Background

Specialized conducting fibers called bundle branches oversee transferring electrical impulses from the atrioventricular node to the ventricles so that a coordinated contraction is possible. 

When there is a pause or disruption in the impulses passing through one of the bundle branches, it results in bundle branch block. 

Smaller divisions of the bundle branches are called fascicles, and anomalies in conduction occur inside these fascicles. These are known as fascicular blocks. 

Anterior fascicular block and posterior fascicular block are the two primary forms of fascicular blockages. 

When there is poor conduction via the left anterior fascicle, the anterior part of the left ventricle activates later than usual, resulting in anterior fascicular block. 

Epidemiology

In the general population, especially among elderly people, bundle branch blocks, in particular right bundle branch block (RBBB), are rather common. 

Age-related increases in the prevalence of RBBB are observed in men at a higher rate than in women. 

Compared to right bundle branch block (RBBB), left bundle branch block (LBBB) is less prevalent and is frequently linked to more serious underlying heart disease. 

Fascicular blocks may occur in a smaller percentage of the general population and are less common than bundle branch blocks. 

More cases of anterior fascicular block (left anterior hemiblock) than posterior fascicular block (left posterior hemiblock) are reported. 

Anatomy

Pathophysiology

Specialized conducting fibers called bundle branches carry electrical impulses from the atrioventricular (AV) node to the ventricles, synchronizing the depolarization sequence of the ventricles. 

Bundle branch block is a condition where normal electrical impulse propagation is disrupted due to delayed or blocked conduction through one of the bundle branches. 

Disruptions in conduction within the fascicles the smaller divisions of the bundle branches called fascicles, including the left anterior fascicle (LAF) and left posterior fascicle (LPF) are the cause of fascicular blocks. 

Anterior fascicular block, also known as left anterior hemiblock, is a condition in which the anterior part of the left ventricle activates later than expected due to poor conduction through the LAF. 

Impaired conduction across the LPF causes posterior fascicular block, also known as left posterior hemiblock, which delays the activation of the posterior part of the left ventricle. 

Etiology

Atherosclerosis and coronary artery disease may cause myocardial infarction. As it can impair the conduction system and result in bundle branch blockages. 

Chronic hypertension may cause left ventricular hypertrophy and other structural heart abnormalities that put a person at risk for bundle branch blockages. 

An acute myocardial infarction occurs in a specific region that is supplied by the coronary arteries. It can cause ischemia, damage to the fascicles, and fascicular blockages. 

Fascicular blocks may result from aging and degenerative diseases that impact the conduction system, encompassing the bundle branch fascicles. 

Genetics

Prognostic Factors

There may be differences between left bundle branch block (LBBB) and right bundle branch block (RBBB).  

Compared to RBBB, LBBB is typically linked to an increased risk of unfavorable cardiovascular events, particularly when it happens in the context of underlying heart disease. 

The prognosis may be impacted by the level of conduction delay or obstruction within the bundle branches.  

The prognostic significance of anterior fascicular block and posterior fascicular block varies based on the underlying heart disease and related comorbidities. 

The prognosis may be affected by the degree of blockage or conduction delay inside the fascicles; more severe anomalies are associated with a higher chance of unfavorable outcomes. 

Clinical History

Age Group:  

Bundle branch blocks can occur at any age, they are more commonly encountered in individuals over the age of 50 or 60 years. 

While fascicular blocks can occur in younger individuals, they are generally less common in this population compared to older adults. 

Associated Comorbidity or Activity:   

Atherosclerosis leading to coronary artery disease can cause ischemic damage to the myocardium, predisposing individuals to bundle branch blocks and fascicular blocks. 

Acute myocardial infarction, especially involving the left ventricle, can result in bundle branch blocks and fascicular blocks due to ischemic injury to the conduction system. 

Various forms of cardiomyopathy, including dilated cardiomyopathy and hypertrophic cardiomyopathy, can affect the myocardium and disrupt the conduction system, leading to BBB and fascicular block. 

Chronic hypertension can lead to left ventricular hypertrophy and structural changes in the heart, increasing the risk of conduction abnormalities such as BBB and fascicular block. 

Acuity of Presentation:  

Bundle branch blocks can present acutely in certain situations, particularly if they are related to acute myocardial infarction or ischemia.  

Fascicular blocks can present acutely in the setting of acute myocardial infarction or ischemia affecting the conduction system. Acute anterior or posterior fascicular blocks may present with symptoms consistent with acute coronary syndrome. 

Physical Examination

• Cardiac Auscultation: Heart sounds should be evaluated for murmurs, gallops, or abnormal heart sounds indicative of underlying valvular heart disease or cardiomyopathy. 
• Pulses: Peripheral pulses should be evaluated for any abnormalities, including diminished or bounding pulses, which may provide clues about the severity of underlying cardiovascular disease. 
• Jugular Venous Distention: Examination of the jugular venous pulse for signs of elevated central venous pressure may indicate heart failure or fluid overload. 
• Signs of Heart Failure: Signs such as pulmonary rales, hepatojugular reflux, or ascites may suggest the presence of heart failure, which can be associated with bundle branch block. 

