atrioventricular blocks - bmh/tele
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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.
www.madsci.com/manu/ekg_rhy.htm