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1/25. Left posteroseptal Mahaim fiber associated with marked longitudinal dissociation.

    We report a patient who underwent radiofrequency catheter ablation of a left posteroseptal atrioventricular (AV) Mahaim fiber with a marked longitudinal dissociation. During atrial pacing, Wenckebach-type atrioventricular block over the accessory pathway was observed with progressive preexcitation and no change in polarity of the delta waves. The AV conduction curve was discontinuous, with a distinct "jump-up" in local AV conduction time of 84 ms. The earliest ventricular activation was recorded from the posteroseptal portion of the mitral annulus, and the unipolar electrogram from a distal electrode had a high, steep deflection with uniphasic QS-like activity with 62 ms of local AV conduction time. ( info)

2/25. Radiofrequency ablation of a right atriofascicular Mahaim fiber and two contralateral left free-wall accessory pathways.

    We report a rare combination of a right atriofascicular Mahaim fiber and two left-sided atrioventricular accessory pathways in a 57-year-old female presenting with an antidromic atrioventricular reciprocating tachycardia. Radiofrequency ablation was first targeted at the left lateral accessory pathway that served as the retrograde limb of the tachycardia. After elimination of the left lateral pathway, a bystander left posterolateral pathway was detected, and it too was successfully ablated. Although no tachycardia was reinducible, the Mahaim pathway was ablated because of its short effective refractory period. A discrete Mahaim potential recorded at the right atrial free-wall successfully guided the ablation. ( info)

3/25. Orthodromic tachycardia with atrioventricular dissociation: evidence for a nodoventricular (Mahaim) fiber.

    We describe a patient in whom two tachycardias with AV dissociation were inducible by ventricular extrastimulation. The first tachycardia was characterized by a narrow QRS preceded by a His deflection with an HV interval identical to that recorded in sinus rhythm (40 ms). Premature ventricular depolarization delivered when the His bundle was refractory advanced the next His deflection. These findings suggest the presence of a nodoventricular bypass tract involved in an orthodromic tachycardia. The second tachycardia was induced after propafenone infusion and exhibited a wide QRS complex with left bundle branch block morphology; each ventricular complex was consistently associated with a His deflection with a HV interval of -15 ms. The second tachycardia may be considered to represent an antidromic tachycardia through the nodoventricular tract. However, a ventricular tachycardia cannot be excluded. ( info)

4/25. Coexistent atrioventricular and nodoventricular pathways in a patient with hypertrophic cardiomyopathy.

    A 17-year-old girl with concentric hypertrophic cardiomyopathy presented with a wide complex tachycardia and underwent electrophysiological study. She was found to have an antidromic tachycardia utilizing a decremental atrioventricular fiber as the anterograde limb with retrograde conduction occurring through the septum. Ablation of a right free-wall pathway rendered tachycardia noninducible, yet ventricular preexcitation remained. After ablation there was evidence of a second nodoventricular connection. We believe this to be the first report of coexistent "Mahaim" fibers; one a decremental atrioventricular connection and the second nodoventricular. ( info)

5/25. Familial Mahaim syndrome.

    We describe the occurrence of Mahaim syndrome in a mother and her son. The occurrence of such a rare disorder in two members of a family is noteworthy, has not been reported before, and suggests the possibility of genetic transmission. A genetic transmission of supraventricular tachycardia has been described only in rare cases for the wolff-parkinson-white syndrome. No such data is available for the Mahaim syndrome. ( info)

6/25. syncope and preexcitation: a case of a Kent and fasciculoventricular Mahaim fibers.

    A case involving an 8-year-old girl with syncope and preexcitation on a surface electrocardiogram (ECG) that was suggestive of wolff-parkinson-white syndrome is presented. An intracardiac electrophysiologic study revealed a posteroseptal bidirectionally conducting Kent fiber. Radiofrequency ablation of the Kent fiber was successful, but the patient had a residual short His-ventricular (HV) interval and a new preexcitation pattern. Atrial extra stimuli and ventricular pacing revealed a fixed, preexcited QRS. Nodal block and loss of preexcitation was provoked with adenosine. The surface QRS and electrophysiologic features are consistent with a left septal fasciculoventricular Mahaim fiber. ( info)

7/25. Latent Mahaim fiber as a cause of antidromic reciprocating tachycardia: recognition and successful radiofrequency ablation.

    The term "Mahaim fiber" usually is applied to an atriofascicular fiber that inserts distally into the right bundle branch and forms the anterograde limb of a reciprocating tachycardia. One of the features that has been used to describe the physiology of Mahaim fibers is the presence of anterograde preexcitation. We describe two patients who had a clinical tachycardia consistent with a "Mahaim tachycardia" in whom there was no evidence or minimal evidence of anterograde preexcitation during sinus rhythm or atrial pacing. In both patients, the tachycardia was rendered noninducible by radiofrequency ablation at the site of Mahaim potentials at the tricuspid annulus, and a long-term cure was achieved. This is the first description of a "latent Mahaim fiber" that does not cause preexcitation but which can support antidromic reciprocating tachycardia. ( info)

8/25. Appraisal of "Mahaim" automatic tachycardia.

    A series of four patients with right-sided accessory pathways with long conducting times and decremental properties is reported. All patients underwent radiofrequency catheter ablation, and target areas were guided by a discrete "Mahaim" potential recorded at the lateral aspect of the tricuspid valve. A slow automatic and irregular rhythm with a QRS morphology similar to that of a fully preexcited QRS complex occurred during radiofrequency current delivery. The occurrence of so-called "Mahaim" automatic tachycardia heralded successful elimination of the accessory pathway in a manner similar to that of junctional automatic rhythm during slow pathway ablation in patients with AV nodal reentrant tachycardia. The observation of an automatic rhythm brought about during radiofrequency current ablation of a Mahaim-like accessory pathway is electrophysiologic evidence of the accessory AV nodal behavior of this structure. ( info)

9/25. Fasciculoventricular pathways: clinical and electrophysiologic characteristics of a variant of preexcitation.

    Fasciculoventricular Fibers. INTRODUCTION: Fasciculoventricular tracts are considered a rare form of ventricular preexcitation. Few fasciculoventricular pathways have been reported, and none have been linked to a reentrant tachycardia. methods AND RESULTS: Four patients with fasciculoventricular bypass tracts underwent electrophysiologic evaluation. Two patients had a single fasciculoventricular pathway, one that inserted anteroseptally and the other in the left ventricle. Two patients also had an AV bypass tract, with anterograde conduction over the fasciculoventricular pathway during orthodromic AV reentrant tachycardia. After ablation of the AV pathways, the ECG during sinus rhythm and the electrophysiologic study showed ventricular preexcitation due to a fasciculoventricular bypass tract inserting into the right ventricle. adenosine triphosphate was helpful in the diagnostic process. CONCLUSION: Electrophysiologists should be able to make the differential diagnosis between a fasciculoventricular bypass tract and an anteroseptal accessory pathway to preclude potential harm to the AV conduction system if a fasciculoventricular pathway is targeted for catheter ablation. ( info)

10/25. Preexcitation masking underlying aberrant conduction: an atriofascicular accessory pathway functioning as an ectopic right bundle branch.

    Preexcitation and aberrant conduction both cause a broad QRS complex. An unusual case of an atriofascicular accessory pathway effectively functioning as an ectopic right bundle branch and responsible for both physiologically normal ventricular activation and pathologic preexcited tachycardias as part of a split AV node-bundle branch system is presented. ( info)
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