ECG Flashcards
Anterior wall leads:
V3 and V4
Septum leads:
V1 and V2
Lateral wall lead:
V5, V6, I and aVL
Blockage in proximal LAD:
ST elevation in leads V1 to V6 with possible I and aVL
(anterior and lateral aspects as well as the septum are supplied by LAD)
This is referred to as an ‘extensive anterior MI’
Purpose of limb leads?
Observe the heart from top to bottom to see if there is a problem inferiorly
Purpose of the chest leads?
Examine the heart from right to left on a horizontal plane
Changes in leads II, III and aVF =
Inferior surface of the heart
Inferior surface of the heart =
Changes in leads II, III and aVF
Changes in leads V1-V4 =
Anterior surface
Anterior surface =
Changes in leads V1-V4
Changes in leads I, aVL, V5 and V6 =
Lateral surface
Lateral surface =
Changes in leads I, aVL, V5 and V6
Changes in leads V1 and aVR =
Right atrium and the cavity of the left ventricle
Right atrium and the cavity of the left ventricle =
Changes in leads V1 and aVR
What do you set the gain to?
10mm/mV
What do you set the speed to?
25mm/sec
Broad p wave indicates what?
Left atrium is very large
Tall peaky p wave indicates what?
Right atrium is bigger (right sided disease e.g. pulmonary hypertension)
Where are the p waves +ve?
Leads I and II (upright in sinus rhythm)
Where are the p waves best seen?
Leads II and V1
In lead V1 the p wave is…
Commonly biphasic
Amplitude and duration of p wave?
<2.5 small squares in amplitude
<3 small squares in duration
PR interval =
0.12-0.2 seconds
3-5 little squares
Time from the start of the p wave to the start of the QRS
Short PR interval can indicate what?
Structure that allows delay from the AVN to be skipped e.g. Wolff-Parkinson-White syndrome
Long PR can be physiologically caused by what?
Vagal stimulation
Broad QRS indicates what?
Slow conduction
Large QRS indicates what?
Large heart muscle
V1 is in the RV whereas V6 is in the LV, what does this mean for QRS deflection?
QRS should show up as -ve on V1 and +ve on V6 due to the disparity in magnitude of conduction between the two ventricles
How does ischaemia and infarction affect the ST segment?
Ischaemia = depressed ST Infarction = elevated ST
T wave characteristics:
Usually upright
Usually goes in the direction of the QRS
Normally inverted in aVR and V1
Occasionally inverted in III
What is the QT interval?
The time from the start of the QRS to the end of the t wave
Encompasses depolarisation and repolarisation
How long is the QT interval?
Men <430ms
Women <450ms
QT too long can lead to?
Torsades de pointes
What is the U wave?
Repolarisation of the His-purkinje system and mid-myocardium
Where is the U wave seen?
V2-4
Prominent in young people
What electrolyte imbalances can cause U waves?
Hypokalaemia
Hypocalcaemia
What are the three main epicardial vessels?
LAD down the anterior surface
Circumflex that extends laterally
Right coronary that feeds the right side and the bottom
What occurs before chest pain?
ECG changes
What can cause ischaemia?
Stenosis of around 75% in the coronaries
Aortic stenosis
Arrhythmia
Hypertrophic cardiomyopathy
What is infarction?
Muscle dying due to vessel blockage causing ST elevation
Why does ST elevate?
Different depolarisation happening in dying cells
Anterior wall infarction (muscle dies) =
Decreased R wave as less depolarisation in that area
Increased amplitude of the Q wave as the area of muscle on the opposite side shines through
T wave inversion (can normalise months later)
Posterior wall infarction =
Larger R wave and ST depression
Anterior infarction (LAD) =
V1-4
Massive anterior infarction =
V1-6
Antero-septal infarction =
V1-2
Anterolateral infarction (circumflex) =
V5-6
Superior lateral infarction (circumflex) =
I, aVL
Inferior infarction =
II, III, aVF
Posterior infarction =
V1-3
Horizontal/down-sloping ST depression =
Ischaemia
Up-sloping ST depression =
Normal
Left-sided leads:
I
aVL
V4-6
Right-sided leads:
III
aVR
V1-3
