The signs of heart block depend on the degree to which the electrical current is interrupted or blocked.
First-degree heart block may produce no noticeable symptoms.
In second-degree heart block, the heartbeat may be slow, irregular or both.
In third-degree heart block, the ventricles (lower chambers) beat very slowly — less than 50 beats per minute or even as slowly as 30 beats per minute. With this condition, the person may feel tired, dizzy or faint. The lower the heart rate, the more severe the symptoms will be.
Causes and Risk Factors
A variety of factors can cause heart block including:
- Age. Most types of heart block are more common among older people.
- Drugs, particularly ones that slow conduction of the electrical impulses through the atrioventricular node, such as beta-blockers, Diltiazem, Verapamil and Miodarone.
- Fitness level. First-degree heart block is common among well-trained athletes, teenagers and young adults.
- Having a highly active vagus nerve.
- Having had certain diseases, including rheumatic fever, sarcoidosis that affects the heart or other diseases that are caused by structural defects in the heart.