Heart Block Flashcards
Define 1st Degree AV Block?
Prolonged conduction through the AV node
Define Mobitz Type 1 (Wenckebach) 2nd Degree AV Block?
Progressive prolongation of AV node conduction culminating in one atrial impulse failing to be conducted through the AV node
The cycle ten begins again
Define Mobitz Type II 2nd Degree AV Block?
Intermittent or regular failure of conduction through the AV node
Also defined by the number of normal conductions per failed or abnormal one (e.g. 2:1 or 3:1)
Define 3rd Degree (Complete) AV Block?
No relationship between atrial and ventricular contraction
Failure of conduction through the AV node leads to ventricular contraction generated by a focus of depolarisation within the ventricle
What is the epidemiology of Heart Block?
250,000 pacemakers are implanted every year and they are mostly for heart block
What is the aetiology and risk factors of heart block?
MI or Ischaemic heart disease (most common)
Infection (e.g. rheumatic fever, infective endocarditis)
Drugs (e.g. digoxin)
Metabolic (e.g. hyperkalaemia)
Infiltration of conducting system (e.g. sarcoidosis)
Degeneration of the conducting system
What are the presenting symptoms of 1st Degree Heart Block?
Asymptomatic
What are the presenting symptoms of 2nd Degree Heart Block?
Usually asymptomatic
What are the presenting symptoms of Mobitz Type II and 3rd Degree Heart Block?
Stokes-Adams Attacks Dizziness Palpitations Chest Pain Heart Failure
What are the signs of heart block on physical examination?
Often NORMAL
Check for signs of a potential cause of heart block
What are the signs of Complete Heart Block?
Slow large volume pulse
JVP may show cannon a waves
What are Stokes-Adams Attacks?
Syncope caused by ventricular asystole
What are Cannon A waves?
Waves seen occasionally in the jugular vein of humans with certain cardiac arrhythmias
This occurs when the atria and ventricles contract simultaneously
What are the signs of Mobitz Type II and 3rd Degree Heart Block?
Signs of reduced cardiac output (e.g. hypotension, heart failure)
What is the gold standard investigation for heart block?
ECG
What might you see on an ECG for First Degree Heart Block?
Fixed prolonged PR interval (> 0.2s)
What might you see on an ECG for Mobitz Type I Heart Block?
Progressively prolonged PR interval, culminating in a P wave that is not followed by a QRS complex
The pattern then begins again
‘going, going, gone’
What might you see on an ECG for Mobitz Type II Heart Block?
Intermittently a P wave is not followed by a QRS
There may be a regular pattern of P waves not followed by QRS
What might you see on an ECG for Complete Heart Block?
No Relationship between P waves and QRS complexes
If QRS is initated in the Bundle of His - narrow complex
More Distally - wide complex and slow rate (roughly 30bpm)
What might we see on a CXR for heart block?
Cardiac Enlargement
Pulmonary oedema
What bloods would we do for Heart Block?
TFTs
Digoxin Level
Cardiac Enzymes
Troponin
What might we see on an Echocardiogram for Heart Block?
Wall motion abnormalities
Aortic Valve Disease
Vegetations
What management plan would we do for Chronic Heart Block?
Permanent pacemaker is recommended in:
- Complete Heart Block
- Advanced Mobitz Type II
- Symptomatic Mobitz Type I
What management plan would we do for Acute Heart Block?
If associated with clinical deterioration use IV atropine Consider temporary (external) pacemaker
What are some complications of Heart Block?
Asystole
Cardiac Arrest
Heart Failure
Complications of any pacemakers inserted
What is the prognosis for patients with Heart Block?
Mobitz type II and 3rd degree block usually indicate serious underlying cardiac disease
