First degree AV block
First-degree atrioventricular block (First-degree AV block) is a type of heart block in which there is a delay, but not an interruption, in the transmission of electrical impulses between the atria and the ventricles. This condition is identified on an electrocardiogram (ECG) by a prolonged PR interval of more than 200 milliseconds. Despite the delay, every electrical impulse from the atria is conducted to the ventricles, distinguishing it from more severe forms of AV block.
Causes[edit | edit source]
First-degree AV block can be caused by a variety of factors, including:
- Increased vagal tone
- Medications such as beta-blockers, calcium channel blockers, and digoxin
- Myocardial infarction
- Cardiomyopathy
- Lyme disease
- Electrolyte imbalances
Symptoms[edit | edit source]
Most individuals with first-degree AV block are asymptomatic and the condition is often discovered incidentally during an ECG for another reason. When symptoms do occur, they may include:
- Fatigue
- Dizziness
- Lightheadedness
Diagnosis[edit | edit source]
The diagnosis of first-degree AV block is made by observing a PR interval of more than 200 milliseconds on an ECG. The ECG will show each P wave followed by a QRS complex, indicating that all atrial impulses are conducted to the ventricles, albeit with a delay.
Treatment[edit | edit source]
In most cases, first-degree AV block does not require treatment. Management focuses on addressing any underlying conditions or modifying medications that may contribute to the block. Continuous monitoring may be recommended for individuals with symptoms or those who are at risk of progressing to higher degrees of AV block.
Prognosis[edit | edit source]
The prognosis for individuals with first-degree AV block is generally good, especially when there is no underlying heart disease. However, it is important to monitor for progression to more severe forms of AV block, which can require intervention.
See also[edit | edit source]
- Atrioventricular block
- Electrocardiogram
- Heart block
- Second-degree atrioventricular block
- Third-degree atrioventricular block
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