4. Normal conduction pathway:
SA node -> atrial muscle -> AV node -> bundle of His ->
Left and Right Bundle Branches -> Ventricular muscle
5.
6.
7.
8.
9. DEFINITION
Heart block is an abnormal heart rhythm where
the heart beats too slowly (bradycardia).
In this condition, the electrical signals that tell the heart to
contract are partially or totally blocked between the upper
chambers (atria) and the lower chambers (ventricles).
10. TYPES
• They are further classified as,
First degree heart block ( first degree AV
block)
second degree heart block (second degree AV
block)
third degree heart block (third degree AV
block)
11.
12. FIRST DEGREE HEART BLOCK
• First-degree atrio-ventricular block (AV block), or PR
prolongation, is a disease of the electrical conduction
system of the heart in which the PR interval is
lengthened beyond 0.20 seconds.
13.
14. The following are the most common causes of first-
degree AV block:
• Intrinsic AVN disease
• Acute myocardial infarction (MI), particularly acute
inferior wall MI
• Myocarditis
• Electrolyte disturbances (eg, hypokalemia,
hypomagnesemia)
• Drugs (especially those drugs that increase the refractory
time of the AVN, thereby slowing conduction)
15. First Degree Heart Block (1º)
• SA Node – normal
• Normal P wave
• AV Node conducts more slowly than normal
• Prolonged PR Interval
• Rest of conduction is normal
• Normal QRS
18. Second Degree Heart Block (2º)
Mobitz Type I
(Wenkebach)
• Conduction through the AV Node – progressively delayed until
a drop beat is seen
19. Second-degree atrio-ventricular (AV) block, or
second-degree heart block, is characterized by
disturbance, delay, or interruption of atrial impulse
conduction through the AV node to the ventricles.
21. Second Degree Heart Block (2º)
Mobitz Type I
(Wenkebach)
• PR Interval prolongs with each beat until a dropped beat
is seen
• The PR Interval is NOT constant
• After each dropped beat, the PR interval is normal and
the cycle starts again
22. Second Degree Heart Block (2º)
Mobitz Type I
(Wenkebach)
PR PR PR DROPPED BEAT
23. Significance
• Clinical Significance
• Slight symptoms e.g.. Lethargy,
Confusion
• Treatment
• Pacemaker if during day &/or
symptoms
• No treatment if at night
• Note – this can progress to 3º Heart Block
24. Second Degree Heart Block (2º)
Mobitz Type II
• Conduction through the AV node is constant.
• PR interval is normal and constant
• Occasionally a dropped beat is seen
27. Third Degree Heart Block (3º)
(Complete)
• Complete failure of the AV Node
• No impulses from Sinus Node will pass through to the
ventricles
• Some part if the conducting system will take over as
pacemaker of the heart (even a myocardial cell 10-15
bpm)
28. Third-degree atrioventricular (AV) block, also referred to
as third-degree heart block or complete heart block, is a
disorder of the cardiac conduction system where there is
no conduction through the atrioventricular node.
29. Third Degree Heart Block (3º)
(Complete)
• P wave rate – normal
• Ventricular rate – slow
• Ventricular complex may be broad
• Idioventricular rhythm
• Complete dissociation between P waves & QRS
31. Significance
• clinical significance
• Symptoms LOC, Confusion,
Dizziness, Low BP
• Can lead to standstill, VT or VF
(stokes Adams)
• Treatment - pacemaker
32. NURSING MANAGEMENT
1. Assess the high risk patients
2. Monitor ECG of the patient
3. Assess the family history of heart disease
4. Assess the history of smoking and alcoholism
5. Monitor lab values frequently especially serum
cholesterol levels.
6. Assess for CAD
7. Monitor vital signs
8. Instruct to avoid high fat and oil rich diet
