Bradycardia Flashcards
What is bradycardia?
< 60 bpm.
Causes of sinus bradycardia.
Physical fitness
Vasovagal attacks
Sick sinus syndrome
Drugs like b-blockers, digoxin and amiodarone
Hypothyroidism
Hypothermia
Raised ICP
Cholestasis
How can bradycardia be assessed?
By QRS complex
Rhythm
P-waves
P following QRS
What is a narrow QRS bradycardia with regular rhythm and p waves.
The p-QRS is 1:1.
PR is normal
If there is a normal PR = sinus bradycardia
What is a narrow QRS bradycardia with regular rhythm and p waves.
The p-QRS is 1:1.
PR is prolonged.
First degree HB
What is a narrow QRS bradycardia with regular rhythm and p waves.
The p-QRS is 2:1
Wenkebach’s if there is a drop.
or
Fixed AV block.
What is a narrow QRS bradycardia with regular rhythm and p waves.
There is no relation between P and QRS waves.
Complete HB.
What is a narrow QRS bradycardia with regular rhythm and no p waves or buried in QRS/T?
Junctional rhythm. (This can also be tachycardic)
What is a narrow QRS bradycardia with irregular rhythm?
AF with slow VR.
What is a broad QRS bradycardia with irregular rhythm?
AF with slow BBB.
What is a broad QRS bradycardia with regular rhythm and no p waves?
AF with complete HB.
What is a broad QRS bradycardia with regular rhythm and p waves.
The p-QRS is 1:1.
PR is normal
Sinus brady with BBB
What is a broad QRS bradycardia with regular rhythm and p waves.
The p-QRS is 1:1.
PR prolonged.
1st degree HB with BBB
What is a broad QRS bradycardia with regular rhythm and p waves.
The p-QRS is 2:1
Fixed AV block
What is a broad QRS bradycardia with regular rhythm and p waves.
There is no relation between P and QRS.
Complete HB
Explain the assessment algorithm of bradycardia.
First degree AV block
2nd degree Mobitz Type 1.
This is Wenkebach AV block.
Each successive QRS, the P-R interval increses until there is a non-conducted P wave.
2nd degree HB.
Mobitz Type II - Ratio of AV conduction varies from 2:1 block or 3:1 block.
Complete AV block.
no relationship between P and QRS.
Treatment of 1st degree AV block.
No treatment indicated.
If the patient is on digoxin check for toxicity.
If there are symptoms such as dizziness or syncope, consider cardiac monitoring.
When might 2nd degree AV block type I (Wenkebach) occur?
Young fit patients with high vagal tone - can be seen during the night if monitored.
Inferior MI.
Treatment of 2nd degree AV block Type I (Wenkebach)
No specific therapy is indicated because it rarely proceeds to complete heart block.
Cardiac monitoring should be done if syncope or dizziness.
Treatment of 2nd degree AV block Type II.
Always requires pacemaker (in the absence of a recent acute coronary event or drugs have been excluded)
This is because it is likely to proceed to complete heart block.
Causes of complete heart block.
IHD (esp inf MI)
Idopathic fibrois
Congenital
Aortic valve calcification
Cardiac surgery/trauma
Digoxin toxicity
Severe hyperkalaemia
Treatment of complete heart block.
If haemodynamically unstable give atropine 600 micrograms to a max of 3 mg.
Isoprenaline at rate of 5 micrograms/min can be tried as well.
Urgent permanent pacemaker is indicated. Should be done within 24 hours in all patients without a likelihood of recovery (such as recent coronary event)
Management of bradycardia (algorithm) Pt 1.
Give O2 if hypoxic, manual BP, ECG 12 leads and IV access.
Identify reversible causes.
Check for adverse signs;
Shock
Syncope
Heart failure
Myocardial ischaemia
Management of bradycardia if no adverse signs.
Assess the risk of asystole;
Recent asystole
Mobitz type II
Complete HB with broad QRS
Ventricular pause >3s.
If there are no risk -> continue observation.
Management of bradycardia in a stable patient with risk of asystole.
Repeat atropine 500 micrograms IV every 3-5 mins (max 3mg)
Transcutaneous pacing
Isoprenaline 5 micrograms/min IVI
Adrenaline 2-10 micrograms/min IVI
Alternatives;
Aminophylline, dopamine, glucagon
Seek expert help and arrange transvenous pacing.
Management of bradycardia in an unstable patient.
Give atropine 500 micrograms IV.
If there is no satisfactory response;
Repeat atropine 500 micrograms IV every 3-5 mins (max 3mg)
Transcutaneous pacing
Isoprenaline 5 micrograms/min IVI
Adrenaline 2-10 micrograms/min IVI
Alternatives;
Aminophylline, dopamine, glucagon
Seek expert help and arrange transvenous pacing.
