A single Mahaim fiber causing both antidromic and orthodromic reciprocating tachycardia.

We describe the case of a 56-year-old woman referred for electrophysiological (EP) testing for medically refractory supraventricular arrhythmias. During the EP study, the patient was found to have a right free wall atriofasicular (Mahaim type) accessory pathway and an inducible left bundle morphology preexcited tachycardia secondary to antidromic reciprocating tachycardia. The patient also had an inducible narrow complex orthodromic reciprocating tachycardia (ORT). Mapping revealed that the earliest site of retrograde atrial activation during ORT was along the lateral tricuspid annulus. This was the same location where the atriofasicular accessory pathway potential was recorded during sinus rhythm. Radiofrequency ablation at this site eliminated inducibility of both tachycardias and any evidence of antegrade or retrograde accessory pathway conduction. This report describes the case of a very rare right free wall Mahaim type fiber with both antegrade and retrograde conduction capabilities responsible for both antidromic and ORT.

Proarrhythmia of circumferential left atrial lesions for management of atrial fibrillation.

BACKGROUND: After circumferential ablation for atrial fibrillation, new onset left atrial flutter (LA Flr) may occur. This study assessed the relationship between induced and clinical episodes of LA Flr, the rate of spontaneous resolution of LA Flr, and the proarrhythmic effect of circumferential ablation. METHODS AND RESULTS: A total 112 patients underwent circumferential LA ablation for atrial fibrillation. Immediately after completion of the ablation, LA Flr was induced in 43 of 112 (38%) patients, but was not targeted for ablation. During follow-up (14 +/- 4 months), new onset LA Flr occurred in 28 of 112 (25%) patients; however, the presence of inducible LA Flr did not identify those patients with clinical LA Flr (P = 0.6). In comparison to episodes of atrial fibrillation occurring before circumferential ablation, LA Flr was associated with a faster ventricular rate (124 +/- 19 beats/min vs 91 +/- 16 beats/min, P < 0.001), and was more likely to be persistent requiring cardioversion (86% vs 32%, P = 0.01). By >or=4 months postcircumferential ablation, clinical LA Flr resolved in 18 of 28 patients (64%). A second ablation procedure for LA Flr was performed in 9 of 10 patients. Of the 17 morphologies, 16 (94%) LA Flr circuits were successfully ablated. CONCLUSIONS: (1) LA Flrs that are induced immediately after circumferential ablation for atrial fibrillation do not identify those patients who require a second ablation procedure for clinical LA Flr; (2) Since the majority of clinical LA Flrs spontaneously resolve, ablation of LA Flr should be postponed several months; and (3) new onset LA Flr after ablation for atrial fibrillation is likely a manifestation of the proarrhythmic effect of ablation lines in the LA.