First-degree atrioventricular block

First-Degree Atrioventricular Block (AV Block)

An electrocardiogram (ECG), the primary tool used to diagnose first-degree AV block.

First-Degree Atrioventricular Block (AV Block) is a condition of the heart's electrical conduction system where the transmission of electrical impulses from the atria to the ventricles through the atrioventricular node (AV node) is slower than normal. It is the mildest form of heart block.

Pathophysiology

In first-degree AV block, every electrical impulse is conducted to the ventricles but with a delay. The delay occurs at the AV node, which normally acts as a gatekeeper to control the impulses between the atria and ventricles.

Symptoms

Typically, first-degree AV block does not cause any overt symptoms and is often discovered incidentally during an electrocardiogram (ECG) for another reason. It is usually not associated with any significant hemodynamic compromise.

Diagnosis

ECG showing first-degree AV block, characterized by a prolonged PR interval.

The diagnosis is made using an electrocardiogram (ECG) and is defined by a PR interval (the time from the onset of atrial depolarization to the onset of ventricular depolarization) of greater than 200 milliseconds.

Progression Risks

While first-degree AV block itself is typically benign, it may occasionally progress to more severe forms of heart block, such as second- or third-degree AV block, particularly in the presence of other heart conditions.

Epidemiology

First-degree AV block affects about 0.65-1.1% of the population. The incidence of new cases is approximately 0.13 per 1000 persons each year. It can occur in healthy individuals, particularly athletes, but is more common in the elderly or those with heart disease.

External Links

• American Heart Association - First-Degree Atrioventricular Block
• Mayo Clinic - Heart Block
  

First-degree atrioventricular block Resources
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