ECG Flashcards
PR segment - when?
End of P to beginning of R
ST segment - when?
S to beginning of T
QT interval - when?
Start of Q - end of T
P wave - what?
Atrial depolarisation
QRS complex - what?
Ventricular depolarisation
T wave - what?
Ventricular repolarisation
Placement of limb leads
Red - right arm
Yellow - left arm
Green - left leg
Black - right leg
Septal view
V1, V2
Anterior view
V3, V4
Lateral view
V5, V6, I, aVL (aVR)
Inferior view
II, III, aVF
V1, V2
Septal
V3, V4
Anterior
V5, V6, I, aVL, (aVR)
Lateral
II, III, aVF
Inferior
Calculate rate
300/number of large squares between R-R complexes
Sinus rhythm
Exactly same distance between each QRS
Each P wave followed by a QRS complex
Each QRS complex preceded by a P wave
Normal cardiac axis
I ↑
II ↑ (by largest amount)
III ↑ or ↓
(aVR most ↓)
Right axis devation
Usually caused by right ventricular hypertrophy
Extra heart muscle causes stronger single to be generated by right side of heart
Can be normal in very tall individuals
I ↓
II ↑ (more than normal)
III ↑ (more than normal)
Left axis deviation
Usually caused by conduction defects
I ↑
II ↓
III ↓
PR interval
Start of P to first deflection of QRS
Normal is 3-5 small squares (0.12-0.2s)
Represents conduction time of AV node
Prolonged = 1st degree heart block
1st degree heart block
Conduction of AV node is slowed, but gets through
Prolonged PR
2nd degree heart block Mobitz I
Progressive prolongation of PR interval culminating in missing QRS complex
2nd degree heart block Mobitz II
Intermittent missing QRS complexes without progressive prolongation of PR interval
PR interval in conducted beats remains constant
P waves constant rate
3rd degree heart block
No relationship between P waves and QRS complexes
Two independent rates
Severe bradycardia
ORS complex
Normal <3 small squares (0.12s)
Broad complex = either conduction delay (bundle branch block) or rhythm arising from the ventrical (VT/VF/heart block)
Q waves
Downward deflection before the R wave Pathological Q waves: • >2 small squares deep • > 1 small square wide • >25% of height of R wave Previous MI NB. Normal in V1
R waves
R wave height progresses across precordial height
Poor R wave progression suggests old anterior infarct
ST segment
Should be isoelectric
Elevated suggests MI
Depressed suggests ischaemic myocardial tissue in the vantricles
T waves
Ventricular repolarisation
Upright in all leads except aVR, V1 (and V2?)
Can get inversion or big broad ones
ECG changes in STEMI
Earliest sign is increase in T wave amplitude
T wave pinted
ST elevation follows
Later - development of Q waves
Right sided leads in patients with inferior MI
Posterior - ST depression V1-V3 and dominant R wave V1
