Heart Block: Understanding Types, Symptoms, and Treatment
Updated: 3 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026
Quick Answer
Heart block is a conduction disorder in which the heart's electrical timing signal is delayed or lost. It ranges from first-degree (mild delay) to third-degree (complete block). Symptoms include tiredness, dizziness, shortness of breath, chest pain and fainting. Third-degree block almost always needs a pacemaker, and phones should stay at least 6 inches from a pacemaker. [1]
What the research says
"Mild" first-degree block is linked to later rhythm problems. In 7,575 Framingham Heart Study participants followed for decades, people with first-degree AV block had about twice the adjusted risk of atrial fibrillation (HR 2.06, 95% CI 1.36–3.12), nearly three times the risk of needing a pacemaker (HR 2.89, 95% CI 1.83–4.57), and a 1.4-fold higher risk of death from any cause (HR 1.44, 95% CI 1.09–1.91). This was an observational study, so it shows association, not cause. (Cheng et al., JAMA, 2009)
Some pacemakers are designed to be MRI-safe. In a small feasibility study, 14 patients with an MRI-conditional leadless pacemaker had cardiac MRI at 1.5 T or 3.0 T. No clinical events occurred, and device settings stayed stable over 3 months. This applies only to MRI-conditional devices, so always confirm yours with your care team. (Blessberger et al., Europace, 2019)
What Is Heart Block?
Heart block occurs when the electrical impulses that coordinate your heartbeat are interrupted. In a healthy heart, signals travel from the upper chambers (atria) to the lower chambers (ventricles) through the AV node, a cluster of cells that links their electrical activity. [1] In heart block, the signals move too slowly, arrive unreliably or do not reach the ventricles at all.
Despite the name, heart block is not a blockage of blood flow like a clogged artery. It is a problem with the heart's wiring, which doctors call an atrioventricular (AV) block or a conduction disorder.
Heart Block Type | Severity | Impact on Signal |
First-degree | Mild | The signal reaches the ventricles but travels more slowly than normal. |
Second-degree | Moderate | Only some signals reach the lower chambers, causing skipped beats. |
Third-degree | Severe | No signals reach the ventricles. This is a complete electrical block. |
Recognizing the Symptoms of Heart Block
Symptoms depend on how much the block affects the heart's pumping. People with first-degree block often have no symptoms and may only find out from a routine EKG. As the block becomes more severe, the heart rate can slow (bradycardia) and symptoms appear.
Common Warning Signs
Fatigue: Feeling unusually tired or weak, even without exertion.
Breathing issues: Shortness of breath or rapid breathing.
Sensory changes: Dizziness, lightheadedness or fainting spells.
Chest discomfort: Pain or pressure in the chest.
Heart rhythm: Palpitations or a feeling that the heart skips a beat.
When to Seek Emergency Care
Fainting or intense chest pain needs immediate medical attention. Without treatment, complete heart block can lead to sudden cardiac arrest.
What Causes Heart Block?
Heart block can be present at birth (congenital), but it is much more common to develop it later in life, often from damage to the heart's conduction system or as a side effect of medical treatment.
Primary Causes
Heart conditions: Heart attacks, coronary artery disease, heart valve problems and cardiomyopathy.
Medical procedures: Damage to the conduction system during open-heart surgery. [1]
Infections and diseases: Lyme disease, thyroid disease and autoimmune conditions such as sarcoidosis. [1]
Medication side effects: Certain blood pressure medicines such as beta-blockers and calcium channel blockers, and some other drugs that slow the heart. [1]
Risk Factors
Your risk is higher if you already have heart disease, sleep apnea or an overactive vagus nerve, which naturally slows the heart rate. Imbalances in minerals such as potassium, calcium and magnesium can also interfere with the heart's electrical system.
Diagnosis and Treatment Options
To diagnose heart block, a cardiologist or electrophysiologist reviews your health history and tests how your heart conducts electricity.
Diagnostic Tools
EKG (electrocardiogram): The main tool for recording the heart's rhythm.
Ambulatory monitors: Portable devices such as Holter monitors or loop recorders that track the heart over days or longer. [1]
Stress tests: Show how the heart responds to exercise.
Electrophysiology study: A specialized test that pinpoints where the electrical signal fails. [1]
Treatment Pathways
Treatment depends on the type and severity of the block.
For some people, adjusting a medicine that causes the block resolves the problem. When the conduction system is permanently scarred, a pacemaker keeps the heart pumping blood effectively.
