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226 Cardio Diabetes Medicine 2017

• There is total AV dissociation Supra HIS Infra HIS
• Junctional or ventricular escape rhythm maintains Block at AV node Block at bundle branch-
life.
es, fascicles
• P wave rate more than QRS rate
Narrow QRS Wide QRS
Etiology
Escape rate faster; 40 – Escape rate slow; < 40/
1. Acute coronary syndrome 60 /minute minute
2. Idiopathic degeneration of the conducting sys- Stable rhythm Unstable rhythm
tem
SA attacks uncommon SA attacks common
3. AV node blocking drugs (beta blockers, calcium
channel blockers, etc) Type I AV block pre- Type II AV block pre-
cedes it cedes it
4. Congenital
Risk stratification Associated with IWMI Associated with AWMI
Conservative approach Needs pacemaker defi-
Patients with complete heart block are at risk of ven- nitely
tricular standstill and syncope or cardiac arrest.If the Good prognosis Prognosis not so good
block is supra HIS, the escape rhythm is of narrow
QRS and has relatively better prognosis. Most of the Summary of AV blocks
congenital complete heart blocks are of this type. In-
tervention is warranted if the patient is symptomatic

Fig 14: third degree AV block with narrow QRS escape Indications for permanent pacemaker
rhythm
- Symptomatic sinus bradycardia
If the block is infra HIS, the escape rhythm is of wide
QRS and has bad prognosis warranting early inter- - Any sinus pause > 2 seconds with symptoms
vention (fig 15) - Identification of distal blocks (infra HIS) which are
likely to produce to for Stoke’s Adam attack

- First degree AV block with bundle branch block
- Mobitz type 2 second degree AV block
- 2:1 AV block
- High grade AV block

- Infra His complete heart block
Suggested reading:-
1. ECG Course - an interactive multimedia tutorial” by Dr.M.Chenniappan;
CD released by ECG and ECHO club of Trichy
2. Leo Schamroth ; an introduction to electrocardiography, 8 edition
th
3. Marriott’s practical electrocardiography; 12 edition
th
Fig 15: third degree AV block with wide QRS escape
rhythm

GCDC 2017