About-Cardio
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We provide our users the most up-to-date and accurate information on the treatment and prevention of cardio pathologies in accordance with current American and European clinical guidelines.
The information provided on this website is for educational purposes only and should not be considered medical advice. Always consult a licensed physician for diagnosis and treatment.
Second-Degree Heart Block on ECG
Introduction
Second-degree heart block is a type of atrioventricular (AV) block where some electrical signals from the atria fail to reach the ventricles. This results in dropped heartbeats and can lead to dizziness, fainting, or more severe arrhythmias.
There are two types of second-degree heart block:
- Mobitz Type I (Wenckebach)
- Mobitz Type II
Mobitz Type I (Wenckebach)
ECG Features:
- Progressive prolongation of the PR interval until a QRS complex is dropped.
- After the dropped beat, the cycle repeats itself.
- Usually benign and may not require treatment unless symptomatic.
Causes:
- High vagal tone (common in athletes)
- Medications (beta-blockers, calcium channel blockers, digoxin)
- Inferior myocardial infarction
Mobitz Type II
ECG Features:
- PR interval remains constant, but intermittent QRS complexes are missing.
- More dangerous because it can progress to complete heart block (third-degree AV block).
Causes:
- Structural heart disease (e.g., fibrosis of the conduction system)
- Myocardial infarction (especially anterior MI)
- Drug toxicity
Diagnosis and Treatment
- ECG is the main diagnostic tool.
- Mobitz I may not need treatment unless symptomatic; if needed, atropine or pacemaker implantation may be considered.
- Mobitz II often requires a pacemaker, as it poses a higher risk of progressing to a complete heart block.
Conclusion
Identifying second-degree AV block on ECG is crucial to determining the need for intervention. Mobitz Type I is generally benign, while Mobitz Type II often requires immediate attention to prevent complications.
Source recommendations
1. American Heart Association – 2023 AHA/ACC/HRS Guideline for the Evaluation and Management of Patients With Cardiac Conduction Disorders
- https://www.ahajournals.org/doi/10.1161/CIR.0000000000001193
- https://www.heartrhythmjournal.com/article/S1547-5271(23)02026-X/fulltext
- https://www.ahajournals.org/doi/10.1161/CIR.0000000000000628
- https://professional.heart.org/en/science-news/periprocedural-management-and-multidisciplinary-care-pathways-for-patients-with-cardiac-implantable
- https://www.jacc.org/doi/10.1016/j.jacc.2024.02.014
2. European Society of Cardiology – 2021 ESC Guidelines on Cardiac Pacing and Cardiac Resynchronization Therapy
- https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Cardiac-Pacing-and-Cardiac-Resynchronization-Therapy
- https://pubmed.ncbi.nlm.nih.gov/34455430/
- https://academic.oup.com/eurheartj/article/42/35/3427/6358547
- https://www.acc.org/Latest-in-Cardiology/ten-points-to-remember/2021/08/31/18/37/2021-ESC-Guidelines-on-Cardiac-Pacing-ESC-2021
- https://academic.oup.com/eurheartj/article/34/29/2281/401445
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If you or your loved ones experience any of these symptoms, you should consult a doctor in time. Remember that self-medication can be dangerous, and timely diagnosis will preserve the quality and life expectancy.
The heart is an organ that does not know how to "keep silent" if something goes wrong. Chest pain, shortness of breath, swelling, dizziness, and rhythm disturbances are the symptoms that require our attention. The best prevention of heart disease is careful attention to your health, regular checkups with a doctor, and a healthy lifestyle. Take care of your heart, and it will serve you for many years!
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