Living With a Pacemaker
A pacemaker is a common treatment for heart block, and you may need to stay overnight in the hospital after it is placed. [1] Recovery time varies, so follow your care team's instructions on activity. Most people with a pacemaker can stay active, with a few safety precautions:
Electronics: Keep cell phones at least 6 inches from your device and avoid carrying them in a shirt pocket over it. [1]
Security screening: Tell airport or courthouse security that you have a pacemaker and ask about alternative screening.
Medical procedures: Tell every doctor and dentist about your pacemaker. MRI can interfere with some pacemakers, while MRI-conditional devices are designed for it. Confirm which type you have before any scan. [1]
Conclusion
A heart block diagnosis can be unsettling, but the outlook is good for most people. With the right diagnosis and treatment, whether that is a medicine change or a pacemaker, many people stay active. Regular follow-up keeps your heart rhythm steady.
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Frequently Asked Questions
Can heart block go away on its own?
If it is caused by a medicine or a temporary problem such as Lyme disease, it may improve once the cause is treated. Heart block caused by scarring of the conduction system is usually permanent.
Is heart block the same as a heart attack?
No. A heart attack is caused by blocked blood flow to the heart muscle, while heart block is an electrical timing problem. A heart attack can, however, damage the conduction system and lead to heart block.
Can children have heart block?
Yes. Some children are born with congenital heart block, which can be linked to heart abnormalities present from birth or to certain maternal autoimmune conditions. [1]
What is the AV node?
The atrioventricular (AV) node is a cluster of cells that links the electrical activity of the upper and lower chambers of the heart. [1]
Can I exercise with heart block?
People with first-degree heart block often have few restrictions. With more severe types, talk with your doctor before exercising, because symptoms such as dizziness or fainting can make exercise unsafe until the block is treated.
How long does a pacemaker battery last?
Pacemaker battery life varies by device and how much you use it. Your care team will check the pacemaker and its battery at regular follow-up visits and plan any replacement.
Does heart block cause high blood pressure?
Not directly. However, some medicines used to treat high blood pressure, such as beta-blockers and calcium channel blockers, can cause or worsen heart block. [1]
What is Wenckebach block?
Wenckebach block is another name for Mobitz type I second-degree heart block, where the electrical signal takes progressively longer until one beat is dropped.
Can I use a microwave if I have a pacemaker?
Modern pacemakers are designed to resist everyday interference, and most household appliances are not a concern. Ask your care team for guidance for your device, and keep phones and similar electronics at least 6 inches away from it. [1]
What happens if third-degree heart block is not treated?
The heart may not pump enough blood. This can cause fainting and injuries from falls, heart failure or sudden cardiac arrest, which is why third-degree block almost always needs a pacemaker. [1]
Can heart block be prevented?
You cannot prevent every case, but managing blood pressure, treating heart disease, avoiding tobacco and reviewing medicines that slow the heart with your doctor can lower your risk.
What is bradycardia?
Bradycardia is a heart rate that is slower than normal. It is a common result of heart block.
Will I feel the pacemaker working?
Most people do not feel the electrical pulses from a pacemaker, although you may feel the device under the skin of your chest.
Can an EKG miss heart block?
A standard EKG records only a few seconds, so it can miss heart block that comes and goes. In that case, an ambulatory monitor or loop recorder that records for days or longer may be used. [1]
What is the vagus nerve's role in heart block?
An overactive vagus nerve can slow the heart's electrical signals and may cause or worsen a block, usually a mild one.
Related Reading
Electrocardiogram (EKG or ECG): Why It's Done, How to Prepare, What Happens and Results explains the EKG test that shows how electrical signals travel through your heart.
References
Cleveland Clinic. Heart Block. Cleveland Clinic. Last updated April 14, 2024. https://my.clevelandclinic.org/health/diseases/17056-heart-block
Cheng S, et al. Long-term outcomes in individuals with prolonged PR interval or first-degree atrioventricular block. JAMA. 2009;301(24):2571-2577. PMID 19549974. https://doi.org/10.1001/jama.2009.888
Blessberger H, et al. Monocenter Investigation Micra® MRI study (MIMICRY): feasibility study of the magnetic resonance imaging compatibility of a leadless pacemaker system. Europace. 2019;21(1):137-141. PMID 29986008. https://doi.org/10.1093/europace/euy143
Medical disclaimer
This article is for general educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified healthcare provider with any questions you may have about a medical condition. Never disregard professional medical advice or delay seeking care because of something you have read here. If you think you may have a medical emergency, call your doctor or emergency services immediately.
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