First degree atrioventricular block

First-degree atrioventricular block
Synonyms	First-degree AV block
Pronounce	N/A
Specialty	N/A
Symptoms	Often asymptomatic
Complications	Progression to higher degree AV block
Onset
Duration
Types	N/A
Causes	Vagal tone, medications, myocardial infarction
Risks
Diagnosis	Electrocardiogram
Differential diagnosis	N/A
Prevention	N/A
Treatment	Often none required
Medication	N/A
Prognosis	Generally good
Frequency
Deaths	N/A

First-degree atrioventricular block (also known as first-degree AV block) is a type of heart block where the electrical conduction between the atria and ventricles of the heart is delayed but not interrupted. It is the mildest form of atrioventricular block and is often asymptomatic.

Pathophysiology

First-degree AV block occurs when there is a delay in the conduction of electrical impulses from the sinoatrial node through the atrioventricular node to the ventricles. This delay is reflected as a prolonged PR interval on an electrocardiogram (ECG). The PR interval is considered prolonged if it is greater than 200 milliseconds.

The delay in conduction is usually due to increased vagal tone, which can be physiological, or due to pathological conditions affecting the AV node. These conditions can include fibrosis, ischemia, or the effects of certain medications such as beta-blockers, calcium channel blockers, and digoxin.

Clinical Presentation

Most individuals with first-degree AV block are asymptomatic and the condition is often discovered incidentally during an ECG performed for another reason. In rare cases, patients may experience symptoms such as fatigue, dizziness, or syncope, but these are more commonly associated with higher degrees of AV block.

Diagnosis

The diagnosis of first-degree AV block is made using an electrocardiogram. The hallmark of first-degree AV block is a prolonged PR interval greater than 200 milliseconds. The rest of the ECG is typically normal, with regular P waves and QRS complexes.

Management

In most cases, first-degree AV block does not require any specific treatment. Management focuses on identifying and addressing any underlying causes, such as discontinuing or adjusting medications that may contribute to the condition. Regular monitoring may be advised to ensure that the block does not progress to a higher degree.

Prognosis

The prognosis for individuals with first-degree AV block is generally excellent. It is considered a benign condition, especially when it occurs in isolation without other cardiac abnormalities. However, there is a small risk of progression to higher degrees of AV block, particularly in the presence of underlying heart disease.

See Also

• Second-degree atrioventricular block
• Third-degree atrioventricular block
• Electrocardiography

External Links

• [Link to relevant cardiology resources]

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