Atrioventricular BlocksAtrioventricular Blocks

Delayed electrical impulses that originate from the SA node.

I Quit!!!

AV BlocksAV BlocksCauses:

• Underlying heart conditions

• Certain drugs

• Congenital anomalies

• Conditions that cause disruption in the cardiac conduction system

AV BlocksAV BlocksConditions that cause TEMPRORARY

disruption in the cardiac conduction system:

MI of the inferior wallDigoxin Toxicity

Acute MyocarditisCalcium Channel BlockersBeta-adrenergic Blockers

Cardiac Surgery

AV BlocksAV BlocksConditions that cause PERMANENT

disruption in the cardiac conduction system:

Changes Associated with AgingMI of the anteroseptal wallCongenital Abnormalities

CardiomyopathyCardiac Surgery

Types of AVB’sTypes of AVB’s1st Degree AV Block

2nd Degree AV Blocks:

Type I or Mobitz 1 or Wenckebach

Type II or Mobitz 2

3rd Degree AV Block

or Complete AV Block

11stst Degree AV Block Degree AV BlockCauses:

Increased vagal tone

Hyperkalemia

Amiodarone, BB’s, CCB’s, or Digitalis

Acute Rheumatic Fever

Myocarditis

Temporary after an inferior wall MI

Degenrative changes associated with aging

Idiopathic

11stst Degree AV Block Degree AV Block

Rhythm: Regular or Irregular (depends on underlying)

Rate: 60 – 100 bpm (depends on underlying); can be faster or slower

P waves: Upright & uniform

PRI: > 0.20 sec (constant)

QRS: usually narrow (< 0.12 sec)

1st Degree AVB

22ndnd Degree AV Block Type I Degree AV Block Type I

Causes:Increased vagal tone

HyperkalemiaAmiodarone, BB’s, CCB’s, or Digitalis

Acute Rheumatic FeverMyocarditis

Temporary after an inferior wall MI

22ndnd Degree AV Block Type I Degree AV Block Type I

A.K.A. - Wenckebach or Mobitz 1

Rhythm: Irregular in a pattern of grouped beats

Rate: atrial normal; ventricular slower than normal

P waves: Upright & uniform; some P waves not followed by QRS complexes

PRI: becomes progressively longer until one P wave is not followed by a QRS complex.

QRS: usually narrow (< 0.12 sec)

2nd Degree AVB Type I

22ndnd Degree AV Block Type II Degree AV Block Type II

Causes:

Anterior wall MI

Degenerative changes related to aging

22ndnd Degree AV Block Type II Degree AV Block Type II

A.K.A. - Mobitz 2Rhythm: Regular or Irregular (depends on underlying)

Rate: atrial usually normal; ventricular usually slow

P waves: Upright & uniform; more P’s than QRS’s

PRI: Normal; sometimes > 0.20 sec

QRS: Narrow (< 0.12 sec)

Emergency Pacemaker (if symptomatic)

Complete AV BlockComplete AV BlockComplete “communication breach” between

the SA node and ventricular conduction known as AV dissociation

The block may occur from within the AV junction or at the bundle branches, a lower

area of the conduction system

This will determine the ventricular rate and the morphology of the QRS complex

3rd Degree AVB

Complete AV BlockComplete AV Block

If the block occurs at the AV junction, the firing rate will usually be 40-60 bpm

with a narrow QRS complex

If the block is in the bundle branches, then the rate will usually be 20-40 bpm

with a wide QRS complex

Complete AV BlockComplete AV Block

Ventricular rate is independent of the atrial rate (60-100)

Some P waves may be hidden within the QRS or T wave

PRI will vary greatly with no apparent pattern (unlike Mobitz 1 and Mobitz 2)

Complete AV BlockComplete AV BlockCauses Temporary Complete AV Block:

Inferior Wall MI, Increased vagal tone, drug effects, hyperkalemia, acute rheumatic fever,

or myocarditis

Causes Permanent Complete AV Block:

Acute Anterior Wall MI

Chronic Degenerative Changes related with Aging

Complete AV BlockComplete AV Block

Emergency Pacemaker (if symptomatic)

Rhythm: Regular or Irregular (depends on underlying)

Rate: atrial usually normal; ventricular usually slow

P waves: Upright & uniform; more P’s than QRS’s

PRI: None; no correlation between P’s and QRS’s

QRS: usually narrow (< 0.12 sec); can be wide

Complete AV BlockComplete AV Block

Complete AV Blovk with a Junctional Focus:

QRS is narrow (rate 40-60)

Complete AV BlockComplete AV Block

Complete AV Block with a Ventricular Focus:

QRS is wide (rate 20-40)

TIME TO WORKOUT!!!TIME TO WORKOUT!!!

ReferencesReferencesBeverage, D. Haworth, K., Labus, D. Mayer, B. H., & Munson, C.

(2005). ECG interpretation made incredibly easy, (3rd ed.). Ambler, PA: Lippincott, Williams, & Wilkins.

Chernecky, C., et al. (2002). Real world nursing survival guide: ECG’s & the heart. United States of America: W. B. Saunders Company.

Huff, J. (2006). ECG workout: Exercises in arrhythmia interpretation (5th ed.). United States of America: Lippincott, Williams & Wilkins.

Walraven, G. (1999). Basic arrhythmias (5th ed.). United States of America: Prentice-Hall, Inc.

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