ECG Flashcards
What does a +ve and -ve deflection mean?
Positive = depolarisation wave moving towards electrode
Negative = away from electrode
What does the P wave represent?
Atrial depolarisation
What does the PR interval represent?
Beginning of atrial contraction to beginning of ventricular contraction
What does the PR segment represent?
AV node delay
What does the QRS wave represent?
Ventricular depolarisation
What does the T wave represent?
Ventricular repolarisation
What does the QT interval represent?
Time taken for ventricular depolarisation + repolarisation
What does the U wave represent?
Represents purkinje fibre repolarisation
What is the y + x axis?
Y = voltage X = time (1mm = 0.4s)
What are the bipolar leads?
I, II, III (Have a positive + negative electrode)
What are the unipolar leads?
AVR, AVL, AVF + chest leads
(Have a positive electrode + rely on combination of others to make up negative electrode)
What are the lateral leads?
I, AVL, V5, V6
What are the inferior leads?
II, III, AVF
What are the septal leads?
V1 + V2
What are the anterior leads?
V3 + V4
Which leads should have an upright P wave?
I, II, AVF
What HR is equal to = 1 block, 2 blocks, 3 blocks, 4 blocks, 5 blocks, 6 blocks?
1 = 300bpm
2 = 150 bpm
3 = 100 bpm
4 = 74 bpm
5 = 60 bpm
6 = 50 bpm
What is a normal PR interval?
0.12-0.2s
3-5 small boxes
What is a normal QRS interval?
<0.12s
(less than 3 small boxes)
How to approach an ECG in an OSCE?
Name + DOB
Date + time
1) HR (number of QRS on 10s strip x 6)
2) Rhythm (regular, regularly irregular, irregularly irregular)
3) Cardiac axis
4) P waves - present, normal, followed by QRS?
5) PR interval
6) QRS complex
7) ST segment
8) T waves
How to determine cardiac axis?
Lead II should have most positive deflection compared to I + III
What does right axis deviation look like?
Lead III most positive Lead I negative
What does left axis deviation look like?
Lead I most positive Lead II + III negative
What does a prolonged PR interval show?
>0.2s AV block
What does a shortened PR interval show?
P wave originating from closer to AV node Atrial impulse getting to ventricle quickly via accessory pathway (delta wave = WPW)
What is a delta wave?
Slurred upstroke of QRS complex
Describe the assessment of the QRS complex
Width (narrow <0.12 or broad >0.12)
Height:
Small = <5mm in limb leads or <10mm in chest leads
Tall = >5 or >10 Morphology
Describe assessment of ST segment
Should be isoelectric line
ST elevation = MI
ST depression = ischaemia
Describe assessment of T wave
Tall = >5mm in limb + >10mm in chest
Inverted = normal in V1 but abnormal in other leads
What do tall T waves indicate?
Hyperkalaemia
Hyperacute STEMI
What do inverted T waves indicate?
Ischaemia
Bundle branch block (V4-6 in LBBB + V1-3 in RBBB)
PE
What does a biphasic T wave indicate?
Hypokalaemia
Ischaemia
What does a flattened T wave indicate?
Ischaemia
Electrolyte imbalance
Difference between AV blocks
1st = fixed prolonged PR interval (>0.2s)
2nd type 1 = PR interval steadily increasing until dropped QRS
2nd type 2 = PR interval fixed but with occasional dropped beats
3rd = P waves + QRS totally unrelated
What does a broad QRS complex indicate?
Abnormal depolarisation sequence eg ventricular ectopic or bundle branch block
What does a LBBB look like?
Broad QRS >0.12
Secondary R waves in V1-V3
Slurred S waves in lateral leads (I, AVL, V5-6)
What does a RBBB look like?
Broad QRS >0.12
Dominant S wave in V1
Absence of Q aves + broad R waves in lateral leads
What does atrial enlargement look like?
Biphasic p waves in lead V1
Amplitude of P waves
What does right ventricular hypertrophy look like?
V1 = huge S
V5 + 6 = Huge R
What does left ventricular hypertrophy look like?
V1 = big R
V5 = big S
What does subendocardial ischaemia look like on ECG + what is its name, and what leads are affected?
Stable angina
ST depression
Often affecting leads I, II, V4, V5 + V6
What does subendocardial infarction look like + what is the name of it, and what leads are affected?
Unstable angina/ NSTEMI
ST depressions
T wave inversion
Most noticeable in chest leads - must be contiguous (leads next to each other)
What does transmural ischaemia look like + whats its name, and what leads are affected?
Unstable angina/ NSTEMI
ST depressions
T wave inversion
Most noticeable in chest leads - must be contiguous (leads next to each other)
What does transmural infarction look like + whats its name?
STEMI
T wave inversions
Hyperacute T waves
ST elevation
Pathological Q waves
Whats the difference between an NSTEMI + unstable angina?
NSTEMI - heart cells produce troponin + CK-MB
What other conditions cause ST elevation?
Coronary artery spasm
left ventricular hypertrophy
Pericarditis
How to locate where the infarction is?
Lead with pathological Q waves
What leads show pathological Q waves in septal wall infarcts?
V1 + V2
What leads show pathological Q waves in anterior wall infarcts?
V3 + V4
What leads show pathological Q waves in anterolateral wall infarcts?
V3, V4, V5, V6 1 AVL
Other causes of pathological Q waves
Bundle branch block
WPW syndrome
How long do ECG changes last for in STEMIs?
ST elevation = days
T wave inversion = weeks to months
Pathological Q waves = months to years
What is the most common cause of left axis deviation?
Defects of conduction system
Which coronary artery is most commonly involved in MI?
Left anterior descending
If leads V1 + V2 show ST segment changes, what area is affected + what artery is likely blocked?
Septal
Left anterior descending
If leads V3 + V4 show ST segment changes, what area is affected + what artery is likely blocked?
Anterior
Left anterior descending
If leads I + AVL show ST segment changes, what area is affected + what artery is likely blocked?
Lateral
Left circumflex artery
If leads II, III + AVF show ST segment changes, what area is affected + what artery is likely blocked?
Inferior
Right coronary artery
What does LVH look like on ECG?
Tall S waves + R waves
What ECG changes are typical of massive PE?
RBBB
S1Q3T3 (deep S wave lead 1, patholgical Q wave + T wave inversion in lead 3)
R axis deviation - 1 + 3 are reaching to each other
