Heart-block symptoms depend on the type of heart block present, and the degree to which the electrical current is interrupted.
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. This abnormally low heart rate can cause the brain and other organs to become oxygen-deprived, which can lead to symptoms such as:
- Shortness of breath
- Chest pain
- Memory difficulties
- Quickly tiring during physical activity
The lower the heart rate, the more severe the symptoms will be.
Causes and Risk Factors
A variety of factors can cause heart block. Although the condition is most commonly diagnosed in older patients, first-degree heart block is common among well-trained athletes, teenagers and young adults.
Drugs, particularly ones that slow conduction of the electrical impulses through the atrioventricular node — such as beta blockers, diltiazem, verapamil and amiodarone — can increase the risk of heart block.
Having a highly active vagus nerve may also put patients at an increased risk of a heart block. This nerve is responsible for controlling the heart rate, moving food through the intestinal tract (gastrointestinal peristalsis), sweating, and several muscle movements in the mouth.
A history of certain diseases that affect the heart — including rheumatic fever and sarcoidosis — or other diseases that are caused by structural defects in the heart can increase a patient’s risk of developing heart block.