ECG- heart block Flashcards
What is heart block?
Block in conduction between AV node and the ventricles causing a prolonged PR interval
Types of heart block? (4)
First degree
Second degree Mobitz I
Second degree Mobitz II
Complete heart block
What are the most common underlying cause of heart block? (2)
MI or ischaemic heart disease
Drugs e.g. beta blockers, calcium blockers
How are Mobitz I and Mobitz II differentiated?
Mobitz I- progressive lengthening of PR interval until a beat is dropped.
Mobitz II- intermittent failure of conduction through the AV node (e.g. every three P waves)
What defines third degree (complete) heart block?
No relationship between P waves and QRS complexes
How is ventricular contraction caused in 3rd degree block and what is typically the rate?
Ventricular escape rhythm around 30-40bpm
When is permanent pacemaker insertion recommended for heart block?
Symptomatic Mobitz I
Mobitz II
Complete heart block
When is atropine used in heart block? How does it work?
In acute situations accompanied with clinical deterioration. Anti-muscarinic effect- increases the heart rate
What are the two shockable cardiac arrest rhythms?
Pulseless ventricular tachycardia
V. Fibrillation
What are the two non-shockable cardiac arrest rhythms?
Pulseless electrical activity
Asystole
What are the reversible causes of cardiac arrest?
Hypoxia Hypothermia Hypovolaemia Hypo/hyperkalaemia Tamponade Tension pneumothorax Thromboembolisn Toxins/metabolic
When should adrenaline/amiodarone be given in cardiac arrest?
After the 3rd shock, then every 3-5 minutes afterwards (adrenaline only)
When is adrenaline given for non-shockables?
Immediately, then every 3-5 minutes afterwards