Atrial pacing and atrioventricular conduction in anomalous atrioventricular excitation (Wolff-Parkinson-White syndrome)

The electrophysiologic effects of intravenous propranolol in the Wolff-Parkinson-White syndrome

Fourteen patients with the Wolff-Parkinson-White (WPW) syndrome were studied by means of intracardiac stimulation techniques, before and after the intravenous administration of propranolol, 0.1 mg./Kg. There were no significant change, or only a slight increase, in the effective refractory periods of all parts of the re-entry tachycardia circuit studied, in either anterograde or retrograde directions. Re-entry tachycardia was initiated in nine patients in the control state, and in 10 patients after propranolol. The rate of re-entry atrioventricular node-accessory pathway tachycardia was decreased, but by only 10 per cent. The duration and outer limit of the tachycardia zone of atrial extrastimuli were not significantly decreased. Propranolol, by rapid intravenous infusion administration, is unlikely to be effective primary therapy for PSVT in the WPW syndrome.

His bundle recordings in a case of complete atrioventricular block combined with pre-excitation syndrome

In a patient with complete A-V block suffering from attacks of dizziness an intermittent A-V conduction with a short P-R interval and a delta wave of the conducted ventricular complex were observed. After accelerating the sinus rate by atropine and by exercise, one-to-one conduction was established with QRS complexes of WPW type A configuration. His bundle recordings revealed a complete block within the normal conduction system at the level of the A-V node. A slow junctional rhythm with a normal H-V interval was activating the ventricle. During atrial pacing a one-to-one conduction through an accessory pathway could be documented at cycle lengths between 800 and 380 msec. sandwiched in between zones of complete block at smaller or longer cycle lengths. During ventricular stimulation no retrograde V-A conduction could be observed. The findings support the thesis of at least two functionally different A-V pathways in patients with pre-excitation syndrome.

The Wolff-Parkinson-White syndrome: pharmacologic effects of procaine amide

The effect of procaine amide, 10 mg. per kilogram via intravenous infusion, was studied in 13 patients with the WPW syndrome. The delta wave was eliminated by procaine amide in 10 and modified in three patients. This effect lasted between 30 minutes and 8 1/2 hours and was unrelated to the total dose administered. Anterograde A-V conduction was assessed by atrial pacing with increasing rates. More rapid atrial pacing rates with 1:1 A-V conduction were observed in patients who maintained rather than lost their delta wave during pacing. Ventriculoatrial conduction was assessed with ventricular pacing at increasing rates; ventricular conduction time was fixed regardless on the pacing rate. Procaine amide significantly prolonged V-A conduction time in six and blocked V-A conduction in one patient. In addition, A-V and V-A refractory periods were measured by the extrastimulus technique. Two types of responses were observed: (1) Type I or (2) line of identity. A-V nodal refractoriness was observed to be within the normal range. Procaine amide converted anterograde line of identity responses to Type I responses in all patients who had their delta waves eliminated. In this patient group, bypass refractoriness was shorter than A-V nodal refractoriness. Procaine amide was not observed to alter significantly normal A-V conduction as assessed by atrial pacing or A-V refractory period measurements. Furthermore, a significant disparity between the effects of procaine amide on anterograde and retrograde bypass refractoriness was observed. Tachycardias could be induced in nine of the 13 patients with a mean rate of 167.2 +/- 7.9 beats per minute; delta waves were abent during all episodes of tachycardia. Procaine amide prevented tachycardia induction in six of the none patients. Procaine amide therefore demonstrates electrophysiologic effects which would be beneficial for prevention or treatment of reciprocating tachycardias in the WPW syndrome. Moreover, procaine amide would be an ideal agent for the prevention of rapid ventricular rates in patients with the WPW syndrome and atrial fibrillation.

