Bifascicular block is a conduction abnormality in the

heart The heart is a muscular organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon dioxide t ...

where two of the three main

fascicle Fascicle or ''fasciculus'' may refer to: Anatomy and histology * Muscle fascicle, a bundle of skeletal muscle fibers * Nerve fascicle, a bundle of axons (nerve fibers) ** Superior longitudinal fasciculus *** Arcuate fasciculus ** Gracile fas ...

s of the His/Purkinje system are blocked. Most commonly, it refers to a combination of

right bundle branch block A right bundle branch block (RBBB) is a heart block in the right bundle branch of the electrical conduction system. During a right bundle branch block, the right ventricle is not directly activated by impulses travelling through the right bu ...

(RBBB) and either

left anterior fascicular block Left anterior fascicular block (LAFB) is an abnormal condition of the left ventricle of the heart, related to, but distinguished from, left bundle branch block (LBBB). It is caused by only the left anterior fascicle – one half of the left bundl ...

(LAFB) or

left posterior fascicular block A left posterior fascicular block (LPFB), also known as left posterior hemiblock (LPH), is a condition where the left posterior fascicle, which travels to the inferior and posterior portion of the left ventricle, does not conduct the electrical i ...

(LPFB), with the former being more common. Some authors consider

left bundle branch block Left bundle branch block (LBBB) is a conduction abnormality in the heart that can be seen on an electrocardiogram (ECG). In this condition, activation of the left ventricle of the heart is delayed, which causes the left ventricle to contract late ...

(LBBB) to be a technical bifascicular block, since the block occurs above the

bifurcation Bifurcation or bifurcated may refer to: Science and technology * Bifurcation theory, the study of sudden changes in dynamical systems ** Bifurcation, of an incompressible flow, modeled by squeeze mapping the fluid flow * River bifurcation, the ...

of the left anterior and left posterior fascicles of the left bundle branch.

Diagnosis

Diagnostic criteria: Clinically, bifascicular block presents with one of two ECG patterns: Right bundle branch block (RBBB) with left anterior fascicular block (LAFB), manifested as

left axis deviation In electrocardiography, left axis deviation (LAD) is a condition wherein the mean electrical axis of ventricular contraction of the heart lies in a frontal plane direction between −30° and −90°. This is reflected by a QRS complex positive ...

(LAD). RBBB and left posterior fascicular block (LPFB), manifested as

right axis deviation The electrical axis of the heart is the net direction in which the wave of depolarization travels. It is measured using an electrocardiogram (ECG). Normally, this begins at the sinoatrial node (SA node); from here the wave of depolarisation travel ...

(RAD) in the absence of other causes.

Treatment

In those with bifascicular block and no symptoms, little with respect to treatment is needed. In those with syncope, a pacemaker is recommended.

References

Olshansky B. Bradyarrhythmias – Conduction System Abnormalities. In: Arrhythmia Essentials 2e, 2017. Vijayaraman P. Clinical Cardiac Pacing, Defibrillation and Resynchronisation Therapy 5e, 2017 Goldberger A. Ventricular Conduction Disturbances.. In: Goldberger’s Clinical Electrocardiography 9e, 2018.

External links

Cardiac arrhythmia {{circulatory-disease-stub