Post-myocardial infarction incessant supraventricular tachycardia due to concealed accessory pathway

Accessory atrioventricular node with properties of a typical accessory pathway: anatomic-electrophysiologic correlation

We report an accessory AV node producing ventricular preexcitation and comprising the retrograde limb of AV reentrant tachycardia (AVRT). A 66-year-old man presented with an anteroseptal myocardial infarction and thereafter developed recurrent, drug-refractory AVRT requiring multiple cardioversions. Electrophysiologic findings were typical for a concealed anteroseptal accessory pathway 0.5 cm anterior to the His bundle. The patient died of intractable heart failure after endocardial resection for a left ventricular aneurysm and coronary bypass grafting. Pathologic examination revealed a para-Hisian accessory AV node connecting the right atrium to ventricular myocardium immediately anterior to the His bundle at a depth of 4 mm from the endocardium. No typical AV accessory pathway was found. This is the first report of an accessory AV node that participated in AVRT. It was deeper than typical radiofrequency catheter ablation lesions.

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.

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.

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.

Wide QRS tachycardia: multiple mechanisms in a patient after myocardial infarction

A 34-year-old man was hospitalized for extensive antero-apical myocardial infarction. Eight weeks after discharge from the hospital, he had intermittent rapid palpitations. During several episodes, a rapid, regular, wide-QRS-complex tachycardia with left bundle branch (LBB) morphology was recorded. All antiarrhythmic agents administered to the patient were unsuccessful in alleviating his symptoms, which were thought to be due to supraventricular tachycardia (SVT) with aberration. An electrophysiologic study was performed and revealed three morphologically distinct types of wide complex tachyarrhythmias: 1) Tachycardia 1 was determined to be A-V re-entry with antegrade conduction utilizing the normal A-V conducting system and retrograde conduction over a concealed accessory pathway located in the left A-V groove; 2) tachycardia 2 was identified as ventricular tachycardia (VT); and 3) tachycardia 3 was considered to be a second morphologic type of ventricular tachycardia as the morphology was identical to some of the episodes documented clinically. The patient was treated with oral amiodarone which was unsuccessful until combined with quinidine; this regimen has suppressed recurrence of VT during a four-month period of follow-up. The occurrence of wide-QRS-complex tachycardia in this patient immediately suggested the diagnosis of VT, but our other findings were unexpected. This case illustrates the need for considering all possible mechanisms when seeking to manage tachyarrhythmias, even if the diagnosis appears obvious.