Pacing studies after cardiac surgery

The diagnostical use of pacemaker after cardiac surgery is presented. Temporary pacemaker electrodes have been inserted during surgery into the wall of atrial and ventricular myocardium. With the aid of these electrodes, an analysator wire of 6 volts, and a Medtronic 5840 type pacemaker electrophysiological studies have been performed. The diastolic and supernormal stimulation threshold, the duration of atrial and ventricular relative refractory period were measured, the clinical significance of latency was analysed. It has been found that decrease of stimulation threshold, shortening of relative refractory period, and appearance of latency phenomenon promote arrhythmias. By investigating the conduction capacity of atrioventricular conduction system, latent conduction disturbances could be revealed, and a significant difference could be demonstrated between the atrioventricular conduction of WPW syndrome and that of other kinds of PR interval shortening. In addition the optimal heart rate requirement (optimal pacing rate) following heart surgery was defined. These parameters present more precise information on the electrophysiological condition of the heart than does the generally used ECG monitoring. When these parameters are repeatedly determined, the significance of patient's arrhythmias can be evaluated more safely and accurately; in a number of cases, even in the absence of any rhythm disturbances, impending arrhythmias can be predicted. "Pacemaker monitoring" of the postoperative heart patients, therefore, affords greater possibility for preventing the development of major cardiac arrhythmias.

Wolff-Parkinson-White syndrome type B with His depolarization occurring after the QRS. Further evidence that WPW-QRS is a fusion beat

His bundle electrograms were recorded in a patient with Wolff-Parkinson-White syndrome (type B) during atrial pacing studies and during the induction of premature atrial depolarization at varying coupling intervals. Early ventricular depolarization (preexcitation) occurred simultaneously with the His depolarization, suggesting that conduction occurred via both the Kent and the normal A-V nodal-His-Purkinje pathway during sinus rhythm. Atrial pacing at increasing rates showed progressive advance of the His spike into the QRS and increasing duration of the delta wave until the appearance of broad bizarre QRS complexes with prolonged P-J intervals, suggesting major, if not total, depolarization of the ventricle by the Kent pathway. PAD's induced at coupling intervals of 360, 330, and 300 msec caused progressive delay of the His bundle depolarization, with the His spike occurring after the QRS at S(1)-H intervals of 230, 265, and 325 msec, respectively, and Q-H intervals of 123, 160 and 220 msec, respectively. These findings suggest that during sinus rhythm the QRS was a fusion beat. With early premature atrial stimulation, conduction occurred solely via the Kent pathway, with conduction via the normal A-V nodal pathway encountering increasing delay. The finding of His depolarization occurring after the QRS suggests retrograde myocardial-His block, and may explain the absence of paroxysmal supraventricular tachycardias in this patient.

Wolff-Parkinson-White Syndrome. A review

Recent developments in the field of electrophysiology and surgical therapy in selected cases of Wolff-Parkinson-White syndrome (W-P-W) support the concept of anomalous A-V pathways. Impulse transmission usually occurs simultaneously through both the normal and anomalous pathways resulting in a fusion QRS complex. Atrial tachycardia is usually due to reentry through the normal and anomalous A-V pathways. However, reentry may occur independently in the A-V node alone exclusive of the anomalous pathway. Anomalous connections, despite varying anatomic locations, may result in similar electrocardiographic manifestations characteristic of W-P-W. His bundle recordings together with electrophysiologic studies may be clinically useful (1) to differentiate various types of anomalous connections, (2) for possible determination of the reentry circuit, (3) to predict the maximum ventricular rate possible during supraventricular tachycardia by evaluating the refractory period of the A-V pathways, or (4) to compare the efficacy of different drugs in a given patient. Surgical interruption of the anomalous pathway in selected cases with W-P-W (type B) is feasible but is most commonly not necessary. The indications for medical and surgical management of symptomatic cases with W-P-W are reviewed.

Refractory supraventricular tachycardias

This essay is designed to review some of the basic and more recent contributions to our understanding of supraventricular tachyarrhythmias, their mechanisms, pertinent points in diagnosis, and treatment. Supraventricular tachycardia is discussed under the concept of reentrant mechanisms versus accelerated ectopic pacemakers. Atrial fibrillation and flutter, multifocal atrial tachycardia, supraventricular tachyarrhythmias associated with brady-tachy syndrome, and supra-ventricular tachycardias in ventricular preexcitation are likewise discussed. An outline of the different forms of therapy for refractory supraventricular tachyarrhythmias is provided.

