First degree atrioventricular block
- William H Sauer, MD
William H Sauer, MD
- Associate Professor of Medicine
- University of Colorado School of Medicine
Atrioventricular (AV) block is defined as a delay or interruption in the transmission of an impulse from the atria to the ventricles due to an anatomic or functional impairment in the conduction system. The conduction disturbance can be transient or permanent, with conduction that is delayed, intermittent, or absent. Commonly used terminology includes:
●First degree AV block – Delayed conduction from the atrium to the ventricle (defined as a prolonged PR interval of >200 milliseconds) without interruption in atrial to ventricular conduction.
●Second degree AV block – Intermittent atrial conduction to the ventricle, often in a regular pattern (eg, 2:1, 3:2), or higher degrees of block, which are further classified into Mobitz type I (Wenckebach) and Mobitz type II second degree AV block.
●Third degree (complete AV) block – No atrial impulses conduct to the ventricle.
●High-grade AV block – Two or more consecutive blocked P waves.
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