First Time User? Sign Up Now
First Time User? Enroll now.
Home > Health Library > Heart Block
Heart block refers to an abnormality in the way electricity passes through the normal electrical pathways of the heart. The abnormality "blocks" the electrical impulse from continuing through the normal pathways and usually results in a slower heart rate.
Heart block can be caused by many things that affect the electrical system of the heart. Examples include:
Heart block is more common in older people and may be the result of age and a combination of factors listed above.
The electrical activity of the heart starts in the sinoatrial (SA) node in the upper chamber (atrium) and travels through the atrioventricular (AV) node to reach the lower chamber (ventricle). Heart block may occur at any point along this electrical pathway. Heart block of the AV node can be of several types, and a doctor generally can diagnose these by looking at the person's electrocardiogram (EKG, ECG).
First-degree AV block
In first-degree block, the electrical impulses take longer to travel between the upper chamber (atrium) and lower chamber (ventricle) of the heart. This type of heart rhythm may or may not be associated with a slow heart rate.
It does not usually require treatment. But this type of heart block may raise your risk of heart rhythm problems, such as atrial fibrillation.
Second-degree AV block
In second-degree heart block, some of the electrical impulses are blocked between the upper and lower chamber of the heart. These electrical impulses may or may not have a clear pattern. The blocking of the impulse can come and go, resulting in "dropped heartbeats." A second-degree type II block may progress to complete or third-degree heart block.
Second-degree heart block can be categorized into two types:
How second-degree AV block is treated can depend on the type and what is causing it. Treatment can also depend on your symptoms. If heart block doesn't cause symptoms, it may not be treated. Treatment may be a pacemaker. You and your doctor can decide what treatment is right for you.
Complete or third-degree block
In third-degree heart block, all of the electrical impulses are completely blocked between the upper and lower chambers of the heart. When this occurs, the atria and ventricles beat at completely different rates.
Complete heart block is caused by the aging process, medicines, heart attacks, infiltrative heart diseases (amyloidosis, sarcoidosis), and infectious diseases (endocarditis, Chagas disease). It may also occur after heart surgery and can be present from birth (congenital).
Complete heart block frequently causes symptoms of lightheadedness or fainting and usually requires the placement of a permanent pacemaker.
Bundle branch block can affect the heart's rhythm. The heart has structures, like wires, that are called bundle branches. They are part of the heart's electrical pathway. When a branch is diseased, it is called "blocked," because the electrical signals can't travel down the branch.
Some people with bundle branch block don't have any symptoms and don't need treatment. But when a block causes the heart to beat too slowly, it can cause symptoms such as tiredness and fainting spells. A pacemaker may be used to get the heartbeat back to normal.
Health Tools help you make wise health decisions or take action to improve your health.
Other Works Consulted
Cheng S, et al. (2009). Long-term outcomes in individuals with prolonged PR interval or first-degree atrioventricular block. JAMA, 301(24): 2571–2577.
Olgin JE, Zipes DP (2015). Specific arrhythmias: Diagnosis and treatment. In DL Mann et al., eds., Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 10th ed., vol. 1, pp. 748–797. Philadelphia: Saunders.
Current as of: April 9, 2019
Author: Healthwise StaffMedical Review: E. Gregory Thompson MD - Internal MedicineMartin J. Gabica MD - Family MedicineAdam Husney MD - Family MedicineRakesh K. Pai MD, FACC - Cardiology, Electrophysiology
Current as of:
April 9, 2019
Medical Review:E. Gregory Thompson MD - Internal Medicine & Martin J. Gabica MD - Family Medicine & Adam Husney MD - Family Medicine & Rakesh K. Pai MD, FACC - Cardiology, Electrophysiology
To learn more about Healthwise, visit Healthwise.org.
© 1995-2019 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.
10208 Cerny St.
Raleigh, NC 27617
4201 Lake Boone Trail
Raleigh, NC 27607
1505 SW Cary Parkway
REX Healthcare of Cary, Suite 300
Cary, NC 27511
2076 NC Highway 42 W.
Johnston Professional Plaza, Suite 100
Clayton, NC 27520
603 Beaman St.
Clinton, NC 28328
UNC REX Healthcare4420 Lake Boone TrailRaleigh, NC 27607, USA919-784-3100
Chosen for Excellence
Co-Worker & Physician Login
UNC Health Talk
Copyright 2019 UNC Health Care. All rights reserved.