A potential medical emergency needing Atropine and pacing
- There is a complete failure of communication between atria and ventricles
- Atria beat but do not stimulate the ventricles
- Ventricles beat at intrinsic escape rate which may be 30-40 bpm.
- The anatomically higher the escape rhythm the faster and narrower the QRS
- Atrial rate: usually 60-100 beats/min; impulses completely independent (“dissociated”)
from ventricular rate
- Ventricular rate: depends on rate of the ventricular escape beats that arise:
- Ventricular escape beat rate slower than atrial rate = third-degree heart block (20-40
- Ventricular escape beat rate faster than atrial rate = AV dissociation (40-55 beats/min)
- Rhythm: both atrial rhythm and ventricular rhythm are regular but independent (“dissociated”)
- PR: by definition there is no relationship between P wave and R wave
- P waves: typical in size and shape
- QRS complex: narrow (=0.10 sec) implies high block relative to the AV node; wide
(>0.12 sec) implies low block relative to the AV node
- Acutely due to Inferior RCA infarct talking out AV nodal branch
- Anterior MI suggest large MI taking out conducting tracts and myocardium
- Medications - Beta-blockers, Digoxin, Calcium channel blockers
- Fibrosis of both bundle branches in the elderly.
- Drugs, post-surgery, rheumatic fever, myocarditis, endocarditis.
- Diphtheria, Lyme disease
- Acutely Symptomatic usually, Low BP, Shocked
- Chronic: reduced exercise tolerance, fatigue, syncope
- JVP: Cannon 'a' waves are seen with Complete heart block
- Acute setting; ECG, U&E, LFTS, TFTs
- ECG - No coordination between P wave and QRS complex, Slow Ventricular rate, Broad QRS. No P waves in AF.
- ABC as needed and Resuscitation
- Consider Atropine, Isoprenaline and Temporary pacing.
- Treat any potential causes
- Patients usually all need a PPM (Permanent Pacemaker)
- Untreated mortality is 50% per annum