Surgical correction of anomalous left ventricular pre-excitation: Wolff-Parkinson-White (type A)

Effect of amiodarone in the Wolff-Parkinson-White syndrome. A clinical and electrophysiological study

Six patients with Wolff-Parkinson-White (WPW) syndrome were given long-term treatment with amiodarone. Symptomatic relief was obtained in all. Tolerance to the drug was good. Reversible corneal changes appeared after some weeks' treatment in five patients. No thyroid side-effects were noticed. Prior to treatment, dual atrioventricular (AV) conduction was demonstrated on His bundle electrograms in all six patients. Recordings were made at varied heart rates, using atrial and ventricular pacing. Reciprocating tachycardia was readily provoked by properly timed extra stimuli in all patients. When amiodarone treatment had become clinically effective, a second comparative study was made in four patients after 26--85 days' treatment. Amiodarone reduced heart rate and second degree AV block appeared at a lower atrial pacing rate. It increased the refractory periods of right atrium, AV node, and the accessory pathway in proportion to the duration of treatment. Induction of tachycardia was effectively prevented by the drug. It appears that amiodarone in chronic treatment has a predictable and unique depressant action on cardiac conduction, supporting the opinion that this compound, despite side-effects, has an important role to play in the treatment of refractory arrhythmias in patients with the WPW syndrome.

An overview of contemporary approaches to antiarrhythmic therapy

This review discusses the evolution in the approach to the therapy of cardiac arrhythmias that has occurred during the past 2 decades. The major changes have been driven by advances in understanding arrhythmia mechanisms, in bioengineering, and in clinical trials. It seems likely that progress in understanding the cellular and molecular basis of arrhythmias and their response to drug therapy may allow further identification of patient subsets in which specific therapies are indicated or contraindicated.

Techniques of intraoperative electrophysiologic mapping

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

Enhanced atrioventricular nodal conduction in a patient with dual extranodal pathways

A patient was admitted to the hospital with wide complex tachycardia and a history of recurrent palpitations. Electrophysiologic studies showed evidence of dual atrioventricular (AV) accessory pathways. One proved to be an anteroseptal (possible right anterior) pathway probably capable of only unidirectional conduction. The other pathway was in the posterior septum and conducted only in the retrograde direction. The tachycardia circuit involved anterograde conduction via either the AV node-His axis or the anteroseptal pathway and retroconduction over the posteroseptal accessory pathway. In addition, enhanced AV nodal conduction coupled with two accessory AV nodal pathways has rarely been described in English medical literature. Previous reports have carefully described anatomic, electrocardiographic, and electrophysiologic evidence of more than one accessory pathway in patients with the Wolff-Parkinson-White syndrome. The introduction of surgical techniques for ablation of an accessory pathway demands precision in the electrophysiologic evaluation of patients with ventricular preexcitation. Reported herein is a patient with the unique finding of two extranodal accessory pathways and enhanced atrioventricular (AV) nodal conduction (or AV nodal bypass).

Body surface distribution of QRS deflection areas in experimental ventricular preexcitation

The utility of QRS isoarea maps for recognition of preexcitation sites was evaluated in chronic experiments in dogs. Pacing electrodes were surgically implanted on the atrium and ventricular sites near the AV ring. Electrocardiograms from 192 torso sites were simultaneously recorded during pacing of the atrium together with each of the ventricular sites. Time phase of atrial and ventricular stimuli was varied to yield both preexcitation with clear delta waves and more subtle forms of preexcitation with sites activated earlier than normal but after onset of the normal QRS. QRS area maps were determined by integrating QRS amplitudes at 1 msec intervals over the QRS duration. Results showed a systematic relation between the body surface location of the minimum in the QRS area maps and the preexcitation site. In additon there was a linear relation between the magnitude of maximum and minima in the QRS isoarea maps over different degrees of preexcitation, and the slope of curves showing this relation differed for different sites of preexcitation. Findings suggest that a single display of the QRS isoarea map may permit identification and localization of preexcitation including subtle forms occurring after the onset of the QRS.

Elimination of the delta wave in the Wolff-Parkinson-White syndrome. A misleading indicator of therapeutic effectiveness

A 66-year-old white woman with a greater than 20-year history of electrocardiographic evidence of the Wolff-Parkinson-White syndrome, including documented recurrent supraventricular tachycardias, was studied. Despite the disappearance of the delta wave after initiation of therapy with digoxin and quinidine sulfate, the patient continued to have frequent episodes of supraventricular tachycardia. At a time when the serum levels of digoxin and quinidine were in the therapeutic range, extensive electrophysiologic studies were performed. Supraventricular tachycardia at a rate of 160 beats per minute was initiated by induced atrial premature depolarizations. The circuit of tachycardia involved anterograde conduction through the pathway of the atrioventricular node and His bundle and retrograde conduction through the bypass tract. We concluded that elimination of the delta wave and other electrocardiographic characteristics of the Wolff-Parkinson-White syndrome cannot be relied upon to indicate successful pharmacologic prophylaxis for induction of tachyarrhythmia associated with this syndrome.

