ECGChapter 6

Atrioventricular Blocks

First-Degree AV Block – pg. 61

• Delay in the conduction from the atria to the ventricles. With first degree blocks, every PR interval is >0.20 seconds or 5 boxes in length. Every “p” wave causes a “QRS” or every atria depolarization reaches the ventricles.

So what is this?

Second-Degree AV Block Type I (Mobitz Type I, or Wenckebach), pg. 62-63

P to QRS Ratio• The ratio may remain constant or vary. – Pg. 62-63

What’s This?

Second-Degree AV Block Type II (Mobitz Type II)

3:1

2:1

What is this?

Third-Degree AV Block

Third-Degree AV Block

• Complete dissociation between the atria and ventricles or complete heart block.

• Atria are depolarizing but not conducting to ventricles so another pacemaker must take over in the ventricles.

• True 3rd degree heart block will have the atria rate > the ventricular rate.

Idioventricular rhythm pacing the ventricles

Junctional escape rhythm pacing the ventricles

• Complete dissociation between the atria and ventricles or complete heart block.

• Atria are depolarizing but not conducting to ventricles so another pacemaker must take over in the ventricles.

• True 3rd degree heart block will have the atria rate > the ventricular rate.

AV Dissociation: Ventricular rate is faster than the arial rate. • Transient, non – lethal condition