Elsevier

Heart Rhythm

Volume 2, Issue 1, January 2005, Pages 1-6
Heart Rhythm

Electrocardiogram in patients with fasciculoventricular pathways: A comparative study with anteroseptal and midseptal accessory pathways

https://doi.org/10.1016/j.hrthm.2004.10.009Get rights and content

Objectives

The purpose of this study was to describe the ECG profile of a cohort of patients with fasciculoventricular pathways and compare the profile with the ECG of patients with anteroseptal and midseptal accessory pathways.

Background

Electrophysiologic findings suggest fasciculoventricular pathways insert into the septal region. Findings also suggest the 12-lead surface ECG during sinus rhythm is similar to the ECG of patients with anteroseptal and midseptal bypass tracts.

Methods

Four different observers analyzed the 12-lead ECG of seven patients with fasciculoventricular pathways (group I) and the ECG of 20 patients with midseptal AV accessory pathways (group II) and 20 patients with anteroseptal AV accessory pathways (group III). The following variables were analyzed: ECG frontal plane QRS and delta wave axis; angle between the QRS and the delta wave axis; QRS width; R/S ratio in lead III; presence of a negative delta wave in inferior leads; and precordial lead transition to R/S >1.

Results

The ECG of fasciculoventricular pathways shows a variable pattern. It shares some features with an anteroseptal accessory pathway and others with a midseptal accessory pathway. A narrower QRS width was the most important variable in distinguishing a fasciculoventricular pathway from a septally located AV bypass tract (P <.0001). The angle between the QRS and the delta wave frontal plane axis could differentiate a fasciculoventricular pathway from an anteroseptal bypass tract (P <.0001) but not from a midseptal accessory pathway.

Conclusions

The sinus rhythm ECG of patients with fasciculoventricular pathways shows similarities with ECGs of patients with anteroseptal and midseptal accessory pathways, but the QRS complex usually is narrower. The ECG recorded during sinus rhythm cannot reliably differentiate fasciculoventricular pathways with a broad QRS complex from anteroseptal or midseptal bypass tracts.

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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