It is a partial or complete interruption of
impulses transmission from Atrium to
Acute myocardial Infarction:
specially Inferior MI .
Medications : Beta Blockers ,
calcium channel blockers or
Inflammation : myocarditis ,
Rheumatic fever or Lupus .
Infections :Toxoplasmosis .
Causes of permanent block
Acute myocardial infarction :
specially Anterior MI .
Degeneration of Conduction
system due to : advanced age or
cardiac calcification of mitral or
aortic valve .
Latrogenic damage : due to
arrhythmia Ablation at the site of
AV Junction or Valve surgery
(Tricuspid valve replacement) .
According to relation between Atrium andVentricle ,
we can detect three degrees of AV heart block :
▪ First Degree Heart Block :
slowing of Conduction .
▪ Second Degree Heart Block :
intermittent interruption of conduction
subtype into :
▪ Mobitz Type I .
▪ Mobitz Type II .
▪ Third Degree ( Complete ) Heart Block :
Complete interruption of conduction .
It is not consider complete block ,it is just slow
down of impulses that come from SA node
more than the normal .
ECG Manifestation :
Prolongation of PR interval more than 0.2 second or
more than 5 small squares .
Constant PR interval from beat to another .
Regular Rhythm .
Normal Rate or slightly slow .
This problem occur at the level of AV node itself .
It also is not considered a complete block .
ECG Manifestations :
It is characterized by progressive prolongation of PR
interval until dropped QRS , then the cycle start again .
Constant PP interval .
Irregular Rhythm .
Normal or slightly slow Rate .
This type of block occur below AV node at the level of Hiss
Also is considered incomplete but high risk to be
Some of electrical impulses are unable to reach ventricles .
ECG Manifestation :
Recurrent appearance of non-conducted P waves which
is blocked and not followed by QRS complex ( indicate
to block of impulses to reach ventricle ) .
PR interval and PP interval are constant .
QRS usually normal but sometimes become Wide .
Characterized by Atrio-ventricular dissociation .
This blockage level is infra-nodal ( Bilateral Bundle
Branches ) .
Atrial and ventricular activities are unrelated due to
complete block of electrical impulses to reach the
Another pacemaker distal to
the block takes over in order to
activate the ventricles or
ventricular standstill will occur.
ECG manifestation :
Dissociation between P wave and QRS
P wave may overlap on T wave or QRS complex .
PR interval is not constant
Rate usually less than 40 .
QRS complex usually wide and sometimes normal .
Usually first degree and sometimes second degree
are asymptomatic .
The most common signs and symptoms :
Sever Bradycardia .
Syncope ( fainting ) .
Chest pain .
General Management :
Cardiac monitoring : for close observation .
Oxygen supply : to Manage de-saturated patients .
IV Line :To support blood pressure with fluids .
Atropine standby : to treat bradycardia specially
incomplete degrees .
Management of heart block depend on symptoms
First degree heart block :
this type usually is asymptomatic and not indicated for treatment :
Close observation of Hemodynamic status .
Discontinue of some medication that cause bradycardia such as :
▪ Beta-blockers : Concor
▪ Digoxins : Lanoxine
▪ calcium channel blockers : Diltiazem .
Second Degree and Complete heart block :
Usually these degrees are associated with sever bradycardia which can be
treated by atropine .
Associated conditions should be treated correctly such as :
▪ Myocardial infarction.
▪ Electrolyte disturbance (hyperkalemia).
▪ Digitals intoxication.
Transvenous temporary pacemaker is indicated for pt with sever
bradycardia who has no effect of Atropine administration (For 24 hours : 48
Transcutanous permanent pace-maker is indicated for
chronic AV block .
Nursing priorities :
Decrease cardiac output related to failure of the heart to pump
enough blood to meet metabolic needs of the body as manifested by
Acute chest Pain related to decrease blood flow to myocardium
through coronary arteries .
Ineffective Tissue perfusion related to decrease cardiac output as
manifested by pt syncope .
Fatigue related to increase hypoxic tissue and slowed removal of