Bradycardia - signs of symptoms and causes

2021-03-16 12:00 AM

There are so many possible causes of bradycardia, so the specificity of the marker for a disease is low. If seen in a patient who should have a normal heart rate, it is usually likely a sign of a very serious underlying disease.


Heart rate <60 times / minute.


The causes of a slow heart rate are too many to list. These include, but are not limited to:


Heart attack.

Sinus node disease.

Drugs (eg beta-blockers, calcium channel blockers, amiodarone).


Atrioventricular node disease.

Block heart.

Heart degeneration / aging.

Less common

Lack of oxygen cells.


Electrolyte imbalance.

Inflammatory diseases (eg systemic lupus erythematosus).

Sleep apnoea due to obstruction.

Iron pigmentation.

Congenital abnormality.


The individual mechanisms for each pathology that cause bradycardia are numerous. Mechanically, bradycardia is caused by:

Interrupt or interrupt the conduction of electrical impulses in the heart or increased the effects of the vague nerve on the heart. This disorder may manifest in the sinoatrial (SA) node, atrioventricular (AV) node, His bundle, or right or left arm.

Heart attack

Can cause heart block, especially if the right coronary (enlarged sinus node and atrioventricular node in most normal people) is blocked. Reduced blood flow to the nodes causes ischemia, and thus dysfunction of the sinoatrial and atrioventricular nodes.

Lack of oxygen cells

Hypoxemia for any reason (although usually due to ischemia) can depolarize the sinoatrial node potential, slow heart rate, and severe hypoxia, which completely stops pacing.

Sinus node disease

Damage or degeneration of the sinus node leads to many problems such as an irregular heart rate or subsequent discontinuation or obstruction. All of these abnormalities can cause bradycardia.

Block heart

Damage or disruption at the atria, atrioventricular node, the bundle of His or branch can slow cardiac conduction and cause heart block.

Electrolyte imbalance

Potassium, in particular, affects myocardial membrane activity as well as the sinoatrial and atrioventricular nodes. Significant changes in potassium levels will affect membrane polarization and heart rate. Bradycardia is associated more with hyperkalemia than hypokalaemia, although both can occur.

Iron pigmentation

Iron infiltrates damage both the heart muscle cells and the conduction system, have been shown to slow heart rate.


The drug works by several mechanisms that contribute to slow heart rate:

Calcium channel blockers inhibit Ca2 + flow, causing Ca2 + to slowly enter the cell during the sinus node action potential phase.

Beta-blockers and muscarinic systems act directly on autoreceptors, block sympathetic activity or enhance parasympathetic activity.

Digoxin increases the effects of vagus nerve on the AV node that slows the heart rate.


There are so many possible causes of bradycardia, so the specificity of the marker for a disease is low. However, if found in a patient who should have had a normal heart rate, it is often likely that it is a sign of a very serious underlying disease that should definitely be examined immediately.