AVnodal

AVnodal is a term used in electrophysiology to denote the atrioventricular nodal region and its conduction properties, the part of the heart's electrical system that synchronizes atrial and ventricular activity. The AV node sits on the atrial septum, near the coronary sinus ostium, and acts as the principal gateway for impulses traveling from the atria to the ventricles. By slowing conduction, it creates the PR interval and provides a necessary delay to optimize ventricular filling and coordinate myocardial contraction.

Anatomy and conduction: The node comprises compact nodal tissue and transitional cells. It demonstrates decremental conduction and autonomic modulation, with sympathetic input increasing conduction velocity and parasympathetic input decreasing it.

Clinical significance: AVnodal conduction abnormalities are central to several conditions. First-degree AV block reflects prolonged AV nodal conduction. Mobitz type I AV block represents progressive slowing within the AV node. AV nodal reentrant tachycardia (AVNRT) is a common arrhythmia arising from reentry within the AV nodal region. Therapeutic approaches include medications that affect AV nodal conduction (beta-blockers, calcium channel blockers) and catheter ablation targeting slow-pathway tissue to treat AVNRT. In some cases, AV nodal block may necessitate pacing.

History and terminology: The AV node was identified in the late 19th and early 20th centuries as part of mapping the heart's conduction system. The term AVnodal is used in literature and clinical notes as a shorthand for the nodal region and its conduction properties, though most formal references use "AV node" or "atrio-ventricular node."

See also: atrioventricular node, conduction system, AVNRT, AV block.