ECGs Flashcards
What are the 3 types of ECG leads?
- Limb leads (bipolar)
- Augmented limb leads (unipolar)
- Chest leads (unipolar)
What type of deflection does re-polarisation away from an ECG lead produce?
Positive deflection
What type of deflection does depolarisation away from an ECG lead produce?
Negative deflection
What is the normal amplitude of a QRS complex in mV?
<2.5mV
What is the normal range for a P-R interval?
0.12- 0.2 seconds
3-5 small squares
How wide should a QRS complex be on an ECG?
0.06-0.12 secs
<3 small squares
Anything wider than 3 small squares is considered a “broad complex”
What are the causes of tachycardia with broad QRS?
VT
What are the causes of tachycardia with narrow QRS?
Irregular: AF or atrial flutter
Regular: SVT, atrial tachycardia (rare) or atrial flutter
What could cause a PROLONGED PR interval? (>5 small squares)
1st degree heart block
What could cause a SHORTER PR interval? (<3 small squares)
Wolf Parkinson White (Accessory pathway)
Where does ventricular depolarisation normally originate?
Atria, passes down Bundle of His
When may a QRS complex be broad (>3 small squares) WITHOUT tachycardia?
- Ventricle-ventricle conduction eg. Ventricular ectopics
- Bundle branch block
- Hyperkalaemia
Which 2 leads should be added together to see if there is ventricular hypertrophy?
V1 + V5
If > 7 squares suggests hypertrophy
What might a pathological Q wave suggest?
Old MI
What causes a tall tented T wave?
Hyperkalaemia
What causes a flat T wave?
Hypokalaemia
What causes an inverted T wave?
- Normal in lead V1, aVR
- Old MI (weeks)
- Bundle branch block
- Ischemia
What ECG changes are seen in Hyperkalaemia?
- Tall tented T wave
- Broad QRS complex
- Flat P wave
What causes ST depression?
- NSTEMI
- Posterior MI
- Digoxin toxicity
What does the ECG trace look like in 1st degree heart block?
Prolonged PR interval >5 small squares
No missed beats
What does the ECG trace look like in Mobitz type 1 heart block (Wenckebach)?
Beat by beat prolongation of PR interval until a missed QRS complex
What does the ECG trace look like in Mobitz type 2 heart block?
QRS complexes are regularly missed eg. P, QRS, P
Can have a 2:1 block or 3:1 block
What does the ECG trace look like in 3rd degree heart block?
Complete dissociation between P and QRS complex
No impulses are passed from atria to ventricles, so can lead to bradycardia
Which ECG leads represent the ANTERIOR territory of the heart?
V1-V4
Which ECG leads represent the LATERAL territory of the heart?
V5, V6, I and aVL
Which ECG leads represent the INFERIOR territory of the heart?
II, III and aVF
Which coronary artery supplies the anterior heart?
Left anterior descending
Which coronary artery supplies the lateral heart?
Left circumflex
Which coronary artery supplies the inferior heart?
Right coronary artery
What does the ECG trace look like in Left Bundle Branch Block?
- QRS > 3 small squares in V4, V5 and V6
- V1 has downwards QRS with “W” shape
- V5 has “M” shape WRS
- T wave inversion in V5, V6, aVL and I
What are the causes of LBBB?
- Ischemic heart disease
- Left ventricular hypertrophy
- Cardiomyopathy
- Hypertension
What does the ECG trace look like in Right Bundle Branch Block?
- Broad QRS in V1, V2 and V3
- V1 has “M” shape RSR in the QRS
- V6 has “W” shape slurred S
- Inverted T waves in V1, V2 and V3
What are the causes of RBBB?
- Isolated RBBB
- Right ventricular hypertrophy
- Cor pulmonale
- PE
- Atrial septal defect
- Ishemic heart disease
How may a NSTEMI appear on ECG?
- Inverted T waves
2. ST depression
What causes a broad QRS complex tachycardia?
Ventricular tachycardia (VT)
What causes a narrow QRS complex tachycardia that is IRREGULAR?
Atrial fibrillation
Atrial flutter
What causes a narrow QRS complex tachycardia that is REGULAR?
- SVT
- Atrial flutter
- Atrial tachycardia (very rare)
What is the cause of an SVT?
Area conducting directly from atria to ventricles without passing through the AV node (Pathway)
Has no parsympathetic or sympathetic involvement
What is the classical history of a patient with an SVT?
Sudden onset tachycardia of around 160bpm
Can go away
How can SVT be proven?
Give adenosine/ do vagal manouvres which will block the AV node
The tachycardia will remain if it is an SVT
What are the common ventricular rates in atrial flutter?
Factors of 300:
100
150
What are the different types of ventricular tachycardia? (Broad QRS complex)
- Ventricular fibrillation- chaotic with no pattern
- Ventricular tachycardia
- Torsades de pointes
List 10 causes of Atrial Fibrillation (AF)?
- Heart failure
- Hypertension
- Mitral valve disease
- Ischemic heart disease
- PE
- Hyperthyroidism
- Pneumonia
- Caffeine, alcohol
- Post operative
- HYPOkalaemia/ HYPOmagnesia
- Cardiomyopathy
What is Atrial Fibrillation (AF)?
Arrhythmia caused by a chaotic irregular atrial rhythm at 300-600bpm
The AVN responds intermittantly
Results in irregularly irregular pulse
What are the SIGNS of AF?
Irregularly irregular pulse
Signs of LVH
1st heart sound may change in intensity
What are the SYMPTOMS of AF?
Palpitations
Chest pains
Dyspnoea
What 3 tests should be done in a patient where AF is suspected?
- ECG- absent P wave, irregular QRS
- Bloods- UandEs, thyroid function, cardiac enzymes
- Echo- look for mitral valve disease, signs of LVH, signs of left atrial enlargement
What are the main aims in treating chronic AF?
- Anticoagulation
2. Rate control
What is sinus bradycardia?
Sinus rhythm at rate <60 bpm
How does SA node disease (bradycardia) appear on ECG?
- No P wave
- Ventricular escape rhythm of 20-30bpm (ventricular myocyte to myocyte conduction is slow so broad QRS)
- If no ventricular escape rhythm
What can a permanent pacemaker be used for?
- Complete heart block (3rd degree)
- Mobitz Type II
- AV node block after MI
- Symptomatic bradycardias eg. sick sinus syndrome
What is WPW syndrome?
Congenital abnormality with accessory pathway between atria and ventricles
Has slurred upstroke QRS and shortened PR interval
What is Sick sinus syndrome?
Fibrosis of SA node in elderly affects SA node activity
Can cause syncope, light-headedness, palpitations
