First-degree heart block

First-degree heart block is a type of heart block, a condition that affects the electrical conduction system of the heart. It is the mildest form of heart block and often does not cause any noticeable symptoms or require treatment.

Definition

First-degree heart block, also known as first-degree atrioventricular block or PR prolongation, is defined by a delay in the conduction of electrical impulses from the atria to the ventricles. This delay is reflected on an electrocardiogram (ECG) as a prolonged PR interval, which is the time between the start of the P wave (representing atrial depolarization) and the start of the QRS complex (representing ventricular depolarization).

Causes

First-degree heart block can be caused by a variety of conditions and factors. These include coronary artery disease, rheumatic heart disease, myocarditis, Lyme disease, and certain medications such as beta blockers and calcium channel blockers. It can also be a normal variant in some healthy individuals, particularly athletes.

Symptoms

Most individuals with first-degree heart block do not experience any symptoms. However, if the condition is caused by underlying heart disease or other medical conditions, symptoms related to those conditions may be present.

Diagnosis

The diagnosis of first-degree heart block is typically made based on the findings of an ECG. The key diagnostic feature is a PR interval of more than 200 milliseconds.

Treatment

Treatment for first-degree heart block is usually not necessary unless the condition is causing symptoms or is associated with significant underlying heart disease. In such cases, treatment is directed at the underlying condition.

Prognosis

The prognosis for individuals with first-degree heart block is generally good. However, in some cases, the condition can progress to more severe forms of heart block.