'Incessant' tachycardias in Wolff-Parkinson-White syndrome. I: Initiation without antecedent extrasystoles or PR lengthening, with reference to reciprocation after shortening of cycle length

Spontaneous Initiation and Termination of Complex Rhythms in Cardiac Cell Culture

INTRODUCTION

Complex cardiac arrhythmias often start and stop spontaneously. These poorly understood behaviors frequently are associated with pathologic modification of the structural heterogeneity and functional connectivity of the myocardium. To evaluate underlying mechanisms, we modify heterogeneity by varying the confluence of embryonic chick monolayer cultures that display complex bursting behaviors. A simple mathematical model was developed that reproduces the experimental behaviors and reveals possible generic mechanisms for bursting dynamics in heterogeneous excitable systems.

METHODS AND RESULTS

Wave propagation was mapped in embryonic chick myocytes monolayers using calcium-sensitive dyes. Monolayer confluence was varied by plating cultures with different cell densities and by varying times in culture. At high plating densities, waves propagate without breaks, whereas monolayers plated at low densities display spirals with frequent breaks and irregular activation fronts. Monolayers at intermediate densities display bursting rhythms in which there is paroxysmal starting and stopping of spiral waves of activity. Similar spatiotemporal patterns of activity were also observed as a function of the time in culture; irregular activity dominates the first 30 hours, followed by repetitive bursting dynamics until 54 hours, after which periodic target patterns or stable spirals prevail. In some quiescent cultures derived from older embryos, it was possible to trigger pacemaker activity following a single activation. We are able to reproduce all of these behaviors by introducing spatial heterogeneity and varying neighborhood size, equivalent to cell connectivity, in a spontaneous cellular automaton model containing a rate-dependent fatigue term.

CONCLUSION

We observe transitions from irregular propagating waves, to spiral waves that spontaneously start and stop, to target waves originating from localized pacemakers in cell culture and a simple theoretical model of heterogeneous excitable media. The results show how physiologic properties of spontaneous activity, heterogeneity, and fatigue can give rise to a wide range of different complex dynamic behaviors similar to clinically observed cardiac arrhythmias.

Paroxysmal starting and stopping of circulating waves in excitable media

Levels of intracellular Ca2+ were monitored using fluorescence from Ca2+-sensitive dyes in chick embryonic heart cells cultured in an annular geometry. There was spontaneous starting and stopping of reentrant waves of activity. The results are modeled using modified FitzHugh-Nagumo equations representing pacemakers embedded in a conducting medium. These results provide a potential mechanism for spontaneous abnormal cardiac rhythms in which there are rapid heart beats (tachycardias) that repetitively start and stop.

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.

Provocation of supraventricular tachycardias by an intravenous class I antiarrhythmic drug

Antiarrhythmic drugs may aggravate or induce ventricular arrhythmia. The induction of a supraventricular tachycardia or its facilitation has rarely been reported. The purpose of the study was to know whether the potential for supraventricular proarrhythmic effect of a class Ia intravenous antiarrhythmic drug can be exposed during electrophysiologic study. Ajmaline was chosen because of its short duration of action. The protocol of the study consisted of an electrophysiological study and programmed atrial stimulation using 1 and 2 extrastimuli on driven rhythm and atrial pacing up to second-degree atrioventricular block. Then 1 mg/kg of ajmaline was injected and atrial pacing was performed 3 minutes after its injection. Supraventricular proarrhythmic effect of ajmaline was defined as the spontaneous occurrence of a supraventricular tachycardia or the facilitation of its induction. Seventy patients among 1955 presented a proarrhythmic effect: 63 developed a supraventricular tachyarrhythmia (atrial flutter, fibrillation, tachycardia) and 7 an atrioventricular reentrant tachycardia, either spontaneously (n = 23) or during atrial pacing (n = 47). Risk factors were identified in most patients: old age, underlying heart disease, history of spontaneous supraventricular tachycardia and/or induction of a supraventricular tachycardia by 2 extrastimuli on driven rhythm in the control state (34 patients), sinus node dysfunction (22 patients). Compared with patients without proarrhythmic supraventricular effect only the history of spontaneous supraventricular tachycardia and the existence of a sinus node dysfunction were significantly more frequent (P less than 0.05) in patients with proarrhythmic effect of ajmaline. In conclusion, the supraventricular proarrhythmic effect of intravenous ajmaline exists and is related both to the electrophysiologic characteristics of the drug and to the arrhythmia substrate. The results indicate that a supraventricular tachyarrhythmia may be induced by a class I antiarrhythmic drug.

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.

