ECG Interpretation Flashcards
Describe the leads of a normal 12-lead ECG.
Which ones are unipolar, and which ones are bipolar?
UNIPOLAR:
Limb leads: aVR, aVL, aVF
Chest leads: V1-V6
BIPOLAR: Lead I (right arm - left arm) Lead II (right arm - left leg) Lead III (left arm - left leg)
What are the 5 parts of a normal ECG wave?
What part of the electoral conduction system does each one indicate?
P wave - atrial depolarisation
PQ segment - AV junction/AVN conduction; conduction through bundle branches
QRS complex - ventricular depolarisation
ST segment - plateau phase of repolarisation
T wave - final rapid repolarisation
There are 4 different views of the heart measured by an ECG. Which leads indicate each view?
Inferior view: II, III, aVF
Lateral view: I, aVL, V5, V6
Anterior view: V3, V4
Septal view: V1, V2
How many electrodes are used in a 12-lead ECG?
Describe the proper placement of each ECG electrode.
10 electrodes
CHEST LEADS:
V1 - 4th intercostal space, right sternal edge
V2 - 4th intercostal, left sternal edge
V3 - halfway between V2 and V4
V4 - 5th intercostal space, midclavicular line
V5 - 5th intercostal space, left anterior axillary line
V6 - 5th intercostal space, mid-axillary line
LIMB LEADS: aVR - right shoulder aVL - left shoulder aVF - left leg Grounding electrode - right leg
List, step by step, how you would approach an ECG. (4)
What are the 5 things, in order, you would look at on an ECG?
- Clinical context
- Check patient details, including:
a) Time/date of ECG
b) Patient name
c) Patient DOB - Assess technical quality:
a) Artefacts
b) Paper speed
c) Gain - Look at ECG:
a) Identify P/QRS/T waves
b) Check HR
c) Check ECG intervals
d) Check QRS axis
e) Check P/QRS/T morphology
When assessing technical quality of an ECG, what is normal for:
a) Paper speed?
b) Gain?
Paper speed: 25mm/s
Gain: 10mV/mm
List 3 methods by which you could determine heart rate from an ECG.
- Automatic reading at the top of the print out
- Number of QRS complexes across the whole ECG (10 seconds) x 6
- HR = 300 / (no. of large squares between each QRS complex)
When assessing ECG intervals, what is normal for:
a) PR interval?
b) QRS complex?
c) QT interval?
PR interval: <200ms (or <1 large square)
QRS complex: <120ms (or <3 small squares)
QT interval: <440ms (or <11 small squares)
When looking at the QRS axis on an ECG, what are the 4 possible axes?
Normal (-30° to +90°)
Left deviation (-30° to -90°)
Right deviation (+90° to +180°)
Extreme deviation (+180° to -90°)
When looking at P/QRS/T wave morphology on an ECG, what is normal? (3)
P wave is positive in inferior leads
ST segment is flat
T wave has same polarity as QRS
On an ECG, what are the features of:
a) Normal QRS axis?
b) Left QRS axis deviation?
c) Right QRS axis deviation?
d) Extreme QRS axis deviation?
HINT: normal and extreme are opposites, and right and left are opposites.
NORMAL:
Positive QRS in: I, II
Negative QRS in: aVR
LEFT DEVIATION:
Positive QRS in: I
Negative QRS in: II, aVF
RIGHT DEVIATION:
Positive QRS in: aVF
Negative QRS in: I
EXTREME DEVIATION:
Positive QRS in: aVR
Negative QRS in: I, II
What can cause left QRS axis deviation on an ECG? (1)
Conduction defects
What can cause right QRS axis deviation on an ECG? (2)
Right ventricular hypertrophy
Pulmonary conditions
What can cause extreme QRS axis deviation on an ECG? (1)
Ventricular tachycardia
What are the features of left bundle branch block on an ECG? (5)
Long QRS Dominant S wave in V1 Broad R wave in lateral leads Absent Q wave in lateral leads Notched R wave in V6
What are the features of right bundle branch block on an ECG? (5)
Long QRS Second R wave (M-shape) in V1 Wide, slurred S wave in V6 ST depression in V1-3 T wave inversion in V1-3
Which 2 features allow you to differentiate between left and right bundle branch block?
LEFT BUNDLE BRANCH BLOCK:
- Notched R wave in V6
- Dominant S wave in V1
RIGHT BUNDLE BRANCH BLOCK:
- Second R wave in V1
- Wide, slurred S wave in V6
List 8 examples of arrhythmias that can be seen on an ECG.
Sinus bradycardia Junctional bradycardia Second degree AV block (Mobitz type 1) Second degree AV block (Mobitz type 2) Complete AV block Atrial fibrillation Supraventricular tachycardia Ventricular tachycardia
On an ECG, what is the difference between sinus bradycardia and junctional bradycardia? (1)
SINUS BRADYCARDIA:
-Normal wave form
JUNCTIONAL BRADYCARDIA:
-No P waves present
Describe the features of second degree AV block on an ECG. Consider:
a) Mobitz type 1 (3)
b) Mobitz type 2 (3)
MOBITZ TYPE 1 AV BLOCK:
Irregular QRS complex (slowest rate: <60 bpm)
P:QRS complex is NOT 1:1
-Increasing PR interval
-Then a dropped beat (i.e. a P wave without a QRS complex)
MOBITZ TYPE 2 AV BLOCK Irregular QRS complexes (slowest rate: <60 bpm) P:QRS complex is NOT 1:1 -Constant PR interval -Intermittent dropped beats
What are the features of complete AV block on an ECG? (3)
Slow HR (<60 bpm)
Regular, broad QRS complexes
No relation between P waves and QRS complexes
What are the features of atrial fibrillation on an ECG? (3)
Irregularly irregular, fast HR
Irregular, narrow QRS complexes
No P waves
What is the difference between supraventricular tachycardia (2) and ventricular tachycardia (3)?
SUPRAVENTRICULAR TACHYCARDIA
- High HR (150+ bpm)
- P waves may not be present
VENTRICULAR TACHYCARDIA
- High HR (120+ bpm)
- Regular, broad QRS complexes
- P waves are variable
Describe the features of an acute STEMI on ECG. (4)
Regional ST elevation
- Anterior: left anterior descending coronary artery (LAD)
- Lateral: circumflex artery
- Inferior: right coronary artery
Hyperacute T waves
Q waves
New left bundle branch block
Describe the features of an acute NSTEMI on ECG. (3)
ST segment depression
T wave inversion
T wave flattening
Describe the features of pericarditis on ECG. (5)
Clinical features NOT consistent with MI ST elevation in every lead Concave ST elevation No reciprocal ST depression PR depression
What is the main feature of hyperkalaemia on an ECG? (1)
Peaked, tented T waves
