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

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.

Pre-excitation due to accessory sinoventricular connexions associated with coronary sinus aneurysms. A report of two cases

Ventricular pre-excitation occurred in two cases in which the accessory pathways between the atria and the ventricles were histologically identified as being associated with aneurysmal malformations of the coronary sinus. In one case the connexions were in the posterior wall of the coronary sinus aneurysm and were not related to the atrioventricular annulus; in the other, a connexion was situated in the anterior wall of the aneurysm in close apposition to the annulus and superficially resembled a Kent fibre. These connexions were considered to be of sinus venosus origin and to represent a modification of the muscular sheath that normally surrounds the coronary sinus but does not continue along the coronary veins. One of the posterior wall connecting bundles was composed of abnormally large Purkinje-like fibres; this may have played some role in the manifestation of the pre-excitation by reducing any mismatch impedance.

Coexistent posteroseptal and right-sided atrioventricular bypass tracts

Twelve patients with a posteroseptal accessory pathway underwent complete electrophysiologic studies, and four were found to have a second atrioventricular (AV) bypass tract that was right anterior, right anteromedial or right anterolateral in location. In two of these four patients, the presence of the right-sided AV bypass tract was confirmed by intraoperative epicardial mapping or after catheter-induced abolition of retrograde conduction through the posteroseptal bypass tract. In three of the four patients with a dual AV bypass tract, the delta wave pattern was clearly atypical of the pattern seen with an isolated posteroseptal accessory pathway. Instead of a transition from an isoelectric or slightly positive delta wave in lead V1 to markedly positive delta waves in leads V2 to V6, the delta waves were negative or only slightly positive in leads V2 to V5. However, in a fourth patient with dual AV bypass tracts, the only atypical electrocardiographic finding was an intermittently positive delta wave in lead II; at times this patient's electrocardiogram was consistent with an isolated posteroseptal bypass tract, with negative delta waves in the inferior leads. There appears to be an association between posteroseptal and right-sided accessory pathways. In patients with a posteroseptal accessory pathway who are candidates for catheter or surgical bypass tract ablation, a complete mapping study of the tricuspid anulus is mandatory, even when the electrocardiogram is typical of an isolated posteroseptal bypass tract.

Quintuple pathways participating in three distinct types of atrioventricular reciprocating tachycardia in a patient with Wolff-Parkinson-White syndrome

Electrophysiologic studies were performed in a patient with recurrent supraventricular tachyarrhythmias. Sinus and paced atrial beats had QRS complexes characteristic of atrioventricular (A-V) conduction through a manifest left lateral accessory pathway (Wolff-Parkinson-White syndrome, type A). Three distinct types of A-V reciprocating tachycardia and three different modes of retrograde atrial activation were demonstrated. Type 1 tachycardia involved the slow A-V nodal pathway and a second (left lateral or left paraseptal) accessory A-V pathway capable of retrograde conduction only. Type 2 tachycardia was of the slow-fast A-V nodal pathway type. Type 3 tachycardia involved in heretofore undescribed circuit in that retrograde conduction occurred through an accessory A-V pathway with long retrograde conduction times and anterograde conduction through both the manifest left lateral accessory A-V pathway and fast A-V nodal pathway. Premature ventricular beats delivered late in the cycle of this tachycardia advanced (but did not change) the retrograde atrial activity without affecting the timing of the corresponding anterograde H deflection. In summary, this patient had five (three accessory and two intranodal) pathways participating in three different types of A-V reciprocating tachycardia; the recurrence of these were prevented with oral amiodarone therapy.

Interruption of multiple accessory conduction pathways in the Wolff-Parkinson-White syndrome

Of 35 patients with Wolff-Parkinson-White syndrome operated on, 5 were seen with two accesory conduction pathways each; all of these were successfully interrupted. In one patient, one accessory conduction pathway each was located in the right and left side of the heart; in the other 4, both pathways were confined to the right side. In 2 patients with unilateral (right side) multiple accessory conduction pathways, Ebstein's anomaly was also present. In 1 patient with Ebstein's anomaly, the second unilateral accessory conduction pathway was discovered intraoperatively and was successfully interrupted. The remaining 4 patients required a second operation to interrupt the other pathway. A delta wave completely different from the preoperative one appeared 4 to 10 days after interruption of the first major pathway, and the second operation was performed 14 days, 42 days, four months, or five years after the first operation. All 5 patients survived, and long-term follow-up revealed no signs of morbidity.

