Mahaim Electrophysiological Characteristics Of Fiber And Catheter Ablation

Part I:Electrocardiogram characteristics of atriofascicular and decremental atrioventricular pathways during sinus rhythm and Mahaim tachycardiaBackgroundIn patients with anterograde decrementally conducting accessory pathways, the impulse may be conducted only through the AV node, only through the accessory pathway, and simultaneously through the AV node and the accessory pathway, resulting in various kinds of QRS configuration. Data on the sinus rhythm and Mahaim tachycardia electrocardiographic characteristics are limited.MethodsThirteen patients with accessory pathways of anterograde decremental conduction properties were studied retrospectively (4atriofascicular pathways and9decremental atrioventricular pathways). All patients had a pre-excited atrioventricular tachycardia with anterograde conduction over anterograde decrementally conducting fiber.ResultsSeven patients fulfilled criteria of minimal pre-excitation during sinus rhythm before ablation. In4patients, delta wave was minimal. In3patients (23%),delta wave was absent, and the only abnormality was terminal QRS slurring or notching on the ECG. It was mainly in leads I, V5, and V6. After ablation, terminal QRS slurring or notching disappeared in all3patients. The mean tachycardia cycle length of atriofascicular pathway and decremental atrioventricular pathway was336.0±54.2ms vs336.4ms±30.4respectively (P>0.05), and the during time of QRS wave was117.3±14.5ms vs128.8±14.6ms respectively (P>0.05). The r wave of leads V1～V3were all less than40ms in atriofascicular pathway. But in6decremental atrioventricular pathways originating from right lateral, r wave of leads V1～V3was widen than40ms in4patients, narrower than40ms in1patients, and had no r wave in the remaining patients.ConclusionsThis study showed a high prevalence of terminal QRS slurring or notching in patients with atriofascicular or decremental atrioventricular pathways. It can be the sole manifestation of such accessory pathways during sinus rhythm, and disappearance of terminal slurring or notching can be the only hallmark of successful ablation visible on the surface ECG. decremental atrioventricular pathways originating from right lateral often have a widen r wave in leads V1～V3. Part II:Electrophysiological characteristics of atriofascicular and decremental atrioventricular pathways and results of radiofrequency catheter ablationBackgroundAtriofascicular and decremental atrioventricular pathways are the most common type of Mahaim fibers. In contrast to atriofascicular pathway, data about decremental pathway is limit. The purpose of this study was to evaluate the electrophysiological features and radiofrequency ablation of atriofascicular and decremental atrioventricular pathways by comparative analysis.MethodsThirteen patients (4atriofascicular pathways and9decremental atrioventricular pathways) with accessory pathways of anterograde decremental conduction properties were studied retrospectively in clinical feature, electrophysiological study results and radiofrequency catheter ablation results.ResultsAll patients had a pre-excited atrioventricular tachycardia with anterograde conduction over anterograde decremental ly conducting fiber. Adenosine blocked conduction in3(75%) atriofascicular pathways and3(33%) decremental atrioventricular pathways respectively. During radiofrequency catheter ablation, a Mahaim automatic tachycardia occurred in2(50%) atriofascicular pathways and2(22%) decremental atrioventricular pathways. One (25%) atriofascicular pathway show short-run antomatic rhythm during sinus rthythm. Mahaim potential was recorded in2(22%) atrioventricular pathways and all4(100%) decremental atriofascicular pathways.ConclusionsMost of the decremental atrioventricular pathways participate in the Mahaim tachycardia. In contrast to atriofascicular pathways, less decremental atrioventricular pathways have A-V node-like features. Mahaim potential is of more value in mapping and ablation of atriofascicular pathways. Part III:Electrocardiogram and electrophysiological characteristics of fasciculoventricular pathwaysBackgroundFasciculoventricular (FV) accessory pathways are rare variants of preexcitation syndrome, and their ECGs may be misinterpreted as WPW with anteroseptal accessory pathways. In addition, FV pathways sometimes are associated with other paroxysmal supraventricular tachycardia. We analyzed the electrocardiographic characteristics of the patients with FV pathways and electrophysiological characteristics.MethodsFrom Sep2008to Oct2012, of311WPW patients, ten consecutive patients with FV pathways were enrolled. Clinical feature, electrocardiogram characteristics during sinus rhythm, and electrophysiological study result were analysized.ResultsTwo FV pathways are associated with rapidly conducting bypass tracts. After ablation of associated pathway, the ECG during sinus rhythm was similar to anteroseptal accessory pathway. Atrial pacing produces AH prolongation due to atrioventricular nodal delay without change of preexcitation degree. Ventricular activation at distal His bundle was the earliest. Atrial and ventricular stimulation did not induce any tachycardia in all10patients. Radiofrequency catheter ablation was carried out in5patients. Catheter ablation interrupted the conduction of FV pathway in4of5patients. Ablation failed in the remaining patient.ConclusionsECG of FV pathway is similar to WPW with anteroseptal accessory pathway. Most of the distal part is closely located to His bundle. Catheter ablation could interrupted the conduction of FV pathway. Because it is not directly responsible for arrhythmias, this form of preexcitation does not requeir treatment.