Complete Heart Block (CHB) in Cardiology

Introduction

Complete heart block (CHB), also known as third-degree atrioventricular (AV) block, is a serious cardiac condition in which electrical signals from the atria fail to reach the ventricles. This leads to an independent beating of atria and ventricles, causing severe bradycardia and potentially life-threatening complications.

Causes

CHB can arise due to multiple reasons, including: - Congenital: Present at birth and often associated with maternal autoimmune diseases. - Acquired: - Ischemic heart disease (e.g., myocardial infarction) - Cardiomyopathies (e.g., dilated cardiomyopathy) - Fibrosis/sclerosis of the cardiac conduction system - Inflammatory or infectious diseases (e.g., Lyme disease, myocarditis) - Cardiac surgery or trauma - Drug toxicity (e.g., beta-blockers, calcium channel blockers, digoxin)

Symptoms

The symptoms depend on heart rate and the presence of an escape rhythm: - Fatigue and dizziness - Syncope (fainting) due to reduced cardiac output - Shortness of breath - Chest pain (in cases of ischemic heart disease) - Heart failure symptoms, such as leg swelling and fluid retention

Diagnosis

The primary diagnostic tool is the Electrocardiogram (ECG), which shows: - No relation between P-waves and QRS complexes (atrioventricular dissociation) - A slow ventricular rate (junctional or ventricular escape rhythm)

Other tests include: - Echocardiography to assess heart function - Blood tests (checking for electrolyte imbalances, infections, or drug toxicity) - Holter monitoring for intermittent block - Electrophysiological studies in uncertain cases

Treatment

The mainstay of treatment for CHB is pacemaker implantation: - Temporary pacemaker in emergency cases - Permanent pacemaker for long-term management

Emergency treatment may also include atropine or isoproterenol infusion while preparing for definitive management.

Prognosis and Follow-up

With a permanent pacemaker, most patients can lead a near-normal life. Regular follow-up is necessary to ensure pacemaker function and detect potential complications such as lead dysfunction or battery depletion.

Conclusion

CHB is a serious condition that requires immediate recognition and treatment. If treated with timely pacemaker implantation, most patients can achieve good quality of life.

Source recommendations

1. 2023 ESC Guidelines on Cardiac Pacing and Cardiac Resynchronization Therapy

1. https://www.heartrhythmjournal.com/article/S1547-5271(23)02026-X/fulltext
2. https://academic.oup.com/eurheartj/article/42/35/3427/6358547
3. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Cardiac-Pacing-and-Cardiac-Resynchronization-Therapy
4. https://pubmed.ncbi.nlm.nih.gov/34455430/
5. https://www.hrsonline.org/guidance/clinical-resources/2023-hrsaphrslahrs-guideline-cardiac-physiologic-pacing-avoidance-and-mitigation-heart-failure

2. 2023 ACC/AHA/HRS Guidelines for the Evaluation and Management of 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.ahajournals.org/doi/10.1161/CIR.0000000000001193
4. https://www.jacc.org/doi/abs/10.1016/j.jacc.2018.10.044
5. https://www.heartrhythmjournal.com/article/S1547-5271(23)02026-X/fulltext