Age group

Associated comorbidity

Associated activity

Acuity of presentation

Differential Diagnoses

• Normal Variants: Some individuals may have benign variants of bundle branch block that do not indicate underlying pathology. These include incomplete right bundle branch block (RBBB) or incomplete left bundle branch block (LBBB). 
• Acute Coronary Syndrome (ACS): Acute myocardial infarction, particularly involving the anterior or inferior myocardial walls, can cause changes on the ECG that mimic bundle branch block. 
• Myocarditis: Inflammation of the myocardium can lead to changes on the ECG resembling bundle branch block. 
• Hypertrophic Cardiomyopathy (HCM): HCM can cause abnormal electrical conduction patterns on the ECG, including findings like bundle branch block. 
• Dilated Cardiomyopathy (DCM): DCM can also lead to conduction abnormalities on the ECG, mimicking bundle branch block. 

Laboratory Studies

Imaging Studies

Procedures

Histologic Findings

Staging

Treatment Paradigm

• Observation and Monitoring: Asymptomatic bundle branch block or fascicular block without evidence of underlying heart disease may not require specific treatment and can be managed with regular monitoring. 
• Treatment of Underlying Conditions: Addressing underlying cardiovascular conditions such as coronary artery disease, hypertension, valvular heart disease, or cardiomyopathy is essential in managing bundle branch block and fascicular block. 
• Management of Associated Symptoms: Symptomatic patients with bundle branch block or fascicular block may require treatment aimed at managing their symptoms. 
• Arrhythmia Management: Patients with bundle branch block or fascicular block may be at increased risk of arrhythmias such as atrial fibrillation, ventricular tachycardia, or complete heart block. 

by Stage

by Modality

Chemotherapy

Radiation Therapy

Surgical Interventions

Hormone Therapy

Immunotherapy

Hyperthermia

Photodynamic Therapy

Stem Cell Transplant

Targeted Therapy

Palliative Care

use-of-non-pharmacological-approach-for-bundle-branch-block-and-fascicular-block

• Healthy Diet: Encourage a heart-healthy diet rich in fruits, vegetables, whole grains, lean proteins, and healthy fats. Limit intake of saturated fats, trans fats, cholesterol, sodium, and added sugars. 

• Regular Exercise: Advocate for regular physical activity as part of a healthy lifestyle. Encourage individuals to engage in activities that they enjoy and can sustain over time. 

• Smoking Cessation: Provide support and resources for smoking cessation for individuals who smoke. 

• Stress Management: Encourage stress-reducing activities such as mindfulness meditation, yoga, deep breathing exercises, or progressive muscle relaxation. 
• Weight Management: Provide support and resources for individuals who need assistance with weight loss or weight management. 

Use of Angiotensin-converting enzyme (ACE)

• Enalapril: It is a commonly used ACE inhibitor indicated for the treatment of hypertension, heart failure, and asymptomatic left ventricular dysfunction. It works by inhibiting the angiotensin I to angiotensin II conversion which leads to vasodilation and reduced aldosterone secretion. 

Use of Anticoagulants

• Apixaban: Apixaban is a direct oral anticoagulant (DOAC) that inhibits factor Xa, thus preventing the formation of thrombin and reducing the risk of thromboembolic events.

Use of Antiplatelet Agents

• Aspirin: It is the most used antiplatelet agent and is indicated for the prevention of cardiovascular events, including myocardial infarction, stroke, and peripheral arterial disease. Aspirin irreversibly inhibits cyclooxygenase (COX) enzyme hence inhibiting platelet aggregation and thromboxane A2 production. 

use-of-intervention-with-a-procedure-in-treating-bundle-branch-block-and-fascicular-block

• Pacemakers are typically used for patients with bradycardia or conduction abnormalities without a significant risk of sudden cardiac death, while ICDs are indicated for patients at risk of ventricular arrhythmias or sudden cardiac death. The procedure is usually performed in a cardiac catheterization laboratory or electrophysiology laboratory under sterile conditions and local anesthesia. Access to the heart is gained via a vein in the upper chest or neck region. Leads are advanced through the venous system and positioned in appropriate locations within the heart, typically in the right atrium and right ventricle for pacemakers or in the right ventricle. The leads are connected to a pulse generator (the pacemaker or ICD device), which is typically implanted under the skin of the chest or abdomen. 

use-of-phases-in-managing-bundle-branch-block-and-fascicular-block

• Assessment and Diagnosis: This involves obtaining a detailed medical history, including symptoms (if any), past medical conditions, medications, family history, and risk factors for cardiovascular disease. 
• Physical Examination: A thorough physical examination is performed to assess for signs of cardiovascular disease, including heart murmurs, abnormal heart sounds, peripheral edema, and jugular venous distention. 
• Symptomatic Management: Symptomatic treatment may be necessary for patients experiencing symptoms related to the conduction abnormality or underlying cardiac disease.  
• Lifestyle Modifications: Encouraging lifestyle modifications such as a heart-healthy diet, regular physical activity, smoking cessation, weight management, and stress reduction is important for overall cardiovascular health and may help mitigate risk factors contributing to bundle branch block or fascicular block. 

Medication

Future Trends

Media Gallary

References

Bundle branch block – Symptoms & causes – Mayo Clinic 

Fascicular block (hemiblock): Left anterior & left posterior fascicular block – Cardiovascular Education (ecgwaves) 

Bundle Branch and Fascicular Blocks – Lecturio