ECG Flashcards
How to measure HR
No. of R waves in 15 large squares
Multiply by 20
Normal HR
60-80 BPM
What does differing RR intervals mean
Heart block
How big should P wave be
No more than 2 small squares
What does PR interval signify
Time between start of depolarisation of atria and start of depolarisation of ventricles
How long should PR interval be
120-200ms
PR interval > 200ms
Heart Block
Prolonged PR interval
Hypokalaemia, Acute rheumatic fever, Carditis
QRS wave is indicator of
Indicator of the synchronisation of the contraction of the ventricular muscle
QRS duration
Less than 120ms
Long QRS duration means
Part of ventricle not contracting properly
Lengthened QT interval meaning
Ventricular arrhythmia
Large ECG signal signifies
Muscle membrane potential changing
Epicardial AP length (outside) vs Endocardial AP length (inside)
Epicardial shorter
Which part of muscle more susceptible to ischaemia
Endocardial–> reduces duration
Endocardial muscle layer
inside
Epicardial muscle layer
outside
If endocardial becomes shorter compared to epicardial
Inverted T wave
Class 1 Anti-arrhythmic drugs
Na+ channel blockers
Class 2 Anti-arrhythmic drugs
Beta blockers
Class 3 Anti-arrhythmic drugs
K+ channel blockers
Class 4 Anti-arrhythmic drugs
Calcium channel blockers
Sinus Bradycardia
HR less than 60bpm
Sinus Tachycardia
HR more than 100bpm
Originates from SA node
Ventricular tachycardia
180-190bpm
Prolonged QRS
No P wave seen
Regular same pattern
Ventricular tachycardia reasons
Abnormal tissues in ventricles generating rapid + irregular heart rhythm
Ventricular Fibrillation
Irregular rhythm
300+ BPM
No QRS
No P wave
Ventricular Fibrillation reasons
Different parts of heart contracting at different times
Desynchronisation
Irregular pattern and amplitude
First Degree Heart block
PR interval >200ms
Regular rate
First Degree Heart block reasons
AV node problem- can be v sensitive to electrolyte changes
Second Degree Heart block TYPE 1 (Wenkenback)
PR interval gets progressively longer until P wave not followed by QRS
Repeats
Second Degree Heart block TYPE 2
P wave regular
Rate irregularly irregular
AV node randomly fails to respond to atrial impulses
Often damage to AV node
Third Degree Heart Block
P waves random
May have bradycardia
No induction from atria to ventricles- ventricles generate own signal
QRS split
Atrial Fibrillation
100-160 BPM Irregularly irregular rhythm Normal QRS No P wave Abnormal aortic tissue- multiple excitatory focuses
Atrial Flutter
High HR (110BPM)
Regular rhythm
P wave replaced by multiple F (flutter) waves
Abnormal tissue is in atria- but only one abnormal excitatory focus
Junctional rhythm
Damage to SA node/block in conduction pathway in atria
AV node takes over as pacemaker
40-60 BPM
Normally absent P wave
Supraventricular Tachycardia (SVT)
140-220 BPM
P wave absent/preceding T wave
Higher frequency impulses at AV node
AV node re-entrant tachycardia
W>M
P wave hidden in QRS complex, or seen after
Palpitations
Depressed ST segments
Coronary ischaemia
Hypokalaemia
STEMI
ST elevation in 2 or more adjacent ECG leads
80bpm
NSTEMI
less serious
areas of cardiac ischaemia but not necessarily death
Right Bundle Branch Block
Problem with right side of heart
Left Bundle Branch Block
Indication of heart disease
Bundle Branch block
QRS Prolonged
Depolarisation delay through ventricular muscle
Usually due to hypoxia/ischaemia damage
Notch on R wave
Pathological Q wave
Larger than normal Q wave
Damage to muscle of interventricular septum
