Left anterior fascicular block

Left Anterior Fascicular Block

Introduction

A Left Anterior Fascicular Block (LAFB) is an electrocardiographic finding characterized by a slightly widened QRS duration.

Pathophysiology

ECG showing Left Anterior Fascicular Block.

LAFB occurs due to a conduction delay or blockage in the left anterior fascicle of the heart's ventricular conduction system, leading to altered electrical activity.

ECG Characteristics

Key ECG features of LAFB include:

• Slightly widened QRS complex (typically <120 ms)
• Left axis deviation
• Small q waves and tall R waves in the lateral leads

Causes

LAFB can be associated with:

• Hypertensive heart disease
• Aortic stenosis
• Cardiomyopathies
• Myocardial infarction
• Degenerative changes in the conduction system

Clinical Significance

While LAFB itself usually does not cause symptoms, it can be indicative of underlying heart disease and may affect the interpretation of the ECG in the context of myocardial ischemia.

Diagnosis

Diagnosis of LAFB is primarily based on ECG findings. Additional tests might include echocardiography or MRI to assess structural heart abnormalities.

Treatment

LAFB does not typically require specific treatment but managing underlying conditions is crucial. Regular cardiac evaluation is recommended.

Prognosis

The prognosis of LAFB varies depending on the associated cardiac conditions.

Epidemiology

LAFB is more commonly seen in older adults and those with hypertension or other forms of heart disease.

See Also

• Bundle branch block
• Electrocardiography
• Cardiac arrhythmia

External Links

• American Heart Association - Understanding Your EKG
• Medscape - Left Anterior Fascicular Block

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