second-degree atrioventricular (AV) block

Classification

2 types of 2nd degree AV block are recognized:

• type 1 2nd degree AV block
• type 2 2nd degree AV block

The distinction is clinically important as prognostic implications & management differs.

Pathology

• some of the atrial impulses are conducted to the ventricle at times when the ventricle is refractory to depolarization (technically, when some of the atrial impulses are not conducted to the ventricle at times when the AV node is not refractory)

Diagnostic procedures

• electrocardiogram
  • dropped beats, P wave not followed by QRS
  • progressive prolongation of PR interval (Mobitz type 1)
  • constant PR interval in conducted beats (Mobitz type 2)

Management

• Mobitz type 2 AV block may precede 3rd degree AV block

More general terms

• atrioventricular (AV) block

More specific terms

• Mobitz type 1 second-degree atrioventricular (AV) block (Wenckebach)
• Mobitz type 2 second-degree atrioventricular (AV) block