About-Cardio
-
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.
First-Degree Atrioventricular (AV) Block: Causes and Explanation
Introduction
First-degree atrioventricular (AV) block is a condition in which the electrical signals between the atria and ventricles in the heart are delayed but still conducted. This results in a prolonged PR interval (greater than 200 milliseconds) on the ECG without skipped beats.
Causes of First-Degree AV Block
1. Intrinsic Cardiac Causes
- Aging: The conduction system of the heart degenerates over time.
- Ischemic Heart Disease: Reduced blood flow to the heart may affect conduction.
- Cardiomyopathies: Structural changes in the heart tissue can affect electrical signals.
- Congenital Heart Defects: Some individuals are born with AV conduction abnormalities.
2. Medication-Induced First-Degree AV Block
- Beta-Blockers (e.g., metoprolol, atenolol) – slow conduction.
- Calcium Channel Blockers (e.g., verapamil, diltiazem) – depress AV node activity.
- Digitalis (Digoxin) – increases vagal tone, slowing AV conduction.
- Antiarrhythmic Drugs (e.g., amiodarone, flecainide) – can prolong conduction times.
3. Electrolyte Imbalances
- Hyperkalemia – increases resting membrane potential, slowing conduction.
- Hypokalemia – affects repolarization and conduction.
- Hypermagnesemia – can depress AV node conduction.
4. Increased Vagal Tone
- Seen in athletes due to high parasympathetic activity.
- May occur during deep breathing or in individuals with high vagal tone.
5. Systemic Diseases Affecting the Conduction System
- Hypothyroidism – slows metabolic and conduction activity.
- Lyme Disease – can involve the heart (Lyme carditis).
- Rheumatic Fever – damages conduction pathways.
- Sarcoidosis or Amyloidosis – infiltration of the heart muscle.
When to Worry?
- First-degree AV block is usually benign and does not require treatment.
- However, if it progresses to more severe block (e.g., second-degree or third-degree AV block) or is associated with symptoms like dizziness or fainting, further investigation is necessary.
Conclusion
First-degree AV block is often a benign condition caused by various factors including medication, electrolyte imbalances, and underlying heart disease. Most cases do not require treatment but monitoring may be necessary.
Source recommendations
1. American Heart Association Guidelines on Bradyarrhythmias
- https://www.heart.org/en/health-topics/arrhythmia/about-arrhythmia/bradycardia--slow-heart-rate
- https://cpr.heart.org/-/media/cpr-files/cpr-guidelines-files/algorithms/algorithmacls_bradycardia_200612.pdf
- https://www.ahajournals.org/doi/10.1161/CIR.0000000000000628
- https://cpr.heart.org/en/resuscitation-science/cpr-and-ecc-guidelines/algorithms
- https://pubmed.ncbi.nlm.nih.gov/30412710/
2. European Society of Cardiology Guidelines on Cardiac Conduction Disorders
- https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Cardiac-Pacing-and-Cardiac-Resynchronization-Therapy
- https://www.ahajournals.org/doi/10.1161/CIR.0000000000000628
- https://www.escardio.org/static-file/Escardio/Guidelines/Documents/ehaa612.pdf
- https://academic.oup.com/europace/article/24/8/1307/6562982
- https://www.heartrhythmjournal.com/article/S1547-5271(24)00243-1/fulltext
-
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!
Our advantages:
Best practices from USA, EU and Japan
Our answers to your questions are based on the clinical recommendations of countries with the most developed healthcare systems in the field of cardiology in the USA, the EU and Japan.
Always up-to-date information
On a daily basis, we monitor for you all new scientific research publications in leading scientific journals on medical issues of interest to you.
We monitor all innovations and changes in the field of cardiac disease treatment on a daily basis.
We monitor all innovations and changes in the field of cardiac disease treatment on a daily basis.
Get second opinion
Here you can learn everything that even your doctor may not know about cardiology (if he does not speak English and he does not read 117 leading medical journals on cardiology every month).
The most comprehensive and up-to-date collection of free cardiology materials
Our website contains the most comprehensive and up-to-date collection of free cardiology materials in your country.
Every 3-5 years, half of the scientific approaches to treatment in the field of cardiology are reviewed as a result of specialized scientific discoveries. With us, you don't have to wait these years to learn about the best ways to treat you and your loved ones.
Every 3-5 years, half of the scientific approaches to treatment in the field of cardiology are reviewed as a result of specialized scientific discoveries. With us, you don't have to wait these years to learn about the best ways to treat you and your loved ones.