Complete Heart Block (3rd Degree Atrioventricular Block) Treatment

Introduction

Third-degree atrioventricular (AV) block, also known as complete heart block, is a severe disorder where electrical impulses from the atria do not reach the ventricles. This results in an independent ventricular rhythm, which can lead to severe symptoms such as dizziness, fainting, and even cardiac arrest.

Causes and Risk Factors

Complete heart block can be caused by: - Age-related degeneration (most common in elderly patients) - Ischemic heart disease (e.g., after myocardial infarction) - Myocarditis or infections (such as Lyme disease) - Cardiac surgery complications - Electrolyte imbalances and drug toxicity (e.g., from beta-blockers, calcium channel blockers, digoxin)

Symptoms

• Severe bradycardia (slow heart rate)
• Fatigue and weakness
• Lightheadedness or syncope (fainting)
• Chest pain or shortness of breath (if associated with ischemia)

Diagnosis

Diagnosis is made using an ECG (electrocardiogram), which shows complete dissociation between P waves and QRS complexes. Additional tests include: - Holter monitoring (for intermittent blocks) - Electrophysiological studies (to assess AV conduction) - Echocardiography (to evaluate structural heart disease)

Treatment Options

1. Immediate Management (Emergency Cases)

• Atropine (may be ineffective in high-degree blocks)
• Temporary transcutaneous or transvenous pacing
• Correction of reversible causes (electrolytes, drug intoxication, ischemia)

2. Permanent Pacemaker Implantation

Indications:

• Symptomatic third-degree AV block
• Asymptomatic AV block with a ventricular rate <40 bpm
• AV block caused by structural or irreversible conditions
• Post-myocardial infarction if persistent

The most common pacemaker type used is a dual-chamber pacemaker (DDD mode), which maintains atrial-ventricular synchrony.

Prognosis

With proper pacemaker implantation, most patients can lead normal lives with reduced risk of syncope and sudden death. However, regular follow-ups are necessary to ensure pacemaker function.

Summary

• Third-degree AV block is a life-threatening condition.
• Treatment includes temporary pacing followed by permanent pacemaker implantation.
• Addressing underlying causes is crucial to long-term management.

References

Please consult official guidelines for detailed recommendations.

Source recommendations

1. American College of Cardiology/American Heart Association/HRS Guidelines for the Evaluation and Management of Patients With Bradycardia and Cardiac Conduction Delay

1. https://www.ahajournals.org/doi/10.1161/CIR.0000000000000628
2. https://pubmed.ncbi.nlm.nih.gov/30412710/
3. https://www.jacc.org/guidelines/bradycardia
4. https://pubmed.ncbi.nlm.nih.gov/30586772/
5. https://www.hrsonline.org/guidance/clinical-resources/2018-accahahrs-guideline-evaluation-and-management-patients-bradycardia-and-cardiac-conduction

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

1. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Cardiac-Pacing-and-Cardiac-Resynchronization-Therapy
2. https://academic.oup.com/eurheartj/article/42/35/3427/6358547
3. https://pubmed.ncbi.nlm.nih.gov/34455430/
4. https://academic.oup.com/eurheartj/article/34/29/2281/401445
5. https://pubmed.ncbi.nlm.nih.gov/23801827/