ECG Flashcards
What is your system to reading ECGs? (8)
- patient symptoms
- demographics
- name, age and DOB, date, time - calibrated at 25mm/s and 1mV (1 millivolt)
- rhythm - p wave = sinus, piece of paper measure between r waves
- rate
- axis - leads I, II, III, AVL and AVF
- QRS and p wave
- ST segments
- others QTc
How many mm/s is a whole strip?
25 mm/s
how many m/s and s is 1 large square?
0.2s or 200ms
How many m/s or s is 1 small square?
0.04 s or 40ms
Where do you start reading the PR interval from?
the beginning of the p wave to the beginning of the q wave
How long should the PR interval be?
120-220 ms
What is standard rates?
R-R interval Heart rate (bpm)
1 300
2 150
3 100
4 75
5 60
6 50
What do leads I, II and VL look at?
left lateral surface of the heart
What do leads III and VF look at?
the inferior surface
What does lead VR look at?
right atrium
Where do leads V1-6 look at the heart?
they look at the heart from the horizontal plane
Rhythm strip - what is it
whichever lead shows the p wave most clearly usually lead II
What are the deflection in VR and II usually?
VR - downwards
II - upwards
What deflection are leads I, II and III associated with and why?
upwards deflection
- depolarising waves is spreading towards these leads
what is right axis deviation?
deflection in lead I becomes negative
deflection in lead III become more positive
right ventricle becomes hypertrophied
normal axis
lead I, II and III all positive deflections
lead II with most positive deflection
left axis deviation
lead I - small positive deflection
lead II - negative deflection
lead III - negative deflection
left ventricle is hypertrophied
What is first degree heart block?
PR interval is prolonged
- delay somewhere along the conduction pathway
- sign of coronary artery disease, acute rheumatic carditis, digoxin toxicity or electrolyte disturbance
What is second degree heart block?
excitation completely fails to pass through the AV node or bundle of His.
This occurs intermittently
What is seen in Mobitz type I/ Wenebach second degree heart block?
- progressive lengthening of the PR interval
- failure of conduction of an atrial beat
- followed by a conducted beat with a shorter PR interval
- this cycle repeats
What is seen in Mobitz type II?
- PR interval is constant
- occasionally there is one p wave without ventricular depolarisation
- one p wave is not followed by a QRS complex
What is third degree heart block?
this is complete heart block
- atrial contract is normal
- nothing gets to ventricles
- on ecg QRS complexes are abnormally shaped
- transient MI
- chronic due to fibrosis around the bundle of His
What is right bundle branch block?
- V1 lead
- see a RSR pattern
think Marrow
Left bundle branch blcok
Willaim
- v6 lead - M
- v1 lead - W
- braod QRS
What is supra ventricular/atrial tachycardia?
- p waves are superimposed on the T waves of the preceding beats
- QRS intervals are short
- QRS are the same shape
What is an atrial flutter?
atrial rate is greater than 250/min
- pawave - saw tooth appearance
- four p waves per QRS
- ventricular activity is perfectly regular
What is ventricular tachycardia?
no p waves
- regular QRS
- broad QRS
- no t waves
Atrial fibrillation
- no p waves
- irregular QRS complexes
- normal shaped QRS
Ventricular fibrillation?
- no QRS
- loss of consciousness
Pacemaker
- occasional P waves visible
- p waves not related to QRS complex
- spike before QRS complex - pacemaker stimulus
- broad QRS
ST elevation
- acute myocardial injury
ANTERIOR DAMAGE
-V leads
INFERIOR DAMAGE
- leads III and VF
LATERAL DAMAGE
- leads I, II, VL
