Second-Degree AV Block · Mobitz I

PR intervals lengthen before a nonconducted P wave; the cycle then restarts.

Programmatically generated teaching example. Morphology and supporting values are simplified.

Typical rate: Ventricular rate below atrial rate
Regularity: Grouped beating
P waves: Regular atrial activity
PR interval: Progressively lengthens, then drops
QRS: Usually narrow

Sources and review status

This guide uses RhythmDock’s centralized educational definitions. See reference sources and limitations. Published September 13, 2026. Independent medical review is pending; this is not a clinical interpretation tool.