Electrophysiological demonstration of anterograde concealed conduction in accessory atrioventricular pathways capable only of retrograde conduction

Anterograde concealed conduction into the concealed accessory atrioventricular (AV) pathway has been postulated to be one of the factors preventing the reciprocating process via the accessory pathway in patients with the concealed Wolff-Parkinson-White(WPW) syndrome but its presence has not been documented. To demonstrate the occurrence of anterograde concealment, 12 patients with the concealed WPW syndrome were selected for study. A pacing protocol was designed in which the retrograde conduction of the ventricular extrastimulus over the accessory pathway was assessed during ventricular pacing alone (conventional method) and during the AV simultaneous pacing (simultaneous method); the results were then compared. When the high right atrium was simultaneously paced, the effective refractory period of the concealed accessory pathway shortened as compared with the conventional method in five of 12 patients (from 341.7 +/- 110.8 to 312.5 +/- 108.2 msec, n = 12), whereas, it decreased in all patients studied when the coronary sinus near the accessory pathway was simultaneously paced (from 375.7 +/- 135.0 to 287.1 +/- 116.1 msec, n = 7). These results demonstrate that the AV simultaneous pacing frequently shortens the refractoriness of the concealed accessory AV pathway and such facilitation seems to be well explained by the probable anterograde concealment in it and peeling back of the refractory barrier.

Isoprenaline as an aid to the induction of catecholamine dependent supraventricular tachycardias during programmed stimulation

The effects of isoprenaline on the induction of supraventricular tachycardia by programmed stimulation were studied in 67 patients to see whether they correlated with spontaneous catecholamine mediated symptoms during exercise testing and Holter monitoring. Thirty seven control patients (group 1) did not have spontaneous arrhythmias either during exercise testing or Holter monitoring. Thirty patients (group 2) had documented exercise or stress related supraventricular tachycardias--that is paroxysmal junctional tachycardia (24) or atrial arrhythmia (6). Programmed electrical stimulation was performed before and during the infusion of isoprenaline. No group 1 patient developed sustained supraventricular tachycardia during isoprenaline infusion. In 21 patients with paroxysmal junctional tachycardia and all the patients with atrial arrhythmias electrical stimulation during isoprenaline infusion produced the same tachycardia that had been seen during exercise testing and Holter monitoring. Changes in electrophysiological variables and the concentrations of serum potassium were not associated with the induction of supraventricular tachycardia by isoprenaline. Infusion of isoprenaline safely facilitated the induction of supraventricular tachycardia by programmed stimulation in patients who had spontaneously occurring catecholamine mediated symptoms.

Permanent form of junctional reciprocating tachycardia involving an atrio-hisian accessory pathway: electrophysiologic and histologic correlations

We present clinical, electrophysiologic and morphologic correlations of a patient with a permanent form of junctional reciprocating tachycardia, who died from a lung tumor. At electrophysiologic study, the tachycardia circuit was suspected to involve an atrio-Hisian accessory pathway antegradely and the AV node retrogradely; a ventriculo-atrial accessory pathway was excluded. Pathologic examination revealed a right-sided atrio-Hisian accessory pathway and an area of abnormal dispersion in the distal His bundle fibers. This case is consistently different from another previously reported case in which a concealed, serpiginous, septal atrioventricular accessory pathway was demonstrated by anatomic examination. Thus, different substrates seem to be responsible for the permanent form of junctional reciprocating tachycardia.

The long R-P' tachycardias

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

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.

Preexcitation syndromes. Mechanisms and management

Ventricular preexcitation occurs when, in relation to atrial events, some or all of the ventricular muscle is activated earlier by the atrial impulse than would be expected if conduction of the impulse activated the ventricles by way of the normal atrioventricular conduction system. The purpose of this article is to review the pathophysiology of the variants of preexcitation and to discuss the therapeutic approach to patients who have tachyarrhythmias.

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.

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.

Long-term control of reciprocating paroxysmal tachycardia by ventricular pacing in a case of Wolff-Parkinson-White syndrome

A patient is described with a complex electrocardiographic pattern, including preexcitation, grade 1 atrioventricular block, reciprocal rhythm of atrial origin, and frequent attacks of reciprocating tachycardia at a rate of about 135 beats per minute. Long-term control of these attacks was obtained by synchronous ventricular pacing at 80 beats a minute, which was below the rate during the attacks of tachycardia and above the spontaneous heart rate between the attacks.

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.

Electrophysiological assessment of amiodarone in treatment of resistant supraventricular arrhythmias

Oral amiodarone has been used to treat 21 patients with various supraventricular arrhythmias; 13 had Wolff-Parkinson-White syndrome, which was complicated by atrial fibrillation and re-entry atrioventricular tachycardia in four, and re-entry tachycardia alone in the other nine. The remaining eight patients had paroxysmal atrial fibrillation or flutter without pre-excitation. All were refractory to conventional treatment and had undergone intracardiac electrophysiological study. Fifteen have been controlled with amiodarone, this treatment proving most effective in atrial fibrillation or flutter with or without pre-excitation. Amiodarone was successful in only four of the nine patients with re-entry atrioventricular tachycardia. In two patients who responded well the drug had to be discontinued because of side effects.

Concealed retrograde bypass tracts and enhanced atrioventricular nodal conduction. An unusual subset of patients with refractory paroxysmal supraventricular tachycardia

The clinical and electrophysiologic features of eight patients with unusually rapid, medically refractory paroxysmal supraventricular tachycardia are described. Exercise induction of tachycardia and functional bundle branch block patterns during tachycardia were common. Tachycardia resulted from anterograde enhanced atrioventricular nodal conduction combined with retrograde conduction by a concealed left atrial-left ventricular accessory pathway producing rates ranging from 200 to 300 beats/min. Management and late follow-up study were characterized by generally unsuccessful electrophysiologic-pharmacologic testing and inconsistent rhythm control with continued drug therapy. Three patients underwent successful surgical interruption of the concealed accessory pathway, with elimination of recurrent tachycardias. These patients represent a unique subgroup with an identifiable electrophysiologic basis for unusually rapid tachycardias, potentially benefiting from invasive study and aggressive therapy.

