior was typically observed for a wide range of delays. Episodes of bursting at a rate faster (slower) than control were followed by overdrive suppression (underdrive acceleration). We use a simple nonlinear model, based on the interaction between excitability and overdrive suppression, to describe these dynamics. A modified version of the Shrier-Clay ionic model of electrical activity of the embryonic chick heart cell aggregates that includes a simplified Na+ pump term is also presented. We show that the complex patterns during fixed-delay stimulation arise as a result of delicate interactions between overdrive suppression and phase resetting, which can be described in terms of the underlying ionic mechanisms. This study may provide a basis for understanding incessant tachycardias in the intact heart, as well as an alternative mechanism for the emergence of bursting activity in other biologic tissue.

Spontaneous incessant AV reentrant tachycardia related to left bundle branch block and concealed left-sided accessory AV pathway

Three patients in whom permanent AV reentrant tachycardia became the clinical manifestation of Wolff-Parkinson-White syndrome are described. The substrate for the arrhythmia was created by coexistence of a concealed left-sided accessory pathway and an ipsilateral bundle branch block. Pharmacologic therapy in all three patients failed to control the tachycardia, which in two cases led to severe left ventricular failure. After successful radiofrequency ablation of the accessory pathway (in two) or AV junction (in one), left ventricular function gradually returned to normal.

Dr Dennis M Krikler: editor of the British Heart Journal 1981-91

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Effect of atrial pacing on the frequency of tachycardia in patients with recurrent junctional tachycardia

In order to assess whether atrial pacing reduced the frequency of tachycardia in patients with recurrent junctional tachycardias, ten patients with recurrent junctional tachycardias with atrial Intertach antitachycardia pacemakers in situ were paced in a random order in atrial demand mode at 50 ppm (AAI 50), 80 ppm (AAI 80), and 100 ppm (AAI 100) for a period of up to 1 month. The numbers of tachycardias detected by the pacemaker over this period were recorded and compared with the number seen when unpaced (000). Correct arrhythmia detection by the pacemaker was confirmed by Holter monitoring. The number of tachycardias in 000 was 44.7 +/- 19.8 (mean +/- SEM). No significant reduction in tachycardia frequency was seen in any pacing mode. Back-up atrial pacing at 50 ppm tended to reduce the frequency of tachycardias (32.3 +/- 12.8 tachycardias; P = 0.06). The higher pacing rates increased the number of tachycardias (AAI 80; 57.1 +/- 24.6 tachycardias, P = 0.20: AAI 100; 81.8 +/- 30.2 tachycardias; P = 0.31). Symptoms increased with each pacing mode and palpitations were statistically more severe in AAI 100 mode. Four patients had disabling symptoms at this rate and had to drop out. Atrial back-up pacing may be of use in some patients with junctional tachycardia, but overdrive pacing is not helpful.

Type A Wolff-Parkinson-White syndrome obscured by left bundle branch block associated with a vascular malformation of the coronary sinus

A case of Wolff-Parkinson-White syndrome type A with coexisting ipsilateral bundle branch block is presented. The diagnosis was suspected because of subtle electrocardiographic changes and was confirmed at electrophysiological study. Necropsy showed a vascular anomaly of the coronary sinus that contained bundles of myocardial muscle which crossed the atrioventricular ring at a site that was consistent with the predicted accessory pathway.

Procainamide-induced incessant supraventricular tachycardia in the Wolff-Parkinson-White syndrome

A patient with the Wolff-Parkinson-White syndrome presented with incessant orthodromic atrioventricular tachycardia following initiation of procainamide therapy. This finding was repeatedly documented both clinically as well as during electrophysiologic testing. Escape atrial complexes, which occurred following junctional premature complexes, failed to initiate tachycardia in the control state but tachycardia was always reinitiated by an identical escape sequence after procainamide. In addition, the tachycardia persisted and was repeatedly spontaneously reinitiated for prolonged periods after procainamide. The pro-arrhythmic effects of procainamide may be explained on the basis of both its vagolytic action on the atrioventricular node as well as by prolongation of refractoriness in the accessory pathway. These observations add to the literature on pro-arrhythmic effects of commonly used antiarrhythmic drugs.

