ECG: Conduction Block

1. ECG OF THE WEEK
PROF.VIJAYARAGHAVAN’S UNIT
M 7
BHARGAVI.K

2. HISTORY IN BRIEF
27 YR OLD FEMALE P2L2A2 WITH C/O
BREATHLESSNESS AT REST ON/OFF
FOR 1 MONTH.
C/O SWELLING OF LEGS FOR 20
DAYS.
COUGH WITH EXPECTORATION FOR
15 DAYS.
CONDITION: PALLOR, BPPE+,B/L
CREPTS+, SM + TA.

4. INTERPRETATION
12 leaded ecg showing a complete heart
block-AV DISSOCIATION
Atrial rate-100:ventricular rate:67-68/min
RAD
PR INTERVAL CANNOT BE COMMENTED
QRS-BROAD N WIDE
RBBB LIKE,ST DEPRESSION N T
INVERSION V1-V4.

6. Rhythms Produced by Conduction Block
AV Block (relatively common)
1
st
degree AV block
Type 1 2
nd
degree AV block
Type 2 2
nd
degree AV block
3
rd
degree AV block
SA Block (relatively rare)

7. Causes
Ischemic heart disease, cardiomyopathy and
degenerative changes
Drugs that depress AV conduction,DIGITALIS
TOXICITY
Myocardial infarction, infiltration (e.g., tumor)
Trauma (e.g., surgery; therapeutic ablation)
Lev disease: fibro calciferous involving aortic valve
extending to conducting sys
Lenegres disease: sclero degenarative process
involving conducting system
CHAGAS DISEASE
Congenital abnormalities

8. Congenital Acquired
ISOLATED
HEREDITARY
CONNECTIVE TISSUE
QRS 40-50 bpm
QRS DURATION
NORMAL
RATE ^WITH
ATROPINE
PROXIMAL BLOCK
PACE MAKER
MANDATORY
IWMI/AWMI
LEVE’S
LENEGRE
QRS 20-30bpm
PROLONGED
NOT SO
DISTAL
NOT SO

9. FIRST-DEGREE HEART BLOCK
OCCURS WHEN THERE IS A PARTIAL
INTERRUPTION ANYWHERE IN THE ATRIAL OR
AV JUNCTIONAL CONDUCTION SYSTEM.
THE IMPULSE IS EVENTUALLY CONDUCTED
BUT IS DELAYED.
EKG Characteristics:Prolongation of
the PR interval, which is constant
All P waves are conducted

10. MOBITZ I HEART BLOCK
 MOBITZ I ( WENCKEBACH OR SECOND-DEGREE
HEART BLOCK, TYPE I).
PROGRESSIVE BLOCK.
IMPULSE FROM THE ATRIA IS INTERRUPTED AT THE
AV JUNCTION.
(1)The P-R interval becomes longer and longer
(2)The R-R interval gets shorter and shorter.
THE INTERRUPTION BECOMES LONGER WITH EACH
IMPULSE DELAYING DEPOLARIZATION OF THE
VENTRICLES UNTIL A COMPLETE INTERRUPTION
BLOCKS THE IMPULSE.

11. II
Bloc
k
P P P PP
Second Degree AV Block - Type I
(Wenkebach or Mobitz I Block)

12. MOBITZ II HEART
BLOCK
OCCURS DUE TO AN INTERMITTENT
INTERRUPTION NEAR OR BELOW THE
AV JUNCTION.
INTERRUPTION IS NOT
PROGRESSIVE, BUT OCCURS
SUDDENLY
P WAVES BEFORE EVERY QRS
COMPLEX AND ALL ARE THE SAME
SIZE AND SHAPE.

13. Second Degree AV Block -
Type II
P P P P P
Block

14. THIRD-DEGREE HEART BLOCK
COMPLETE HEART BLOCK OR COMPLETE AV
DISSOCIATION.
IMPULSE IS COMPLETELY BLOCKED BETWEEN THE
ATRIA AND THE VENTRICLES.
USUALLY TAKES PLACE BETWEEN THE AV JUNCTION
AND BUNDLE OF HIS.
1).The atrial and the ventricular rhythms are
absolutely
independent of one another .
2).There is no P-R to QRS relationship.
3).The atrial rate is more rapid than the ventricular
rate.
4).regular P-P interval .
5).rugular R-R interval

15. 3
rd
Degree (Complete) AV Block
EKG Characteristics: No relationship between P waves and QRS complexes
Relatively constant PP intervals and RR intervals
Greater number of P waves than QRS complexes
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16. MANAGEMENT
1
ST
DEGREE BLOCK – ASSESS AND MONITOR THE
PATIENT.
MOBITZ I ( 2
ND
DEGREE, TYPE I) – USUALLY DOES NOT
REQUIRE TREATMENT, BUT IF THE PATIENT IS
MEDICALLY UNSTABLE OR POOR CARDIAC OUTPUT
ATROPINE IS USED IF THE OVERALL RATE IS
BRADYCARDIC.
MOBITZ II (2ND DEGREE, TYPE II) – OXYGEN, IV
FLUIDS,ATROPINE IF OVERALL RATE IS BRADYCARDIC,
ARTIFICIALPACEMAKER, DOPAMINE OR EPINEPHRINE.
IF HEART RATE IS GREATER THAN 100 BUT LESS THAN
150 DILTIAZEM, DIGOXIN, OR BETA BLOCKERS.
3RD DEGREE BLOCK – OXYGEN, IV FLUIDS, ATROPINE
IFBRADYCARDIC, DOPAMINE, EPINEPHRINE, OR
ARTIFICIALPACEMAKER.