Suppression of long-standing incessant ventricular tachycardia by amiodarone

A 25 year old man had experienced virtually incessant ventricular tachycardia since the age of 16 years, and complained of increasing lethargy and shortness of breath over the past 5 years. Despite medical therapy with numerous conventional antiarrhythmic agents, no single drug or combination of drugs had successfully controlled the tachycardia. Isotope and contrast angiography revealed an enlarged left ventricle with poor function. Electrophysiological studies demonstrate earliest endocardial activation at the left ventricular apex. No electrical procedure terminated tachycardia. Following institution of amiodarone, continuous ECG monitoring revealed periods of sinus rhythm alternating with periods of ventricular bigeminy. Repeat isotope angiography indicated a considerable improvement in L.V. function. There was a corresponding reduction in heart size on the chest radiograph. Clinical improvement was evidenced by disappearance of lethargy and shortness of breath. This report demonstrates that amiodarone, a new antiarrhythmic agent, may suppress long standing incessant ventricular tachycardia resistant to other antiarrhythmic agents. The marked reduction in heart size on amiodarone may suggest that the associated cardiomegaly is secondary to tachycardia.

Atrial reentry in chronic repetitive supraventricular tachycardia

Atrial reentrance as a mechanism of the tachycardia was demonstrated in a 28-year-old patient suffering from chronic repetitive supraventricular tachycardia. Criteria for diagnosis included the following: (1) Repetitive supraventricular tachycardia was induced and terminated by properly timed atrial extrastimuli. (2) Return cycles of all atrial extrastimuli not abolishing the tachycardia were fully compensatory. (3) A-H prolongation was not a prerequisite to induce the tachycardia. (4) The contours of P and A waves during tachycardia differed from those in sinus rhythm, but atrial activation remained antegrade. (5) A concealed anomalous pathway could not be proved.

Atrioventricular reciprocal rhythm and chronic reciprocating tachycardia in a newborn infant with concealed Wolff-Parkinson-White syndrome

A case of atrioventricular reciprocal rhythm and chronic reciprocating tachycardia in a newborn infant is presented. Electrophysiological studies suggest that these rhythm disturbances are related to the presence of a right-sided atrioventricular accessory pathway capable only of retrograde conduction (concealed Wolff-Parkinson-White syndrome). The technique of recording the sequence of atrial activation during the tachycardia is described and its clinical importance emphasised.

Mechanisms of atrioventricular junctional tachycardia. Role of reentry and concealed accessory bypass tracts

Electrophysiologic investigations with programmed stimulation of the human heart have clearly established the participation of the atrioventricular (A-V) junction in three different types of junctional reciprocating tachycardia: (1) paroxysmal supraventricular tachycardia in the Wolff-Parkinson-White syndrome: (2) the vast proportion of "paroxysmal atrial tachycardia" without evidence of preexcitation during sinus rhythm with antegrade conduction; and (3) the permanent or almost permanent (chronic relapsing) form of supraventricular tachycardia with its characteristic rate-dependent initiating mechanism. The obvious presence of the Wolff-Parkinson-White syndrome during sinus rhythm does not necessarily imply that the accessory pathway will be utilized during supraventricular tachycardia. Conversely, in the absence of preexcitation, the mechanism of A-V junctional reciprocating tachycardia has been traditionally attributed to pure intranodal dissociation, often without definite direct proof. Concealed accessory pathways (with unidirectional block) may be more frequent than realized and should be carefully searched for. Proof that supraventricular tachycardia utilizes an accessory pathway for retrograde conduction to the atrium often requires meticulous electrophysiologic studies- Conslucions based on the absence of various findings may be misleading. Emphasis must be placed on positive viagnostic features. One or more of the following observations may prove or disprove participation of a Kent bundle during supraventricular tachycardia: (1) induction of A-V block during tachycardia: (2) influence of electrically induced ventricular premature beats upon tachycardia; (3) patterns of retrograde atrial activation during tachycardia; or (4) influence of functional bundle branch block on the rate of the tachycardia. Analysis of events at the onset of rather than during the tachycardia is probably less important but may also provide suggestive clues about the mechanism of reentry. Observation of the following variables may be helpful: (1) behavior of antegrade conduction at the onset of tachycardia; (2) relation of atrial and ventricular activation at the onset of tachycardia; (3) presence of retrograde ventriculoatrial (V-A) conduction; (4) prolongation of the H-V interval at the onset of tachycardia; and (5) atrial stimulation at various sites. Precise understanding of the pathophysiology of supraventricular tachycardia is important because specific therapy (pharmacologic, pacemaker or surgical) may ultimately depend on accurate knowledge of the underlying mechanisms.