Modes of onset ("initiating events") for paroxysmal atrial tachycardia in infants and children

Observations of spontaneous onset of paroxysmal atrial tachycardia (PAT) in infants and children have been infrequently reported. This study reports on modes of spontaneous onset of PAT in 22 infants and 8 children in whom onset of PAT was recorded during continuous electrocardiographic recording. During PAT, all 30 patients used the normal specialized atrioventricular conduction system for ventricular activation, with atrial activation occurring through an accessory atrioventricular connection (orthodromic reciprocating tachycardia). Wolff-Parkinson-White syndrome was present in 7 patients. Analysis of the mode of onset of PAT revealed that infants initiated PAT with atrial extrasystoles or sinus acceleration (a gradual shortening of the P-P interval). In 10 infants more than 10 PAT onsets were recorded, and in these infants the mode of onset was sinus acceleration. In 7 infants, both atrial extrasystole and sinus acceleration were observed to initiate PAT. In the older children, onset of PAT followed atrial extrasystole (3 patients), ventricular extrasystole (2 patients), and sinus pause with junctional escape (3 patients). It has been previously recognized that the natural history of these "initiating events" varies with patient age. Variations in frequency of spontaneous episodes of PAT may relate to chronologic variations in frequency and type of initiating events.

"Incessant" atrioventricular (AV) reciprocating tachycardia utilizing left lateral AV bypass pathway with a long retrograde conduction time

Two patients with incessant or nearly incessant episodes of atrioventricular (AV) reciprocating tachycardia were studied and were found to be unique because of the location of a slowly conducting retrograde AV bypass pathway in the left lateral position. During the tachycardia in both patients, negative P waves were present not only in ECG leads II, III, and aVF, but also in leads I and aVL. The R-P'/P'-R ratios were 1.3 and 1.9, respectively. Cardiac electrophysiologic study revealed that in both tachycardias, retrograde ventriculoatrial conduction occurred utilizing a concealed left lateral AV bypass pathway with a long conduction time. Verapamil prolonged conduction over the AV bypass pathway in both patients. One patient was successfully treated with oral verapamil. The other patient underwent successful surgical interruption of the AV bypass pathway.

Anatomic and electrophysiologic substrate of the permanent form of junctional reciprocating tachycardia

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.

Ten years of experience with amiodarone

Arrhythmias may be controlled in most patients with recurrent supraventricular tachycardia or atrial fibrillation with small to moderate maintenance doses of amiodarone (100 to 400 mg/day). Moderate doses (400 mg/day) are also highly effective in suppressing "warning" ventricular arrhythmias in patients with chronic ischemic heart disease, particularly if the goal of treatment is to eliminate ventricular couplets, runs of ventricular tachycardia (VT), and the "R on T" phenomenon. Treatment and prevention of sustained recurrent VT and the malignant arrhythmias of chagasic myocarditis require, however, doses of about 800 mg/day, which may be higher than those needed for ischemic heart disease complicated by VT and ventricular fibrillation. Clinical studies suggest an elimination half-life for amiodarone of about 30 days (range 15 to 100 days). Thus there is a pretherapeutic latency period that varies according to the type of arrhythmia and the doses employed. The maximal effects (as well as the most significant adverse effects) are not attained before 90 to 150 days of treatment, and the antiarrhythmic protection may persist for varying intervals, up to 150 days or more, after the drug has been discontinued. Side effects are not negligible but are generally dose dependent. Despite these side effects, many patients have been treated by us with amiodarone for as long as 5 to 8 years--and for up to 10 years in some cases. Amiodarone appears to be one of the most promising drugs for the possible prevention of ventricular fibrillation and sudden death.

Antegrade slow bypass conduction after closed-chest ablation of the His bundle in permanent junctional reciprocating tachycardia

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.

