What Is Left Posterior Fascicular Block?

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Are you curious about the Left posterior fascicular block and its implications on heart health? Look no further!

Left posterior fascicular block: (LPFB) is a cardiac condition that occurs when there is a delay or blockage in the electrical conduction through the left posterior fascicle in the heart.1 LPFB is an extremely rare electrocardiography finding of 0.06% to 0.1% in the general population.2 This disturbance can result from various factors, such as coronary artery disease, hypertension, or structural heart abnormalities.3

If you want to learn more about the causes, signs, and symptoms of LPFB, how it is diagnosed, and the management strategies available, keep reading! Understanding this condition can empower you to take proactive steps toward maintaining a healthy heart.


The human heart is an incredible organ, beating tirelessly to pump blood throughout our bodies and keep us alive. However, the heart's complex electrical system can sometimes experience disruptions, leading to various cardiac conditions.1 One such condition is Left Posterior Fascicular Block (LPFB). This article will explore LPFB in simple terms, covering its causes, signs and symptoms, diagnosis, and management.

Causes of left posterior fascicular block

Understanding LPFB requires a basic grasp of the heart's electrical system. Electrical impulses that travel through specific pathways govern the heart's rhythm. LPFB arises when there is a blockage or delay in the conduction of electrical impulses through the left posterior fascicle, a specialized pathway in the heart (1).

The causes of LPFB may include:

  1. Coronary Artery Disease:4 Atherosclerosis, a condition where the arteries supplying blood to the heart become narrowed due to plaque buildup, can disrupt the electrical signals.
  2. Left ventricular hypertrophy:2 The muscular wall of the left ventricle, the main pumping chamber of the heart, becomes thicker than normal.
  3. Hypertension (High Blood Pressure):3 Prolonged high blood pressure can strain the heart and affect its electrical conduction system.
  4. Myocardial Infarction (Heart Attack):4 A heart attack can damage the heart muscle and interfere with the electrical pathways.
  5. Structural Heart Abnormalities:5 Certain congenital or acquired heart abnormalities may disrupt the heart's electrical signals.

Signs and symptoms of left posterior fascicular block

LPFB might not always cause noticeable symptoms, and some individuals may remain asymptomatic. However, when symptoms do occur, they are usually mild and nonspecific. Common signs and symptoms include

  1. Fatigue: Unexplained tiredness or a decrease in energy levels
  2. Palpitations: Sensation of abnormal heartbeats, such as skipped or extra beats
  3. Dizziness: Brief episodes of dizziness or lightheadedness
  4. Shortness of Breath: Severe cases of LPFB may cause shortness of breath, particularly during physical activity

Management and treatment for left posterior fascicular block

Diagnosing LPFB requires a thorough evaluation by a qualified healthcare professional. The diagnostic process may involve:

  1. Electrocardiogram (ECG):2 This painless test records the heart's electrical activity, and specific patterns on the ECG can indicate LPFB.
  2. Echocardiogram: An ultrasound of the heart that helps assess its structure and function.
  3. Holter Monitor or Event Recorder: These devices can be worn to monitor the heart's electrical activity continuously or during specific periods to detect irregularities.


The primary focus of LPFB management is addressing the underlying cause and managing symptoms. Treatment options may include:

  1. Medications: Depending on the underlying condition, medicines may be prescribed to control blood pressure, manage heart disease, or regulate heart rhythm.
  2. Lifestyle changes: Adopting a heart-healthy lifestyle, including regular exercise, a balanced diet, and stress management, can significantly improve heart health.
  3. Implantable: Sometimes, a pacemaker may be recommended to regulate the heart's rhythm and ensure proper beating.
  4. Treatment of underlying conditions: Treating underlying heart conditions like coronary artery disease can help alleviate LPFB.


How can I prevent the left posterior fascicular block?

Prevention involves adopting a heart-healthy lifestyle, including regular exercise, a balanced diet, managing hypertension, and avoiding risk factors like smoking and excessive alcohol consumption.

How common is the left posterior fascicular block?

LPFB is relatively rare compared to other cardiac conditions, and its prevalence varies among different populations.

Who is at risk of left posterior fascicular block?

Individuals with coronary artery disease, hypertension, heart disease, or structural heart abnormalities may have an increased risk of developing LPFB.

What can I expect if I have a left posterior fascicular block?

The symptoms of LPFB can be mild or absent in many cases. Proper diagnosis and management are crucial to prevent complications and ensure a healthy heart.

When should I see a doctor?

If you experience any heart-related symptoms, such as palpitations, dizziness, or unexplained fatigue, it is essential to consult a healthcare professional promptly for evaluation and appropriate care.


Left Posterior Fascicular Block (LPFB) is a cardiac condition characterized by a delay or blockage in the electrical conduction through the left posterior fascicle in the heart. It can be caused by factors such as coronary artery disease, hypertension, or structural heart abnormalities). While LPFB may not always present noticeable symptoms, early diagnosis and appropriate management are crucial to prevent potential complications. Treatment options may include medications, lifestyle modifications, and, in specific cases, implantable devices like pacemakers to regulate the heart's rhythm. Understanding LPFB helps individuals to take proactive steps towards maintaining a healthy heart. Consultation with a healthcare professional is advised for personalized guidance and care.


  1. Tan NY, Witt CM, Oh JK, Cha YM. Left Bundle Branch Block. Circulation: Arrhythmia and Electrophysiology. 2020 Apr;13(4).
  2. Pérez-Riera AR, Barbosa-Barros R, de Rezende Barbosa MPC, Daminello-Raimundo R, de Abreu LC, Nikus K. Left bundle branch block: Epidemiology, aetiology, anatomic features, electro vector cardiography, and classification proposal. Annals of Noninvasive Electrocardiology. 2018 Jun 22;24(2):e12572.
  3. Li ZB, Wachtell K, Okin PM, Gerdts E, Liu JE, Nieminen MS, et al. Association of left bundle branch block with left ventricular structure and function in hypertensive patients with left ventricular hypertrophy: the LIFE study. Journal of Human Hypertension. 2004 Apr 8;18(6):397–402.
  4. Madias JE. Serial ECG recordings via marked chest wall landmarks: An essential requirement for the diagnosis of myocardial infarction in the presence of left bundle branch block. Journal of Electrocardiology. 2002 Oct;35(4):299–302.
  5. Left Posterior Fascicular Block: Causes & Treatment [Internet]. Cleveland Clinic. [cited 2023 Jul 21]. Available from: https://my.clevelandclinic.org/health/diseases/23288-left-posterior-fascicular-block#:~:text=Left%20posterior%20fascicular%20block%20is

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This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Marcella de Aviz Callil

Master's degree (M.Sc), Biological Science: Physiology, Federal University of Rio de Janeiro

I am a highly experienced biomedical scientist with expertise in both basic and clinical research in genetics, reproductive health and physiology. My professional journey has been enriched by the opportunity to teach and deliver lectures, sharing my knowledge with enthusiasm and clarity. Furthermore, my proficiency in scientific writing has allowed me to contribute to the dissemination and advancement of knowledge in my field of expertise. My dedication to science and education has shaped my career path and brought me professional fulfillment throughout the years.

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