His bundle recording and electrical stimulation of atria in patients with Wolff-Parkinson-White syndrome type A

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His bundle electrograms in two cases of Wolff-Parkinson-White (pre-excitation) syndrome

The catheter technic for recording the electrical activity of the specialized conducting system in the human heart showed in two patients studied that ventricular pre-excitation was apparently due to a bypass of the His bundle. Intermediate forms of WPW complexes appeared to be combination beats resulting from the activation of the ventricles through impulses traversing both the His bundle and accessory communications. Preferential iatrogenic activation of an intra-atrial (and perhaps even of an atrioventricular) tract appeared to occur in one of the patients. The patients with the WPW (pre-excitation) syndrome and long histories of paroxysmal arrhythmias were successfully treated with a combination of oral propranolol and implanted (transvenous) demand pacemaker.

Long-term control of intractable supraventricular tachycardia by ventricular pacing

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Study of atrioventricular conduction in man using electrode catheter recordings of His bundle activity

The technique of recording electrograms of the His bundle, using a tripolar electrode catheter positioned across the tricuspid valve, was applied in a physiological study of atrioventricular conduction in man. Increasing the heart rate to 160 beats/min by right atrial pacing produced progressive prolongation of the P-H interval while the H-Q interval remained constant. At any given paced heart rate, digitalis caused a prolongation of the P-H interval. Isoproterenol and atropine markedly shortened the P-H interval at any given heart rate. Neither drug had any significant effect on the H-Q interval. Coupled premature atrial stimulation produced prolongation of the P-H interval alone when the resultant ventricular depolarization was normal, and prolongation of both the P-H and H-Q intervals when the resultant ventricular depolarization was aberrant.

Successful surgical interruption of the bundle of Kent in a patient with Wolff-Parkinson-White syndrome

Recurrent supraventricular tachycardia is a frequent complication in patients with the Wolff-Parkinson-White (WPW) syndrome. Our patient was unusual in that the arrhythmia was the predominant rhythm, and it was felt that the sustained tachycardia was responsible for signs and symptoms of congestive heart failure. The arrhythmia could not be controlled adequately with digitalis, quinidine, diphenylhydantoin, or propranolol. Atrial or ventricular pacing also failed to prevent recurrent episodes of tachycardia.

Physiological and pharmacological studies suggested that an anomalous pathway was responsible for the WPW abnormality and participated in a re-entrant circuit which sustained the episodes of tachycardia. Isopotential body surface mapping suggested anomalous ventricular excitation at the lateral aspect of the right atrioventricular groove. Epicardial mapping at the time of surgery was used to localize the earliest area of anomalous ventricular activation, and surgical transection of the atrioventricular junction at that point abolished the electrocardiographic features of WPW and the recurrent tachycardia. Five months after surgery neither the ECG features of WPW nor the tachycardia has recurred. The signs and symptoms of congestive heart failure have subsided, and the patient has returned to work.

Paradoxical use of a demand pacemaker in treatment of supraventricular tachycardia due to the Wolff-Parkinson-White syndrome. Observation on termination of reciprocal rhythm

This paper describes a new technique for terminating attacks of supraventricular tachycardia in a patient with Wolff-Parkinson-White syndrome by using a demand pacemaker. The circuitry of this demand pacemaker generator is designed so that a magnet held near the generator converts the unit from demand to fixed mode at a pre-set discharge rate of 72/min. During an attack of tachycardia, a magnet held near the generator pocket activates a fixed rate discharge and produces competitive pacing. Retrograde atrial depolarization occurs with resultant reversion to sinus rhythm.

Atrial fibrillation produced by atrial stimulation

Twenty-six episodes of atrial fibrillation and flutter-fibrillation, each lasting less than 23 sec, were recorded in three normal subjects during atrial pacing studies. The cause of these atrial arrhythmias was determined to be the result of stimulation within the atrial vulnerable period.