Session 6 Interpreting ECGs Flashcards
(53 cards)
How to determine if it’s a normal sinus rhythm?
- Regular rhythm?
- HR 60-100 bpm?
- P waves upright in leads I and II?
- Normal PR interval? (3-5 small boxes)
- Every P wave followed by QRS?
- QRS normal? (< 3 small boxes)
- Corrected QT interval normal?
What happens in atrioventricular conduction blocks?
Delay or failure of conduction of impulses from atria to ventricles via AVN and bundle of His.
What are the 3 types of heart block?
- First degree heart block
- Second degree heart block (Mobitz type I and II)
- Third degree heart block
What causes heart block?
- Degeneration/fibrosis of electrical conducting system with age
- Acute MI
- Medication
- Valvular heart disease
How to spot a first degree heart block?*
- Regular rhythm and QRS
- All normal P waves followed by QRS
- Prolonged PR interval (> 0.2 seconds)
How to spot a second degree Wenkebach heart block (Mobitz type I)?*
- Successively longer PR intervals until one QRS is dropped
- Signifies that electrical signal is not conducted to ventricles
- Cycle starts again
- Not typically pathological
How to spot a Mobitz type II second degree heart block?*
- PR intervals do not lengthen
- QRS dropped suddenly (must look if QRS present every p wave)
- Regular atrial rhythm
- Irregular ventricular rhythm
- High risk progression to complete heart block
What is third degree heart block and how to spot it?*
Atria and ventricles are depolarising independently and there is no AV conduction
- Ventricular pacemaker takes over and pumps at 20-40 bpm (slow ventricular rate)
- Atrial rate at approx. 100bpm (fast, narrow P wave)
- Wide QRS complex
- Bizarre shape QRS
URGENT PACEMAKER REQUIRED
What is bundle branch block and how to spot it?*
Delayed conduction within the bundle branches - can either be left or right.
- P wave and PR intervals are normal
- Wide QRS as ventricular depolarisation takes longer
Where may supraventricular arrhythmias arise from?
- Atrium itself
- Sinoatrial node
- Atrioventricular node
Where may ventricular arrhythmias arise from?
Ventricles
How do supraventricular arrhythmias present?*
- Normal QRS (narrow)
- Issues with P wave
How do ventricular arrhythmias present?*
- Wide and bizarre QRS
What is atrial fibrillation?*
- Most common supraventricular arrhythmia
- Arises from MULTIPLE ATRIAL FOCI
- Atria do not contract, just quiver
- Rapid, chaotic
- NO P WAVES, JUST WAVY BASELINE
- Irregular R-R intervals as not all impulses conducted and reach AVN at different rates
- When conducted, normal - normal QRS
What are the variations of atrial fibrillation?
- Slow: ventricular response <60 bpm
- Fast: ventricular response > 100 bpm
- Normal: 61-99 bpm
What is coarse fibrillation?*
Amplitude >0.5 mm. Can appear as if there are some P waves
What is fine fibrillation?*
Amplitude < 0.5 mm. Closer to isoelectric baseline in appearance than coarse.
Why are individuals with AFib at a higher risk of ischaemic strokes?
- Loss of atrial contraction leads to increased blood stasis (mainly left atrium)
- Leads to small clots in LA
- Clots can travel through aorta to the brain
What are ventricular ectopic contractions?*
- Occur due to ectopic foci in the ventricles that provide abnormal conduction pathways
- Impulse does not spread via the His-Purkinje system
- Slower depolarisation = wide QRS
- May be asymptomatic
What is ventricular tachycardia?*
- 3 or more consecutive premature ventricular contractions
- Broad complex tachycardia
- High risk progression to Vfib
- Requires urgent treatment
What is ventricular fibrillation?*
MEDICAL EMERGENCY
- Abnormal. chaotic and fast ventricular depolarisation
- Impulses from many ventricular ectopic sites
- No coordinated contraction
- Ventricles quiver
- No cardiac output
- May lead to cardiac arrest if untreated
How are arrhythmias classified?*
SLIDE 20!
How to look at ECG changes when ischaemia and myocardial infarction are present?
- Must look at the PQRST of all 12 leads
- Changes will be seen in leads facing the affected area
- Must know which leads look at which part of the heart
What leads face the inferior surface of ventricles?
II
III
aVF
