Heart Block: A Comprehensive Overview

Introduction

Heart block is a disorder of the electrical conduction system of the heart, which can lead to slow heart rhythms (bradycardia) or missed heartbeats. It occurs when the electrical signals traveling from the atria to the ventricles are delayed or completely blocked. Understanding heart block is essential for proper diagnosis and treatment.

Types of Heart Block

There are three main types of heart block, classified based on the severity of the conduction disturbance:

1. First-Degree Heart Block

• The electrical signal from the atria to the ventricles is delayed but still reaches the ventricles.
• Usually does not cause symptoms and is often detected incidentally on an electrocardiogram (ECG).
• Typically does not require treatment.

2. Second-Degree Heart Block

• Not all electrical signals reach the ventricles, causing occasional missed beats.
• Two subtypes exist:
  • Mobitz Type I (Wenckebach): Progressive delay in conduction before a beat is dropped; often mild and may not require treatment.
  • Mobitz Type II: More serious; sudden loss of ventricular beats that can progress to complete heart block. Often requires a pacemaker.

3. Third-Degree (Complete) Heart Block

• No electrical signals pass from the atria to the ventricles.
• The ventricles generate their own rhythm (escape rhythm), which is usually slow and inadequate for maintaining normal circulation.
• This condition is serious and typically requires urgent intervention with a pacemaker.

Causes of Heart Block

Several conditions can lead to heart block, including: - Aging – Degenerative changes in the conduction system occur with age. - Heart disease – Coronary artery disease, heart failure, and prior heart attacks can damage the conduction pathways. - Electrolyte imbalances – High potassium levels (hyperkalemia) and other disturbances can affect electrical conduction. - Medications – Beta-blockers, calcium channel blockers, and digoxin can slow conduction and cause heart block. - Congenital heart disorders – Some people are born with heart block due to structural defects or genetic conditions.

Symptoms of Heart Block

Symptoms vary depending on the degree of heart block but may include: - Fatigue - Dizziness or fainting (syncope) - Shortness of breath - Chest pain - Palpitations or irregular heartbeats

Diagnosis

Heart block is diagnosed using: - Electrocardiogram (ECG) – Identifies abnormal conduction patterns. - Holter Monitor – A portable ECG device worn for 24 to 48 hours to detect intermittent heart blocks. - Electrophysiology Study (EPS) – A specialized test to assess the electrical pathways of the heart. - Blood Tests – Evaluate electrolyte levels and other underlying causes.

Treatment Options

Treatment depends on the severity of the heart block: - First-degree block – Usually does not require treatment. - Second-degree (Mobitz I) block – May not require intervention unless symptomatic. - Second-degree (Mobitz II) and third-degree block – Typically require pacemaker implantation to ensure proper heart function. - Treating underlying conditions – Managing electrolyte imbalances, adjusting medications, or treating heart disease can help improve conduction abnormalities.

Conclusion

Heart block is a potentially serious condition affecting the electrical conduction in the heart. While mild forms may not require treatment, advanced heart blocks can lead to serious complications and often necessitate pacemaker placement. Early detection and appropriate management are crucial for maintaining heart health.

Source recommendations

1. 2023 American College of Cardiology/American Heart Association Guideline for the Evaluation and Diagnosis of Heart Block

1. https://www.ahajournals.org/doi/10.1161/cir.0000000000000499
2. https://www.jacc.org/doi/10.1016/j.jacc.2023.08.017
3. https://www.ahajournals.org/doi/10.1161/CIR.0000000000001063
4. https://www.jacc.org/doi/10.1016/j.jacc.2024.02.014
5. https://pubmed.ncbi.nlm.nih.gov/30412710/

2. 2021 European Society of Cardiology Guidelines for Cardiac Pacing and Cardiac Resynchronization Therapy

1. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Cardiac-Pacing-and-Cardiac-Resynchronization-Therapy
2. https://pubmed.ncbi.nlm.nih.gov/34455430/
3. https://academic.oup.com/eurheartj/article/42/35/3427/6358547
4. https://pubmed.ncbi.nlm.nih.gov/34455427/
5. https://link.springer.com/article/10.1007/s12471-024-01927-y