ECG Flashcards
What does P wave represent?
Atrial depolarisation
What does PR interval represent?
Time for electrical activity to move between the atria and the ventricles
When does PR interval begin and end?
Begins at the start of the P wave and ends at the beginning of the Q wave
What does QRS complex represent?
Depolarisation of the ventricles
When does ST segment begin and end?
Starts at the end of the S wave and ends at the beginning of the T wave
What does ST segment represent?
Time between depolarisation and repolarisation of the ventricles (i.e. ventricular contraction)
What does T wave represent?
Ventricular repolarisation
When does RR interval begin and end?
Begins at the peak of one R wave and ends at the peak of the next R wave
What does RR interval represent?
Time between two QRS complexes
When does QT interval begin and end?
Begins at the start of the QRS complex and finishes at the end of the T wave
What does QT interval represent?
Time taken for the ventricles to depolarise and then repolarise
How long does each small square on ECG paper represent
0.04 seconds
How long does each large square on ECG paper represent
0.2 seconds
How long does 5 large square on ECG paper represent
1 second
How long does 300 large squares on ECG paper represent
1 minute
Placement of V1 chest electrode…
4th intercostal space at the right sternal edge
Placement of V2 chest electrode…
4th intercostal space at the left sternal edge
Placement of V3 chest electrode…
Midway between the V2 and V4 electrodes
Placement of V4 chest electrode…
5th intercostal space in the midclavicular line
Placement of V5 chest electrode…
Left anterior axillary line at the same horizontal level as V4
Placement of V6 chest electrode…
Left mid-axillary line at the same horizontal level as V4 and V5
Placement of red RA electrode….
Ulnar styloid process of the right arm
Placement of yellow LA electrode….
Ulnar styloid process of the left arm
Placement of green LL electrode….
Medial or lateral malleolus of the left leg
Placement of black RL electrode….
Medial or lateral malleolus of the right leg
Which chest leads have septal view of the heart?
V1 and V2
Which chest leads have anterior view of the heart?
V3 and V4
Which chest leads have lateral view of the heart?
V5, V6, Lead I, aVR, aVL
Which chest leads have inferior view of the heart?
Lead II, Lead III, aVF
When the electrical activity within the heart travels towards a lead, you get a…..
Positive deflection
When the electrical activity within the heart travels away from a lead, you get a……
Negative deflection
If the R wave is greater than the S wave, it suggests depolarisation is moving _________ lead
Towards the
If the S wave is greater than the R wave,it suggests depolarisation is moving ________ that lead
Away from
If the R and S waves are of equal size, it means depolarisation is travelling at exactly __________
90° to that lead
In healthy individuals, the electrical activity of the heart begins at the ________ then spreads to the ________. It then spreads down the __________ and _________ to cause ventricular contraction
Sinoatrial node (SA)
Atrioventricular (AV) node
Bundle of His
Purkinje fibres
In healthy individuals, you would expect the cardiac axis to lie between ________, axis spreads from _________
-30°and +90º
11 o’clock to 5 o’clock
The overall direction of electrical activity in a healthy individual is towards leads _________
I, II and III
In healthy individuals see positive deflection in leads __________ with __________ showing the most positive deflection as it is the most closely aligned to the overall direction of electrical spread
Leads I, II, II
Lead II
In healthy individuals see the most negative deflection in _______ this is because _____ produces viewpoint of the heart from the opposite direction
aVR
Right axis deviation (RAD) involves the direction of depolarisation being ______, cardiac axis ______
Distorted to the right
Between +90º and +180º
Most common cause of RAD is…..
Chronic pulmonary disease
Right ventricular hypertrophy
Left posterior fascicular block
Acute pulmonary embolism
Lateral myocardial infarction
Right axis deviation causes the deflection in _______ to become negative and the deflection in ___________ to be more positive
Lead I
Lead aVF/III
Light axis deviation (LAD) involves the direction of depolarisation being ______, cardiac axis ______
Distorted to the left
Between -30° and -90°
Left axis deviation causes deflection of _______ becoming positive and defelection of _______ becoming negative
Lead I
Lead aVF
Left axis deviation causes deflection of _______ becoming negative (this is only considered significant if the deflection of _______ also becomes negative)
Lead III
Lead II
_______________ usually cause left axis deviation
Conduction abnormalities
Causes of LAD
Left anterior fascicular block
Left bundle branch block
Left ventricular hypertrophy
Inferior myocardial infarction
Normal adult heart rate
60-100 bpm
Tachycardia heart rate
> 100 bpm
Bradycardia heart rate
< 60 bpm
If regular heart rhythm, heart rate can be calculated using the following method….
300 / Number of large squares present within one R-R interval
If irregular heart rhythm, heart rate can be calculated using the following method….
