This document discusses different types of heart block. Second degree heart block involves intermittent conduction of electrical impulses from the atria to the ventricles. Mobitz type I (Wenckebach) involves progressive lengthening of the PR interval followed by a blocked beat, while Mobitz type II involves sudden blocked beats without PR prolongation. Third degree heart block occurs when there is complete absence of conduction between the atria and ventricles. Treatment depends on the severity and type of heart block, ranging from monitoring to pacemaker implantation.

2. Definition
 Mechanism
 Significance
 Treatment


3. Second degree heart block implies
intermittent conduction
 Some impulses are conducted to
ventricles whereas others are not


4. Myocardial infarction
 Myocarditis
 Rheumatic fever
 Drugs i.e beta blockers and digitalis
 Hyperkalemia


5. Mobitz type I
 Mobitz type II
 2:1 block


6. Conduction defect in the AV node
 AV conduction time progressively
lengthens before a blocked beat


7. Progressive lengthening of PR interval
 One non-conducted P wave
 Next conducted beat has a shorter PR
interval than the preceding conducted
beat ,cycle repeats
 Normal QRS complexes


9. 
Mobitz type I is usually benign and
prognosis is good

10. Usually due to block within the bundle of
His
 Most beats are conducted but
occasionally there’s atrial contraction
without subsequent ventricular
contraction


11. PR interval remains constant
 Some P waves are not conducted( i.e
more P waves than QRS complexes)
 QRS complexes are wide


14. 
Risk of progression to complete heart
block is greater than type I

15. May represent as type I or type II block
 Two p waves to each QRS complex
therefore called 2:1 block


16. Asymptomatic Mobitz type I doesn’t
require any treatment
 Atropine for pt’s presenting with asystole
 pacemaker


17. No communication between atria and
ventricles
 Atrial contraction is normal but no beats
are conducted to the ventricles
 Ventricles are excited from depolarizing
focus within the ventricular muscle


18. Normal P waves
 Normal QRS complexes
 No orchestration between the Ps and
QRSs


19. Congenital
 Acquired:
MI
drugs( digoxin, beta blockers)
severe hyperkalemia
Infective endocarditis
acute rheumatic fever


20. Dual chamber permanent pacemaker
 Atropine is effective for early heart
blocks but trial of atropine while waiting
for pacer to be set up is acceptable in
third degree heart block
