Electrocardiogram in patients with fasciculoventricular pathways: A comparative study with anteroseptal and midseptal accessory pathways
Introduction
Fasciculoventricular pathways are rare variants1 of preexcitation that take off from the His bundle or bundle branches and insert into the ventricular septum.2 ECG recognition of a fasciculoventricular pathway is based on finding a minimal preexcitation pattern with a normal QRS frontal plane axis and a variable PR interval.1, 3 Although fasciculoventricular pathways play no active role in tachycardia circuits, fasciculoventricular pathways frequently are associated with rapidly conducting bypass tracts. They must be correctly differentiated from an anteroseptal bypass tract to avoid disrupting AV nodal conduction if the pathways are targeted for catheter ablation.4 Few published data on the ECG of fasciculoventricular pathways are available.3, 4, 5, 6 The purpose of this study was to describe the ECG profile in a cohort of seven patients with fasciculoventricular pathways and to compare their profile with the ECG pattern of patients having AV bypass tracts inserting in the anteroseptal and midseptal region.
Section snippets
Fasciculoventricular pathways (group I)
During the last 9 years, 8 patients (2%) with fasciculoventricular pathways (Figure 1) were diagnosed from a total of 392 patients with manifest ventricular preexcitation referred to our laboratory for electrophysiologic evaluation. In 3 of the 8 patients (38%), the fasciculoventricular pathway could be diagnosed only after catheter ablation of a rapidly conducting bypass tract. One of the eight patients lacked some electrophysiologic data and was excluded from this study. One patient (no. 3)
Fasciculoventricular pathways (group I)
After all associated bypass tracts were ablated, the following ECG and electrophysiologic findings were recorded (Table 2).
Discussion
The septal region is a complex anatomic region harboring not only the fasciculoventricular pathways but approximately 30% of all accessory AV pathways. As a consequence, ECG presentation of fasciculoventricular pathways is expected to share some characteristics with septal AV pathways. Applying previously published algorithms in the differential diagnosis of septal APs in patients with fasciculoventricular pathways, they are categorized as anteroseptal or midseptal bypass tracts.8, 9
Patients
Conclusion
The ECG of patients with fasciculoventricular pathways shows similarities with ECGs of patients with anteroseptal APs and midseptal bypass tracts located at the apex of the triangle of Koch, but the QRS complex usually is narrower. Surface ECG cannot reliably differentiate fasciculoventricular pathways with a large QRS complex from an anteroseptal or midseptal bypass tract.
Definitive diagnosis requires an intracardiac study that observes the presence or absence of changes in the QRS complex
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