Count the number of complexes on the rhythm strip (each rhythm strip is typically 10 seconds long)
Multiply the number of complexes by 6 (giving you the average number of complexes in 1 minute)
Absent P wave on ECG suggest
Irregular rhythm
How long should PR interval be
120-200 ms
3-5 small squares
How long should QRS complex be
70-110 ms
A prolonged PR interval suggests the presence of ___________
Atrioventricular delay (AV block)
Typical ECG findings in first-degree heart block
Fixed prolonged PR interval (>200 ms)
Typical ECG findings in second-degree (Mobitz Type I) heart block
Progressive prolongation of the PR interval until eventually the atrial impulse is not conducted and the QRS complex is dropped
AV nodal conduction resumes with the next beat, and the sequence of progressive PR interval prolongation and the eventual dropping of a QRS complex repeats itself
Typical ECG findings in second-degree (Mobitz Type II) heart block
Consistent PR interval duration with intermittently dropped QRS complexes due to a failure of conduction
The intermittent dropping of the QRS complexes typically follows a repeating cycle of every 3rd (3:1 block) or 4th (4:1 block) P wave
Third-degree (complete) AV block occurs when there is _______________________ due to a complete failure of conduction
No electrical communication between the atria and ventricles
Typical ECG findings in third-degree (complete) heart block
Presence of P waves and QRS complexes that have no association with each other, due to the atria and ventricles functioning independently
Narrow-complex escape rhythms (QRS complexes of <0.12 seconds duration) originate _______________
Above the bifurcation of the bundle of His
Broad-complex escape rhythms (QRS complexes >0.12 seconds duration) originate __________________
Below the bifurcation of the bundle of His
Shortened PR interval indicates ______________ or __________
P wave originates closer to AV node
Atrial impulse getting to ventricle via accessory pathway
Typical ECG finding if atrial impulse getting to ventricle via accessory pathway
Delta wave
A pathological Q wave is _______ the size of the R wave that follows it or _____ in height and______ in width
> 25%
2mm
40ms
ST-elevation is significant when it is _________________ or __________________
> 1 mm (1 small square) in 2 or more contiguous limb leads
> 2mm in 2 or more chest leads
ST elevation most commonly caused by….
Acute full-thickness myocardial infarction
ST depression ≥ 0.5 mm in ≥ 2 contiguous leads indicates……..
Myocardial ischaemia
T waves are considered tall if they are ______ in the limb leads and ________ in the chest lead
> 5mm
10mm
Tall T waves can be associated with……
Hyperkalaemia
Hyperacute STEMI
Inverted T waves normal in….
V1 and lead III
Inverted T wave in leads besides V1 and lead III can indicate
Ischaemia
Bundle branch blocks (V4-6 in LBBB and V1-V3 in RBBB)
Pulmonary embolism
Left ventricular hypertrophy (in the lateral leads)
Hypertrophic cardiomyopathy (widespread)
General illness
Biphasic T waves have two peaks and can indicate ____________ and ____________
Ischaemia
Hypokalaemia
Flattened T waves are a non-specific sign that may represent _____________ or ___________
Ischaemia
Electrolyte imbalance
U wave is a ___________ after the T wave best seen in ______ or ______
> 0.5mm deflection
V2 or V3
The _______ the bradycardia the _______ the U wave
Slower
Larger
Classically, U waves seen in…
Electrolyte imbalances
Hypothermia
Secondary to antiarrhythmic therapy → e.g digoxin, procainamide or amiodarone
Changes in leads with inferior view (II ,III, aVF) of the heart indicate ___________ occlusion
Right coronary artery
Changes in leads with anterior view (V3, V4) of the heart indicate ___________ occlusion
Distal Left Anterior Descending Artery
Changes in leads with septal view (V1, V2) of the heart indicate ___________ occlusion
Left Anterior Descending Artery
Changes in leads with lateral view (I, aVL, V5, V6) of the heart indicate ___________ occlusion
Circumflex artery
Changes in leads I, aVL, V2-V6 of the heart indicate ___________ occlusion
Proximal Left Coronary Artery
Tall R in lead V1 indicate ___________ occlusion
Right Coronary Artery
What does this image indicate?
ST elevation
What does this image indicate?
ST depression
Typical ECG finding in Brugada syndrome
Classic ST elevation with partial right bundle branch block pattern in V1/V2
Persistent coved shape ST elevation with T wave inversion in leads V1-V2
Downsloping ST segment is typical with…
Therapeutic doses of digoxin
Typical ECG finding of RBBB
V1: RSR’ pattern in V1, with (appropriate) discordant T wave changes
V6: Widened, slurred S wave in V6
Typical ECG finding of LBBB
V1: Dominant S wave
V6: broad, notched (‘M’-shaped) R wave
Typical ECG finding of hypokalaemia
Down slopping ST segment (widespread) in association with T wave flattening or inversion and U wave
Typical ECG finding of hyperkalaemia
Peaked T wave
Prolonged QT
Wide QRS complex
P wave flattening
What does this ECG show and how to treat?
Ventricular Tachycardia
Treat with emergency DC Cardioversion
What does this ECG show?
Atrial Flutter
What does this ECG show?
Ventricular fibrillation
What does this ECG show?
Ventricular Flutter