Many diseases affect the heart, but one lesser-known condition is heart block. This is causedd by issues with the electrical workings of the heart. This article will explore everything from causes to treatments, risk factors, and symptoms of this common condition in people with pre-existing heart conditions.
Electrical signals keep the heart beating frequently and regularly. These signals are generated by cells within the heart itself.Sometimes there can be issues with this system, causing heart block, of which there are three main types. Symptoms such as dizziness, fatigue, and shortness of breath are some of the main signs that you may have a heart block, a consequence of your heart not being able to pump enough blood around your body.
Find out more about the three types of heart block, their causes, and how to reduce your risk of developing them. Learn about the signs and symptoms and, importantly, when and if you need to contact a doctor.
Overview
The heart has a group of cells called the SA (sinoatrial) node that generates an electrical signal, controlling how often the heart beats. There are four chambers in the heart: two upper ones called the atria and two lower ones called the ventricles. The SA node is in the right atrium, and electrical signals move downward from the atria to the ventricles through another node called the AV (atrioventricular) node, which connects the electrical signal. If you have a heart block, there is a problem with the electrical connection traveling through the AV node. Although this doesn't mean your heart will stop beating altogether, it can cause it to beat much slower than usual or even skip a beat, leading to the body's organs not receiving enough oxygen.
Types of heart block
There are three main types of heart block:
- First-degree heart block
- Second-degree heart block (of which there are two subtypes)
- Third-degree heart block
First-degree heart block, caused by the electrical impulses moving from the SA node to the AV node slower than usual, causes the heart to contract less frequently and is the mildest form of heart block.
Second-degree heart block is caused by the electrical signals from the SA node being blocked at the AV node every so often, with two subtypes called Mobitz type 1 and Mobitz type 2. Mobitz type 1 is the less severe type caused by the electrical signals getting further apart with each beat, causing your heart to beat slower until a beat skips altogether. In Mobitz type 2, not all of the electrical signals from the SA node reach the AV node, which causes your heart to beat slower than usual but also irregularly.
In a third-degree heart block, no electrical signals from the SA node reach the AV node, which can lead to the ventricles trying to generate their beat. This causes the heart to beat irregularly and is the most severe type of heart block, making it challenging for your heart to pump blood to and around the body. Third-degree heart block is also called complete heart block.
Causes of heart block
The two most common causes of heart block are heart attacks and aging. As the fibres that conduct electricity in your heart weaken, their ability to connect the electrical signals from the top to the bottom of the heart becomes less efficient. Conditions that can damage these heart fibres or weaken the heart muscles can also cause heart blocks, such as coronary artery disease, certain cancers, some lung conditions, thickening of the heart muscle, heart surgery, or any inflammation of the heart.
Electrolyte problems are problems with concentrations of specific molecules in the blood, with high potassium levels resulting in heart block. Some medications that slow your heart rate can also cause heart block. All the reasons listed above are acquired, meaning they develop through life. Heart block can also be congenital, meaning you can be born with it if your mother had certain diseases during pregnancy.
Signs and symptoms of heart block
First-degree heart block does not usually have any obvious clinical signs or symptoms unless an electrocardiogram (ECG) is carried out and shows a slightly slower-than-normal heart rate.
The second-degreee and third-degree heart block have similar symptoms of:
- Dizziness, fainting
- Chest pain
- Feeling tired
- Shortness of breath
- Palpitations
- Irregular heartbeat
Management and treatment for heart block
There is treatment available for all types of heart block. With first-degree heart block, treatment is generally not necessary. However, in second-degree heart block, especially in Mobitz type 2, you may need a pacemaker, which is a small device implanted under the skin of the chest that sends electrical signals to your heart to help it beat regularly.
In a third-degree heart block, a pacemaker is generally required, either temporarily or permanently. Changing medications or treating the underlying cause of the heart block may also be a ways to manage symptoms. Symptoms will vary from person to person, and your cardiologist will determine the best course of treatment for you.
Diagnosis of heart block
As mentioned previously, an electrocardiogram (ECG) is one way to test for heart block. An ECG records the rate and intensity of your heartbeats and can be used to diagnose all three types of heart block.
An implantable loop recorder, another electrical device, is sometimes used to measure your heart rate for up to five years. It is a thin tube injected under the skin of your chest. Overall health and medical history, including a family history of heart block or heart disease, are vital factors in determining whether someone has a heart block. A physical examination is also nearly always conducted to diagnose heart block.
Risk factors
Although heart block can be congenital, some common risk factors include:
- Older age
- Heart attack or coronary heart disease
- High potassium levels
- Advanced kidney disease
- Medicines that slow the heart rate, such as beta-blockers
- After heart surgery
- Autoimmune disease
- High blood pressure
- Underlying medical conditions such as diabetes or thyroid disorders
Complications
Complications of heart block are serious and can be life-threatening. These include:
- Heart failure
- Arrhythmia (irregular heartbeat)
- Heart attack
- Sudden cardiac arrest
- Low blood pressure
- Damage to internal organs
- Fainting with injury
FAQs
How can I prevent heart block?
Prevention of congenital heart block is sometimes possible if the pregnant person can take medication for the specific disease that will reduce the risk of heart block in their baby. Ultimately, it is the management of the risk factors that will aid in preventing heart block.
Not smoking, exercising regularly, and eating a well-balanced diet are a few lifestyle changes that can also help. Additionally, reviewing your medication with a healthcare professional and making changes if needed can reduce your risk of heart block.
How common is heart block?
First-degree and Mobitz type 1 heart blocks are uncommon but not rare, with an estimated 0.5–2% of adults living healthy lifestyles with these types of heart blocks. Mobitz type 2 is rare in the general population but more common in people with pre-existing heart conditions.
An estimated 1 in 30 people with heart failure will develop Mobitz type 2 heart block. Third-degree heart block is a common complication of heart disease, particularly in people over 70. Congenital third-degree heart blocks are rare, occurring in 1 in every 20,000 births.
When should I see a doctor?
Although the symptoms of heart block are also common symptoms of other conditions, you should see your doctor if you feel:
- Dizzy or faint
- Chest pain
- Racing heartbeat or skipped heartbeat
- Weakness
- Shortness of breath
- Swollen feet, ankles, or legs
Additional check-ups may be required if there is a family history of heart block or other risk factors, such as high blood pressure or heart disease, to monitor heart health.
Summary
The main symptoms of heart block include dizziness and fatigue, and if you experience irregular heartbeats, you should contact your doctor. Most treatments involve a pacemaker, and information on living with one can be found on the BHF website. Exercise, a healthy diet, and not smoking can help reduce your risk of developing heart disease. Overall, heart blocks are rare, but with appropriate treatment, the outlook for all types of heart blocks is good.
References
- Mitchell LB. Overview of heart block - heart and blood vessel disorders [Internet]. Merck Manuals Consumer Version. Merck Manuals; 2023 [cited 2023Apr20]. Available from:
- Conduction disorders [Internet]. National Heart Lung and Blood Institute. U.S. Department of Health and Human Services; [cited 2023Apr20].
- Heart conduction disorders [Internet]. www.heart.org. 2023 [cited 2023Apr20].
- 2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay [Internet]. Heart Rhythm Society. [cited 2023Apr20]. Available from: https://www.hrsonline.org/guidance/clinical-resources/2018-accahahrs-guideline-evaluation-and-management-patients-bradycardia-and-cardiac-conduction
