ECG - Rhythms Flashcards
(35 cards)
3 things to check with rhythms
- What are the atria doing?
- What are the ventricles doing?
- Relationship between the ventricles and atria?
Best leads to check for atria activity
V1 and lead II - anatomically closest to heart
Two types of bradycardia
Sinus bradycardia
AV block bradycardia
What is chronotropic incompetence?
Inability for heart to speed up when needed eg when exercising
Causes of sinus bradycardia
- Sick sinus syndrome / inappropriate sinus bradycardia
When do we insert pacemaker for bradycardia?
- Treat when symptomatic
- Dizzy/blackouts + sinus pause for more than 3 seconds in the daytime (more than 3 seconds between P waves)
- OR chronotropic incompetence - if cannot get HR above 75
How do pacemakers work?
- 2 wires
- One in RA one in RV
- Enter via subclavian or axillary veins percutaneously - stay within veins to ensure no clots etc enter arterial system
- Electrodes listen for P waves and QRS complexes
- If none - they kick in
- Have a set demand rate for 60bpm
- We do not pace continiously as pacing causes LBBB (due to wires being on R) can mess up left ventricle
- Pacemakers contain rate responsive element which means demand rate can change 60-130bpm depending on movement
What should you always rule out as causes of bradycardia rather than a cardiac problem?
- Medication eg bisoprolol, diltiazem, memantine, timolol eye drops
- Hypothyroidism
- Addisons
- Anorexia nervosa
3 types of AV nodal block
- 1st degree - PR prolongation
- 2nd degree - Mobitz type 1 (Wenckebach) Mobitz type 2
- 3rd degree - complete heart block
What is 2nd degree heart block Wenckeback (type 1)?
- Gradual PR prolongation then QRS drop (drop a beat)
- Usually a benign phenomena
- Due to increased vagal tone which blocks AV node
What is 2nd degree heart block mobitz type 2?
- PR is fixed but prolonged, sudden drop of QRS
- Something wrong with AV node
- 2:1 ratio sometimes
Which AV node blocks need pacemaker?
Complete heart block
2nd degree Mobitz Type 2
What is complete heart block?
- Complete block of AV node conduction - no atrial impulses through
What happens in complete heart block?
- Automaticity of cardiac cells are always there
- These take over if there is no AV nodal depolarisation
- Escape rhythm (should be called rescue rhythm) takes over
Different origins of escape rhythm
- If from ventricle just below AV node - QRS will still be narrow and HR will be 45-55 - this is ok
- If from middle ventricles - 35bpm
- If from apex of ventricles - BROAD QRS and HR 20-35pm - NOT stable
When to call cardiologist for 3rd degree heart block for urgent pacemaker?
- Ask pt if lost conscioussness or nearly lost consciousness - if yes CALL
- Check how fast and how broad QRS - if BROAD and slow - CALL
- If narrow and fast rate - this is ok, can wait until morning
When is AF + complete heart block on ECG?
- AF rhythm is always irregular
- If rhythm is still regular with AF - complete heart block is present
What is bigeminy on ECG?
- Normal beat with extra beat and then pause
- Can indicate heart is unhappy
- If after MI signals that VT will be soon
- Can also get trigeminy if normal beat normal beat extra beat and pause
4 types of tachyarrhythmias
- Narrow complex - irregular and regular
- Broad complex - irregular and regular
Examples of narrow complex regular tachycardia
- Sinus tachycardia
- SVT - orthodromic AVRT or AVNRT
- Atrial flutter
atrioventricular re-entrant tachycardia + AV nodal RT
What is orthodromic atrioventricular re-entrant tachycarda (AVRT)?
- Accessory pathway - AV node and accessory pathway conduct to ventricles
- Same speed at each ‘attack’
- Adrenergic state can maybe change speed
- Often happens when bend and stand back up
- Accessory pathway goes down AV node and back up (normal direction)
What is atrioventricular node re-entrant tachycardia?
- Accessory pathway through AV node - two ways through
- Circuit is smaller
- Benign often
How to tell difference between orthodromic AVRT and AVNRT?
- In orthodromic AVRT there will be retrograde P waves after QRS comples
- Retrograde P waves are inverted btw ella
What is electrical alterans?
- Alternating QRS complex amplitudes in any or all leads
- Signal of poor ventricular output
