First-Degree AV Block

First-Degree AV Block is a condition that affects the heart's electrical system, specifically the way electrical signals travel from the upper chambers (atria) to the lower chambers (ventricles). It involves a delay in the electrical signal passing through the atrioventricular (AV) node, which can slow down the heartbeat slightly. This delay usually does not cause symptoms or serious health problems but can be detected on an electrocardiogram (ECG). The heart continues to beat in a regular rhythm, but the signal takes longer than normal to reach the ventricles. This condition is often found during routine heart tests and may be related to aging, medications, or other heart conditions. It primarily affects the cardiac conduction system and the overall timing of the heartbeat.

First-Degree AV Block is defined as a prolonged conduction time through the atrioventricular node, resulting in a consistently prolonged PR interval greater than 200 milliseconds on the electrocardiogram. The core pathology involves delayed conduction without interruption of the atrial impulse to the ventricles, typically due to impaired AV nodal conduction. Common causes include increased vagal tone, medications such as beta-blockers or calcium channel blockers, ischemic heart disease, or intrinsic conduction system disease. Although it is usually asymptomatic and benign, it may indicate underlying cardiac pathology or predispose to higher degrees of AV block. The major clinical significance lies in its role as a marker of conduction system disease and its potential progression to more severe blocks. It is important to distinguish this from other AV blocks that cause dropped beats or irregular ventricular response.