The preexcitation syndromes

Current methodology permits one to define the functional basis of the preexcitation syndromes with reasonable certainty and to develop a rationale for instituting trials of medical therapy. Future studies will hopefully result in a more exact definition of the anatomic substrates of preexcitation and their relationship to the pathophysiology of the associated syndromes. New antiarrhythmic agents must also be developed to add to the relatively small number of available drugs. Important questions still remain. Should asymptomatic patients with preexcitation be studied? If found to demonstrate potential for malignant arrhythmias, should they be treated prophylactically? The answers to these questions will require study and long-term follow-up of nonhospital referral patients. Surgery offers a feasible therapeutic alternative for patients with life-threatening or disabling arrhythmias but demands a team equipped to perform precise preoperative and intraoperative mapping studies to define the type and location of underlying anatomic substrates.

Wolff-Parkinson-White syndrome with 1:2 atrioventricular conduction

The QRS complex of the Wolff-Parkinson-White syndrome is thought to represent a fusion beat resulting from conduction over the normal pathway and an anomalous pathway. This report demonstrates utilization of both of these pathways resulting in two ventricular responses from a single supraventricular impulse. The presence of "1:2" atrioventricular conduction in this case firmly supports the fusion beat theory of the Wolff-Parkinson-White syndrome.

Right atrial versus left atrial echo zones: a proposed new criterion for determining the atrial site of retrograde preexcitation

In a patient whose electrocardiogram (ECG) initially (1966) showed a Type A Wolff-Parkinson-White pattern, recurrent supraventricular tachycardia (SVT) developed but never subsequently showed antegrade bypass conduction. Intracardiac pacing studies (1975) revealed that premature high right atrial (induced 250-450 msec after atrial depolarization) or coronary sinus depolarization (250-550 msec) resulted in SVT. Late coronary sinus depolarization resulted in SVT without A-H prolongation. During SVT, P wave morphology changed and the coronary sinus atrial electrogram preceded that from the low right atrium; retrograde ventriculoatrial conduction time was 240 msec. Neither pacing the high right atrium or coronary sinus up to rates of 200 beats/min nor progressive atrial premature depolarizations from the high right atrium or coronary sinus resulted in antegrade bypass conduction. Failure of antegrade bypass conduction does not preclude SVT due to retrograde preexcitation and must be distinguished from atrioventricular (A-V) nodal reentry. Atrial effective refractory period (200 msec) was shorter than the minimal time required for an atrial impulse to return to the atrium (380 msec), suggesting concealed antegrade bypass conduction. Stimulation of the atrium linked to the A-V bypass results in earlier bypass activation and recovery and explains the differing high right atrial vs coronary sinus echo zones.

Mahaim and James fibers as a basis for a unique variety of ventricular preexcitation

This report concerns pathologic findings in a 54 year old woman with intermittent preexcitation who died of carcinoma of the breast. Electrocardiograms revealed predominantly normal sinus rhythm with a normal P-R interval and narrow QRS complex. Episodes of sinus rhythm, short P-R interval and QRS widening (with delta wave) were also recorded. During preexcitation QS complexes were noted in leads II, III, aVF, V1 and V4 to V6. Delta waves were negative in leads II, III, aVF and V1 isoelectric in leads V4 to V6 and positive only in leads I, aVL, V2 and V3. This case thus defies classification into any known variety of preexcitation. Complete serial sections, cut through the entire conduction system and both atrioventricular (A-V) rims, totaled 18,600 sections. These revealed no bundle of Kent. Instead, Mahaim fibers histologically identified as His bundle tissue gave off from the A-V bundle to both the right and the left sides of the septum associated with the normal fibers of James. This case reveals that (1) fibers of James can bypass the A-V node, (2) fibers of Mahaim can conduct, and (3) there are types of preexcitation in addition to types A and B.

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.

Body surface isopotential mapping in Wolff-Parkinson-White syndrome: noninvasive method to determine the localization of the accessory atrioventricular pathway

The body surface isopotential maps of 22 patients with WPM syndrome were obtained from the 85 unipolar lead ECG's using the on-line minicomputer system newly devised by the author's group. The map patterns were classified into three types-I, II, and III (Type I, eight; Type II, seven; Type III, three; and unclassified, four cases). In Type I, the back surface displayed the negative potential throughout the entire ventricular activation, and at the terminal stage the lower precordial area displayed the positive potential and the upper precordial area, the negative one. Type II was characterized by two longitudinal lines, one staying at its place on the back and the other moving right to left on the precordial area following the process of ventricular activation. In Type III, the right precordial area displayed negative potential in the early stage, and in the terminal stage the upper part of the right side of chest surface displayed positive potential and the lower part, negative potential. It was surmised from these patterns that the pre-excited area was located at the posterior region of the ventricles in Type I, at the right ventricle in Type II, and the right ventricular base near the posterior margin of the ventricular septum in Type III. Type A patients in the conventional ECG classification fell under Type I; Type C patients, under Type III; Type B patients under either Type I or Type II.

Problems concerning assessment of anatomical site of accessory pathway in Wolff-Parkinson-White syndrome

Twp patients with type B WPW syndrome and reciprocal tachycardias have been studied using intracardiac electrograms and programmed electrical stimulation of the heart. One patient, who had a right-sided accessory pathway giving the surface electrocardiographic appearances of type B WPW syndrome, was shown to have an additional left-sided accessory pathway as occurs in type A WPW syndrome. This concealed left-sided atrioventricular connexion formed the retrograde pathway during reciprocal tachycardia. In the second patient the appearances of type B WPW syndrome were shown to be caused by an accessory pathway between the atrial septum and the right side of the interventricular septum rather than an accessory pathway in the right atrioventricular groove. The significance of these findings when considering surgical interruption of an accessory atrioventricular conduction pathway is discussed.