Trifascicular block

Overview

ECG showing trifascicular block

A trifascicular block is a type of heart block involving impairment in all three fascicles of the heart's conduction system. These fascicles include the right bundle branch and the left bundle branch, which is further divided into the left anterior fascicle and the left posterior fascicle. Trifascicular block can lead to significant arrhythmias and may require medical intervention.

Anatomy and Physiology

The heart's conduction system is responsible for the propagation of electrical impulses that coordinate the heart's contractions. The system includes the sinoatrial node, atrioventricular node, and the bundle of His, which divides into the right and left bundle branches. The left bundle branch further divides into the left anterior and left posterior fascicles. A trifascicular block involves conduction delay or block in all three of these fascicles.

Pathophysiology

Trifascicular block can result from various underlying conditions that affect the heart's conduction system. Common causes include:

• Ischemic heart disease
• Cardiomyopathy
• Myocarditis
• Degenerative changes associated with aging

The block can lead to a complete heart block if the conduction through all three fascicles is impaired, resulting in a failure of electrical impulses to reach the ventricles.

Clinical Presentation

Patients with trifascicular block may present with symptoms such as:

• Syncope or presyncope
• Dizziness
• Palpitations
• Fatigue

In some cases, patients may be asymptomatic and the block is discovered incidentally on an electrocardiogram (ECG).

Diagnosis

The diagnosis of trifascicular block is primarily made using an ECG. Key findings on an ECG may include:

• Right bundle branch block pattern
• Left anterior or left posterior fascicular block
• Prolonged PR interval indicating first-degree atrioventricular block

Management

Management of trifascicular block depends on the presence and severity of symptoms. Options include:

• Observation in asymptomatic patients
• Pacemaker implantation in symptomatic patients or those with evidence of progression to complete heart block

Prognosis

The prognosis of trifascicular block varies depending on the underlying cause and the presence of symptoms. Patients with symptomatic trifascicular block or progression to complete heart block generally have a worse prognosis and may require permanent pacing.

Related Pages

• Heart block
• Bundle branch block
• Pacemaker