A case of surgically corrected Wolff-Parkinson-White syndrome. Clinical and histological data

A case of type B Wolff-Parkinson-White syndrome, with intractable atrial fibrillation, underwent surgical division of a right-sided accessory atrioventricular bundle of Kent. Pre-excitation and complicating tachyarrhythmias were henceforth abolished for 6 weeks, when the patient died of infective endocarditis. Histological examination showed a divided Kent's accessory atrioventricular pathway and apparently functionless James and Mahaim fibres.

Accelerated atrioventricular conduction during acute myocardial infarction

Three cases are described in which accelerated atrioventricular conduction occurred during an acute myocardial infarction. The first patient, an 82-year-old woman, developed a WPW syndrome suggesting posterior right ventricular preexcitation, a pattern which persisted for four months until her death. An accessory bundle was found on autopsy. Fibrotic changes, associated with acute lesions (hemorrhage, polymorphonuclear infiltrates) were present in the atrioventricular node and His-Purkinje system. Two men, of 47 and 74 years, developed a short PR interval associated with supraventricular tachycardia during the course of an acute myocardial infarction. The PR interval returned to its initial value in one case and remained unchanged for three months in the other. Accessory atrioventricular connections which became functional during myocardial ischemia may explain the various electrocardiographic patterns of preexcitation.

Cardiac pacing and pacemakers II. Serial electrophysiologic-pharmacologic testing for control of recurrent tachyarrhythmias

The place of pacemakers in the treatment of tachyarrhythmias has expanded far beyond the initial role in the brady-tachy syndrome, of providing a "minimum guaranteed rate" while medications suppress the tachycardia. Techniques have been developed for prevention, termination, and duplication of a patient's spontaneous tachycardia under safe catheterization laboratory conditions. Combined with accumulating information about the normal responses to electrophysiologic stresses, these techniques have led to a new dimension in arrhythmia control. Most tachycardias previously felt to be refractory can be controlled after serial electrophysiologic-pharmacologic testing, during which sequential pharmacologic and pacer regimens are tested until a combination is found which prevents induction of tachycardias, and/or a pace mode is found which reliably terminates the tachycardia. Use of such an approach reduces hospital admissions and referral for surgery, and eliminates prolonged hospitalization for assessment of therapy in patients with infrequent but potentially lethal spontaneous tachycardias.

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.

Multiple accessory pathways in patients with the pre-excitation syndrome

We have studied 135 patients with the pre-excitation syndrome and have demonstrated evidence of multiple accessory pathways in 20 patients. Five patients had two distinct accessory atrioventricular (A-V) connections, associated with enhanced A-V node conduction in one patient. Twelve patients had a single accessory A-V connection associated with enhanced A-V conduction. In one of these there was an additional fasciculo-ventricular connection. One patient had an accessory A-V connection associated with a nodoventricular bundle. Two patients had fasciculo-ventricular connections combined with enhanced A-V conduction. The latter two patients had electrocardiograms suggestive of a complete accessory A-V connection. Patients with enhanced A-V conduction had shorter cycle lengths during reciprocating tachycardia, primarily because of a short A-H during the dysrhythmia, than those without such conduction. In addition, patients with enhanced A-V conduction demonstrated more rapid conduction from atrium to His bundle during induced atrial fibrillation and two developed life-threatening ventricular responses during atrial fibrillation. A nodo-ventricular pathway was documented to participate in reciprocating tachycardia in one patient. Surgery was undertaken in 13 patients. In 11, the intraoperative mapping studies confirmed the preoperative predictions. In two patients, the presence of a second accessory A-V connection was documented after ablation of one.

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.

Initial forces of ventricular depolarization in the Wolff-Parkinson-White Syndrome. Analysis based upon localization of the accessory pathway by epicardial mapping

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.

Contribution of cardiac pacing to our understanding of the Wolff-Parkinson-White syndrome

This review discusses the information which can be obtained by cardiac pacing in patients with the Wolff-Parkinson-White syndrome. Programmed electrical stimulation when combined with the recording of intracardiac electrograms and surface electrocardiograph leads, can be extremely useful in the following areas. 1) Determining the type of the accessory atrioventricular connexions; 2) determining the electrophysiological properties of the accessory atrioventricular pathway; 3) localizing the position of the accessory atrioventricular pathway; 4) determining the mechanisms of any tachycardia; 5) assessing effect of drugs; 6) identifying patients likely to be at high risk; and 7)evaluating postoperative conduction.