Latent sinoatrial conduction disturbances in symptomatic patients with Wolff-Parkinson-White syndrome

Sinoatrial conduction abnormalities were studied in fourteen patients with Wolff-Parkinson-White (WPW) syndrome and frequent attacks of supraventricular paroxysmal tachycardia. Sinoatrial conduction time (SACT), obtained by the method of constant atrial pacing, was prolonged in all but two patients. The mean value was 277 +/- 56 ms (mean +/- SD). SACT was measured in the same way in sixteen patients without signs of pre-excitation or sinoatrial disease; SACT was significantly shorter (p less than 0.001) than in the WPW group of patients. The prolongation of SACT in patients with WPW syndrome was confirmed by measuring SACT by the alternative method of programmed atrial stimulation. SACT was found to be prolonged in eight patients (mean +/- SD = 239 +/- 47 ms). Whether our results should be attributed to WPW syndrome or frequent supraventricular tachycardias--both being a characteristic feature of our patients--remains uncertain. The results of this study, however, indicate that in symptomatic patients with WPW syndrome and frequent episodes of supraventricular tachycardia, sinoatrial conduction is frequently impaired. Slackening of the sinoatrial conduction is a possible predisposing factor for initiation of tachycardias in the WPW syndrome.

Sudden sinus slowing with junctional escape: a common mode of initiation of juvenile supraventricular tachycardia

After noting bradycardia-induced supraventricular tachycardia (SVT) in two successive children with SVT, we analyzed Holter monitor recordings done on 66 children with suspected or proved SVT. Ten children had apparent reentry SVT. The most common mode of initiation (eight of 10 patients) was not premature atrial beats, but sudden sinus pause with a junctional escape beat (JEB), usually fused with the delayed sinus P wave, initiating the tachycardia. Electrophysiologic studies in five children who had this mode of initiation showed evidence of reentry in four, possibly by dual atrioventricular nodal (AVN) pathways. Since sudden sinus pause and JEB are relatively uncommon in adults, the disappearance of this phenomenon with age may be the most significant reason why children often have less tachyarrhythmia as they get older. Both propranolol and digoxin significantly increased the numbers of episodes of SVT in the three patients tested with serial Holter monitoring.

Incessant junctional reciprocating tachycardia caused by dual atrioventricular nodal pathways and atrio-nodal bypass tract

A case is described with clinical and electrocardiographic findings of incessant junctional reciprocating tachycardia. Electrophysiological study showed that longitudinal dissociation of the atrioventricular node into two pathways was responsible for the maintenance of the arrhythmia. The two intranodal pathways had different refractory periods but reciprocally related and overlapping conduction times (anterograde fast, retrograde slow, and vice versa). Induction and termination of the arrhythmia was related to the presence of a partial atrio-nodal bypass tract.

The development of permanent unidirectional anterograde block in the accessory pathway of a patient with Wolff-Parkinson-White syndrome and observations on the mechanism of the ensuing incessant circus tachycardia

A case is reported, the sixth in the literature, in which permanent anterograde block occurred in the accessory pathway of a patient with Wolff-Parkinson-White syndrome, so that pre-excitation no longer occurred. Retrograde conduction remained intact and the patient developed incessant tachycardia with ventriculo-atrial conduction occurring over the accessory pathway.

Retrogradely conducting pathways are a common cause of supraventricular tachycardia and this case raises the possibility that many of them may previously have had overt pre-excitation.

Prevention of intra-atrial reentry by chronic atrial pacing

The authors describe a case of so-called "intra-atrial reentry," associated with sinus node dysfunction. The spontaneous initiation of the tachycardia was always preceded by a sinus pause, and external atrial pacing prevented the appearance of tachycardia. Thus an atrial pacemaker was implanted, and after several months, the atrial dysrhythmias disappeared completely, despite interruption of the antiarrhythmic drugs. When a pacemaker dysfunction occurred, the sinus node dysfunction and the tachycardia reappeared. This is analogous with the "incessant" tachycardias seen in the WPW syndrome, and must be differentiated from the usual forms of the sick sinus syndrome which require both a pacemaker and antiarrhythmic drugs.